Chapter 47. General Principles of Intravenous Access

The practice of Emergency Medicine frequently requires access to a patient's venous circulation. Venous access allows sampling of blood as well as administration of medications, nutritional support, and blood products. Devices such as cardiac pacing wires and pulmonary artery catheters can be introduced into the patient's central venous circulatory system.

Percutaneous, as opposed to surgical, venous access is usually rapid, safe, and well tolerated. An understanding of the various techniques available, the venous anatomy, and the indications for the procedure allows the Emergency Physician to choose the appropriate site and method of venous access.

Veins, like arteries, have a three-layered wall composed of an internal endothelium surrounded by a layer of muscle then a layer of connective tissue (Figure 47-1).1 The muscular layer of a vein is much smaller than that of an artery. While veins can dilate and constrict somewhat on their own, they do so mostly in response to the pressure within them. Veins with high pressures become engorged and are easier to access. The use of venous tourniquets, dependent positioning, “pumping” via muscle contraction, and the local application of heat or nitroglycerin ointment all contribute to venous engorgement.2 These maneuvers can be used to aid in the identification of a peripheral vein.3

The connective tissue surrounding veins can be a help or a hindrance during attempts at peripheral venous access. Deficient connective tissue permits the vein to “roll” from side to side and evade the needle. Tough connective tissue can impede the entry of a flexible catheter through the soft tissues and into the vein. This tissue also serves to stabilize the vein and prevent its collapse.

Venous valves are an important aspect of peripheral venous anatomy (Figure 47-2).1 They encourage unidirectional flow of blood back toward the heart. Venous valves prevent blood from pooling in the dependent portions of the extremities due to gravitational forces. Valves can impede the passage of a catheter through and into a vein. Forcing a catheter past venous valves may damage them and contribute to later venous insufficiency. Valves are more numerous at the points where tributaries join larger veins and in the lower extremities. Valves are almost totally absent within the large central veins, the veins of the head, and the veins of the neck.

Veins can be subdivided into central veins and peripheral veins. The important central veins with regard to venous access are the internal jugular, subclavian, and femoral veins. Central veins are usually larger than peripheral veins and have fewer tributaries.

Superficial peripheral veins are generally visible beneath the surface of the skin of the extremities and neck. They are often tortuous and continually merge and divide. Peripheral veins are easiest to access at the apex of the “Y” formed when two tributaries merge into a larger vein or where the vein is straight and free of branches (and hence valves) for approximately 2 cm proximal to the site of puncture (Figure 47-3). These sites tend to be anchored and “roll” less than other sites. The superficial veins of the upper extremity are preferred to those of the lower extremity for peripheral venous access. Indwelling catheters in the upper extremity interfere less with patient mobility and the risk of phlebitis is lower.1

The depth of the vein beneath the epidermis will affect the ease with which it may be accessed. Very superficial veins are often small, fragile, and easily passed “through and through” with a needle, resulting in a hematoma. The deeper veins are often not visible and must be located by surface landmarks and palpation. The angle of insertion of the needle must be varied depending on the depth of the vein being punctured (Figure 47-4). A shallow angle of approximately 30° to 45° should be used for most small and superficial veins (Figure 47-4A). A more obtuse angle of approximately 60° should be used to access deeper veins (Figure 47-4B). This steeper angle allows the vein to be penetrated within a reasonable horizontal distance from the skin puncture site. Very small and superficial veins should be entered at a very acute angle of approximately 15° to 30° (Figure 47-4C).

Venous puncture (venipuncture) with a needle is indicated only for the sampling of venous blood. Medications may be administered as a one-time dose via this technique. The risk of medication extravasation with this technique is high, and it has therefore fallen out of favor.

Venous cannulation is indicated for repeated sampling of venous blood. It is also performed for the administration of intravenous medications, fluid solutions, blood products, and nutritional support. The specific indications for peripheral venous access, central venous access, and the various techniques of venous cannulation are discussed below and in Chapters 48 and 49.

Veins should not be accessed through infected skin. A vein proximal to a running venous infusion should not be used for venous blood sampling. The blood sample will be tainted or diluted by the infused solution. The hole in the vein may allow blood, infused solutions, and medications to extravasate into the surrounding tissues.

Venipuncture and venous cannulation of veins in an extremity with an arteriovenous fistula should be avoided. Veins in the upper extremity that may be needed for arteriovenous fistula construction for hemodialysis in the near future should not be punctured unless absolutely necessary. Scarring of the vein may complicate later surgical procedures.

