What is a requirement for V-AV ECMO flow?

In V-AV ECMO (veno-arteriovenous extracorporeal membrane oxygenation), the total flow of the system must be sufficient to meet the metabolic needs of the patient and ensure effective oxygenation and carbon dioxide removal. A minimum total flow of 4 liters is necessary to provide adequate support for maintaining hemodynamics and ensuring tissue perfusion.

This requirement is based on the physiological demands of the body and the efficiency of the ECMO system in facilitating gas exchange. A total flow of 4 liters indicates that the system can adequately sustain the patient's needs, particularly in cases of severe respiratory or cardiac failure where ECMO is indicated. Additionally, maintaining this flow helps to ensure adequate drainage and delivery of blood through the membrane oxygenator, thus facilitating effective oxygenation.

The other possible choices involve specific flow rates per cannula or drainage flow that may not adequately reflect the total circulatory support needed in V-AV ECMO. Having only 2 or 3 liters per cannula does not guarantee sufficient overall flow, nor would a minimum flow of 1 liter for drainage be adequate for this type of ECMO support.