Chapter 126. Regional Nerve Blocks (Regional Anesthesia)

Regional anesthesia or regional nerve blocks are defined as infiltration of a peripheral nerve with local anesthetic agents to attenuate motor output and sensory input. It provides anesthesia to allow conditions to be treated efficiently and with minimal discomfort. Patients typically tolerate nerve blocks better than direct wound infiltration. Nerve blocks often require less local anesthetic solution than does infiltration of large wounds.

Regional anesthesia provides sensory blockade of a region without altering the normal anatomic features of the area to be repaired. It may be considered for use in the repair of extensive wounds, incision and drainage of abscesses, foreign body removal, wound exploration, burn care, fracture reduction, or pain control. Once familiar with the body's sensory innervation, the Emergency Physician can easily employ regional anesthesia techniques within the Emergency Department.

Locating and anesthetizing a peripheral nerve is accomplished in one of four ways. First is to identify the general location of the nerve using anatomy and landmarks. Infiltrate local anesthetic solution at that site and allow it to diffuse over the area. The second is to locate a nerve by using the injecting needle to elicit paresthesias. Once paresthesias are elicited, withdraw the needle 1 to 2 mm and allow the paresthesias to resolve before injecting the local anesthetic solution. A nerve stimulator can be used to accurately locate peripheral nerves with motor fiber components. Use of a nerve stimulator does not require cooperation on the part of the patient. However, due to its complexity, a physician skilled in its use is required. Nerve stimulators are rarely available in the Emergency Department. US can be used to locate nerves.

The traditional method used by Anesthesiologists to perform regional anesthesia involves a combination of surface landmarks and nerve stimulation. Over the past 10 to 15 years, ultrasound (US) has gained a prominent role in guiding nerve blocks. It offers the advantages of visualizing the nerve and the needle, as well as directly visualizing the deposition of local anesthetic solution around the nerve. Several small studies have shown that Emergency Physicians can safely perform US-guided nerve blocks.1–4

It is common to encounter children complaining of pain in the Emergency Department. Regional anesthesia is frequently overlooked in children. Its use is increasing and serves as an excellent opportunity to minimize pain in the pediatric population.5 It can be administered safely and effectively in these patients. A child may require intravenous or intramuscular sedation in conjunction with nerve blockade in more complicated cases. The use of nitrous oxide with pediatric patients in the Emergency Department has been found to be successful when used for forearm fracture manipulation.6 It can also be used for other procedures. Refer to Chapter 128 regarding the use of nitrous oxide as a supplement or to perform the regional nerve block. The disadvantages of regional nerve blocks in children include the extra time required to perform the block, mandatory technical dexterity, and assistant support because the child may not remain still for the procedure.

This chapter covers regional anesthetic blocks of the head, neck, upper extremity, lower extremity, and two of the many torso blocks (Table 126-1). Dental blocks are discussed in Chapter 176. Refer to Chapter 123 for a more complete discussion on the properties of local anesthetic agents.

There is a topographic arrangement of axons within peripheral nerves (Figure 126-1A).7,8 Axons located in the outer or mantle layer innervate proximal structures. Axons in the center of the nerve or core layer innervate distal structures. Local anesthetic solution injected near a nerve diffuses from the mantle layer to the core layers. This explains why anesthesia slowly spreads along the nerve distribution in a proximal to distal direction.

Avoid intraneural injection when performing peripheral nerve blocks. The nerve has a tough, fibrous outer sheath that acts as a physical barrier to trap intraneural fluid (Figure 126-1B). Injection of local anesthetic agents into the nerve bundle will compress the fragile axons and their capillary blood supply.9,10 This can result in axonal necrosis and permanent nerve damage. Paresthesias elicited upon needle insertion indicate that the tip of the needle is within the nerve bundle. Withdraw the needle 1 to 2 mm and allow the paresthesias to resolve, usually within 15 to 30 seconds. The anesthetic agent can be safely injected when the paresthesias resolve.

Cutaneous innervation is referenced to a segment known as a dermatome.7 This is defined as an area of skin supplied by a single spinal or segmental nerve. This type of innervation is best represented in worms, where each body segment has its own nervous supply. The pattern of segmental innervation still holds true with some minor modifications as one moves up the phylogenetic tree. The truncal dermatomes in humans are represented as simple bands while the extremity dermatomes are serpiginous and follow the embryonic rotation of the limb buds. The most commonly used dermatomal chart is that developed by Keegan and Garrett (Figure 126-2).8 Their model of the extremity dermatomes is in strips of innervation, all originating from the limb base and extending distally. This system is used in clinical medicine today.

Regional anesthesia produces profound analgesia with minimal physiologic or anatomic alteration. These techniques are especially useful in large or extensive lacerations that would otherwise require infiltration of a large and potentially toxic volume of local anesthetic solution. Nerve blocks can avoid a patient being taken to the Operating Room because the volume of local anesthetic required for extensive wound repair may require toxic doses. These techniques are also useful in cosmetic repairs where local infiltration may cause distortion of tissues or loss of anatomic landmarks making approximation and repair difficult. The necessity to palpate deep tissue for excision is also an indication for regional anesthesia.11,12 Regional nerve blocks can be performed prior to burn care, dislocation or fracture reduction, foreign body removal, incision and drainage of abscesses, pain control, wound exploration, and wound care.

US-guided regional anesthesia offers a number of advantages when compared with the anatomic landmark. It is safer and results in fewer complications (e.g., vascular puncture, pneumothorax, and intravascular injection of local anesthetic).13 US achieves higher rates of successful block (over 95%) and delivers a more rapid onset of anesthesia. In addition, a smaller volume of local anesthetic solution is required for the block.13 US can eliminate the need for procedural sedation and analgesia (PSA) and its potential complications (e.g., apnea, hypoxia, and hypotension). Preprocedural fasting is not required as it is a potential requirement in PSA. US-guided nerve blocks reduce Emergency Department lengths of stay compared with patients receiving PSA.1 It facilitates procedures in patients with higher American Society of Anesthesiology (ASA) classification scores, who would otherwise be put at higher risk for complications by the administration of PSA.

There are few contraindications to regional anesthesia.7,14 Absolute contraindications include injection through infected tissue, history of a bleeding disorder or a coagulopathy, or an allergy to the anesthetic agent. Relative contraindications include preexisting neurologic damage prior to the procedure. This should carefully be documented before any anesthetic injection. Additionally, patient uncooperativeness can make the procedure technically more difficult. Therefore, procedural sedation may be a necessary adjunct.5,15 This is particularly true of the pediatric population and those with an altered mental status.16

There are no patient contraindications to the use of US to guide nerve blocks. Emergency Physician contraindications include the lack of familiarity and training with the procedure. Psychomotor coordination and experience with US are required. Caution is advised for the novice ultrasonographer.

Anatomic Landmark-Guided Nerve Blocks

• Sterile gloves
• Sterile drapes
• Povidone iodine or chlorhexidine solution
• Alcohol swabs
• Local anesthetic solution (Table 126-2 and Chapter 123)
• 18 gauge needle to draw up local anesthetic solution
• 20 to 27 gauge noncutting or Quincke needles for injection, 2 inches long
• 22 to 24 gauge noncutting or Quincke spinal needles
• 1, 3, 5, 10, and 60 mL syringes
• Intravenous extension tubing

US-Guided Nerve Blocks

• Above listed supplies
• US machine
• High frequency, linear-array, US probe
• Sterile US probe cover
• Sterile US gel

All of the required equipment is readily available in any Emergency Department. Some have a pre-prepared tray or tackle box containing all the required equipment.

Explain the procedure, its risks, and benefits to the patient and/or their representative. Emphasize that there are few complications with this procedure. However, all possible complications should be discussed beforehand. Inform the patient of the possibility of paresthesias during the procedure and of the expected duration of action of the local anesthetic agent (Table 126-2). Obtain an informed consent for the regional nerve block in addition to the procedure for which it is performed. Ideally, the consent should be documented in the medical record and signed by the patient. Some Emergency Physicians prefer to note on the patient's chart “Indications, risks, and benefits were discussed with the patient” rather than having the patient sign a consent form. This decision is specific to each Emergency Physician, their institution, and state requirements.

Perform and document a neurological examination of the area to be anesthetized before performing regional anesthesia. Include a description of any neurological deficit in the document of informed consent for the procedure. Have the patient sign an agreement that the defect was present prior to the administration of the local anesthetic solution.

Position the patient based upon the specific regional block to be performed. Place the patient supine on a gurney or procedure table prior to the procedure in most cases. If the patient must sit upright, place the patient on an adjustable bed. The patient's comfort should be optimized to prevent unexpected complications such as vasovagal syncope.7,17,18 Expose the area of the injection and identify the anatomic landmarks required for proper needle placement. Clean all dirt and debris from the skin. Scrub the needle insertion site with povidone iodine or chlorhexidine solution and allow it to dry. Apply sterile drapes to delineate a sterile field.

If using US-guidance, prepare the US probe. Always use a sterile US probe cover and sterile US gel when performing nerve blocks to prevent deep infections. Set up a sterile field on a bedside table. Open the US probe cover set onto the sterile field. Instruct an assistant to hold the US probe upright and place standard or sterile US gel on the footprint of the US probe (Figure 50-6A). Apply the sterile probe cover over the US probe (Figure 50-6B). Smooth all the air bubbles away from the footprint of the US probe to prevent imaging artifacts. Secure the cover with rubber bands to prevent it from sliding off the US probe (Figure 50-6C). Place the US probe on the sterile field (Figure 50-6D). Apply sterile US gel onto the cover over the US probe footprint just before scanning.

The general procedure will first be described and specifics will be addressed with each individual nerve block.

Anatomic Landmark Technique

Position the patient. Identify the nerve or nerves to be blocked and their associated anatomic landmarks. Carefully clean and prepare the skin over the injection site in a sterile fashion. Draw up the local anesthetic solution to be injected. The amount will vary based upon the specific block. Always keep in mind the maximum allowable dose of local anesthetic (Table 126-2). Reidentify the anatomic landmarks. Insert the needle into the site. Withdraw the plunger to ensure that the tip of the needle is not within a blood vessel, thus avoiding intravascular injection. If paresthesias are elicited, withdraw the needle 1 to 2 mm and allow them to resolve. Inject the local anesthetic solution. Apply an appropriate bandage to the site. Allow 5 to 15 minutes for the block to take effect. Confirm that anesthesia has been achieved with pinprick prior to performing the procedure for which regional anesthesia was performed. Document the regional anesthesia procedure, the procedure for which regional anesthesia was performed, and any complications in the medical record. A sample regional anesthesia procedure note is described in Table 126-3.

US-Guided Technique

Position and prepare the patient as described above for the anatomic landmark technique. Find the general location of the nerve using anatomic landmarks. Use US to identify the targeted nerve. Use a longitudinal needle approach for all US-guided nerve blocks. The US probe should image the nerve bundle in the short axis, allowing the entire length of the needle to be visualized as it approaches the nerve. Use a noncutting needle, such as a Quincke spinal needle, to reduce the risk of intraneural injection or nerve injury. Place the US machine on the patient's opposite side to allow the Emergency Physician to glance easily and quickly from the field to the US monitor. It is recommended to use an assistant to inject the local anesthetic solution. This allows the Emergency Physician to use their hands to hold the US probe with one hand and manipulate the needle with the other hand. Center the target nerve on the screen.

An important concept regarding the injection of local anesthetic solution around the nerve bundle is the “donut sign.” This is the circumferential spread of local anesthetic solution around the nerve. This is the desired location of the local anesthetic solution around the nerve and it is usually associated with a successful block.

Supraorbital Nerve Block

Anatomy

The supraorbital foramen lies on the supraorbital ridge along a line drawn through the pupil in the midposition (Figures 126-3 & 126-4). The supraorbital foramen may be palpable as an indentation. The supraorbital nerve is a branch of the ophthalmic division of the trigeminal nerve. It emerges through the supraorbital foramen, or notch, at the midline of the superior orbital ridge (Figure 126-4A). Its area of innervation includes the forehead, beginning at the superior orbital ridge and extending superiorly to the vertex of the scalp. It is blocked simultaneously with the supratrochlear nerve, as there is considerable overlap in their areas of innervation.

Patient Positioning

Place the patient supine, or sitting, and facing the Emergency Physician.

Landmarks

Identify, under the eyebrow, the superior orbital rim and the supraorbital foramen by palpation.

Needle Insertion and Direction

Place a skin wheal of local anesthetic solution over the midline of the forehead at the level of the eyebrow. Insert a 25 or 27 gauge needle through the skin wheal and aimed laterally (Figure 126-4B). Advance the needle while infiltrating subcutaneously with 3 to 5 mL of local anesthetic solution. Always maintain the needle just above the supraorbital ridge while advancing it (Figure 126-4B). Stop infiltrating when the needle passes the midline of the bony orbit.

Remarks

This technique will anesthetize both the supraorbital and supratrochlear nerves. Infiltrate 2 mL of local anesthetic solution directly over the supraorbital foramen, or notch, if it is palpable rather than subcutaneously infiltrating above the supraorbital ridge.

Supratrochlear Nerve Block

Anatomy

The supratrochlear nerve is a branch of the ophthalmic division of the trigeminal nerve. It emerges through the trochlea at the supermedial aspect of the bony orbit (Figure 126-4A). It provides innervation to the middle of the forehead beginning at the superior orbital ridge and extending superiorly to the vertex of the scalp. It is often blocked simultaneously with the supraorbital nerve, because there is considerable overlap in their areas of innervation.