Indwelling catheters are made of flexible polymers that are less likely to break or erode through the blood vessel wall than more rigid materials such as steel or glass. Polymer resins, Teflon, and polyurethane are commonly used materials. Latex-containing products should be avoided due to the risk of allergic reactions. Polyurethane catheters may be weakened by alcohol-based solutions.1 Thus, such solutions should not be infused through polyurethane catheters.

All catheters are potentially thrombogenic. They should be left in place only as long as needed. Catheters impregnated with antiseptics, such as chlorhexidine and silver sulfadiazine, are commercially available and may decrease the incidence of catheter-related sepsis.4 Chlorhexidine has been associated with immediate hypersensitivity reactions, most commonly in persons of Japanese descent.5 Silver sulfadiazine has not been proven safe to use in sulfa-sensitive patients. Catheters are also available that, when immersed briefly in an antibiotic solution prior to insertion, allow an antibiotic to bind to the catheter surfaces. These catheters may reduce the risk of infection with organisms susceptible to the chosen antibiotic.

Both the diameter and the length of the infusion device will affect the flow rate through the catheter. Viscous fluids (e.g., blood products and albumin) will infuse more slowly than less viscous fluids (e.g., saline). These relationships can be seen in the solution of Poiseuille's equation for ideal fluid flow through a cylindrical tube:

The pressure gradient and resistance to flow are inversely proportional to the length of the tubing. Changes in catheter diameter will have the most effect on flow rates. The flow rate increases to the fourth power as the catheter's internal radius increases. Flow rates can be maximized by using the largest internal diameter (i.e., smallest gauge) catheter that will fit inside the chosen vein. Large-bore venous catheters are preferred for the highest-volume rapid fluid resuscitations, particularly of viscous blood products. Flow rates decrease as the catheter length increases. Use of the shortest possible catheter to access the chosen vein will permit the highest fluid infusion rates. External pressure applied to the bag of infusion solution will linearly increase the flow rate.

Identifying a peripheral vein can sometimes be quite difficult. Dilating a vein (venodilation) can make a vein larger, easier to identify, and easier to access. These techniques are easy to perform.

Several venodilation techniques do not require any special equipment. Place the extremity in a dependent position.15 This position allows gravity to decrease venous return and dilate the veins.16 Gently tap the skin in the area to dilate the underlying veins.15,16 The exact mechanism of how this works is not known. It may be due to the release of chemical mediators, stimulation of nerve fibers, or a combination of both. Instruct the patient to open and close their hand. The muscular contractions of the forearm muscles increase arterial inflow distally while venous outflow is inhibited by the tourniquet.15,17–19 Try to “milk” the veins in a distal direction. Apply your fingers over the skin, press downward, and then move the fingers distally to “milk” or back-flow the blood and dilate the distal veins.15 Apply a warm compress, heat pack, warm towel, or submerge the extremity in warm water to dilate the veins. Be careful to not use too hot of a temperature to prevent burning the patient.

Several commercially available devices can be used to produce venodilation. The Esmarch Bandage is a tourniquet system used to exsanguinate a limb prior to surgery. Apply it to the upper extremity starting proximally and wrap it distally, the reverse of applying it to exsanguinate the extremity. It will result in blood pooling in the distal veins and subsequent venodilation. The Rhys-Davies Exsanguinator can also be placed proximal to distal to pool blood distally and cause venodilation.20 This device is usually not available in the Emergency Department. A vacuum device was developed to aid in obtaining venous access.21,22 It was cumbersome and is also not available in the Emergency Department.

Topically applied pharmaceuticals can be used to dilate the dorsal hand veins.23–25 Topical nitroglycerine ointment has been used for many years. Apply 1 in. of the ointment and rub it into the skin on the dorsal hand. Use gloves while applying the ointment to prevent the side effects of a headache or hypotension to the healthcare provider. Allow the ointment to sit for 2 minutes then completely wipe it off the skin. Clean any residual nitroglycerine ointment from the skin with an alcohol swab. Identify a vein by palpation. Topical nifedipine is an alternative, but not currently available in the United States.

In recent years, numerous commercial devices have become available to visualize veins. The VeinViewer (Christie Medical Holdings Inc., Memphis, TN) uses polarized near-infrared light from light-emitting diodes to penetrate the skin and subcutaneous tissues.26–28 The device projects the underlying blood-filled veins onto the skin using a visible green light. The AccuVein AV300 (AccuVein LLC, Cold Spring Harbor, NY) and the Veinlite (TransLite, Sugar Land, TX) are similar devices, but handheld. The Venoscope (Venoscope LLC, Lafayette, LA) is a handheld device that is also available in a neonatal version. The major drawback of these devices is their cost.

