Resistive heating is more effective than metallic-foil insulation in an experimental model of accidental hypothermia: A randomized controlled trial

Study objective: We study a resistive-heating blanket in a volunteer model of severe accidental hypothermia to evaluate differences in rates of rewarming, core temperature afterdrop, and body heat content and distribution during active and passive rewarming. Methods: Eight volunteers participated in a crossover design on 2 days. The volunteers were anesthetized and cooled to 33°C (91.4°F); anesthesia was subsequently discontinued, and shivering was prevented with meperidine. On one randomly assigned day, the volunteers were rewarmed passively with reflective foil (passive insulation), whereas on the other they were covered with a carbon fiber–resistive heating blanket set to 42°C (107.6°F; active rewarming). Trunk and head temperature and heat content were calculated from core (tympanic membrane) temperature. Peripheral (arm and leg) tissue temperature and heat content were estimated by using fourth-order regressions and integration over volume from 30 tissue and skin temperatures. Results: Core heat content increased 73±14 kcal (mean±SD) during 3 hours of active warming, but only 31±24 kcal with passive insulation, a difference of 41±20 kcal (95% confidence interval [CI] 27 to 55 kcal; P