Patient Positioning

Place the patient supine, or sitting, and facing the Emergency Physician.

Landmarks

Identify, under the eyebrow, the superior orbital rim by palpation.

Needle Insertion and Direction

Place a skin wheal of local anesthetic solution over the midline of the forehead at the level of the eyebrows. Insert a 25 or 27 gauge needle through the skin wheal, aimed laterally (Figure 126-4B). Advance the needle while infiltrating subcutaneously with 2 to 3 mL of local anesthetic solution. Always maintain the needle just above the supraorbital ridge while advancing it (Figure 126-4B). Stop infiltrating when the needle passes the midline of the bony orbit.

Remarks

Stop infiltrating 1.5 cm from the skin wheal so as to block only the supratrochlear nerve.

Infraorbital Nerve Block, Extraoral Approach

Anatomy

The infraorbital nerve is a branch of the maxillary division of the trigeminal nerve. It emerges through the infraorbital foramen, 1 cm below the middle to medial third of the inferior orbital ridge (Figure 126-5A). It lies in the same plane as the supraorbital foramen and pupil that is in the midposition (Figures 126-3 & 126-5). The nerve exits the infraorbital foramen and travels inferiorly and medially. It provides sensory innervation to the medial cheek, nasal ala, upper lip, and the skin between the upper lip and nose. The infraorbital nerve terminates as the anterior and middle superior alveolar nerves. They provide sensory innervation to the maxillary incisors, canine, and premolar teeth, as well as their bony support and surrounding soft tissues.

Patient Positioning

Place the patient supine, or sitting, and facing the Emergency Physician.

Landmarks

Identify the infraorbital foramen by palpation. Significant tenderness will be elicited when the infraorbital nerve is palpated as it exits the infraorbital foramen.

Needle Insertion and Direction

Insert a 25 or 27 gauge needle just above the infraorbital foramen (Figure 126-5B). Advance the needle until the maxilla is contacted. Inject 1 to 2 mL of local anesthetic solution.

Remarks

The infraorbital nerve can be blocked intraorally. The intraoral route results in the patient experiencing less pain than the extraoral route.

Infraorbital Nerve Block, Intraoral Approach

Anatomy

The anatomy and innervation of the infraorbital nerve is described in the previous section.

Patient Positioning

Place the patient supine, or sitting, and facing the Emergency Physician.

Landmarks

Identify the infraorbital foramen by palpation. It lies in a plane with the supraorbital foramen and the pupil in the midposition (Figures 126-3 & 126-6A).

Needle Insertion and Direction

Place the index finger of the nondominant hand over the infraorbital foramen (Figure 126-6B). Use the nondominant thumb to retract the upper lip. Insert a 2.5 to 4.0 cm, 25 or 27 gauge needle through the mucous membranes, directed at the index finger. Advance the needle until its tip is palpable at the infraorbital foramen by the index finger. The estimated depth of needle penetration is 1.0 to 1.5 cm. Inject 2 mL of local anesthetic solution.

Remarks

This is the preferred route to block the infraorbital nerve. It can also be blocked extraorally.

Mental Nerve Block, Extraoral Approach

Anatomy

The mental nerve is a branch of the mandibular division of the trigeminal nerve. It emerges from the mental foramen. The foramen lies in a vertical plane with the supraorbital foramen, the infraorbital foramen, and the pupil that is midposition (Figures 126-3 & 126-7). The nerve travels inferiorly and anteriorly to provide sensory innervation to the skin of the lower lip and chin.

Patient Positioning

Place the patient supine, or sitting, and facing the Emergency Physician.

Landmarks

Identify the vertical plane consisting of the supraorbital foramen, the infraorbital foramen, and the midposition pupil. Identify the point where the vertical plane crosses the middle of the body of the mandible (Figure 126-7A). This is where the mental nerve exits the mental foramen.

Needle Insertion and Direction

Insert a 25 or 27 gauge needle at the above identified landmark (Figure 126-7B). Place a skin wheal of local anesthetic solution at this intersection. Advance the needle through the skin wheal until the mandible is contacted. Inject 1 to 2 mL of local anesthetic solution.

Remarks

This nerve can also be blocked intraorally.

Mental Nerve Block, Intraoral Approach

Anatomy

The anatomy and innervation of the mental nerve is described in the previous section.

Patient Positioning

Place the patient supine, or sitting, and facing the Emergency Physician.

Landmarks

Retract the lower lip and identify the junction of the first and second premolars. The patient's mouth may be open or closed.

Needle Insertion and Direction

Insert a 25 or 27 gauge needle directed inferiorly and posteriorly through the gingival mucosa at the junction of the first and second premolars (Figure 126-8). Advance the needle one-third the depth of the mandibular body and contact the mandible. Inject 1 to 2 mL of local anesthetic solution.

Remarks

This is the preferred approach to block the mental nerve. The intraoral route results in the patient experiencing less pain than the extraoral route.

Greater Occipital Nerve Block

Anatomy

The greater occipital nerve is a branch of the dorsal ramus of the second cervical nerve. It provides sensory innervation to the posterior neck, extending superiorly to the vertex of the scalp (Figure 126-9). It emerges on the posterosuperior neck, just below the line connecting the external occipital protuberance and the mastoid process (Figure 126-10). The posterior occipital artery accompanies the greater occipital nerve.

Patient Positioning

Place the patient prone.

Landmarks

Identify the external occipital protuberance and mastoid process by palpation (Figure 126-10A). Connect these landmarks with a line. Identify the occipital artery by its palpable pulse, approximately one-third the distance from the external occipital protuberance.

Needle Insertion and Direction

Place a skin wheal of local anesthetic solution over the pulse of the occipital artery. Insert a 25 gauge needle 1 to 2 mm to the left of the occipital artery pulse. Inject 1 mL of local anesthetic solution. Redirect the needle 1 to 2 mm to the right of the pulse and inject 1 mL of local anesthetic solution.

Remarks

This block is useful for laceration repair as well as relief of occipital muscular or tension headaches. If the pulse of the posterior occipital artery is not palpable, divide the line between the external occipital protuberance and the mastoid process into thirds. Infiltrate the middle third subcutaneously with 5 to 8 mL of local anesthetic solution (Figure 126-10A). This technique will also anesthetize the lesser occipital nerve.

Lesser Occipital Nerve Block

Anatomy

The lesser occipital nerve is a branch of the cervical plexus. It provides sensory innervation to the skin and scalp between the ear and the mastoid process (Figure 126-9). It emerges at the middle third of the posterior border of the sternocleidomastoid muscle and travels superiorly toward the mastoid process (Figure 126-10).

Patient Positioning

Place the patient supine or sitting with their head turned toward the side opposite that being anesthetized.

Landmarks

Identify the mastoid process by palpation.

Needle Insertion and Direction

Place a skin wheal of local anesthetic solution just posterior to the mastoid process. Insert a 25 gauge needle directed anteriorly through the skin wheal. Advance the needle while infiltrating local anesthetic solution subcutaneously until the posterior ear is contacted (Figure 126-10B). This requires 3 to 7 mL of local anesthetic solution.

Remarks

The lesser occipital nerve can be blocked at the level of the cervical plexus. Refer to the section on cervical plexus blockade below.

Great Auricular Nerve Block

Anatomy

The great auricular nerve is a branch of the cervical plexus. It emerges at the middle third of the posterior border of the sternocleidomastoid muscle and travels superiorly with the external jugular vein (Figure 126-10B). This nerve provides sensory innervation to the skin and scalp behind the ear, the posterior ear, and the lobule (Figure 126-9).

Patient Positioning

Place the patient supine with their head turned toward the side opposite that being anesthetized.

Landmarks

Identify the lobule of the ear, the mastoid process, and the sulcus behind the ear.

Needle Insertion and Direction

Place a skin wheal of local anesthetic solution just posterior to the mastoid process. Insert a 25 gauge needle directed anteriorly through the skin wheal. Advance the needle while infiltrating local anesthetic solution subcutaneously until the posterior ear is contacted (Figure 126-10B). This requires 3 to 7 mL of local anesthetic solution. Complete and successful anesthesia occurs within 10 minutes.

Remarks

The great auricular nerve block is indicated for lacerations of the auricle, debridement, and hematoma evacuations. It is rarely performed without simultaneous blockade of the auriculotemporal nerve. The great auricular nerve can be blocked at the level of the cervical plexus. Refer to the section on cervical plexus blockade below.

Scalp Block

Anatomy

The scalp receives its sensory innervation from branches of the trigeminal nerve anteriorly and the cervical plexus posteriorly (Figure 126-11). The scalp may be anesthetized anywhere along the anterior midline to the posterior midline. This involves blocking the supratrochlear, supraorbital, auriculotemporal, lesser occipital, great auricular, and greater occipital nerves.

Patient Positioning

Place the patient supine with their head turned toward the side opposite that being anesthetized.

Landmarks

Identify the glabella and the external occipital protuberance by palpation.

Needle Insertion and Direction

Place a skin wheal of local anesthetic solution over the glabella. Insert a 25 gauge needle through the skin wheal. Infiltrate a continuous line of local anesthetic solution subcutaneously between the glabella and the external occipital protuberance (Figure 126-11B). This requires 15 to 20 mL of local anesthetic solution.

Remarks

Infiltrate the local anesthetic solution subcutaneously along the scalp base inferior to the area in which the procedures will be performed to block only a portion of the scalp. It is useful to add epinephrine (1:200,000) to the local anesthetic solution to cause vasoconstriction and prevent excessive blood loss. Significant systemic absorption of the local anesthetic agent does not occur despite the extensive vascularity of the scalp. Scalp blocks provide anesthesia for laceration repair, drainage of superficial abscesses, and the exploration of scalp wounds. Complications are fairly rare. There is a case report of a temporary facial nerve palsy after a scalp block.19

External Ear Block

Anatomy

The ear is a difficult structure to anesthetize. It is innervated by a large number of sensory fibers that originate from the cervical plexus, the trigeminal nerve, and the vagus nerve. The external ear, or pinna, is innervated by the cervical plexus and the auriculotemporal branch of the trigeminal nerve (Figures 126-9 & 126-11).

Patient Positioning

Place the patient supine or sitting upright with their head turned toward the side opposite that being anesthetized.

Landmarks

Identify the angle of the mandible by palpation.

Needle Insertion and Direction

Place a skin wheal of local anesthetic solution over the angle of the mandible. Insert a 25 gauge needle through the skin wheal. Infiltrate local anesthetic solution subcutaneously in an anterior and superior direction, from the angle of the mandible to the superior surface of the ear, to block the auriculotemporal nerve (Figure 126-12A). Infiltrate local anesthetic solution subcutaneously in a posterior and superior direction, from the angle of the mandible to the superior surface of the ear, to block the great auricular and lesser occipital nerves (Figure 126-12A). This requires a total of 8 to 10 mL of local anesthetic solution.

Remarks

Some may prefer to anesthetize the auriculotemporal nerve trunk by injecting local anesthetic solution just above the posterior aspect of the zygomatic arch (Figure 126-12B). It requires less local anesthetic solution and hurts less than subcutaneous infiltration. An alternative technique is to circumferentially infiltrate local anesthetic solution subcutaneously around the ear (Figure 126-12C).

External Auditory Canal Block

Anatomy

The external auditory canal (and the tympanic membrane) receives its innervation from the auriculotemporal nerve and the vagus nerve.

Patient Positioning

Place the patient sitting upright or supine with their head turned toward the side opposite that being anesthetized.

Landmarks

Identify the helix, the tragus, and the lobule of the ear to be anesthetized (Figure 126-13).

Needle Insertion and Direction

Anesthetize the external auditory canal using a four-quadrant block (Figure 126-13). Insert a 25 gauge needle, advance it 0.5 to 0.75 cm, and inject 1 mL of local anesthetic solution at each of the four landmarks identified in Figure 126-13.

Remarks

This block can be quite painful for the patient. The authors recommend to first anesthetize the external ear before anesthetizing the external auditory canal. This block also anesthetizes the tympanic membrane.

Cervical Plexus Block

Anatomy

The cervical plexus originates from the anterior rami of cervical nerves two through four. These rami form numerous loops that anastomose to form nerves that provide sensory innervation to the anterolateral neck, the scalp, the ear, and the infraclavicular area. The four nerves of the cervical plexus become superficial at the midportion of the posterior border of the sternocleidomastoid muscle and then distribute to their respective sensory areas (Figure 126-14A). The cervical plexus provides motor innervation to the strap muscles of the neck.

The four superficial nerves of the cervical plexus are the lesser occipital nerve, the great auricular nerve, the anterior (or transverse) cervical nerve, and the supraclavicular nerve (Figure 126-14A). The lesser occipital nerve travels superiorly and posteriorly to provide sensory innervation to part of the posterior surface of the upper ear and the postauricular skin. The great auricular nerve travels superiorly and anteriorly to provide sensory innervation to the skin over the posterior surface of the ear, the anterior lower half of the ear, and over the angle of the mandible. The anterior, or transverse, cervical nerve of the neck travels anteriorly to provide sensory innervation to the skin of the neck, from the inferior border of the mandible to the sternum. The supraclavicular nerves travel from the clavicle down to the second rib.

Patient Positioning

Place the patient supine with their head turned toward the side opposite of that being anesthetized.