The use of anesthesia prior to venipuncture or venous cannulation is much appreciated by the patient, especially if the patient is a child. The injection of local anesthetic solution will decrease the pain of venous access. Unfortunately, the pain of injection can be just as uncomfortable as the venous access procedure. The application of a topical anesthetic, such as ELA-Max (Ferndale Laboratories, Ferndale, MI) or EMLA (Astra Zenica, Wilmington, DE), that is designed to enhance transdermal absorption requires approximately 30 to 60 minutes to adequately anesthetize the skin and subcutaneous tissues. This time delay limits their use in the Emergency Department. Refer to Chapters 123 and 124 for a more complete discussion of topical anesthetics.

Numerous alternative anesthesia methods can be considered. These are rarely available or used in the Emergency Department. Local anesthetic absorption through the skin can be enhanced to decrease the time it takes to provide anesthesia. These methods include using sound energy (sonophoresis), electrical energy (iontophoresis), and epidermal tape stripping.29–31 A portable, handheld laser used prior to the application of topical anesthesia for 5 minutes effectively reduces the pain of venous access.32,37 Topical vapocoolant spray will briefly anesthetize the skin long enough to allow for venous access.33–35 Local anesthetic patches that are heat activated to increase transdermal absorption of the local anesthetic agent in approximately 20 minutes have been found to be effective.36 Needleless jet injections of local anesthetics effectively anesthetize the skin and subcutaneous tissues.38–40 One study questioned if the anesthesia was due to the local anesthetic agent or the jet injection procedure itself as the placebo group was just as effective in terms of anesthesia.39 The main advantages of these techniques, compared to injectable anesthetics, are the lack of pain during the application and the lack of tissue distortion making identification of the vein difficult.

Five types of devices are used for vascular access (Figure 47-5). There are numerous variations of these devices. The butterfly needle and hollow needle are used for venipuncture. Blood may be withdrawn using a butterfly-type needle (Figure 47-6) or a standard hypodermic needle. The butterfly needle, attached to a short length of plastic tubing, allows for greater control while accessing small and superficial veins. It is often too short to reach deeper veins. Versions with an integral sheath to minimize accidental needlestick injuries are available (Figure 47-7A).

Venous blood sampling can be accomplished by one of several methods. Blood may be allowed to drip from the open end of the butterfly extension tubing into small-volume collection tubes for pediatric patients. Some form of suction is used to withdraw the blood more rapidly in older children and adults. A syringe or a vacuum tube may be used (Figure 47-8). Vacuum tubes reduce the risk of needlestick injuries. The amount of suction provided is fixed and may result in hemolysis of the specimen and cause small veins to collapse. Syringe aspiration allows greater control over the amount of suction applied. Large syringes can be difficult to manipulate while maintaining the tip of the needle within the vein. Use a 5 to 10 mL syringe, as larger syringes result in hemolysis of the specimen and collapse of the vein. Use caution, as the needle used to transfer the specimen from the syringe to the laboratory tubes can cause a needlestick injury.

There are four main techniques of vein cannulation.6–8 The first is the needle-only technique using a butterfly-type needle. This is seldom used today. The catheter-over-the-needle technique is the one most commonly used for peripheral venous cannulation. The catheter-through-the-needle technique is occasionally used but not very popular. The Seldinger wire-guided technique is most commonly used for central venous access. The major advantages and disadvantages of each technique are summarized in Table 47-1.

Identify the vein to be cannulated and the site of the skin puncture. Clean the area of any dirt and debris. Cleanse the skin with isopropyl alcohol, chlorhexidine solution, or povidone iodine solution and allow it to dry. Apply a tourniquet to the extremity, proximal to the venous cannulation site, to engorge the vein. Additional engorgement of the vein or the use of a device to locate a vein, both described previously, can aid in the identification of a peripheral vein. Do not attempt cannulation if the vein cannot be seen, palpated, or otherwise visualized (e.g., ultrasound) in the engorged state. Place a small subcutaneous wheal of local anesthetic solution, or some other previously mentioned alternative, at the skin puncture site to provide some comfort to the patient. The next step is to cannulate the vein by one of the methods described below.

Needle-Only Technique

This technique is used occasionally for short-term venous access in young children and elderly patients with fragile veins. This system is prone to malposition and infiltration. The tip of the needle can easily lacerate the vein if the needle is not secure and allowed to move.

