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

OBJECTIVE: The purpose of this study was to determine the applicability of veno-venous extracorporeal membrane oxygenation (V-V ECMO) to support fetal oxygenation in utero. METHODS: An ECMO system with a centrifugal pump was applied to ten chronically instrumented fetal lambs, at 126 or 127 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 with both routes of ECMO. RESULTS: Oxygen partial pressure (pO(2)) in the fetal cranial carotid artery decreased to 12.9 +/- 0.6 mmHg after reducing the fraction inspiratory oxygen of the mother. After instituting V-A ECMO, pO(2) was found to be 23.5 +/- 2.6 mmHg; after instituting V-V ECMO, pO(2) was found to be 20.3 +/- 1.9 mmHg. Thus, fetal acidosis increased under both procedures. Fetal heart rate and blood pressure were not altered significantly during the experiments. CONCLUSIONS: This study indicates that V-V ECMO could more effectively and less traumatically maintain oxygenation in hypoxic fetal lambs.