Background: The vitalHEAT vH(2) (Dynatherm Medical, Inc., Fremont, California) system transfers heat through a single extremity using a combination of conductive heat (circulating warm water within soft fluid pads) with mild vacuum, which improves both vasodilation and contact between the heating element and the skin surface. We tested the hypothesis that core temperatures were not >0.5°C lower in patients warmed with the vitalHEAT system than with forced air.
Methods: Patients having general anesthesia for open abdominal surgery were randomly assigned to the circulating-water sleeve on 1 arm (n = 37) or an upper-body forced-air warming cover (n = 34). Patients were eligible to participate when body mass index was 20 to 36 kg/m(2), age was 18 to 75 years, and ASA physical status was 1 to 3. Intraoperative distal esophageal (core) temperatures were recorded. Repeated-measures analysis and 1-tailed t tests were used to assess noninferiority of vitalHEAT to forced air using a noninferiority δ of -0.5°C.
Results: Demographic and morphometric characteristics were similar, as were surgical details. Preoperative core temperatures were similar in each group. Intraoperative core temperatures were also similar with each warming system and were significantly noninferior during the first four hours of surgery. The observed difference in means was never more than about 0.2°C. After 4 hours of surgery, the average temperature was 36.3°C ± 0.6°C (mean ± sd) with the circulating-water sleeve (n = 18) and 36.4°C ± 0.5°C with forced air (n = 20), for a difference (95% confidence interval) of -0.21°C (-0.47, 0.06).
Conclusions: The 2 systems thus apparently transfer comparable amounts of heat. Both appear suitable for maintaining normothermia even during large and long operations.