Grasp and fold the wings of the butterfly needle with the dominant index finger and thumb (Figure 47-6B). Briskly insert the needle, with the bevel facing upward, through the skin and into the vein.14 A flash of blood will be seen in the tubing when the tip of the needle enters the vein. Carefully advance the needle an additional 3 to 5 mm into the vein. Attach a 5 mL syringe to the extension tubing and aspirate blood. The flow of blood into the syringe confirms proper intravascular placement of the needle. Remove the tourniquet from the extremity. Securely tape the wings of the butterfly needle to the patient's skin. Remove the 5 mL syringe, attach intravenous tubing to the catheter, and begin the intravenous infusion.

Catheter‐over‐the-Needle Technique

The catheter-over-the-needle systems are the ones most commonly used for venous access. The infusion catheter fits closely over a hypodermic needle. The needle and the catheter are advanced as a unit into the vein. These devices are inexpensive (about $1-4 each), come in a variety of diameters (12- to 24-gauge) and lengths, and are widely available. Versions designed to minimize accidental needlestick injuries are available and their use is encouraged (Figure 47-7B).9

Insert the catheter-over-the-needle, with the bevel facing upward, through the skin and into the vein (Figure 47-9A).14 A flash of blood in the hub of the needle confirms that the tip of the needle is within the vein. Advance the unit an additional 2 to 3 mm to ensure that the catheter is within the vein. Hold the hub of the needle securely. Advance the catheter over the needle until its hub is against the skin (Figure 47-9B). Apply pressure, with the nondominant index finger, over the skin above the catheter to prevent blood from exiting the catheter. Remove the tourniquet from the extremity. Securely hold the hub of the catheter against the skin. Withdraw the needle (Figure 47-9C). Attach intravenous tubing to the hub of the catheter and begin the infusion (Figure 47-9D). Secure the catheter to the skin with tape.

Placement of these catheters is usually quick and simple. Several considerations should always be kept in mind when using the catheter-over-the-needle technique. Intravascular placement of the system is indicated by a flash of blood in the hub of the needle. If the patient's venous pressure is very low or if the needle is long and narrow, both sides of the vessel may be traversed (i.e., through-and-through) before the practitioner realizes that the needle was within the vein (Figure 47-10A). If the tip of the needle has withdrawn from the vein, the catheter will not advance. If the catheter is advanced when the tip of the needle but not the catheter is within the vein, the catheter will not advance. The catheter will push the vein off the needle (Figure 47-10B). Place a finger just distal to the puncture site. Depress the skin and pull it distally to prevent the vein from “rolling” as the catheter-over-the-needle is inserted into the vein (Figures 47-10C & D).

Catheter‐Through‐the-Needle Technique

As opposed to the over-the-needle approach, this technique eliminates the need for a needle that is as long as the catheter and eliminates the possibility of pushing the vein off the end of the needle when the catheter is advanced.10 This system is used most commonly for central, rather than peripheral, venous access. Catheters up to 61 cm (24 in) long are available and allow central venous access from the antecubital vein or the femoral vein. Select a catheter size that is appropriate for the patient and the site of entry. Packaged with each catheter are a needle and a needle guard. The needle will have an inner diameter that is slightly larger than the outer diameter of the catheter. The needle guard has a beveled channel in which the needle can reside. The needle guard hinges closed over the needle to hold it securely and prevent the needle from shearing the catheter. Holes in the corners of the needle guard allow it to be sewn to the patient's skin.

Place the needle on a tuberculin syringe. Insert the needle, with the bevel facing upward, through the skin and into the vein while applying negative pressure to the syringe (Figure 47-11A).14 A flash of blood in the syringe confirms that the tip of the needle is within the vein. Advance the needle an additional 2 mm to ensure that the tip of the needle is completely within the vein. Grasp and hold the needle securely with the nondominant hand. Remove the syringe with the dominant hand. Immediately place the nondominant thumb over the needle hub to prevent air from entering the vein. Remove the tourniquet from the extremity.

Insert the catheter through the hub of the needle (Figure 47-11B). Advance the catheter through the needle until the desired length of catheter is within the vein. If the catheter will not advance, remove the catheter and needle as a unit. Never withdraw the catheter through the needle. The sharp bevel of the needle may cut the catheter as it is being withdrawn and result in a catheter embolism in the central venous circulation.

Withdraw the needle over the catheter (Figure 47-11C). Do not allow the catheter to be withdrawn through the needle. Continue to withdraw the needle until the tip is completely outside the skin. Apply the needle guard over the needle (Figure 47-11D). Attach intravenous tubing to the hub of the catheter and begin infusing fluids through the catheter. Secure the catheter and needle guard to the skin with tape and/or sutures.

