How much is catheter flow influenced by the use of closed luer lock access devices?

BACKGROUND To reduce infection risks in patients on hemodialysis with a long term central venous catheter, different types of closed luer lock access devices are used on the arterial and venous catheter hub. Although those connectors create a mechanically and microbiologically closed system in between two dialysis sessions, no data are available on the resistance those connectors exert on the blood flow during dialysis. Therefore, in the present study, flow resistance was determined in three different connectors. METHODS In an in vitro setup, different connectors were attached in between a male (Bellco BL 307 dialysis tubing) and female luer: BD Q-Syte (Becton-Dickinson, Utah, USA), second edition Tego (ICU Medical, CA, USA), and Swan-LockU connector (Codan, Lensahn, Germany). For a wide range of water flow rates, pressure-flow relationships were measured, simulating catheter inflow as well as catheter outflow, by reversing the flow direction. Resistances were compared to a simple male-female connection, as in a standard bloodline-catheter connection, and mathematical corrections were performed for the use of water instead of blood. RESULTS For a blood flow of 500 mL/min, simulating clinical dialysis, the additional pressure drop is 118 mmHg (Becton Dickinson), 52 mmHg (Codan), and 23 mmHg (Tego) in the case of catheter inflow, while it is 74 mmHg (Becton Dickinson), 40 mmHg (Codan), and 27 mmHg (Tego) in the case of catheter outflow. Resistances are also depending on the type of tubing as used during dialysis. CONCLUSIONS In conclusion, the Tego and Codan connector show promising results for the use on a catheter hub during and in between dialysis sessions. Whether those resistances are in the safe range without the incidence of blood hemolysis will soon be investigated in an in vivo study.