Evaluation of different diameter arterial tubing and arterial cannulae in simulated neonatal/pediatric cardiopulmonary bypass circuits

The objective of this study is to evaluate three different diameters of arterial tubing and three diameters of arterial cannulae in terms of pressure drop, and hemodynamic energy delivery in simulated neonatal/pediatric cardiopulmonary bypass (CPB) circuits. The CPB circuit consisted of a Terumo Capiox Baby FX05 oxygenator (Terumo Corporation, Tokyo, Japan), arterial tubing (1/4in, 3/16in, or 1/8in×150cm), and a Medtronic Bio-Medicus arterial cannula (8, 10, or 12Fr; Medtronic, Inc., Minneapolis, MN, USA). The pseudo patient's pressure was maintained at 50mmHg. 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 and temperatures (35 and 28°C). Flow and pressure data were collected using a custom-based data acquisition system. Using 8Fr arterial cannula at 500mL/min, small diameter arterial tubing generated higher circuit pressure (294.6±0.1mmHg [1/8in], 213.5±0.5mmHg [3/16in], 208.4±0.4mmHg [1/4in] at 35°C) and arterial line pressure drop (158.3±0.1mmHg [1/8in], 79.6±0.1mmHg [3/16in], 62.1±0.1mmHg [1/4in] at 35°C). Using 10 Fr arterial cannula at 1000mL/min, pre-oxygenator pressures were 266.8±0.2mmHg (3/16in) and 248.0±0.3mmHg (1/4in); arterial line pressure drops were 111.6±0.0mmHg (3/16in) and 74.0±0.1mmHg (1/4in) at 35°C. When using 12 Fr arterial cannula at 1500mL/min, preoxygenator pressures reached 324.4±0.3mmHg (3/16in) and 302.5±0.4mmHg (1/4in); arterial line pressure drops were 154.0±0.1mmHg (3/16in) and 92.0±0.2mmHg (1/4in) at 35°C. Pressure drops across arterial line tubing were main CPB circuit pressure drops. High flow rate, hypothermia, small diameter arterial tubing. and arterial cannula created more hemodynamic energy at the preoxygenator site, but energy loss across CPB circuit also increased. Although small diameter (<1/4in ID) arterial tubing may decrease total CPB priming volume, it also led to significantly higher circuit pressure, higher pressure drop, and more hemodynamic energy loss across CPB circuit. Larger diameter arterial cannula had less pressure drop and allowed more hemodynamic energy delivery to the patient.