A fetal lamb model of temperature reduction through amniotic fluid

Abstract

Objective To establish a fetal lamb model of temperature reduction through amniotic fluid and study the influence on the fetus and ewe. To search for an effective and safe method to change the body temperature of fetal lamb. Methods Six ewes at 120 to 140 days of gestation were anesthetized intramuscularly with katamine hydrochloride, incubated and ventilated with a respirator. Anesthesia was maintained with fentanyl and vecuronium. Transfusion of Lactated Ringer's solution and magnesium sulfate were made to maintain the mean blood pressure over 70 mmHg and uterine relaxation. A midline laparotomy was performed and the uterus was exposed. Fetal lamb received fentanyl and vecuronium anesthesia drugs intramuscularly via uterine. A hysterotomy was made after the disappear of fetal movement. A plastic tube was put into utero and the pipe was connected with the variable temperature unit and water tank, which could pump warm and cold normal saline into utero and change the temperature of amniotie fluid. Thus the temperature of the fetus could be regulated. The heart rate, blood pressure and arterial blood gas data of mothers and fetus were recorded. Results The average body weight of fetal lamb was (1.76±0.25) kg and that of maternal lamp was(25.00±5.90)kg. All the ewes and the fetal lambs were kept alive during the experiment.signs of ewes were stable. The heart rate and blood pressure were normal, and the data of arterial blood gas analysis were in their physiological level. The heart rate and blood pressure of fetal lambs were also stable during the experiment. The data of arterial blood gas analysis of fetal lambs were also in their physiological level. The pH value decreased significantly and PaCO2increased remarkably when the temperature decreased. When the nasopharyngeal temperature of fetal lambs reached 28℃, the pH value of arterial blood sample was 7.29±0.05, which was significantly lower than that before temperature reduction 7.41±0.03(P<0.05). The PaCO2 of arterial blood sample was(51.67±7.06)mmHg, which was significantly higher than that before temperature reduction (48.5±6.63) mmHg(P<0.05). All the above index could recover after the intrauterine temperature increase. However, these index could not reach the level as those before experiment. Conclusion Influence on ewes during the experiement is very little. The experiment would affect the metabolism of the fetal lamb. The temperature of fetal lamb can be regulated effectively and safely by amniotie fluid temperature changing. Key words: Model, animal; Fetus; Lamb