Position of draining venous cannula in extracorporeal membrane oxygenation for respiratory and respiratory/circulatory support in adult patients

Abstract

Extracorporeal membrane oxygenation (ECMO) is used in critically ill patients with severe pulmonary and/or cardiac failure. Blood is drained from the venous system and pumped through a membrane oxygenator where it is oxygenated. For pulmonary support, the blood is returned to the patient via a vein (veno-venous ECMO) and for pulmonary/circulatory support it is returned via an artery (veno-arterial ECMO).Veno-venous ECMO can be performed either with a single dual-lumen cannula or with two separate single-lumen cannulas. If the latter is chosen, flow direction can either be from the inferior caval vein (IVC) to the right atrium or the opposite. Earlier research has shown that drainage from the IVC yields less recirculation and therefore the IVC to right atrium route has become the standard in most centers for veno-venous ECMO with two cannulas. However, recent research has shown that recirculation can be minimized using a multistage draining cannula in the optimal position inserted via the right internal jugular vein and with blood return to the femoral vein. The clinical results with this route are excellent.In veno-arterial ECMO the most common site for blood infusion is the femoral artery. If venous blood is drained from the IVC, the patient is at risk of developing a dual circulation (Harlequin syndrome, North-South syndrome, differential oxygenation) meaning a poor oxygenation of the upper part of the body, while the lower part has excellent oxygenation. By instead draining from the superior caval vein (SVC) via a multistage cannula inserted in the right internal jugular vein this risk is neutralized.In conclusion, the authors argue that draining blood from the SVC and right atrium via a multistage cannula inserted in the right internal jugular vein is equal or better than IVC drainage both in veno-venous two cannula ECMO and in veno-arterial ECMO with blood return to the femoral artery.

Keywords: Differential hypoxemia; Draining cannula; Dual circulation; Flow direction; North-south syndrome; Recirculation; Veno-arterial ECMO; Veno-venous ECMO.

Fig. 1

Schematic drawing of the circuit in V-V ECMO. a Draining from the SVC/RA and infusing into the femoral vein; b draining from the IVC and infusing into the SVC. Preoxygenator saturation can be expected to be 70–80% depending on the amount of recirculation. OX oxygenator

Fig. 2

Schematic drawing of the circuit in V-A ECMO. a Draining from the SVC/RA and infusing into either femoral artery; b draining from the IVC and also infusing into either femoral artery. The patient has an ejecting heart and severely failing lungs. a Illustrates the situation where the highly saturated IVC blood enters the pulmonary circulation and is further ejected from the left ventricle to the upper part of the body. The poorly saturated SVC blood is, in turn, drained back to the ECMO machine. b Illustrates instead the situation when the highly saturated IVC blood is drained back to the ECMO machine. In this scenario the ECMO circulation is poorly mixed with the patient’s native circulation resulting into a dual circulation situation. OX oxygenator

Fig. 3

Schematic drawing exemplifying dual circulation in V-A ECMO with severe pulmonary failure when draining from the IVC and reinfusing into the femoral artery. Although preoxygenator saturation is acceptable at 60–80%, the arterial saturation in the aortic arch may be 50–70% and SVC saturation as low as 20–40%. The SVC desaturation may be unnoticed since the venous blood drained to the ECMO circuit mainly originates from the IVC, where venous saturations usually show high normal values. OX oxygenator