The endocrinological responses of veno-venous extracorporeal membrane oxygenation on hypoxic fetal lambs.

OBJECTIVE:The purpose of this study was to observe endocrinological responses of veno-arterial and veno-venous extracorporeal membrane oxygenation (V-A and V-V ECMO) to support fetal oxygenation in utero. METHODS:An ECMO system with a centrifugal pump was applied to six chronically instrumented fetal lambs, at 126-134 days of gestation. Blood was obtained through a double-lumen catheter inserted into the right atrium. After oxygenation, the blood was returned through a single-lumen catheter into either the carotid artery (veno-arterial; V-A ECMO) or the right atrium (V-V ECMO). After fetal hypoxia had been experimentally produced, V-A ECMO or V-V ECMO was instituted to maintain fetal oxygenation. We compared fetal blood gases and concentrations of atrial natriuretic peptide (ANP), epinephrine and norepinephrine with both routes of ECMO. RESULTS:Fetal carotid artery pH did not change during hypoxemia, but decreased after instituting V-A ECMO and V-V ECMO. After instituting V-A ECMO or V-V ECMO for 30 min, oxygen partial pressure (pO2) in the fetal cranial carotid artery recovered from the hypoxic level. The ANP concentration in V-V ECMO was significantly lower than that in V-A ECMO. Fetal serum epinephrine and norepinephrine concentrations significantly increased in association with hypoxic stimulation. There was a further increase in fetal serum epinephrine concentration after instituting V-A ECMO. No significant difference in concentration was found after instituting V-V ECMO from that of after the institution of V-A ECMO. CONCLUSIONS:This study suggested that V-V ECMO may possibly be less invasive than V-A ECMO for fetal heart, because ANP, a cardiac distress index, was lower in V-V ECMO than in V-A ECMO.