Recirculation in Extracorporeal Membrane Oxygenation: The Warning Comes From the Cannula

We are writing to point out a simple clinical sign in a pedagogic way, about recirculation in venovenous extracorporeal membrane oxygenation (ECMO). These last years, ECMO has emerged as a rescue therapy in severe acute respiratory distress syndrome (ARDS). Extracorporeal membrane oxygenation effectiveness can decrease if a large amount of reinfused oxygenated blood is immediately aspirated by the drainage cannula instead of being delivered in the patient circulation. It is the so-called recirculation phenomenon, which depends on ECMO pump flow, cardiac output, right atrial volume, and position of the cannulas. Misplacement of the cannulas is one of the main avoidable causes of such dysfunction. Various techniques exist for measuring recirculation, but few techniques are described to detect it. We describe here a visual sign easy to detect of ECMO recirculation due to cannula misplacement.

In conclusion, poor oxygenation under ECMO with alternation of bright red and dark red blood in the drainage cannula must refer to recirculation by cannula misplacement. Transesophageal echocardiography must be performed first when there is a lack of oxygenation during venovenous ECMO.