[Anesthetic management during cardiac bypass in fetal lambs].

Objective: To summarize the anesthetic management in fetal lamb cardiac bypass.

Methods: Five ewes at 120-140 days of gestation were anesthetized intramuscularly with katamine hydrochloride, intubated and ventilated with a respirator. Anesthesia was maintained with fentanyl and vecuronium. Lactated Ringer's solution and magnesium sulfate were infused to maintain the mean blood pressure (MAP) over 70 mmHg and uterine relaxation. The fetal lambs received anesthesia with fentanyl and vecuronium intramuscularly via the uterine wall. Fetal cardiac bypass was established with pulmonary artery and right atrium cannulation, lasting for 30 min. The hemodynamic and blood gas data of the ewes and fetal lambs were recorded before bypass, at 30 min during bypass, and at 1 and 2 h after cessation of bypass. The pulse index of the umbilical artery (PIua) and the ewe's uterine artery (PIeu) were monitored simultaneously.

Results: The MAP and heart rate (HR) of the fetus remained normal during the anesthesia. PIua increased significantly after cessation of bypass (P<0.05). Although the fetal oxygen tension in the axillary artery remained normal, the fetal lambs showed hypercarbia and acidosis after cessation of bypass (P<0.05). The maternal MAP and HR remained normal. The PIeu decreased significantly during bypass (P<0.05) and recovered the normal level after cessation of bypass. The arterial blood gas of the ewes was normal during the experiment.

Conclusion: Maintaining high hemodynamics in the ewes, application of uterine relaxation and intensive care during anesthesia are crucial in anesthetic management of cardiac bypass in fetal lambs.