The main disadvantage of this technique is the possibility of the needle tip shearing off the catheter, causing a catheter embolism in the venous circulation. This can be prevented by not withdrawing the catheter through the needle and applying the needle guard immediately after the needle is withdrawn from the skin. The contaminated needle must be handled to some extent, creating a potential risk for a needlestick injury. The needle used for the venipuncture must be larger in diameter than the catheter. This limits the practical diameter of the catheter. The needle punctures a hole in the vessel larger than the catheter and increases the risk of hematoma formation.

Seldinger Technique

First described by Seldinger in 1953, this technique allows for the placement of a catheter over a wire rather than directly over a needle.11,12 The wire used must be longer than the catheter. The needle used to insert the wire can be short and of a smaller gauge than the catheter. If desired, the catheter type may be changed later without the need for a new venous puncture. Materials needed for catheter insertion are commercially available in a prefabricated kit (Teleflex Medical, Cleveland, OH; Cook Medical Inc., Bloomington, IN).

The Seldinger technique is most commonly used for central venous catheter insertion. It can be used for peripheral venous access if a short, thin guidewire is available. Ultrasound may be a useful adjunct with this technique.13 Please refer to Chapter 50 regarding ultrasound-guided vascular access for a complete discussion. All-in-one arterial line kits are commercially available. They are intended for peripheral arterial line placement but can also be used to place catheters in peripheral veins, the brachial veins, and the external jugular veins.

The Seldinger technique for venous catheter insertion is described briefly here. Refer to Chapter 49 (central venous access techniques) for a more complete discussion. Choose the puncture site. Prepare the patient for the procedure. Clean and prepare the puncture site as previously described. The vein may first be located with a small “finder” needle if there is doubt about its exact location. Insert a 25 or 27 gauge needle attached to a 5 mL syringe, with the bevel facing upward, through the skin. Advance the needle while applying negative pressure to the syringe. A flash of blood signifies that the tip of the needle is within the vein. Note the depth and location of the vein based on the depth and direction of the “finder” needle.

Insert the thin-walled introducer needle while applying negative pressure to the syringe. The introducer needle has a tapered hub on the proximal end to guide the wire into the needle lumen. Avoid using a standard hypodermic needle, as it does not allow for the passage of the guidewire. A flash of blood in the needle hub signifies that the tip of the needle is within the vein (Figure 47-12A). Advance the needle an additional 1 to 2 mm into the vein. Hold the needle securely in place and remove the syringe.

Occlude the needle hub with a sterile gloved finger. This will prevent air from entering the venous system. Insert the guidewire through the hub of the needle (Figure 47-12B). Advance it to the desired depth, ensuring that it is at least several centimeters beyond the beveled end of the needle. To prevent loss of the wire into the venous circulation, never let go of the guidewire with both hands at the same time. Hold the guidewire securely in place. Remove the needle over the guidewire (Figure 47-12C). Make a small nick in the skin adjacent to the guidewire with a #11 scalpel blade (Figure 47-12D). Direct the sharp edge of the scalpel blade away from the guidewire to prevent nicking the guidewire.

Place the dilator over the guidewire. Advance the dilator over the guidewire to enlarge the subcutaneous passage for the catheter. Continue to advance the dilator until its hub is against the skin. Withdraw the dilator over the guidewire while leaving the guidewire in place. Advance the catheter over the guidewire until its hub is against the skin (Figure 47-12E). A twisting motion of the catheter may aid in its advancement through the subcutaneous tissues and into the vein. Securely hold the hub of the catheter. Remove the guidewire through the catheter (Figure 47-12F).

Aspirate blood from the catheter with a syringe to confirm intravenous placement. Flush the catheter with sterile saline or begin an infusion. Secure the catheter to the skin with sutures and tape. While this technique seems complicated at first glance, it is easy to learn and can be performed in a few minutes by an experienced Emergency Physician.

Complications specific to each technique and site are discussed more fully in the following chapters. Venous catheters should be assessed immediately after their placement and also be reassessed frequently. The assessment must include the skin puncture site, catheter function, the extremity distal to the catheter, and the patient's overall condition. Some of the common problems are noted in Table 47-2. Other specific complications of peripheral and central venous access are discussed in the following chapters.

Venous access is an essential skill for all providers of care to the acutely ill and injured. As with most procedures, success rates increase and complication rates decrease with experience. Successful venipuncture or cannulation is not the end of the provider's obligation to the patient. Frequent reassessment of the venous access site, the equipment, and the patient is essential to prevent complications.