Forced-air surface warming versus oesophageal heat exchanger in the prevention of peroperative hypothermia

Background: In a prospective, randomized, placebo-controlled study we investigated the efficacy of 2 different heating methods in 24 patients undergoing abdominal surgery of at least 2 h expected duration.
Methods: Group I: control, no active warming. Group II: forced-air surface warming on upper extremities and upper thorax. Group III: warming with oesophageal heat exchanger. All patients had a standardized, combined general and epidural anaesthesia. Core and skin temperatures were measured at induction of general anaesthesia, and subsequently every 30 min, and changes in total body temperature were calculated.
Results: There were no statistically significant differences between the 3 groups regarding demographic data. Patients in groups I and III developed hypothermia, while this was not the case with patients in group II. When using analysis of variance with repeated measurements, there was no significant difference in core temperature, comparing group I and group III ( P =0.299) or the interaction between time and treatment of these groups ( P =0.373). As a consequence, data from groups I and III were pooled and regarded as an internal group on the one hand, and group II as an external group on the other hand. Core temperature, the mean skin temperature and total body temperature were significantly different comparing the internal group and the external group. The interaction between time and treatment was likewise found to be significantly different.
Conclusions: We conclude that in major abdominal procedures lasting 2 h or more, serious hypothermia develops unless effective measures to prevent hypothermia are used. Forced-air warming of the upper part of the body is effective in maintaining normothermia in these patients, while central heating with an oesophageal heat exchanger, at least in its present form, does not suffice to prevent hypothermia.