Impact of Catheter Design on Catheter Survival in Chronic Hemodialysis Patients

The use of tunneled cuffed catheters (TCCs) as vascular access is discouraged in the NKF DOQI guidelines, because of their propensity for infection, thrombosis, inadequate and/or irregular blood flow rates and damage to large central veins. In addition, emerging data suggest a link between catheter use and cardiovascular morbidity and mortality. Nevertheless, they are still frequently used in the hemodialysis population, either because of documented inadequate vascular access anatomy, or as a bridge to a functional permanent access.

A large number of TCC are available, that mainly differ with respect to material type, lumen diameter and design, tip design, as well as presence and design of side holes. There is currently no proven advantage of one long-term catheter design over another.

The design of the catheter tip may affect the propensity for thrombosis and hence intraluminal infection, as well the percentage of recirculation, especially when arterial and venous blood tubing are reversed. Commonly used catheters have a staggered tip design, meaning that the outflow tip extends several centimetres (typically a minimum of 2.5 cm) beyond the inflow tip, to prevent recirculation. Other designs are a split tip, or a symmetrical tip. In the latter type, used in the Palindrome® (Covidien) catheter, a spiral separator is incorporated allowing either lumen to be used as the arterial port.

Many catheters have multiple side holes, to decrease shear rate and increase flow on the arterial side and reflecting the belief that backup inflow is necessary in the case of obstruction. However, side holes can also promote thrombosis and infection due to the irregularity of their cut surfaces. Especially the distal side holes comprise a low flow zone with an increased clotting risk. The Palindrome® (Covidien) catheter has laser cut side holes, which are thought to have a smoother surface and a lower tendency to cause thrombosis.

Inadequate blood flow in a catheter is often mended by reversal of the inlet and outlet lumens. However, reversal of flow leads to a substantial increase of recirculation (from 2%-3% to 10%), affecting the efficiency of treatment. It should therefore never be used except temporarily until the problem is definitively corrected. The symmetrical tip design of the Palindrome® (Covidien) catheter allows lumen reversal without increased recirculation.