Background. A recent heat-balance study in volunteers suggested that greater efficacy of
circulating-water garments (CWGs) results largely from increased heat transfer across the
posterior skin surface since heat transfer across the anterior skin surface was similar with
circulating-water and forced-air. We thus tested the hypothesis that the combination of
a circulating-water mattress (CWM) and forced-air warming prevents core temperature
reduction during major abdominal surgery no worse than a CWG does.
Methods. Fifty adult patients aged between 18 and 85 yr old, undergoing major abdominal
surgery, were randomly assigned to intraoperative warming with a combination of forcedair
and a CWM or with a CWG (Allon ThermoWrap). Core temperature was measured in the
distal oesophagus. Non-inferiority of the CWM to the CWG on change from baseline to
median intraoperative temperature was assessed using a one-tailed Student’s t-test with
an equivalency buffer of 20.58C.
Results. Data analysis was restricted to 16 CWG and 20 CWM patients who completed the
protocol. Core temperature increased in both groups during the initial hours of surgery. We
had sufficient evidence (P¼0.001), to conclude that the combination of a CWM and forcedair
warming was non-inferior to a CWG in preventing temperature reduction, with mean
(95% CI) difference in the temperature change between the CWM and the CWG groups
(CWM2CWG) of 0.468C (20.098C, 1.008C).
Conclusions. The combination of a CWM and forced-air warming is significantly non-inferior
in maintaining intraoperative core temperature than a CWG.
Trial registry: This trial has been registered at clinical trials.gov, identifier: NCT 00651898.