BACKGROUND: Redistribution hypothermia can be modified by the effects of induction anesthesia on the systemic vascular resistance. This study compared the effects of etomidate and propofol on redistribution hypothermia during general anesthesia.

METHODS: Forty patients were randomly allocated into one of two groups, based on the induction agent used: Group E (n = 20) received 0.2 mg/kg of etomidate and group P (n = 20) received 2.5 mg/kg propofol. After intubation, anesthesia was maintained with sevoflurane and 50% nitrous oxide in oxygen in both groups. The core and peripheral temperatures were measured, and the peripheral temperature gradients (forearm minus fingertip) were used as an index of an arteriovenous shunt.

RESULTS: The patients in both groups demonstrated intense vasoconstriction prior to the induction of anesthesia with similar skin-temperature gradients. After induction, group P showed more rapid and significant vasodilation than group E (P = 0.02). The difference in vasodilation between the two groups disappeared from 5 minutes after intubation. The pre-induction core temperatures were similar in both groups. After induction, the core temperatures in group P were consistently lower than those in group E (P < 0.01). The core temperatures during the first hour of anesthesia decreased by 1.5 ± 0.4 ℃ in group P but only by 0.9 ± 0.4 ℃ in group E.

CONCLUSIONS: Propofol caused more rapid and aggravated redistribution hypothermia during surgery than etomidate due to the earlier arteriovenous shunt vasodilation.