Venous access for medication administration, nutritional support, hemodialysis, and blood sampling is essential for the management of many chronic diseases. A variety of indwelling central venous access devices have been developed to avoid repeated venipunctures and permit direct access to the central circulation. These devices may be partially or completely implanted under the patient's skin. The Emergency Physician must be able to access these devices to administer medications and withdraw blood samples without damaging the device or causing it to clot off. The necessary procedures for successfully accessing indwelling central venous lines are described in this chapter.
Indwelling central venous lines allow access to the central venous circulation from a peripheral site.1,2 This is accomplished through either the end of a partially implanted catheter or through the skin into a subcutaneous reservoir of a fully implanted catheter (Figure 52-1). The proximal tip of the central venous line may lie in the superior vena cava or in the right atrium. Catheters designed for right atrial placement are made of softer and more pliable material than are catheters used for short-term transcutaneous central venous access. These catheters are unlikely to erode through or perforate the thin right atrial wall.
Indwelling central venous lines. A. The partially implanted central venous line. The distal end of the line emerges from the chest wall. Contamination of the implanted portion is prevented by a subcutaneous tunnel and a Dacron cuff around the catheter. B. The fully implanted central venous line. The catheter is connected to a reservoir that is contained in a subcutaneous pocket.
The internal jugular, subclavian, and femoral veins can all be utilized as a route for a central venous line to access the superior vena cava or right atrium. The subclavian veins are most commonly used to maximize patient comfort and mobility. When the line is initially inserted, the vein is punctured transcutaneously, the catheter is inserted into the vein, and its distal end is tunneled under the skin. If the line is partially implanted, the distal end of the catheter is brought external to the skin through a small puncture (Figure 52-1A). If the line is fully implanted, its distal end is connected to a subcutaneous reservoir that is placed in a pocket dissected under the skin of the chest wall (Figure 52-1B).
Partially Implanted Catheters
Partially implanted central venous catheters (Figures 52-1A & 52-2) are those whose distal end emerges from the skin via a subcutaneous tunnel.3 This tunnel helps prevent the spread of skin flora along the outside of the catheter and toward the central circulation. Most partially implanted catheters use a subcutaneous Dacron cuff to further insulate the proximal catheter from skin flora and help anchor the catheter in place.4