Landmarks

Identify the posterior border of the sternocleidomastoid muscle by palpation. Divide this border into thirds.

Needle Insertion and Direction

Place a skin wheal of local anesthetic solution over the middle third of the posterior border of the sternocleidomastoid muscle. Insert a needle through the skin wheal. Infiltrate 5 to 10 mL of local anesthetic solution subcutaneously over the middle third of the posterior border of the sternocleidomastoid muscle (Figure 126-14B).

Remarks

This block is useful when managing burns or suturing lacerations on the anterolateral neck.

Brachial Plexus Block

The brachial plexus innervates the entire upper extremity. Blockade of the brachial plexus can be performed to repair tendons or extensive lacerations, to reduce fractures and dislocations, or to provide anesthesia for burn care, to name a few uses. Protect the arm from injury if this procedure is to be performed by properly supporting the arm, padding the ulnar nerve and pressure points, and not extending or displacing the arm posteriorly.

The brachial plexus arises from the C5 to T1 nerve roots (Figure 126-15). The nerve roots fuse to form three trunks. Each trunk divides into an anterior and posterior division that then redistributes to form the lateral, medial, and posterior cords. These cords divide in the region of the axilla to form the musculocutaneous nerve, the median nerve, the ulnar nerve, the axillary nerve, the radial nerve, and several cutaneous nerves. The brachial plexus crosses the midclavicle to enter the axilla (Figure 126-16A).

The brachial plexus may be blocked from the supraclavicular, interscalene, infraclavicular, or axillary approach. The preferred method for the Emergency Physician is the axillary block.

Brachial Plexus Block, Supraclavicular Approach

Anatomy

The anatomy of the brachial plexus is described above. This approach blocks the brachial plexus at the level of the trunks, where it is most compactly arranged.

Patient Positioning

Place the patient supine with their head turned 45° from the midline and toward the side opposite that being anesthetized (Figure 126-16A). Place the ipsilateral arm in any position of comfort for the patient.

Landmarks

The subclavian artery is the main landmark. Palpate the subclavian artery immediately lateral to the clavicular head of the sternocleidomastoid muscle in the interscalene groove. Identify the midpoint of the clavicle.

Needle Insertion and Direction

Place a skin wheal of local anesthetic solution 2 cm above the midclavicle. Insert a 25 gauge needle directed caudally through the skin wheal (Figures 126-16B & C). Advance the needle until the patient experiences paresthesias. Withdraw the needle 1 mm and allow the paresthesias to resolve. Aspirate to ensure that the tip of the needle is not within a blood vessel. Inject 40 mL of local anesthetic solution. Reduce the volume based upon the patient's body size and the maximal allowable dose to prevent toxicity.

US-Guided Block

Place the US probe in an oblique coronal plane above the clavicle and lateral to the sternocleidomastoid muscle (Figure 126-16D). Locate the subclavian artery. It is a pulsatile, round, and hypoechoic structure in cross section. The trunks of the brachial plexus are located adjacent to the subclavian artery (Figure 126-16E). Posterior to the subclavian artery lies the first rib, and the pleural line can be seen sliding in real time. Use color/power Doppler to confirm the location of the subclavian artery and any branches or take-offs, all of which must be avoided (Figure 126-16F). Anesthetize the skin. Position the spinal needle lateral to the US probe and parallel to its long axis. Slowly insert and advance the needle. Visualize the entire length of the needle as it is introduced through the subcutaneous tissue toward the brachial plexus. Advance the needle through the nerve sheath. Aspirate to ensure the needle tip is not in a blood vessel. Inject a test dose of 1 to 2 mL of local anesthetic solution. Watch the spread of anesthetic around the nerves. If it is satisfactory, inject the remainder of the local anesthetic solution to achieve the “donut sign” (Figure 126-16G). If the test dose is not satisfactory, reposition the needle and inject another test dose.

Remarks

This block is characterized by a quick onset of anesthesia and a complete block. A high volume of anesthetic is required with a quick onset of anesthesia. There is no chance of missing peripheral or proximal nerve branches because of failure of the local anesthetic solution to spread along the sheath of the brachial plexus. Unfortunately, this technique is difficult to teach and to master without considerable experience. This technique has a high incidence of an iatrogenic pneumothorax, reportedly up to 6%. Other complications include blockade of the phrenic nerve, subclavian artery puncture, and Horner's syndrome. Unintentional intravascular injection can result in high blood levels of the local anesthetic agent.

Brachial Plexus Block, Interscalene Approach

Anatomy

The anatomy of the brachial plexus is described above. This approach blocks the brachial plexus at the level of the trunks (Figure 126-17A).

Patient Positioning

Place the patient supine with their head turned 45° from midline and toward the side opposite that being anesthetized (Figure 126-17A). Place the ipsilateral arm in any position of comfort for the patient.

Landmarks

Identify the posterior border of the clavicular head of the sternocleidomastoid muscle by palpation. Move the palpating finger laterally until it rolls into the interscalene groove between the anterior and middle scalene muscles, at the level of the cricoid cartilage (Figure 126-17B).

Needle Insertion and Direction

Place a skin wheal of local anesthetic solution in the interscalene groove, at the level of the cricoid cartilage. Slowly insert a 25 gauge needle through the skin wheal in a dorsal, medial, and caudal direction (Figure 126-17B). Advance the needle until the patient experiences paresthesias. Withdraw the needle 1 mm and allow the paresthesias to resolve. Aspirate to ensure that the tip of the needle is not within a blood vessel. Inject 30 to 40 mL of local anesthetic solution. Reduce the volume based upon the patient's body size and the maximal allowable dose to prevent toxicity.

US-Guided Block

This block is performed at the level of the internal jugular vein and carotid artery in the neck. Place the US probe on the neck, less than a third of the way up from the clavicle (Figure 126-17C). Identify the carotid artery and internal jugular vein. Move the US probe laterally to find the muscle bellies of the anterior and middle scalene muscles (Figure 126-17D). Between the muscles lie the nerve roots of the brachial plexus in cross section. It is represented by hypoechoic circles within the hyperechoic rings of the nerve sheaths (Figure 126-17D). Use color Doppler to identify any blood vessels in the field, and note their location so as to avoid them. Anesthetize the skin. Using a posterior approach, insert the spinal needle connected by extension tubing to a 20 mL syringe filled with local anesthetic solution. Advance the needle and visualize it approaching the brachial plexus. The needle path will usually go through the middle scalene muscle. Once the brachial plexus is close to the needle tip, use a short and controlled jab to penetrate through the nerve sheath. Aspirate to verify that the needle tip is not in a blood vessel. Instruct an assistant to deliver a test dose of 1 to 2 mL of local anesthetic solution. If the anesthetic spreads around the nerves, slowly deliver the remainder of the local anesthetic solution to obtain the “donut sign.” If the test dose is not satisfactory, reposition the needle and inject another test dose.

Remarks

The advantages and disadvantages are similar to those of the supraclavicular approach with the exception of possibly not achieving anesthesia of the lower trunk. This may require supplementary blockade of the median and ulnar nerves. The interscalene brachial plexus block, although ideal for regional anesthesia of the shoulder, has been associated with recurrent laryngeal nerve paralysis and an almost 100% incidence of phrenic nerve paralysis.20 This can be significant in patients with respiratory comorbidities (e.g., COPD, obesity).21 The supraclavicular brachial plexus block is associated with lower rates of these complications.2

Brachial Plexus Block, Axillary Approach

Anatomy

The anatomy of the axillary brachial plexus nerve block is rather simple. The neurovascular bundle is easily found at the anterior axillary fold by palpating for the pulsations of the axillary artery. The neurovascular bundle is surrounded by the fibrous axillary sheath (Figure 126-18A). The axillary sheath is bound medially by skin and connective tissue, anteriorly by the biceps and coracobrachialis muscles, inferiorly by the triceps muscle, and laterally by the neck of the humerus. The axillary artery is the central reference structure within the neurovascular bundle. Within the axillary sheath, the median nerve is anterior, the radial nerve is posterolateral, and the ulnar nerve is posterior to the axillary artery. The axillary vein is medial to the artery. The medial antebrachial cutaneous nerve and the medial brachial cutaneous nerve are medial to the artery (Figure 126-18A). The only sensory nerve outside the neurovascular bundle is the musculocutaneous nerve. This nerve exits the axillary sheath as it crosses the clavicle.

Patient Positioning

Place the patient supine with their head turned toward the side opposite that being anesthetized (Figure 126-18B). Abduct the arm 90°. Flex the elbow 90° so that the forearm is parallel to the long axis of the body and the palm is facing upward.

Landmarks

Identify the brachial artery by its palpable pulse. Trace it proximally to the anterior axillary fold, formed by the pectoralis major muscle. Use the index and middle fingers of the nondominant hand to secure the neurovascular bundle (identified by the pulse) against the humerus (Figure 126-18B).

Needle Insertion and Direction

Place the skin wheal of local anesthetic solution overlying the axillary artery pulse, just posterior to the anterior axillary fold. Insert a 22 gauge spinal needle just above the fingertip on the axillary pulse, directed toward the apex of the axilla and in the direction of the neurovascular bundle (Figure 126-18B). Advance the needle. A “pop” will be felt as the axillary sheath is penetrated. The correct needle position is confirmed by eliciting paresthesias, observing blood flow in the needle, or observing pulsations of the needle that match the pulse (Figure 126-18C). Instruct an assistant to attach the distal end of intravenous extension tubing to the hub of the needle, and the proximal end to a 60 mL syringe containing local anesthetic solution. The Emergency Physician must always maintain pressure against the neurovascular bundle with the nondominant hand while stabilizing the needle with the dominant hand. Instruct the assistant to aspirate to ensure that the tip of the needle is not within a blood vessel. Withdraw the needle 2 mm if blood flow or paresthesias are elicited.

Apply digital pressure to the neurovascular bundle just distal to the tip of the needle with the nondominant fingers. This prevents the local anesthetic solution from flowing distally. Inject the local anesthetic solution into the axillary sheath after the paresthesias have resolved and a negative aspiration has been achieved. Instruct the assistant to inject a volume of approximately 40 mL in the adult patient. This volume has been shown to consistently block the entire brachial plexus. Reduce the volume based upon the patient's body size and the maximal allowable dose to prevent toxicity. Continue to apply digital pressure to the neurovascular bundle just distal to the needle during and after injection of the local anesthetic solution.

Withdraw the needle while the assistant simultaneously injects 3 to 5 mL of local anesthetic solution into the subcutaneous tissue. This blocks the medial brachial cutaneous nerve and the intercostobrachial nerve. Abduct the patient's arm 30° to 45° after the needle is withdrawn. Maintain this position, while continuing to apply digital pressure to the neurovascular bundle just distal to the needle insertion site, for 2 to 3 minutes.

US-Guided Block

This block is performed at the level of the terminal branches of the brachial plexus within the axillary sheath. These branches are visualized as hyperechoic nodules around the pulsatile and hypoechoic axillary artery (Figures 126-18D & E). Place the US probe with the marker pointing cephalad at the superior axillary crease (Figure 126-18F). Locate the axillary artery and vein in cross section (Figure 126-18G). The musculocutaneous nerve can be seen between the biceps muscle and the coracobrachialis muscle. Use color Doppler to confirm the location of the axillary artery, vein, and any branches or take-offs (Figure 126-18G). Anesthetize the skin. Position the spinal needle inferior or superior to the long axis of the US probe (Figure 126-18F). Slowly insert and advance the needle. Visualize the entire length of the needle as it is advanced. Aim the needle between the axillary artery and vein. Advance through the nerve sheath. Aspirate to ensure the needle tip is not in a blood vessel. Inject a test dose of 1 to 2 mL of local anesthetic solution. Watch the spread of local anesthetic solution around the subclavian artery. If it is satisfactory, inject the remainder of the local anesthetic solution to produce the “donut sign.” If the test dose is not satisfactory, reposition the needle and inject another test dose.

Remarks

The axillary approach to the brachial plexus is the most commonly used and preferred technique. The procedure is easily mastered, has no major complications, and is easily performed in the obese patient. The disadvantages of this technique include insufficient anesthesia of the shoulder and upper arm. The musculocutaneous nerve provides sensory innervation to the radial aspect of the forearm and may be missed by the local anesthetic agent. The subcutaneous infiltration of local anesthetic solution usually blocks the musculocutaneous nerve. Proximal flow of the local anesthetic solution is required to ensure adequate anesthesia. Abduction of the arm while maintaining pressure on the neurovascular bundle allows proximal flow of the local anesthetic solution. It also prevents the humeral head from limiting proximal spread due to compression of the brachial plexus.

Brachial Plexus Block, Infraclavicular Approach

This approach to the brachial plexus has many advantages and few serious complications. Unfortunately, this technique requires considerable experience on the part of the Emergency Physician and a nerve stimulator to locate the brachial plexus (Figures 126-19A & B). For these reasons, the anatomic landmark approach will not be described. The US-guided technique is described below.

Anatomy

The anatomy of the brachial plexus is described above. This approach blocks the brachial plexus at the level of the cords (Figure 126-15A).

Patient Positioning

Place the patient supine with their head turned 45° from midline and toward the side opposite that being anesthetized (Figure 126-19A). Place the ipsilateral arm extended 90°.

Landmarks

Identify the middle third of the clavicle.

