Immunology

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Abstract

The effect of maternal hyperthermia on uterine activity and maternal and fetal cardiovascular and acid-base state has been investigated in the pregnant baboon. Twentysix near-term animals were used. Under nitrous oxide and halothane anesthesia, the uterus was opened and catheters placed in maternal and fetal arteries and veins and in the amniotic cavity; thermocouples were implanted in the maternal colon and fetal esophagus. The uterus and the abdominal wall of the mother were then closed. In twelve animals maternal temperature was raised to between 41 and 42°C by applying external heat. Hyperthermia was maintained for 1 h, then decreased to 38°C. Three animals were given pyrogen intravenously. The remaining eleven animals served as normothermic controls with body temperature at 38 QC. The temperature gradient between fetus and mother (LlTF-M) was 0.47"C under steadystate conditions, in both the control and experimental groups when the maternal temperature was 38°C. In the externally induced hyperthermic group, LlTF-M rose to 0.75°C at 4rC. Pyrogen failed to increase maternal temperature over rc; LlTF-M increased initially, then decreased and reversed as the fetus deteriorated. Hyperthermia and pyrogen caused a significant increase in uterine activity; a metabolic acidosis developed in the mother and fetus and a profound hypoxia developed in the fetus. There was also a marked fall in blood pressure and a rise in heart rate in both mother and fetus; late deceleration of the fetal heart rate occurred at a higher pHa and oxyhen level than previously observed under normothermic conditions. During the course of externally induced hyperthermia, major complications were observed; two out of twelve fetuse"s. died and one mother developed heat prostration and shock. In the pyrogen group, all fetuses died during the study, as did two mothers shortly after the experiment. From these experiments it is concluded that maternal hyperthermia causes a marked increase in uterine activity, leading to fetal deterioration. Accepted: June 30, 1974.