Impact of cannula size and line length on venous line pressure in pediatric VA-/VV-ECLS circuits.

ABSTRACT

The objective of this study was to do an in vitro evaluation of venous line pressure using different venous line lengths and venous cannula sizes in pediatric venoarterial extracorporeal life support (VA-ECLS) and venovenous ECLS (VV-ECLS) circuits. The pediatric VA-ECLS circuit consisted of a Xenios i-cor diagonal pump, a Maquet Quadrox-i pediatric oxygenator, a Medtronic Biomedicus arterial cannula, a Biomedicus venous cannula, and 1/4″ ID arterial and venous tubing. The pediatric VV-ECLS circuit was similar, except it included a Maquet Avalon ELITE bi-caval dual lumen cannula. Circuits were primed with lactated Ringer's solution and packed red blood cells (hematocrit 40%). Trials were conducted at various flow rates (VA-ECLS 250-1250 mL/min, VV-ECLS 250-2000 mL/min) using different venous tubing lengths (2, 4, and 6 feet) and cannula sizes (VA-ECLS A8Fr/V10Fr, A10Fr/V12Fr and A12Fr/V14Fr, VV-ECLS 13Fr, 16Fr, 19Fr, 20Fr and 23Fr) at 36°C. Real-time pressure and flow data were recorded for analysis. The use of a small-caliber venous cannula significantly increased the venous line pressure in the 2 pediatric circuits (P < 0.01). Shorter venous tubing lengths significantly reduced the venous line pressure at high flow rates (P < 0.01). The VV-ECLS circuit had larger negative pre-pump pressure drops (7.2 to -102.2 mm Hg) when compared to the VA-ECLS circuit (0.7 to -60.7 mm Hg). Selecting an appropriate venous cannula and a shorter venous tubing when feasible may significantly reduce the pressure drop of the venous line in pediatric VA-ECLS and VV-ECLS circuits and improve venous drainage.