ABSTRACT
This study was conducted on 60 patients undergoing open abdominal surgery under general anesthesia to evaluate the effect of premedication with H2 antagonists on thermoregulation. The patients were randomly allocated into three groups, each group consisted of 20 patients according to the premedication given. The first group was given a placebo [control group], the second group was given famotidine 40 mg tablet and the third group was given ranitidine 150 mg tablet at 1 hour before anesthesia. Induction of anesthesia was done by 1-2 ug/kg fentanyl, 5-7 mg/kg thiopental and endotracheal intubation was facilitated by vecuronium bromide 0.1 mg/kg. Anesthesia was maintained by nitrous oxide 66% in oxygen and isoflurane 0.6% to 0.8%. Nasopharyngeal temperature [core temp], forearm temperature and index finger temperature, hemodynamic parameters [heart rate and mean arterial blood pressure] were measured before induction [baseline], then every 15 minutes till the end of surgery. The results demonstrated that famotidine has central thermoregulatory inhibitory effect that augments core hypothermia and decrease vasoconstriction threshold