[Air-convection heater for abdominal surgery. Study of the relation between surgical time and the efficacy of body temperature maintenance]. / Calentador por convección de aire en cirugía abdominal. Estudio de la relación tiempo quirúrgico-eficacia del mantenimiento de la temperatura corporal.

ABSTRACT

OBJECTIVES: 1) To quantify the efficacy of forced air warming for maintaining body temperature during general anesthesia of adults, and 2) to study the relation between the duration of surgery and the level of thermal protection provided by the device used. PATIENTS AND METHODS: We studied 30 adult patients of both sexes who were scheduled for abdominal surgery involving laparotomy. After three patients were excluded because surgery was unfeasible, the remaining 27 were allocated randomly to a control group (n = 14) or a group (n = 13) to be warmed by a Bair Hugger (Augustine Medical Inc.) heater. Esophageal temperature was checked every 30 min by one probe of a modular thermometric channel (Mon-a-therm) 6510 Mallincrodt, while ambient temperature was monitored by the second probe. RESULTS: Significant differences in esophageal temperature were observed between the two groups from the second hour after start of surgery, and the differences increased over time. Differences were observed at the end of surgery (Bair group 36.4 +/- 0.5 degrees C; control group 34.7 +/- 1.1 degrees C) and upon admission to the intensive care recovery unit (Biar group 36.3 +/- 0.6 degrees C; control 34.8 +/- 1.0 degrees C) (p < 0.0001). CONCLUSIONS: The Bair Hugger heater is effective during abdominal operations lasting two or more hours. The device not only prevented hypothermia from deepening during surgery, but also reversed hypothermia in spite of being used after anesthetic induction and in spite of the loss of heat produced by secondary vasodilation.