Infraclavicular Block

This block is performed below the clavicle. The cords of the brachial plexus lie below the pectoralis major and minor muscles. They appear as distinct hyperechoic nodules positioned laterally, medially, and posteriorly around the subclavian artery (Figures 126-19C & D). Prep and drape the infraclavicular region. Place the US probe with the marker pointing cephalad below the clavicle, medial to the coracoid process (Figure 126-19E). Locate the subclavian artery (which is pulsatile) and vein in cross section. Use color Doppler to confirm the location of the subclavian artery, vein, and any branches or take-offs (Figure 126-19F). Anesthetize the skin. Position the spinal needle inferior or superior to the long axis of the US probe (Figure 126-19E). Insert and advance the needle. Visualize the entire length of the needle as it is advanced. Aim the needle between the subclavian artery and vein. Advance the needle. Continue to advance the needle through the nerve sheath. Aspirate to ensure that the needle tip is not in a blood vessel. Inject a test dose of 1 to 2 mL of local anesthetic solution. Watch the spread of local anesthetic solution around the subclavian artery. If satisfactory, inject the remainder of the local anesthetic solution to produce the “donut sign.” If the test dose is not satisfactory, reposition the needle and inject another test dose.

Remarks

This block can result in an iatrogenic pneumothorax due to the proximity of the needle to the lung apex.

Median Nerve Block at the Elbow

Anatomy

The median nerve innervates all the muscles of the anterior forearm except the flexor digitorum profundus to the ring and little fingers and the flexor carpi ulnaris.12,22,23 It innervates the thenar muscles and the lumbrical muscles to the index and middle fingers in the hand. It provides sensory innervation to the palmar aspect of the thumb, index finger, middle finger, radial portion of the ring finger, and the lateral half of the palm (Figure 126-20A). The median nerve provides a variable amount of sensory innervation to the dorsal distal surfaces of the lateral three and one-half fingers.12

Patient Positioning

Place the patient supine with their arm abducted 45°, the elbow in full extension, and the hand supinated (Figure 126-21A).

Landmarks

Identify the medial and lateral epicondyle of the humerus by palpation. Connect the epicondyles with a straight line (Figure 126-21A). Identify the brachial artery by palpating for its pulse just medial to the biceps tendon and over the line just drawn. Mark the site of the palpable pulse with a marker.

Needle Insertion and Direction

Place a skin wheal of local anesthetic solution just medial to the pulse, at the level of the intercondylar line. Insert a 25 gauge needle perpendicular to the skin and slowly advance it. If paresthesias are elicited, withdraw the needle 1 to 2 mm and allow the paresthesias to resolve. Inject 3 to 5 mL of local anesthetic solution. If paresthesias are not elicited, slowly move the needle in a fan-like pattern to elicit paresthesias. Withdraw the needle 1 to 2 mm, allow the paresthesias to resolve, and inject 3 to 5 mL of local anesthetic solution.

US-Guided Block

Place the US probe in the crease of the antecubital fossa. Locate the pulsatile brachial artery in the middle of the antecubital fossa (Figure 126-21B). Anesthetize the skin medial to the brachial artery. Place the spinal needle inferior to the short axis of the US probe directly over the median nerve, which should be medial to the brachial artery. Only the tip of the needle will be visualized in this view. Insert and advance the needle until its tip is at the median nerve. Aspirate to ensure that the needle tip is not in a blood vessel. Inject a test dose of 1 to 2 mL of local anesthetic solution. Watch the spread of the local anesthetic solution around the median nerve. If satisfactory, inject the remainder of the local anesthetic solution to produce the “donut sign.” If the test dose is not satisfactory, reposition the needle and inject another test dose.

Remarks

The median nerve has no sensory branches in the forearm. Therefore, there is no advantage to blocking the median nerve at the elbow. Inserting the needle to elicit paresthesias can be quite painful for the patient. Blockade at the wrist is usually easier to perform, especially in obese patients.9

Median Nerve Block at the Wrist

Anatomy

The median nerve lies in the carpal tunnel on the volar aspect of the wrist. It is located between the tendons of the flexor carpi radialis and palmaris longus muscles (Figure 126-21C). The innervation of the median nerve is described in the previous section.

Patient Positioning

Place the patient supine with their arm abducted 45°, the elbow in full extension, and the hand fully supinated (Figure 126-21A).

Landmarks

Identify the palmaris longus tendon by flexing the patient's clenched hand against resistance. Mark the radial border of the palmaris longus tendon. Note the position of the proximal and distal wrist creases.

Needle Insertion and Direction

Place a skin wheal of local anesthetic solution along the radial border of the palmaris longus tendon, between the proximal and distal wrist creases. Insert a 25 gauge needle perpendicular to the skin wheal and advance it slowly (Figure 126-21C). If paresthesias are elicited, withdraw the needle 1 to 2 mm and allow them to resolve. Inject 3 to 5 mL of local anesthetic solution. If paresthesias are not elicited, inject 5 to 10 mL of local anesthetic solution. Injection of the local anesthetic solution should not raise a skin wheal and should flow effortlessly if the needle is within the carpal tunnel.12

US-Guided Block

Place the US probe over the middle of the wrist with the marker pointing laterally (Figure 126-21D). The Palmaris longus tendon should be visible in the middle of the wrist. The median nerve is hyperechoic and directly lateral to this tendon (Figure 126-21E). The radial artery is lateral to the median nerve (Figure 126-21C). Anesthetize the skin lateral to the palmaris longus tendon. Place the needle inferior to the short axis of the US probe and directly over the median nerve (Figure 126-21D). Insert and advance the needle until its tip is at the median nerve. Aspirate to ensure that the needle tip is not in a blood vessel. Inject a test dose of 1 to 2 mL of local anesthetic solution. Watch the spread of the local anesthetic solution around the median nerve. If satisfactory, inject the remainder of the local anesthetic solution to produce the “donut sign.” If the test dose is not satisfactory, reposition the needle and inject another test dose.

Remarks

A small percentage of the population (10% to 15%) does not have a palmaris longus tendon. Identify the flexor carpi radialis tendon by the same method as identifying the palmaris longus tendon. Inject the local anesthetic solution 1 cm medial to the ulnar edge of the flexor carpi radialis tendon, between the proximal and distal wrist creases. The technique is otherwise as noted above.

Ulnar Nerve Block at the Elbow

Anatomy

The ulnar nerve lies in the ulnar groove of the humerus at the elbow, between the olecranon process and medial condyle of the humerus (Figure 126-22A). It provides motor innervation to the flexor carpi ulnaris, the ring and little finger portion of the flexor digitorum profundus, the palmaris brevis, the hypothenar muscles, the third and fourth lumbricals, the interossei, and the adductor pollicis muscles. It provides sensory innervation to the medial one-third to one-half of the palm, the palmar aspect of the ulnar half of the ring finger, and the entire little finger (Figure 126-20B). The ulnar nerve provides sensory innervation to the dorsomedial half of the hand, the little finger, and the ulnar half of the ring finger on the dorsal surface of the hand.24

Patient Positioning

Place the patient supine with their elbow flexed 90° and the shoulder flexed 45° (Figure 126-22A).

Landmarks

Identify the olecranon process and the medial epicondyle of the humerus by palpation. Palpate the groove between the olecranon process and the medial epicondyle. The ulnar nerve is located within this groove.

Needle Insertion and Direction

Place a skin wheal of local anesthetic solution 1 to 2 cm proximal to the ulnar groove. Insert a 25 gauge needle through the skin wheal and directed toward the ulnar groove. Aim the needle parallel to the ulnar groove and the course of the nerve (Figure 126-22A). Advance the needle into the ulnar groove and inject 5 to 7 mL of local anesthetic solution. If paresthesias are elicited, withdraw the needle 1 mm and allow them to resolve before injecting the local anesthetic solution.

US-Guided Block

Place the US probe in the crease between the olecranon process and the medial epicondyle, with the marker pointing laterally. Two hyperlucent structures should be seen, the medial epicondyle medially and the olecranon process closer to the marker. The ulnar nerve is hyperechoic and courses between these two hyperlucent structures. Anesthetize the skin. Place the needle inferior to the short axis of the US probe and directly over the ulnar nerve. Only the tip of the needle will be visualized in this view. Insert and advance the needle until its tip is at the ulnar nerve. Aspirate to ensure that the needle tip is not in a blood vessel. Inject a test dose of 1 to 2 mL of local anesthetic solution. Watch the spread of local anesthetic solution around the ulnar nerve. If satisfactory, inject the remainder of the local anesthetic solution to produce the “donut sign.” If the test dose is not satisfactory, reposition the needle and inject another test dose.

Remarks

The ulnar nerve has no sensory branches in the forearm and thus may be blocked at the wrist or at the elbow. Blockade of the ulnar nerve at the elbow is not recommended. A fibrous sheath surrounds the ulnar nerve at the elbow requiring intraneural injection for a successful blockade. This can lead to residual neuritis and nerve dysfunction. Blocking the ulnar nerve several centimeters above the elbow may prevent these complications. Blockade at the wrist is very reliable and does not have the associated complications as at the elbow.

Ulnar Nerve Block at the Wrist

Anatomy

The ulnar nerve lies between the distal and proximal flexor skin creases of the wrist, lateral (or radial) to the flexor carpi ulnaris tendon and medial (or ulnar) to the ulnar artery (Figure 126-22B). The innervation of the ulnar nerve is described in the previous section.

Patient Positioning

Place the patient supine with their arm abducted 45° to 90°, the elbow fully extended, and the hand supinated (Figure 126-22B).

Landmarks

Identify the flexor carpi ulnaris tendon by flexing the patient's clenched hand against resistance. Mark the medial aspect of the flexor carpi ulnaris tendon. Identify the ulnar artery by its palpable pulsations between the proximal and distal wrist crease. Note the position of the proximal and distal wrist creases.

Needle Insertion and Direction

Place a skin wheal of local anesthetic solution in the quadrangle defined by the proximal flexor skin crease, the distal flexor skin crease, the lateral aspect of the flexor carpi ulnaris tendon, and medial to the ulnar artery. Insert a 25 gauge needle perpendicular to the skin wheal and slowly advance it 0.5 cm (Figure 126-22B). If paresthesias are elicited, withdraw the needle 2 mm and allow them to resolve. Inject 2 mL of local anesthetic solution once the paresthesias resolve. If paresthesias are not elicited, inject 3 to 5 mL of local anesthetic solution.

US-Guided Block

Place the US probe over the middle of the wrist with the marker pointing laterally (Figure 126-22C). The Palmaris longus tendon should be visible in the middle of the wrist. Move the US probe medially until the ulnar artery is visible. The ulnar nerve is hyperechoic and directly medial to the ulnar artery (Figure 126-22D). Anesthetize the skin medial to the ulnar artery. Position the needle inferior to the short axis of the US probe and directly over the ulnar nerve (Figure 126-22C). Insert and advance the needle until its tip is at the ulnar nerve. Aspirate to ensure that the needle tip is not in a blood vessel. Inject a test dose of 1 to 2 mL of local anesthetic solution. Watch the spread of local anesthetic solution around the ulnar nerve. If satisfactory, inject the remainder of the local anesthetic solution to produce the “donut sign.” If the test dose is not satisfactory, reposition the needle and inject another test dose.

Remarks

This is the preferred approach to block the ulnar nerve. Blockade of the ulnar nerve at the wrist is very reliable and does not have the associated complications as at the elbow.25

Radial Nerve Block at the Elbow

Anatomy

The radial nerve and the sensory branch of the musculocutaneous nerve run together in the sulcus between the biceps and the brachioradialis muscle on the anterolateral aspect of the elbow. The radial nerve provides sensory innervation to portions of the dorsal arm and forearm, the dorsolateral half of the hand, and the dorsal proximal aspects of the thumb, index, middle, and radial half of the ring fingers (Figure 126-20).12 It provides motor innervation to the muscles on the posterior aspect of the arm, forearm, and hand.

Patient Positioning

Place the patient supine with their elbow flexed 15° to 30°.

Landmarks

Palpate the tendon of the biceps muscle in the antecubital fossa. Identify the flexion skin crease of the elbow. Palpation of the biceps tendon is greatly facilitated by having the patient flex their elbow 90° then contract and relax their biceps muscle. Identify the medial and lateral condyles of the humerus. Draw a line between the humeral condyles (Figure 126-23A). This line should be located at the level of the antecubital crease.

Needle Insertion and Direction

Place a skin wheal of local anesthetic solution 2 cm lateral to the biceps tendon and 1 cm proximal to the antecubital crease (Figure 126-23A). Insert a 25 gauge needle through the skin wheal and perpendicular to the skin (Figure 126-23A). Advance the needle 1 to 2 cm. Probe in a fan-like pattern until paresthesias are elicited. Withdraw the needle 1 to 2 mm and allow the paresthesias to resolve. Inject 5 to 7 mL of local anesthetic solution.

US-Guided Block

Position the patient with their arm abducted 45°, the elbow in full extension, and the hand supinated. Place the US probe on the lateral aspect of the crease of the antecubital fossa. The radial nerve is lateral to the biceps tendon and the brachial artery (Figure 126-23A). Anesthetize the skin over the radial nerve. Place the needle inferior to the short axis of the US probe and directly over the radial nerve. Only the tip of the needle will be visualized in this view. Insert and advance the needle until its tip is at the radial nerve. Aspirate to ensure that the needle tip is not in a blood vessel. Inject a test dose of 1 to 2 mL of local anesthetic solution. Watch the spread of local anesthetic solution around the radial nerve. If satisfactory, inject the remainder of the local anesthetic solution to produce the “donut sign.” If the test dose is not satisfactory, reposition the needle and inject another test dose.

