Effects of PEEP on the thermoregulatory responses during TIVA in patients undergoing tympanoplasty

During general anesthesia, core temperature decreases, largely due to heat loss caused by peripheral vasodilation, resulting in heat redistribution to peripheral tissues. Multiple factors contribute to body temperature regulation during general anesthesia. It was reported that baroreceptor unloading by positive end-expiratory pressure (PEEP) attenuates anesthetically-induced hypothermia. So, we evaluated the effects of PEEP on thermoregulatory responses during total intravenous anesthesia (TIVA). Forty healthy patients scheduled for tympanoplasty were allocated two groups, Group ZEEP (zero end-expiratory pressure, n = 20) and Group PEEP (PEEP application of 5 cmH(2)O, n = 20). Ambient temperature was maintained at 22-24℃, and anesthesia was induced and maintained with propofol-remifentanil. The core temperature and the temperature difference between forearm and fingertip skin were monitored before and after the induction of general anesthesia having a duration of 180 minutes. The core temperature gradient (Ti-Tf) was higher in patients with ZEEP than with PEEP. The core temperature was maintained at a higher level in patients with PEEP. Additionally, the vasoconstriction threshold was higher in patients with PEEP. It seems that PEEP attenuates anesthetically-induced hypothermia during TIVA.