Extracorporeal Membrane Oxygenation

Abstract

Background: Veno-venous extracorporeal membrane oxygenation (VV-ECMO) and veno-arterial extracorporeal membrane oxygenation (VA-ECMO), also known as extracorporeal life support (ECLS), can both be used to treat patients with acute pulmonary or cardiovascular failure.

Methods: This review is based on publications retrieved by a selective search in PubMed on the topics of cardiogenic shock and acute pulmonary failure, also known as the acute respiratory distress syndrome (ARDS), as well as on ECMO. Attention was given chiefly to randomized, controlled trials and guidelines.

Results: Initial findings from prospective, randomized trials of VV-ECMO are now available. Trials of ECLS therapy are now in progress or planned. A meta-analysis of two randomized, controlled trials of VV-ECMO for ARDS revealed more frequent survival 90 days after randomization among patients treated with VV-ECMO, compared to the control groups (36% vs. 48%; RR = 0.75 [95% confidence interval 0.6; 0.94]). For selected patients, after evaluation of the benefit-risk profile, VV-ECMO is a good treatment method for severe pulmonary failure, and ECLS for cardiogenic shock and resuscitation. The goal is to secure the circulation so that native heart function can be stabilized in the patient's further course or a permanent left-heart support system can be implanted, or else to support lung function until recovery.

Conclusion: ECMO is a valid option in selected patients when conservative treatment has failed.

Figure 1

Different cannulations for VV-ECMO and ECLS a) Veno-venous ECMO. A cannula is usually inserted via the femoral vein so that its tip lies at the level of the renal veins or the inferior vena cava near the right atrium. The drained blood is oxygenated, decarboxylated, and returned to the venous system through a cannula located in the jugular vein an adequate distance away from the draining cannula. b) Femoral veno-arterial ECMO/ECLS. A cannula is inserted via the femoral vein so that its tip lies at the level of the right atrium. The drained blood is subsequently oxygenated and decarboxylated and returned to the arterial system via a cannula in the femoral artery. An antegrade leg perfusion cannula has also been inserted to prevent limb ischemia. VV-ECMO, veno-venous extracorporeal membrane oxygenation; ECLS, extracorporeal life support

Figure 2

Femoral veno-arterial ECMO/ECLS and additional femoral trans-aortic microaxial pump: A cannula is inserted via the femoral vein so that its tip lies at the level of the right atrium. The drained blood is oxygenated, decarboxylated, and returned to the arterial system via a cannula in the femoral artery. A microaxial pump, inserted via the femoral artery and through the aortic valve into the heart, pumps blood from the left ventricle into the aortic root. ECLS, extracorporeal life support; ECMO, extracorporeal membrane oxygenation

Figure 3

Kaplan-Meier curves from recently published ECLS trials, modified from Yannopoulos et al. and Schrage et al. (14, 16). (a) Survival after ECLS-assisted versus conventional resuscitation: data from the prospective, randomized ARREST trial. (b) Mortality after left ventricular unloading during ECLS: data from a retrospective registry study. CI, confidence interval; ECLS, extracorporeal life support; ECMO, extracorporeal membrane oxygenation; eCPR, ECLS-supported cardiopulmonary resuscitation; lvU, left ventricular unloading

eFigure 1

Thoracic veno-arterial ECMO/ECLS. A cannula is inserted via the right atrial appendage into the right atrium. Blood is drained, oxygenated and decarboxylated, and then returned to the arterial system through a cannula in the ascending aorta. The cannulae are led out of the chest and the chest is provisionally closed. Definitive chest closure is performed after weaning from ECLS and decannulation. ECLS, extracorporeal life support; ECMO, extracorporeal membrane oxygenation

eFigure 2

Axillary veno-arterial ECMO/ECLS. A cannula is inserted via the femoral vein so that its tip lies in the right atrium. The drained blood is oxygenated, decarboxylated, and returned to the arterial system via a prosthesis anastomosed to the axillary artery. ECLS, extracorporeal life support; ECMO, extracorporeal membrane oxygenation.