The patient’s vasculature can be accessed using either a central venous catheter (CVC) or a connection between an artery and vein (fistula or graft). A CVC used for dialysis contains two lumens and is inserted into a large central vein. The rapid and substantial amount of flow (up to 400 to 500 mL/min) drawn from these veins allows blood to efficiently exit the vein through one lumen, enter the dialysis circuit, and return to the vein through another lumen. The high blood flow also prevents stasis, which could lead to clotting, and optimizes the exchange of solutes across the membrane. Heparin is often used at intervals to prevent clotting within the dialysis circuit.

The main disadvantage of CVCs is their infection risk. To decrease this risk, catheters are often tunneled, meaning they are passed through a subcutaneous tract before being inserted into the central vein. This process lengthens the distance that skin flora must travel before being able to cause a systemic infection.