Regional Variation in Arterial Saturation and Oxygen Delivery during Venoarterial Extracorporeal Membrane Oxygenation

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.