Remarks

Blockade of the radial nerve at the elbow is difficult, has limited applications, is painful for the patient, and often results in a large antecubital hematoma. The preferred technique is blockade at the wrist.

Radial Nerve Block at the Wrist

Anatomy

The radial nerve at the wrist consists of a trunk and terminal branches that arise in the forearm (Figure 126-23C). The innervation of the radial nerve is described in the previous section.

Patient Positioning

Place the patient supine with their arm abducted 45°, the elbow fully extended, and the hand midway between supination and pronation (Figure 126-23C).

Landmarks

Identify the radial artery by its pulsation at the level of the proximal wrist crease.

Needle Insertion and Direction

Place a skin wheal of local anesthetic solution 1 mm lateral to the radial pulse. Insert a 25 gauge needle 1 mm lateral to the radial pulse, through the skin wheal, and perpendicular to the skin (Figure 126-23C). Advance the needle 0.5 cm. If paresthesias are elicited, withdraw the needle 1 to 2 mm and allow them to resolve. Inject 2 mL of local anesthetic solution. If paresthesias are not elicited, inject 3 to 5 mL of local anesthetic solution. This will anesthetize the terminal trunk of the radial nerve. Infiltrate 5 to 7 mL of local anesthetic solution at the level of the extensor wrist crease, from the lateral aspect of the radius to the base of the fourth metacarpal (Figure 126-23C). This will anesthetize the terminal branches that arise in the forearm.

US-Guided Block

Place the US probe over the middle of the wrist with the marker pointing laterally. The palmaris longus tendon should be visible in the middle of the wrist. Move the US probe laterally until the radial artery is visualized. The radial nerve is hyperechoic and directly lateral to the radial artery (Figures 126-23D). Anesthetize the skin lateral to the radial artery and directly over the radial nerve. Place the needle inferior to the short axis of the US probe and directly over the radial nerve. Insert and advance the needle until its tip is at the radial nerve. Aspirate to ensure that the needle tip is not in a blood vessel. Inject a test dose of 1 to 2 mL of local anesthetic solution. Watch the spread of local anesthetic solution around the radial nerve. If satisfactory, inject the remainder of the local anesthetic solution to produce the “donut sign.” If the test dose is not satisfactory, reposition the needle and inject another test dose.

Remarks

This is the preferred technique for blockade of the radial nerve.

Wrist Block

Perform the wrist block by blocking the radial, ulnar, and median nerves at the wrist. The technique for each specific nerve block was discussed previously. The wrist block provides complete anesthesia to the hand and is commonly used in hand surgery. It can be performed in the Emergency Department to provide anesthesia for burn management, foreign body removal, wound exploration, or extensive laceration repair. Wrist blockade is reliable but slow, as it requires extended time to block all three nerves at the wrist.12

Intermetacarpal Nerve Block

Anatomy

The principal nerves supplying the finger are the palmar digital nerves, which originate from the deep volar branches of the ulnar and median nerves in the region of the wrist. These nerves follow the artery along the lateral aspects of the bone and supply sensation to the volar skin, the interphalangeal joints, the distal finger, and the fingertip of all five digits.

Two dorsal and two palmar nerves supply each finger. These nerves run along the phalanxes in the 2, 4, 8, and 10 o'clock positions.26 These nerves also supply the dorsal, distal aspect of the finger, including the fingertip and nail bed. The dorsal digital nerves originate from the radial and ulnar nerves that wrap around the dorsum of the hand. They supply the nail bed of the thumb and small finger and the dorsal aspect of all five digits up to the distal interphalangeal joints. The palmar and dorsal nerves need to be blocked in the case of the thumb and fifth finger.

Patient Positioning

Place the patient sitting upright or supine with their hand pronated on a bedside examination table.

Landmarks

Locate the web spaces and the metacarpal heads on each side of the finger to be blocked.

Needle Insertion and Direction

Insert a 25 gauge needle into the dorsal aspect of the web space on one side of the digit to be anesthetized (Figure 126-24A). Advance the needle approximately 0.5 cm. Inject 1 mL of local anesthetic solution. Repeat the procedure on the other side of the digit to be blocked. When blocking the second and fifth digits, a half-ring block is required on the ulnar aspect of the fifth digit and radial aspect of the second digit. When blocking the thumb, infiltrate the dorsum and sides in a half-ring manner.

An alternative is the metacarpal head block. This technique can be used to anesthetize any of the fingers. Insert a 25 gauge needle perpendicular to the dorsum of the hand and adjacent to the metacarpal head on one side of the finger to be blocked (Figure 126-24B). Advance the needle 0.5 cm and inject 1 mL of local anesthetic solution. Repeat the procedure on the other side of the finger to be blocked. Some physicians prefer to perform this block on the volar aspect of the hand (Figure 126-24C). This technique is extremely painful and should be avoided.

Remarks

This block produces less swelling than does the ring block. Subsequently, there is less risk of vascular compromise. This is a less painful technique than the ring block.

Digital Nerve Block (Ring Block) of the Finger

Anatomy

The anatomy and innervation of the digital nerves are described in the previous section.

Patient Positioning

Place the patient sitting upright or supine with their hand pronated on a bedside examination table.

Landmarks

Locate the dorsum of the proximal phalanx to be anesthetized.

Needle Insertion and Direction

Insert a 25 gauge needle on the dorsal surface of the base of the proximal phalanx (Figure 126-24D(1)). Inject 1 mL of local anesthetic solution along the dorsal surface of the finger. Remove the needle and reinsert it downward, perpendicular to the phalanx and to a depth just past the base of the phalanx (Figure 126-24D(2)). Inject 1.0 to 1.5 mL of local anesthetic along the lateral aspect of the finger. Withdraw the needle, reinsert it on the other side of the finger to be blocked, and inject 1.0 to 1.5 mL of local anesthetic solution (Figure 126-24D(3)).

An alternative is the half-ring block (Figure 126-24E). It is a variant of the ring block (Figure 126-24D). Inject 1.0 to 1.5 mL of local anesthetic solution on one side of the base of the proximal phalanx to be anesthetized. Repeat this procedure on the other side of the finger. The injection of local anesthetic on one side of the finger is termed the half-ring block. It takes two half-ring blocks to anesthetize a finger.

Remarks

The indications for a digital block include repair of finger lacerations and amputations, reductions of fractures and dislocations, incision and drainage of infections, removal of fingernails, and relief of pain from burns. Do not inject more than 5 mL of local anesthetic solution into a digit. Using local anesthetic agents that contain epinephrine is not recommended because the finger contains end arteries and may experience ischemia from the vasoconstrictive effects of epinephrine.

Intercostal Nerve Block

Anatomy

The intercostal nerves originate from the thoracic spinal cord and have four major branches (Figure 126-25). The first is the gray rami communicans to the sympathetic ganglion. The second branch is the posterior cutaneous nerve that supplies the paravertebral muscles and overlying skin. The third branch is the lateral cutaneous nerve that arises about the midaxillary line. It divides into an anterior and posterior division to supply most of the chest and the abdominal wall. The final branch is the terminal anterior cutaneous nerve. It supplies the anterior chest and abdominal wall adjacent to the midline. Each intercostal nerve travels within a neurovascular bundle behind the inferior border of each rib (Figure 126-25B). The intercostal nerve lies inferior to the intercostal vein and artery. The intercostal nerve may be blocked at several sites along its course. The most common site is at the angle of the rib. The technique described will be the blockade of the intercostal nerves at the angle of the rib.

Patient Positioning

Place the patient prone with a pillow under the midabdomen to straighten the lumbar curve and increase the size of the intercostal spaces posteriorly.

Landmarks

The most important step is to correctly identify the anatomy of the patient. Draw a line along the vertebral spines corresponding to the levels to be anesthetized. Palpate laterally from the vertebral spines to the edge of the paraspinal muscles. This is the location where the ribs are most superficial. This distance can vary from 6 to 8 cm from the midline in the average adult. Draw vertical lines parallel to the first line and along the edge of the paraspinal muscles (Figure 126-26A). These lines must angle slightly medially over the upper ribs to avoid the scapula. Palpate and mark the inferior edge of each rib along these two vertical lines (Figure 126-26A).

Needle Insertion and Direction

This procedure requires the utmost of care to prevent inducing a pneumothorax. Inject local anesthetic solution to make a skin wheal at the intersection of the horizontal lines with the vertical paraspinal muscle lines. Use the index finger of the nondominant hand to pull the skin at the lower edge of the rib up onto the rib (Figure 126-26B). Grasp the syringe in the dominant hand. Insert the 25-gauge needle at a 60° angle along the tip of the nondominant index finger while the dominant hand is resting on the patient's back (Figure 126-26C). Advance the needle until the rib is contacted (Figure 126-26C, inset).

Reposition the nondominant hand so that it is resting against the patient's back and holding the needle between the thumb, index, and middle fingers (Figure 126-26D). Use the nondominant hand to slowly and carefully “walk” the needle off the inferior rib margin (Figure 126-26E). Advance the needle 3 mm with the nondominant hand (Figure 126-26F). It is imperative that the needle not be advanced more than 3 mm after it is “walked” off the inferior border of the rib to prevent an iatrogenic pneumothorax. Aspirate to ensure that the tip of the needle is not within a blood vessel or the lung. Inject 1 to 2 mL of local anesthetic solution (Figure 126-26G). Remove the needle and repeat the procedure at the other desired interspaces.

Remarks

Local anesthetic solution for intercostal blocks should contain 1:200,000 or less of epinephrine. Obtain a postprocedural upright chest radiograph to ensure that the patient does not have an iatrogenic pneumothorax.27

Penile Block

The penis may be anesthetized for the purposes of circumcision, laceration repair, foreign body removal, zipper entrapment, or to perform the release of a phimosis or paraphimosis. The dorsal nerves of the penis provide sensory innervation to the penis. They emerge from under the pubis, just lateral to the symphysis, and course along the dorsal surface of the penis. These nerves are located approximately 0.5 cm from the dorsal penile midline. These nerves are blocked at the base of the penis. Refer to Chapter 146 for the complete details of the penile block.

The sensory innervation of the lower extremity is illustrated in Figure 126-27. Note that the nerves provide patches of innervation rather than stripes of innervation beginning at the torso and extending to the foot.

Femoral Nerve Block

Anatomy

The femoral nerve is formed from the lumbar plexus. It travels in the pelvis between the iliacus and psoas major muscles. It enters the thigh below the inguinal ligament, midway between the anterior superior iliac spine and the pubic tubercle (Figure 126-28A). The femoral nerve lies anterior to the iliopsoas muscle and lateral to the femoral artery in the proximal thigh (Figure 126-28B). The femoral nerve has both sensory and motor components. It provides motor innervation to the anterior thigh muscles. It provides sensory innervation for the anterior thigh, anteromedial thigh, medial thigh, medial leg, and the medial border of the foot (Figure 126-27).

Patient Positioning

Place the patient supine with their hip and knee extended and the leg slightly externally rotated.

Landmarks

Identify the anterior superior iliac spine and the pubic tubercle by palpation. Connect these landmarks with a straight line to roughly approximate the position of the inguinal ligament. Identify the femoral artery by its palpable pulse 1 to 2 cm below the midpoint of the inguinal ligament.

Needle Insertion and Direction

Place a skin wheal of local anesthetic solution just lateral to the femoral artery pulse. Insert a 25 gauge needle through the skin wheal and perpendicular to the skin (Figure 126-28B). Slowly advance the needle while remaining perpendicular to the skin. The femoral nerve is identified once paresthesias are elicited. Withdraw the needle 2 mm and allow the paresthesias to resolve. Inject 15 to 20 mL of local anesthetic solution.

US-Guided Block

Place the US probe along the inguinal crease, midway between the anterior superior iliac spine and the pubic tubercle (Figure 126-28C). Identify the femoral artery and femoral vein. The femoral nerve is hyperechoic and located 0.5 to 1 cm lateral and posterior to the common femoral artery (Figure 126-28D). Apply pressure with the US probe to distinguish the compressible femoral vein from the incompressible femoral artery. Use color Doppler to confirm the location of the femoral artery and any branches or take-offs. Place the needle lateral to the long axis of the US probe (Figure 126-28C). Slowly insert and advance the needle. Visualize the entire length of the needle as it is inserted and approaches the femoral nerve. Continue to advance the needle and penetrate the fascia lata and fascia iliaca so that the tip of the needle is adjacent to the femoral nerve. Aspirate to ensure that the needle tip is not in a blood vessel. Inject a test dose of 1 to 2 mL of local anesthetic solution. Watch the spread of local anesthetic solution around the femoral nerve. If satisfactory, inject the remainder of the local anesthetic solution to produce the “donut sign.” If the test dose is not satisfactory, reposition the needle and inject another test dose.

Remarks

The femoral nerve is contained within a fibrous sheath that is separate from the other contents (femoral artery and vein) of the femoral triangle (Figure 126-28B). Paresthesias must be elicited to confirm the proper position of the tip of the needle before injecting the local anesthetic solution. Deposition of the local anesthetic solution outside of the fibrous sheath will not result in any anesthesia except in the area of the injection.

