Regional variation in arterial saturation and oxygen delivery during venoarterial extracorporeal membrane oxygenation.

UNLABELLED Venoarterial extracorporeal membrane oxygenation (VA-ECMO) can be lifesaving in patients with cardiopulmonary collapse. However, observation studies have implied that oxygenated blood does not pass in a retrograde fashion from the VA-ECMO circuit to the aortic root and arch when the femoral artery (FA) is used. This study aims at accurately measuring the oxygen saturation in various arteries during VA-ECMO through different cannula sites. A total of 20 patients with VA-ECMO were in the study. Fourteen patients had FA cannulation, two patients received axillary arterial (AA) cannulation, and four patients received cannulation of the ascending aorta. Oxygen saturation was measured simultaneously in the radial artery and oxygenator outlet. In the patient group with FA cannulation, the oxygen saturation was lower in the radial artery (97%) when compared with the oxygenator outlet (> 99%). In the subset group of patients with severe lung dysfunction, oxygen saturation was even lower in the radial artery (73% saturation). In the patient group with AA cannulation, the oxygen saturation and partial oxygen pressure (PO2) in the oxygenator outlet and radial artery were similar (99% or greater). In the patient group with direct ascending aorta cannulation, the oxygen saturation and PO2 in the oxygenator outlet and radial artery were similar as well. Regional variations occur in the blood oxygen saturation depending on the site of the arterial cannulation in patients with VA-ECMO. With FA cannulation, the oxygen saturation in the radial artery is significantly lower than the one in the oxygenator outlet. This may imply that the coronaries and the brain receive hypoxic blood from the left ventricle. These results suggest that antegrade cannulation for VA-ECMO improves oxygen delivery to the proximal aorta distribution. KEYWORDS VA-ECMO, arterial oxygen saturation.