Negative pressure rewarming vs. forced air warming in hypothermic postanesthetic volunteers

We compared changes in core temperature and systemic heat balance with a ne w negative pressure/wanning device (Vital Heat(R)) that uses negative press ure combined with heat to facilitate warming in vasoconstricted postoperati ve patients to those resulting from passive insulation or forced air. Seven healthy volunteers were anesthetized and cooled to a tympanic membrane tem perature near 34 degreesC. Anesthesia was discontinued and shivering was pr evented by using meperidine. The vasoconstricted volunteers were rewarmed f or 2 h using three randomly assigned methods: 1) Vital Heat(R) plus cotton blanket; 2) one layer of cotton blanket; 3) forced-air warming. Thermal flu x was recorded from 15 skin-surface sites; metabolic heat production was es timated from total body oxygen consumption. Metabolic heat production remai ned constant throughout the study. Systemic heat loss remained constant dur ing warming with cotton blankets but decreased significantly during the oth er treatments. Systemic heat balance increased significantly more with forc ed air (140 +/- 21 kcal) than with Vital Heat(R) (66 +/- 19 kcal) or cotton blankets (47 +/- 18 kcal). Core temperature increased no faster with Vital Heat(R) warming (1.3 +/- 0.4 degreesC) than with a cotton blanket (1.2 +/- 0.4 degreesC). In contrast, core temperature increased more rapidly with f orced air warming (2.6 +/- 0.6 degreesC). In this study we show that calori es from a negative pressure rewarming device are largely constrained to the forearm and that heat does not flow to the core thermal compartment.