Saphenous Nerve Block at the Knee

Anatomy

The saphenous nerve is the terminal branch of the femoral nerve. It travels across the anterior thigh in a medial direction to become superficial at the medial knee after emerging between the tendons of the gracilis and sartorius muscles (Figure 126-29A). It follows the great saphenous vein from above the knee to below the medial malleolus (Figure 126-29B). It provides sensory innervation to the anteromedial leg, medial leg, posteromedial leg, and medial border of the foot to the ball of the great toe (Figure 126-27). It has no motor component.

Patient Positioning

Place the patient supine with their ankle supported on a pillow or blanket, the knee extended, and the leg externally rotated.

Landmarks

Identify the femoral condyle above the knee or the tibial condyle below the knee by palpation.

Needle Insertion and Direction

Place a skin wheal of local anesthetic solution over the posteromedial aspect of either condyle (femoral or tibial). Insert a 25 gauge needle through the skin wheal. Infiltrate 7 to 10 mL of local anesthetic solution subcutaneously in a transverse line from the posteromedial to the anteromedial aspect of either condyle (Figure 126-29C).

US-Guided Block

Identify the femoral artery and femoral nerve at the inguinal crease (see femoral nerve block). Move the US probe inferiorly and medially, keeping the femoral artery in the center of the screen. At the mid-thigh, the saphenous nerve travels with the femoral artery and the nerve to the vastus medialis muscle. These structures lie posterior to the sartorius muscle and medial to the vastus medialis muscle (Figure 126-29D). Continue to move the probe inferiorly and medially until the probe is at the distal third of the thigh. Use color Doppler to confirm the location of the femoral artery and any branches or take-offs. The saphenous nerve is medial to the femoral artery and posterior (deep) to the sartorius muscle (Figure 126-29D). The small saphenous nerve may not be visualized by US at this level. The target is the fascial plane between the sartorius and vastus medialis muscle.

Place the needle lateral to the long axis of the US probe. Insert and advance the needle. Visualize the entire length of the needle as it is inserted and approaches the fascial plane between the sartorius and vastus medialis muscles. Aspirate to ensure the needle tip is not in a blood vessel. Inject a test dose of 1 to 2 mL of local anesthetic solution. Watch the test dose spread the local anesthetic solution around the 12 o'clock to 2 o'clock position of the femoral artery. If it is satisfactory, inject another 5 to 10 mL of the local anesthetic solution. If the test dose is not satisfactory, reposition the needle and inject another test dose.

Remarks

The saphenous nerve may be blocked at the ankle if anesthesia of the medial leg is not required.

Saphenous Nerve Block at the Ankle

Anatomy

The saphenous nerve divides into numerous terminal branches in the distal leg. These terminal branches travel across the anteromedial ankle (Figure 126-29B) to innervate the anteromedial aspect of the ankle and foot (Figure 126-27).

Patient Positioning

Place the patient supine with their ankle supported on a pillow or blanket, the knee extended, and the leg externally rotated.

Landmarks

Identify the anterior border of the medial malleolus and the great saphenous vein by palpation.

Needle Insertion and Direction

Place a skin wheal of local anesthetic 1.5 cm superior and anterior to the medial malleolus. Insert a 25 gauge needle through the skin wheal. Infiltrate 3 to 5 mL of local anesthetic solution subcutaneously in a fan-like pattern around the great saphenous vein.

US-Guided Block

Identify the great saphenous vein anterior to the medial malleolus. Use color Doppler to confirm the location of the great saphenous vein. The saphenous nerve is adjacent to the great saphenous vein. The small saphenous nerve may not be visualized by US at this level. Place the needle lateral to the long axis of the US probe. Insert the needle until its tip is adjacent to the great saphenous vein. Aspirate to ensure the needle tip is not in a blood vessel. Inject a test dose of 1 to 2 mL of local anesthetic solution. Watch the test dose spread the local anesthetic solution around the great saphenous vein. If it is satisfactory, inject another 2 to 3 mL of the local anesthetic solution. If the test dose is not satisfactory, reposition the needle and inject another test dose.

Remarks

Alternatively, infiltrate 5 to 7 mL of local anesthetic solution subcutaneously in a transverse line from the anterior border of the medial malleolus to the anterior border of the anterior tibial ridge (Figure 126-29E).

Lateral Femoral Cutaneous Nerve Block

Anatomy

The lateral femoral cutaneous nerve enters the thigh through or below the inguinal ligament, 1 to 2 cm medial to the anterior superior iliac spine (Figure 126-30A). It crosses through or over the sartorius muscle to lie on its anterior surface and deep to the fascia lata. This nerve provides sensory innervation to the anterolateral and lateral thigh (Figure 126-27). It has no motor components.

Patient Positioning

Place the patient supine with their hip and knee extended.

Landmarks

Identify the anterior superior iliac spine by palpation.

Needle Insertion and Direction

Place a skin wheal of local anesthetic solution 2 to 3 cm inferior and 2 to 3 cm medial to the anterior superior iliac spine. Insert a 25 gauge needle perpendicular to the skin wheal. Advance the needle through the fascia lata. A “pop” will be felt as the needle traverses through the fascia lata. Infiltrate 10 mL of local anesthetic solution subcutaneously in a superior to inferior fan-like pattern.

A second approach begins with making the same skin wheal. Insert the needle through the skin wheal, directed laterally and superiorly. Advance the needle to contact the iliac bone just medial and inferior to the anterior superior iliac spine. Infiltrate 10 mL of local anesthetic solution subcutaneously in a fan-like pattern about the iliac bone.

US-Guided Block

Place the US probe along the inguinal ligament and just medial to the anterior superior iliac spine. Move the US probe medially and inferiorly. Identify the fascia lata, fascia iliaca, and sartorius muscle (from superficial to deep, respectively). It may be difficult to identify the small lateral femoral cutaneous nerve between the fascia lata and fascia iliaca, just above the sartorius muscle.

Place a skin wheal of local anesthetic solution. Place the needle lateral to the long axis of the US probe. Insert and advance the needle. Visualize the entire length of the needle as it is inserted and approaches the lateral femoral cutaneous nerve. If the nerve cannot be identified, direct the needle immediately medial and inferior to the anterior superior iliac spine near the sartorius muscle insertion site. Advance the needle tip between the fascia lata and fascia iliaca. Aspirate to ensure the needle tip is not in a blood vessel. Inject a test dose of 1 to 2 mL of local anesthetic solution. Watch the test dose spread in the fascial plane of fascia lata and fascia iliaca. If it is satisfactory, inject another 5 to 10 mL of the local anesthetic solution. If the test dose is not satisfactory, reposition the needle and inject another test dose.

Remarks

A third, or alternative, approach is often used (Figure 126-30B). Place a skin wheal of local anesthetic solution just medial to the anterior superior iliac spine. Insert the needle through the skin wheal and perpendicular to the skin. Advance the needle until a “pop” is felt as the needle transverses the aponeurosis of the external oblique muscle. Continue to slowly advance the needle until a second “pop” is felt as the needle transverses through the internal oblique muscle and underlying iliac fascia. Inject 5 to 10 mL of local anesthetic solution. This approach blocks the nerve in its canal as it begins to pass under the inguinal ligament.

Obturator Nerve Block

Anatomy

The obturator nerve originates from the lumbar plexus. It passes through the pelvis and obturator canal to exit the obturator foramen into the thigh with its accompanying artery and vein (Figure 126-31A). It divides within the obturator canal into anterior and posterior branches. The anterior branch provides the sensory innervation to the hip and motor innervation to the anterior adductor muscles. There may also be a small and inconsistent area of cutaneous innervation over the medial thigh (Figures 126-27 & 126-31B). The posterior branch provides motor innervation to the deep adductor muscles and sensory innervation to the knee joint.

Patient Positioning

Place the patient supine with their hip and knee extended. Abduct the hip 10° to 20°.

Landmarks

Identify the pubic tubercle by palpation.

Needle Insertion and Direction

Place a skin wheal of anesthetic solution 1.5 cm inferior and 1.5 cm lateral to the pubic tubercle. Insert a 7 to 10 cm, 22 to 25 gauge spinal needle directed medially through the skin wheal. Advance the needle until it contacts the horizontal ramus of the pubic bone (Figure 126-31C(1)). Withdraw the needle slightly (2 to 3 mm) and redirect it 45° superiorly. Advance the needle to identify the superior bony portion of the obturator canal (Figure 126-31C(2)). Withdraw the needle slightly (2 to 3 mm). Redirect the needle slightly laterally and inferiorly toward the obturator canal. Advance the needle 2 to 3 cm (Figure 126-31C(3)). Inject 10 to 15 mL of local anesthetic solution.

US-Guided Block

Place the US probe along the medial third of the inguinal crease. Scan distally from the inguinal crease and identify the adductor longus, adductor brevis, and adductor magnus muscles (from superficial to deep, respectively). The obturator nerve divides into two branches distal to the inguinal crease, the anterior and posterior branches. The anterior branch lies in the fascial plane between the adductor longus and adductor brevis. The posterior branch lies in the fascial plane between the adductor brevis and adductor magnus. Both branches are small nerves and may or may not be identified under US.

Place a skin wheal of local anesthetic solution. Place the needle lateral to the long axis of the US probe. Insert the needle in the plane of the long axis of the US beam. To block the anterior branch of the obturator nerve, visualize the entire length of the needle as it is inserted and approaches the fascial plane between the adductor longus and brevis. To block the posterior branch, insert the needle into the fascial plane between the adductor brevis and magnus. Once the needle tip is in between the fascial planes, aspirate to ensure the needle tip is not in a blood vessel. Inject a test dose of 1 to 2 mL of local anesthetic solution. Watch the test dose spread the two fascial planes. If it is satisfactory, inject another 10 to 15 mL of the local anesthetic solution. If the test dose is not satisfactory, reposition the needle and inject another test dose.

Remarks

The purpose of this block is to provide analgesia for an acute hip fracture when the administration of intravenous analgesics is contraindicated. The technique requires significant experience and is time-consuming. The obturator nerve must be anesthetized within the bony canal if using the landmark technique to prevent the needle from perforating the bladder or vagina. This block is rarely, if ever, performed in the Emergency Department.

Sciatic Nerve Block, Classic or Posterior Approach

Anatomy

The sciatic nerve arises from the lumbosacral plexus and leaves the pelvis through the greater sciatic foramen, inferior to the piriformis muscle (Figure 126-32). It is located midway between the ischial tuberosity and the greater trochanter of the femur. The nerve is superficial and accessible at the inferior border of the gluteus maximus muscle. The sciatic nerve provides the motor innervation to the muscles of the posterior thigh, leg, and foot. It provides sensory innervation to the posterior thigh, anterolateral leg, posterolateral leg, lateral leg, and almost the entire foot. There are four techniques for sciatic nerve blockade. These approaches were developed to allow sciatic nerve blockade from a variety of positions, therefore eliminating positioning problems that are encountered in the elderly, the infirm, and the trauma patient.

Patient Positioning

Place the patient on the side opposite that to be blocked. Flex the hip and knee of the upper leg until the heel is over the dependent knee (Figure 126-33A).

Landmarks

Identification of the anatomic landmarks is the key to success (Figure 126-33B). Identify the greater trochanter of the femur and the posterior superior iliac spine by palpation. Connect these two landmarks with a straight line. Identify the midpoint of this line and draw a perpendicular bisector downward for 3 cm. This point represents the site of local anesthetic injection. Verify the position for injection with a second line. Reidentify the greater trochanter of the femur and the sacral cornu. Draw a line starting from 1.5 cm below the sacral cornu to the greater trochanter. This line should cross the end of the perpendicular bisector and be directly over the sciatic nerve.

Needle Insertion and Direction

Place a skin wheal of local anesthetic solution at the identified injection site. Insert a 22 gauge needle perpendicular to the skin wheal. Advance the needle until paresthesias are elicited. If paresthesias are not elicited, redirect the needle to find the sciatic nerve. The nerve must be located prior to infiltration with the local anesthetic solution to achieve proper anesthesia. Withdraw the needle 2 mm and allow the paresthesias to resolve. Inject 20 to 30 mL of local anesthetic solution.

US-Guided Block

Place the US probe over the previously identified intersection point (Figure 126-33B). Place the long axis of the US probe along the line between the greater trochanter and the sacral hiatus. Identify the ischial bone, as a hyperechoic line with a bony shadow underneath, medial to the sciatic nerve. Identify the gluteus maximus muscle superficial (posterior) to the sciatic nerve. The sciatic nerve appears wide and flat between the gluteus maximus muscle and the ischial bone (Figure 126-33C). Scan cephalad and caudad to obtain the best view of the sciatic nerve.

Place a skin wheal of local anesthetic solution. Place the needle lateral to the long axis of the US probe. Insert the needle in the plane of the long axis of the US beam. Advance the needle toward the sciatic nerve. Stop advancing the needle when its tip is adjacent to the sciatic nerve. Aspirate to ensure that the needle tip is not in a blood vessel. Inject a test dose of 1 to 2 mL of local anesthetic solution. Watch the spread of local anesthetic solution around the sciatic nerve. If satisfactory, inject 15 to 20 mL of local anesthetic solution to produce the “donut sign.” If the test dose is not satisfactory, reposition the needle and inject another test dose.

