Variability in systemic arterial pressure during closed- and open-bridge extracorporeal life support: An in vitro evaluation

Objective: To compare fluctuations in systemic arterial pressure (SAP) resu lting from changes in systemic vascular resistance (SVR) during closed- and open-bridge extracorporeal life support (ECLS). Design: In vitro laboratory study. Setting: Physiology laboratory of a tertiary care pediatric hospital. Methods: A standard neonatal ECLS circuit with simulated SAP was establishe d using normal saline as circulating fluid. Our reference setting included an extracorporeal flow rate of 300 mL/min, a simulated SAP of 60 mm tig, an d a postoxygenator pressure of 150 mm Hg. The simulated SVR was modified by changing the degree of occlusion of the arterial catheter distal to the br idge. For this purpose, we used a graduated clamping device. Subsequently, the pressure changes were measured at four ports in the circuit. They were located as follows: a) on the venous tubing of the circuit between the brid ge and the reservoir; b) on the arterial tubing of the circuit between the heat exchanger and the bridge; c) between the first and the second resistan ce clamps on the arterial tubing of the circuit for monitoring the simulate d systemic arterial pressure; and d) at the reservoir. The experiment was r epeated with various extracorporeal flow rates to the reservoir (100-300 mL /min) and through the bridge (100-300 mL/min using a custom-made clamp). Va riations in the simulated SAP created by varying degrees of occlusion and f low rates were compared with repeated measures analysis of variance followe d by the Tukey-Kramer test. Measurements and Main Results: The open-bridge ECLS significantly reduced t he variations in the simulated SAP by 15% to 45% (p < .001) compared with t he closed-bridge. During closed-bridge ECLS, flashing of the bridge resulte d in a decrease in the SAP and transient reversal of flows through the arte rial and venous cannulae. Conclusions: Open-bridge ECLS decreases the fluctuations in the SAP that oc cur because of changes in the SVR. Open-bridge ECLS prevents transient iatr ogenic changes in blood flow and blood pressure, caused by flashing of the bridge. Other potential advantages and disadvantages of the open-bridge ECL S are discussed. The application of prolonged open-bridge ECLS to the patie nts needs to be evaluated in animal models.