Cardiopulmonary bypass in ewe's fetus: advances and setbacks in our learning curve.

ABSTRACT

Fetal cardiac surgery represents a surgical challenge and several centers are attempting to establish a suitable methodology in animals. We present our experience with extra-corporeal bypass procedures in preterm and term sheep fetuses. Twenty-two fetuses (103-139 days gestation, mean 115 days gestation) underwent a 1-hour period of right heart-to-pulmonary artery extracorporeal circulation followed by 1 hour of observation. Animals were divided into group 1 and group 2, according to gestational age (above and below 0.85). Three pumps were used centrifugal without (group 1) reservoir, centrifugal with (group 2) reservoir, and roller with reservoir (group 2). Experiments were completed in 75% of fetuses in group 1 and in 37% of fetuses in group 2. Bleeding was the main cause of failure, especially for group 2. A slow deterioration of blood gas status was noted in group 1, while this trend could be partially reversed in group 2 with corrective measures. Complete heart bypass could not be achieved in either group, and residual fluctuations in arterial pressure were observed. During bypass, body temperature decreased more in group 2 than in group 1. We conclude that cardiac bypass is feasible over a short period in near-term fetuses. A successful outcome may also be obtained in younger fetuses, but better measures need to be implemented for the prevention of surgical bleeding.