The effect of short time periods of pre‐operative warming in the prevention of peri‐operative hypothermia

TLDR

The study evaluated whether different durations of active pre‑operative skin‑surface warming prevent peri‑operative hypothermia and postoperative shivering. Two hundred patients undergoing 30–90‑minute general anaesthesia were randomized to passive insulation or forced‑air warming for 10, 20, or 30 minutes, with tympanic temperature measured and shivering visually graded. Pre‑warming for 10 or 20 minutes markedly reduced hypothermia (from 69% to 7–13%) and shivering (from 10 to 3–1 patients), with no additional benefit from 30‑minute warming.

Abstract

The aim of our study was to evaluate the performance of different durations of active pre-operative skin-surface warming (pre-warming) to prevent peri-operative hypothermia and postoperative shivering. We randomly assigned 200 patients, scheduled for surgery of 30-90 min under general anaesthesia, to receive passive insulation or forced-air skin surface warming for 10, 20 or 30 min. Body temperature was measured at the tympanic membrane. Shivering was graded by visual inspection. There were significant differences in changes of core temperature between the non-pre-warmed group and all the pre-warmed groups (p < 0.00001), but none between the three pre-warmed groups (p = 0.54). Without pre-warming, 38/55 (69%) patients became hypothermic (< 36 °C) at the end of anaesthesia, whereas only 7/52 (13%), 3/43 (7%) and 3/50 (6%) patients following 10, 20 or 30 min pre-warming, respectively, became hypothermic (p < 0.001 vs no pre-warming). Shivering was observed in 10 patients without, and in three, three and one patients with pre-warming in the respective groups (p = 0.02). Pre-warming of patients for only 10 or 20 min before general anaesthesia mostly prevents hypothermia and reduces shivering.