In Vitro Hemodynamic Evaluation of Five 6 Fr and 8 Fr Arterial Cannulae in Simulated Neonatal Cardiopulmonary Bypass Circuits

The objective of this study was to evaluate five small-bore arterial cannulae (6Fr and 8Fr) in terms of pressure drop and hemodynamic performance in simulated neonatal cardiopulmonary bypass (CPB) circuits. The experimental circuits consisted of a Jostra HL-20 roller pump, a Terumo Capiox Baby FX05 oxygenator with integrated arterial filter, an arterial and a venous tubing (1/4, 3/16, or 1/8 in × 150cm), and an arterial cannula (Medtronic Bio-Medicus 6Fr and 8Fr, Maquet 6Fr and 8Fr, or RMI Edwards 8Fr). The circuit was primed using lactated Ringer's solution and heparinized packed human red blood cells (hematocrit 30%). Trials were conducted at different flow rates (6Fr: 200-400mL/min; 8Fr: 200-600mL/min) and temperatures (35 and 28°C). Flow and pressure data were collected using a custom-based data acquisition system. Higher circuit pressure, circuit pressure drop, and hemodynamic energy loss across the circuit were recorded when using small-bore arterial cannula and small inner diameter arterial tubing in a neonatal CPB circuit. The maximum preoxygenator pressures reached 449.7±1.0mmHg (Maquet 6Fr at 400mL/min), and 395.7±0.4mmHg (DLP 8Fr at 600mL/min) when using 1/8 in ID arterial tubing at 28°C. Hypothermia further increased circuit pressure drop and hemodynamic energy loss. Compared with the others, the RMI 8Fr arterial cannula had significantly lower pressure drop and energy loss. Maquet 6Fr arterial cannula had a greater pressure drop than the DLP 6Fr. A small-bore arterial cannula and arterial tubing created high circuit pressure drop and hemodynamic energy loss. Appropriate arterial cannula and arterial tubing should be considered to match the expected flow rate. Larger cannula and tubing are recommended for neonatal CPB. Low-resistance neonatal arterial cannulae need to be developed.