Efficacy of Head and Torso Rewarming Using a Human Model for Severe Hypothermia.

INTRODUCTION

To evaluate the rewarming effectiveness of a similar amount of heat (from a charcoal heater) applied to either the head or torso in a human model for severe hypothermia in which shivering is pharmacologically inhibited in mildly hypothermic subjects.

METHODS

Six male subjects were cooled on 3 different occasions, each in 8°C water for 60 min, or to a lowest core temperature of 35°C. Shivering was inhibited by intravenous meperidine (1.5 mg·kg), administered during the last 10 min of the cold-water immersion. Subjects then exited from the cold water, were dried, and were placed in a 3-season sleeping bag for 120 min in one of the following conditions: spontaneous rewarming only, charcoal heater on the head, or charcoal heater on the torso. Supplemental meperidine (to a maximum cumulative dose of 3.3 mg·kg) was administered as required during rewarming to suppress shivering.

RESULTS

No significant differences were found in the postcooling afterdrop amount or core rewarming rates among the 3 conditions (0.8°C·h). During the last 30 min of rewarming the net heat gain was significantly higher in the head (85.8±25.3 W) and torso (81.5±6.3 W) conditions compared with the spontaneous condition (56.9±12 W) (P<0.05).

CONCLUSIONS

In our study, head and torso warming had the same core rewarming rates when shivering was pharmacologically inhibited in mildly hypothermic subjects. Therefore, in nonshivering cold subjects, head warming is a viable alternative if torso warming is contraindicated (eg, when performing cardiopulmonary resuscitation or working on open chest wounds).