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.