Effects of the pulmonary cross - clamping at different temperature on the fetal heart

Abstract

Objective To determine the protective effects of mild hypothermia on the fetal heart of the pulmonary cross-clamping model. Methods Eighteen ewes at 120 to 140 days of gestation were randomly divided into hypothermic group (group H, n=6), normothermic group (group N, n=6) and control group (group C, n=6). We maintained the fetal temperature of the group N and group C at 39 ℃ by amniotic fluid bypass. We cooled and then maintained the group H fetuses at 32 ℃. All the fetuses in the 3 groups were performed sternotomy. Then the main pulmonary artery was cross-clamped in the group H and group N for 30 min. Fetuses in the group H were rewarmed to temperature of 39 ℃ after the release of the clamp. Fetal heart rate, blood pressure, plasma creatine kinase MB (CK-MB), and plasma cardiac troponin I (cTnI) were recorded before fetal sternotomy (T1), 30 min after pulmonary cross-clamping (T2), 1 h after the release of the cross-clamp (T3), and 2 h after the release of the cross-clamp (T4). Results All the mothers and the fetuses were alive in the 3 groups. The heart rate, blood pressure and blood gas data of the mothers were normal during the experiments. The heart rate and blood pressure among the 3 groups had no significant difference (P>0.05). There was no significant difference in plasma CK-MB among the 3 groups (P>0.05). The difference in plasma cTnI among the 3 groups was significant (P<0.05), and the group N had the highest mean value. The pathological and the ultrastructural exams of the fetal heart after the experiments showed that the structural changes in the group N were more significant than in the group H. Conclusion The fetal pulmonary cross-clamping model had significant influence on the fetal heart. Mild hypothermia created by amniotic fluid bypass could attenuate the lesions caused by the cross-clamping of the main pulmonary artery. Key words: Fetal lamb; Cardiac surgery; Hypothermia