Figure 40-18 During the preinduction period (-120 to 0 minutes), volunteers were either actively warmed or passively cooled (no warming). At induction of anesthesia (time = 0 minutes), active warming was discontinued and volunteers were exposed to the ambient environment. Initial tympanic membrane temperatures were similar before each preinduction treatment. During the 60 minutes after induction of anesthesia, core temperature decreased less when volunteers were prewarmed. (ΔT = −1.1°C ± 0.3°C) than when the same volunteers were not warmed (ΔT = −1.9°C ± 0.3°C). Data are presented as means ± SD. (Redrawn from Hynson JM, Sessler DI, Moayeri A, et al: The effects of pre-induction warming on temperature and blood pressure during propofol/nitrous oxide anesthesia. Anesthesiology 79:219–228, 1993.)