24-22: Procedural Guidance: Ultrasound-Guided Nerve Blocks

Clinical Summary

Managing pain due to painful conditions or procedures is a core component of emergency care. While landmark-based nerve blocks have traditionally been used, the use of ultrasound at the bedside can enhance the safety and effectiveness of nerve blocks. Patients should be monitored both during and after the procedure to evaluate for any signs of toxicity due to the anesthetic of choice.

Femoral Nerve Block and Fascia Iliaca Compartment Block

Nerve Anatomy

The femoral nerve provides sensory innervation via two branches. The anterior branch of the femoral nerve provides sensation to the anteromedial thigh via two additional branches, the medial cutaneous nerve of the thigh and the intermediate cutaneous nerve. The posterior branch of the femoral nerve provides sensation to the anteromedial portion of the lower leg and the region overlying the patella via two additional branches, the saphenous nerve and the infrapatellar nerve. These four nerves (two in the anterior branch and two in the posterior branch) are blocked with the femoral nerve block. The fascia iliaca compartment (FIC) block is a planar block that includes the femoral nerve and the lateral femoral cutaneous nerve (LFCN). The LFCN, as its name would suggest, provides sensation to the anterolateral thigh. The FIC block can also affect the obturator, ilioinguinal, accessory obturator, and genitofemoral nerves.

Indications

• Femur fracture

• Proximal tibia fracture

• Analgesia for incision and drainage of leg abscess within affected sensory distribution

• Analgesia for laceration closure on leg within affected sensory distribution

Equipment

• Skin disinfection agent and sterile gloves

• Sterile ultrasound probe cover

• Skin marker

• 27-gauge needle and 10-mL syringe for skin wheal of anesthetic of choice

• 20-gauge Tuohy epidural needle (for block) (or other blunt-tipped needle)

• 6- to 24-inch pressure tubing (flushed with saline and connected to block needle)

• Saline syringes (10 mL × 2) for hydrodissection

• Empty syringe (20 mL × 2) for injection of diluted local anesthetic

• Local anesthetic of choice

Patient Preparation

• Supine and in Trendelenburg if pannus covers inguinal crease (to assist in pannus retraction)

Technique

For FIC block:

• Probe is placed parallel to and distal to the inguinal ligament.

• The femoral artery is identified medially with the femoral nerve just lateral and inferior to the artery.

• The femoral nerve and LFCN run under the fascia iliaca, so the plane to target for anesthetic spread is the potential space between the iliacus muscle and the overlying ...