Remarks

Blockade of the sciatic nerve can be used for fracture reduction, extensive laceration repair, incision and drainage of abscesses, wound exploration, or anesthesia from burns or trauma. The posterior approach is the most commonly performed technique.28

Sciatic Nerve Block, Anterior Approach

Anatomy

The anatomy and innervation of the sciatic nerve are described in the previous section. This approach can be used for patients who cannot be turned onto their side.

Patient Positioning

Place the patient supine with their hip and knee extended.

Landmarks

Identification of the anatomic landmarks is the key to success (Figure 126-34A). Identify the anterior superior iliac spine and the pubic tubercle by palpation. Connect these points with a straight line (Figure 126-34A, Line 1). This line represents the location of the inguinal ligament. Trisect the inguinal ligament line into three equal parts. Draw a line perpendicular from the junction of the medial and middle thirds (Figure 126-34A, Line 2). Identify the tuberosity of the greater trochanter by palpation. Draw a line from the tuberosity medially across the anterior thigh and parallel to the line representing the inguinal ligament (Figure 126-34A, Line 3). The point of intersection of this line (Figure 126-34A, Line 3) with the perpendicular line from the inguinal ligament (Figure 126-34A, Line 2) represents the point of injection.

Needle Insertion and Direction

Place a skin wheal of local anesthetic solution at the identified injection site. Insert a 10 to 15 cm long, 22 gauge needle perpendicular to the skin and aimed slightly lateral. Advance the needle until the femur is contacted (Figure 126-34B(1)). Withdraw the needle 1 cm and redirect it medially. Advance the needle 5 cm past the location where the bone was found (i.e., 6 cm; Figure 126-34B(2)). The needle should be within the neurovascular bundle containing the sciatic nerve. The average distance from the surface of the femur to the neurovascular bundle is 4.5 to 6.0 cm in adults. Inject a small test dose of local anesthetic solution to determine the ease of injection. The tip of the needle is within muscle or a fascial plane if significant resistance is encountered. Advance the needle until resistance to injection is at a minimum. Eliciting paresthesias is extremely helpful in identifying the correct location of the needle. If paresthesias are elicited, withdraw the needle 2 mm and allow them to resolve. Inject 15 to 30 mL of local anesthetic solution.

Remarks

The posterior femoral cutaneous nerve, which accompanies the sciatic nerve, may sometimes be missed with this approach. This technique is extremely painful and not often performed.

Sciatic Nerve Block, Lithotomy Approach

Anatomy

The anatomy and innervation of the sciatic nerve are described in the previous section. The sciatic nerve lies anterior to the gluteus maximus muscle when the patient is in the lithotomy position. The nerve is more superficial in this position than in the other approaches.

Patient Positioning

Place the patient supine. Maximally flex the hip and knee of the extremity to be anesthetized. Use a bed or examination table with foot stirrups if available and not contraindicated.

Landmarks

Identify the ischial tuberosity and the greater trochanter of the femur by palpation. Connect these landmarks with a straight line. Identify the midpoint of this line.

Needle Insertion and Direction

Place a skin wheal of local anesthetic solution at the midpoint of the line from the ischial tuberosity to the greater trochanter. Insert a 10 to 15 cm long, 22 gauge spinal needle perpendicular to the skin wheal. Slowly advance the needle until paresthesias are elicited. Withdraw the needle 2 mm and allow the paresthesias to resolve. Inject 20 to 25 mL of local anesthetic solution.

US-Guided Block

Place the US probe over the midpoint of the line between the greater trochanter and the ischial tuberosity, with the long axis of the US probe along the line between the bony landmarks. Identify the gluteus maximus muscle superior (posterior) to the sciatic nerve. Identify the sciatic nerve between the greater trochanter and the ischial tuberosity, anterior (deep) to the gluteus maximus muscle. Scan cephalad and caudad to obtain the best view of the sciatic nerve.

Place a skin wheal of local anesthetic solution. Place the needle lateral to the long axis of the US probe. Insert the needle in the plane of the long axis of the US beam. Advance the needle toward the sciatic nerve. Stop advancing the needle when its tip is adjacent to the sciatic nerve. Aspirate to ensure that the needle tip is not in a blood vessel. Inject a test dose of 1 to 2 mL of local anesthetic solution. Watch the spread of local anesthetic solution around the sciatic nerve. If satisfactory, inject 15 to 20 mL of local anesthetic solution to produce the “donut sign.” If the test dose is not satisfactory, reposition the needle and inject another test dose.

Remarks

This approach is more difficult to master than the previous two techniques. It is time-consuming and requires locating the sciatic nerve by eliciting paresthesias if using the landmark technique prior to injecting the local anesthetic solution.

Sciatic Nerve Block, Lateral Approach

The lateral approach will not be described. This approach requires considerable experience, a nerve stimulator, and does not provide any advantage over the other approaches.

Popliteal Fossa Nerve Block, Anatomical or Posterior Approach

Anatomy

The popliteal fossa is a diamond-shaped area on the posterior aspect of the knee (Figure 126-35). Its boundaries are the long head of the biceps femoris muscle superolaterally, the semimembranous and semitendinous muscles superomedially, and the medial and lateral heads of the gastrocnemius muscle inferiorly. This space contains the tibial and common peroneal nerves, the popliteal artery and vein, and loose fatty connective tissue (Figure 126-35A). The nerves are superficial to the arteries and veins, midway between the skin and the posterior surface of the femur. The average distance between the skin and the nerves is 1.5 to 2.0 cm in adults. These nerves are responsible for the motor innervation of all the muscles below the knee. They also provide sensory innervation to the entire leg below the knee except the area innervated by the saphenous nerve.

Patient Positioning

Place the patient prone with a pillow or blanket under their ankle to position the knee in slight flexion (10° to 20°).

Landmarks

Identify the borders of the popliteal fossa. Divide the fossa into a superior and inferior triangle with a line drawn medial to lateral across the skin fold or crease (Figure 126-35B). Draw a line from the apex to the base of the superior triangle, making two smaller and equal triangles. Identify the spot 5 cm superior and 1 cm lateral to the midline of the upper triangle (Figure 126-35B). This spot represents the landmark for needle insertion.

Needle Insertion and Direction

Place a skin wheal of local anesthetic solution 5 cm superior and 1 cm lateral to the midline of the upper triangle (Figure 126-35B). Insert a 25 gauge needle through the skin wheal, directed superiorly and at a 45° to 60° angle to the skin surface. Advance the needle anteriorly and superiorly until paresthesias are elicited. Withdraw the needle 2 mm and allow the paresthesias to resolve. Infiltrate 35 to 45 mL of local anesthetic solution.

US-Guided Block

Place the US probe 10 cm proximal to the skin crease. The sciatic nerve lies between the biceps femoris muscle laterally and the semimembranosus and semitendinosus muscles medially (Figure 126-35C). Scan cephalad and caudad to obtain the best view of the sciatic nerve and to identify where the sciatic nerve branches into the tibial and the common peroneal nerves.

Place a skin wheal of local anesthetic solution. Place the needle lateral to the long axis of the US probe. Insert the needle in the plane of the long axis of the US beam. Advance the needle toward the sciatic nerve. Stop advancing the needle when its tip is adjacent to the sciatic nerve. Aspirate to ensure that the needle tip is not in a blood vessel. Inject a test dose of 1 to 2 mL of local anesthetic solution. Watch the spread of local anesthetic solution around the sciatic nerve. If satisfactory, inject 10 to 15 mL of local anesthetic solution to produce the “donut sign.” If the test dose is not satisfactory, reposition the needle and inject another test dose.

Remarks

This block is difficult to use in patients who cannot lie in the prone position. This includes pregnant patients, the morbidly obese, spinal injury patients, hemodynamically unstable patients, and those on mechanical ventilation.28

Common Peroneal Nerve Block

Anatomy

The common peroneal nerve originates in the popliteal fossa as one of the terminal branches of the sciatic nerve (Figure 126-36A). It courses posterolaterally around the neck of the fibula where it can be palpated. It provides motor innervation to the peroneal muscles and the muscles of the anterior leg and foot. It provides sensory innervation to the anterior leg, dorsum of the foot and toes, and to the medial great toe (Figure 126-27).

Patient Positioning

Place the patient lying on the side opposite that being anesthetized. Alternatively, place the patient supine with their leg internally rotated.

Landmarks

Identify the head and neck of the fibula and the common peroneal nerve by palpation.

Needle Insertion and Direction

Place a skin wheal of local anesthetic solution over the neck of the fibula (Figure 126-36B). Insert a 25 gauge needle through the skin wheal to elicit paresthesias. Withdraw the needle 2 mm and allow the paresthesias to resolve. Inject 3 to 5 mL of local anesthetic solution. If paresthesias are not elicited, subcutaneously infiltrate the area with 5 to 7 mL of local anesthetic solution.

US-Guided Block

Place the patient prone with a pillow or blanket under their ankle to position the knee in slight flexion (10° to 20°). Identify the biceps femoris muscle laterally, the semimembranosus and semitendinosus muscles medially, and the popliteal crease. Place the US probe 10 cm proximal to the crease. The sciatic nerve is located between the biceps femoris muscle laterally and the semimembranosus and semitendinosus muscles medially (Figure 126-35C). Scan cephalad and caudad to obtain the best view of the sciatic nerve and to identify where the sciatic nerve branches into the tibial and the common peroneal nerves. Move the probe caudally until the sciatic nerve branches into the tibial nerve medially and the common peroneal nerve laterally.

Place a skin wheal of local anesthetic solution. Place the needle lateral to the long axis of the US probe. Insert the needle in the plane of the long axis of the US beam. Advance the needle toward the common peroneal nerve. Stop advancing the needle when its tip is adjacent to the common peroneal nerve. Aspirate to ensure that the needle tip is not in a blood vessel. Inject a test dose of 1 to 2 mL of local anesthetic solution. Watch the spread of local anesthetic solution around the common peroneal nerve. If satisfactory, inject 10 to 15 mL of local anesthetic solution to produce the “donut sign.” If the test dose is not satisfactory, reposition the needle and inject another test dose.

Remarks

The common peroneal nerve may not always be palpable. Apply digital pressure over the neck of the fibula. Significant discomfort will be elicited when compressing the nerve against the fibula. This site is the location of the common peroneal nerve.

Superficial Peroneal Nerve Block

Anatomy

The superficial peroneal nerve is one of the terminal branches of the common peroneal nerve (Figure 126-37A). It perforates the investing fascia of the anterior leg to become subcutaneous in the lower third of the leg. It provides motor innervation to the peroneus longus and brevis muscles. It provides sensory innervation to the anterolateral leg, medial great toe, and dorsum of the foot and toes except the first web space and the area covered by the saphenous and sural nerves (Figure 126-27).

Patient Positioning

Place the patient supine with their ankle supported on a pillow or blanket.

Landmarks

Identify the anterior border of the medial and lateral malleolus by palpation.

Needle Insertion and Direction

Place a skin wheal of local anesthetic solution anterior to the distal aspect of the lateral malleolus. Insert a 25 gauge needle through the skin wheal. Infiltrate 6 to 10 mL of local anesthetic solution subcutaneously in a transverse line to the anterior border of the medial malleolus (Figure 126-37B).

US-Guided Block

Place the US probe along the anterior border of the lateral malleolus. Identify the dorsalis pedis artery. Use color Doppler to confirm the location of the dorsalis pedis artery. Place a skin wheal of local anesthetic solution. Place the needle lateral to the long axis of the US probe. Insert the needle in the plane of the long axis of the US beam. Visualize the entire length of the needle as it is advanced in the subcutaneous tissues in a transverse line from the lateral malleolus to the medial malleolus, avoiding the dorsalis pedis artery. Aspirate to ensure the needle tip is not in a blood vessel. Inject 3 to 5 mL of local anesthetic solution as the needle is withdrawn from the medial malleolus to the lateral malleolus.

Remarks

The superficial peroneal nerve may also be blocked at the level of the ankle. Infiltrate 4 to 8 mL of local anesthetic solution subcutaneously in a transverse line from the anterior border of the lateral malleolus to the anterior tibial ridge.

Deep Peroneal Nerve Block

Anatomy

The deep peroneal nerve is one of the terminal branches of the common peroneal nerve. It descends over the interosseous membrane into the dorsal foot, medial to the dorsalis pedis artery (Figure 126-38A). It travels between the tendons of the tibialis anterior and extensor hallucis longus muscles at the level of the ankle joint and above. It travels between the tendons of the extensor digitorum longus and the extensor hallucis longus muscles at the level of the malleoli. It may or may not contribute a motor branch to the peroneus longus muscles. It provides sensory innervation to only the first web space (Figure 126-27).

Patient Positioning

Place the patient supine with their ankle supported on a pillow or blanket.

Landmarks

Identify the tendons of the tibialis anterior and the extensor hallucis longus muscles by palpation. Identify the anterior tibial artery by its pulse at the level of the ankle joint.

Needle Insertion and Direction

Place a skin wheal of local anesthetic solution between the two tendons and just medial to the anterior tibial artery (Figure 126-38B). Insert a 25 gauge needle through the skin wheal and perpendicular to the skin. Advance the needle 3 mm and inject 3 to 5 mL of local anesthetic solution.

