Comparison of maternal and fetal cardiovascular functions in acute and chronic experiments in the sheep

Abstract

Comparative studies have been made of various maternal and fetal circulatory functions and blood respiratory gases and pH obtained from pregnant sheep under acute experimental condition and from chronically instrumented animals. The maternal and fetal values observed in pregnant animals studied under pentobarbital anesthesia were compared to those observed in ewes studied under spinal anesthesia. In addition, the impact of various anesthetic agents on the behavior of maternal and fetal vasomotor tones and regional circulation was investigated. The data show that anesthetic agents affect cardiovascular functions in different ways. Some anesthetic agents abolish totally or partially maternal and fetal neural reflexes controlling circulatory functions; they also alter the vascular responses to vasoactive substances. Despite these alterations, the values for maternal and fetal circulatory functions in the acute anesthetized animal were not significantly different from those observed in the chronically instrumented, unanesthetized animal. In terms of research objectives, the data was used to discuss: (a) the criteria for defining the animal's health condition; (b) knowledge of the effects of anesthesia on a given maternal and fetal function; (c) the place of the acute and the chronic experimental preparation; and (d) the care to be observed in comparing data with the published literature.