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 . kg(-1) . 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 the 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 II 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.