Impact of Venous Cannula Size and Venous Line Length on Venous Line Pressure in Pediatric VA-/VV-ECLS Circuits.

OBJECTIVE: 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.

METHODS: 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: 250-1,250 ml/min, VV-ECLS: 250-2,000 ml/min) using different venous tubing lengths (2 feet, 4 feet 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.

RESULTS: The use of a small-caliber venous cannula significantly increased the venous line pressure in the two 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 mmHg - -102.2 mmHg) when compared to the VA-ECLS circuit (0.7 mmHg - -60.7 mmHg).

CONCLUSIONS: 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. This article is protected by copyright. All rights reserved.