Fructose administration increases intraoperative core temperature by augmenting both metabolic rate and the vasoconstriction threshold

Background: The authors tested the hypothesis that intravenous fructose ameliorates intraoperative hypothermia both by increasing metabolic rate and the vasoconstriction threshold (triggering core temperature). Methods: Forty patients scheduled to undergo open abdominal surgery were divided into two equal groups and randomly assigned to intravenous fructose infusion (0.5 g center dot kg(-1) center dot h(-1) for 4 h, starting 3 h before induction of anesthesia and continuing for 4 h) or an equal volume of saline. Each treatment group was subdivided: Esophageal core temperature, thermoregulatory vasoconstriction, and plasma concentrations were determined in half, and oxygen consumption was determined in die remainder. Patients were monitored for 3 h after induction of anesthesia. Results: Patient characteristics, anesthetic management, and circulatory data were similar in the four groups. Mean final core temperature (3 h after induction of anesthesia) was 35.7 degrees +/- 0.4 degrees C (mean +/- SD) in the fructose group and 35.1 degrees +/- 0.4 degrees C in the saline group (P = 0.001). The vasoconstriction threshold was greater in the fructose group (36.2 degrees +/- 0.3 degrees C) than in the saline group (35.6 degrees +/- 0.3 degrees C; P < 0.001). Oxygen consumption immediately before anesthesia induction in the fructose group (214 +/- 18 ml/min) was significantly greater than in the saline group (181 +/- 8 ml/min; P < 0.001). Oxygen consumption was 4.0 l greater in the fructose patients during 3 h of anesthesia; the predicted difference in mean body temperature based only on the difference in metabolic rates was thus only 0.4 degrees C. Epinephrine, norepinephrine, and angiotensin H concentrations and plasma renin activity were similar in each treatment group. Conclusions: Preoperative fructose infusion helped to maintain normothermia by augmenting both metabolic heat production and increasing the vasoconstriction threshold.