US-Guided Block

Place the US probe along the anterior border of the lateral and medial malleolus. Identify the tendons of the extensor digitorum longus and extensor hallucis longus muscles and the dorsalis pedis artery. Use color Doppler to confirm the location of the dorsalis pedis artery. Place a skin wheal of local anesthetic solution medial to the dorsalis pedis artery. Place the needle lateral to the long axis of the US probe. Insert the needle in the plane of the long axis of the US beam. Visualize the entire length of the needle as it reaches the medial aspect of the dorsalis pedis artery. Avoid penetrating the dorsalis pedis artery and any tendons. Aspirate to ensure the needle tip is not in a blood vessel. Inject 3 to 5 mL of local anesthetic solution on the medial aspect of the dorsalis pedis artery. Watch the local anesthetic solution spread around the dorsalis pedis artery.

Remarks

The deep peroneal nerve may also be blocked at the level of the malleoli. Identify the tendons of the extensor digitorum longus and extensor hallucis longus muscles by palpation and the dorsalis pedis artery by its pulse at the level of the malleoli. Place a skin wheal of local anesthetic solution between the tendons and medial to the dorsalis pedis artery. Insert the needle perpendicular to the skin. Advance the needle 3 mm and inject 2 to 4 mL of local anesthetic solution.

Sural Nerve Block

Anatomy

The sural nerve originates from the tibial nerve and the common peroneal nerve in the popliteal fossa. It is superficial after its origin and travels on the lateral leg and foot (Figure 126-39). It has already divided at the level of the ankle into numerous superficial branches, all located behind the lateral malleolus. The sural nerve provides sensory innervation to the anterolateral surface of the foot and little toe (Figure 126-27).

Patient Positioning

Place the patient prone with their ankle supported on a pillow or blanket and the leg externally rotated. Alternatively, place the patient supine with their ankle supported on a pillow or blanket and the leg internally rotated.

Landmarks

Identify the posterior border of the lateral malleolus and the Achilles tendon by palpation.

Needle Insertion and Direction

Place a skin wheal of local anesthetic solution, at the level of the lateral malleolus, just lateral to the Achilles tendon. Insert a 25 gauge needle through the skin wheal and angled toward the lateral malleolus (Figure 126-39). Infiltrate 5 mL of local anesthetic solution subcutaneously in a transverse line to the lateral malleolus.

US-Guided Block

Place the US probe behind the lateral malleolus. Identify the lateral malleolus. Place a skin wheal of local anesthetic solution. Place the needle lateral to the long axis of the US probe. Insert the needle in the plane of the long axis of the US beam. Visualize the entire length of the needle as it is inserted and contacts the posterior aspect of the lateral malleolus. Aspirate to ensure the needle tip is not in a blood vessel. Inject 3 to 5 mL of local anesthetic solution posterior to the lateral malleolus.

Remarks

Ensure that the needle is not within the Achilles tendon before injecting the local anesthetic solution.

Posterior Tibial Nerve Block

Anatomy

The posterior tibial nerve travels in the posterior leg and exists medial to the Achilles tendon, several centimeters above the ankle. It is superficial at the ankle, midway between the medial malleolus and the heel (Figure 126-40). It lies between the tendons of the flexor digitorum longus and flexor hallucis longus muscles. It travels with, and slightly posterior to, the posterior tibial artery. The posterior tibial nerve divides at the inferior border of the calcaneus to form the medial and lateral plantar nerves. It provides motor innervation to the intrinsic foot muscles. The lateral plantar nerve provides sensory innervation to the lateral one-third of the sole and plantar surface of the lateral one and one-half toes (Figure 126-27). The medial plantar nerve provides sensory innervation to the medial two-thirds of the sole and the plantar surface of the medial three and one-half toes (Figure 126-27).

Patient Positioning

Place the patient supine with their ankle supported on a pillow or blanket and the leg externally rotated.

Landmarks

Identify the medial malleolus by palpation and the posterior tibial artery by its pulsation.

Needle Insertion and Direction

Place a skin wheal of local anesthetic solution, at the level of the upper border of the medial malleolus, just posterior to the posterior tibial artery or medial to the Achilles tendon. Insert a 25 gauge needle through the skin wheal and perpendicular to the skin. Advance the needle to the tibia or until paresthesias are elicited. If paresthesias are elicited, withdraw the needle 2 mm and allow them to resolve. Inject 3 to 5 mL of local anesthetic solution. If paresthesias are not elicited, infiltrate 5 to 7 mL of local anesthetic solution starting against the posterior tibia as the needle is withdrawn.

US-Guided Block

Place the US probe behind the medial malleolus. Use color Doppler to confirm the location of the posterior tibial artery. Identify the tendon of the flexor hallucis longus lateral to the tibial nerve. Place a skin wheal of local anesthetic solution. Place the needle lateral to the long axis of the US probe. Insert the needle in the plane of the long axis of the US beam. Visualize the entire length of the needle as its tip reaches the tibial nerve. Aspirate to ensure the needle tip is not in a blood vessel. Inject 3 to 5 mL of local anesthetic solution around the tibial nerve to produce the “donut sign.”

Remarks

This block is especially useful before exploring puncture wounds, repairing lacerations, or removing foreign bodies from the sole.

Ankle Block

The ankle block is performed to achieve complete anesthesia of the foot. It requires anesthesia of the posterior tibial nerve, the sural nerve, the superficial peroneal nerve, the deep peroneal nerve, and the saphenous nerve (Figure 126-41A). The ankle can be thought of as diamond-shaped in cross section (Figure 126-41B). This diamond requires three subcutaneous and two deep injections (Figure 126-41B). The subcutaneous injections are to anesthetize the sural, superficial peroneal, and saphenous nerves. The deep injections are to anesthetize the posterior tibial and deep peroneal nerves. The techniques for these individual nerve block injections were described previously.

Digital Block of the Toe

Anatomy

Two dorsal and two volar nerves supply each toe.29 These nerves branch from the major nerves of the ankle. The dorsal digital nerves are the terminal branches of the deep and superficial peroneal nerves. The volar nerves are branches of the posterior tibial and sural nerves. The nerves lie in the 2, 4, 8, and 10 o'clock positions.

Patient Positioning

Place the patient supine with their hip and knee flexed so that the sole of the foot is flat against the examination table or gurney.

Landmarks

Locate the dorsal aspect of the base of the toe to be anesthetized.

Needle Insertion and Direction

Place a skin wheal of local anesthetic along the dorsolateral or dorsomedial aspect of the toe. Insert a 25 gauge needle through the skin wheal. Perform the three-sided ring block (Figure 126-42A). Direct the needle across the dorsum of the toe and infiltrate 1.0 to 1.5 mL of local anesthetic solution (Figure 126-42A(1)). Withdraw the needle and reinsert it on the medial aspect of the toe while infiltrating with 1.0 to 1.5 mL of local anesthetic solution (Figure 126-42A(2)). Repeat the infiltration on the lateral aspect of the toe (Figure 126-42A(3)). Anesthesia should be complete within 10 minutes. The great toe, due to its unique nerve supply, requires an additional anesthetic injection on the plantar aspect (Figure 126-42B).

Remarks

This technique is commonly employed in the Emergency Department. The indications include repair of lacerations, incision and drainage of infections, removal of toenails, manipulations of fractures and dislocations, and painful procedures requiring anesthesia. Other techniques to anesthetize the toes are similar to those of anesthetizing the fingers (Figure 126-24).

Allow 5 to 10 minutes for most regional anesthesia blocks to take effect. Up to 20 minutes may be required for blockade of major nerves (i.e., axillary, femoral, sciatic, and popliteal fossa). Incomplete or inadequate anesthesia is the result of not properly identifying the anatomic landmarks or not inserting the needle properly. The procedure may be repeated if the administration of a second dose of local anesthetic solution does not result in the patient receiving a toxic dose of the anesthetic agent (Table 126-2).

Perform frequent neurovascular checks until baseline function has returned. Injury to the anesthetized limb can result if the patient is permitted to use it, to use heat or cold application, or to perform wound care before the anesthesia has worn off.18 If extensive or major nerve blockade was performed, discharge the patient home only after the sensation and function have returned to baseline. The patient may be discharged home immediately after minor blockade, but should be properly cautioned. Avoid compression dressings as they may result in ischemia, which is improperly sensed by the anesthetized area or limb.

Complications can occur from the injection of local anesthetic solutions, most of which are minor. Significant complications are rare; yet, they do occur. Complications generally result from poor technique. General precautions include measures to minimize nerve injury, intravascular injection, and systemic toxicity. The Emergency Physician must be prepared to institute quick and immediate abortive care, cardiac monitoring, and airway control if complications do arise.

Allergic Reactions

Allergic reactions can occur from hypersensitivity to the local anesthetic solution. Symptoms can range from mild itching and urticaria to circulatory collapse and death. Severe allergic reactions are extremely rare but may occur. The preservative in the local anesthetic solution is often the cause of an allergic reaction. Local anesthetic solutions containing no preservatives are an alternative. One example is “cardiac” lidocaine that is used for Advanced Cardiac Life Support (ACLS) protocols. Topical ice or vapor coolant is an acceptable alternative to nothing if one is concerned about a potential allergic reaction from the local anesthetic solutions. A solution of 1% to 2% diphenhydramine can also be used as an injectable local anesthetic.7 Refer to Chapters 123 and 124 for the complete details of alternative anesthetic techniques.

Hemorrhage

Significant bleeding is extremely rare. Injection of a local anesthetic solution can be performed safely in patients who are anticoagulated or have a bleeding disorder.7 A hematoma may commonly develop due to an arterial puncture. The application of direct pressure can be helpful if significant external hemorrhage occurs. However, if bleeding continues, treatment may be required to reverse the anticoagulant or replace clotting factors.

Overdosage

Central nervous system (CNS) complications primarily result from local anesthetic toxicity. These symptoms range from tremors to convulsions. The most severe complication is respiratory compromise resulting in intubation. The maximum dose of local anesthetic solution should not exceed the doses listed in Table 126-2.7,9 Toxicity after intravascular injection requires even less anesthetic than subcutaneous infiltration.

Infection

Infection can occur when the needle penetrates unclean skin. The risk of infection is significantly reduced if proper aseptic technique is used. The risk of infection is negligible when the skin is properly cleansed, sterile technique is used, puncture through obviously infected skin is avoided, and penetrating the needle through a skin lesion that may harbor microorganisms is avoided.

Vasovagal Reactions

The patient may experience an increase in vagal tone from apprehension, needle phobias, and/or pain. Vasovagal reactions are relatively common and may be associated with light-headedness and/or fainting. Always perform regional anesthesia with the patient on a stretcher or in a chair that reclines to prevent secondary injury. Vasovagal reactions are self-limited and only require reassurance.7

Nerve Injury

Inflammation of the nerve is the most common nerve injury seen after regional anesthesia. Neuritis is a rare complication. Patients may complain of paresthesias, motor deficits, and/or sensory deficits. Most cases are transient and resolve completely, requiring only supportive care and close follow-up. Nerve damage results from direct needle trauma, ischemia due to intraneural injection, and chemical irritation from the anesthetic solution.29 Proper needle style, positioning, and manipulation can minimize direct nerve damage. Intraneural injection can cause nerve ischemia with resultant injury. Elicitation of paresthesias or severe pain indicates that the needle has made contact with the nerve. Withdraw the needle slightly and allow the paresthesias to resolve before injecting the local anesthetic solution. Concentrated anesthetics can produce chemical irritation of the nerve.

Intravascular Injection

Intravascular injection results in both systemic and limb toxicity. Inadvertent intravascular injection produces high blood levels of the anesthetic agent and resultant toxicity. Particular care must be taken when administering large amounts of local anesthetic solution in close proximity to large blood vessels.

Intraarterial injection of local anesthetic solution containing epinephrine may cause peripheral vasospasm and subsequent ischemia that further compromises injured tissue. The local anesthetic solution is not toxic to the limb itself, although it may produce transient blanching of the skin by displacing blood from the vascular tree. Alpha-adrenergic antagonists have been used with success in relieving arterial vasospasm secondary to intraarterial injection of local anesthetics.30

Ultrasound-Associated Complications

The use of US during the establishment of regional nerve blocks is associated with several complications and pitfalls. The chance of a nerve injury, intraneural injection, or intravascular injection is higher if a regular (i.e., cutting) needle is used. Always use a noncutting needle for nerve blocks. Ensure the identification of blood vessels by routinely turning on the power Doppler window when scanning for nerves. Accidental intravascular injection of large quantities of local anesthetic agents can lead to seizures, arrhythmias, apnea, and death. Failure to “pop” through the nerve sheath will not produce the “donut sign” and will likely lead to a failed block.

There is no standardized training for the Emergency Physician to learn US-guided nerve blocks. Regional anesthesia has evolved into an Anesthesia subspecialty, and brachial plexus blocks can take considerable time to master. The use of phantom and simulation models for training, as well as careful supervision, are highly recommended. Novice sonographers may want to start with forearm, femoral nerve, popliteal, and lower leg blocks before tackling brachial plexus blocks.

Regional anesthesia can serve as a valuable adjunct to the Emergency Physician's armamentarium. It is used for wound anesthesia prior to exploration, irrigation, debridement, and repair. Regional anesthesia may also be used to reduce the pain of procedures such as reduction of fractures and dislocations. Nerve blocks are especially useful when pain-sensitive structures such as fingers, toes, hands, and feet are involved. The application of regional anesthesia is frequently overlooked and underutilized in the emergency care of not only adults but even more so in the case of children. The use of regional nerve blocks is simple, safe, and effective for providing analgesia in the Emergency Department.