Novel Zero-Heat-Flux Deep Body Temperature Measurement in Lower Extremity Vascular and Cardiac Surgery.

Objective The aim of this study was to compare deep body temperature obtained using a novel noninvasive continuous zero-heat-flux temperature measurement system with core temperatures obtained using conventional methods. Design A prospective, observational study. Setting Operating room of a university hospital. Participants The study comprised 15 patients undergoing vascular surgery of the lower extremities and 15 patients undergoing cardiac surgery with cardiopulmonary bypass. Interventions Zero-heat-flux thermometry on the forehead and standard core temperature measurements. Measurements and Main Results Body temperature was measured using a new thermometry system (SpotOn; 3M, St. Paul, MN) on the forehead and with conventional methods in the esophagus during vascular surgery (n = 15), and in the nasopharynx and pulmonary artery during cardiac surgery (n = 15). The agreement between SpotOn and the conventional methods was assessed using the Bland-Altman random-effects approach for repeated measures. The mean difference between SpotOn and the esophageal temperature during vascular surgery was+0.08°C (95% limit of agreement –0.25 to+0.40°C). During cardiac surgery, during off CPB, the mean difference between SpotOn and the pulmonary arterial temperature was –0.05°C (95% limits of agreement –0.56 to+0.47°C). Throughout cardiac surgery (on and off CPB), the mean difference between SpotOn and the nasopharyngeal temperature was –0.12°C (95% limits of agreement –0.94 to+0.71°C). Poor agreement between the SpotOn and nasopharyngeal temperatures was detected in hypothermia below approximately 32°C. Conclusions According to this preliminary study, the deep body temperature measured using the zero-heat-flux system was in good agreement with standard core temperatures during lower extremity vascular and cardiac surgery. However, agreement was questionable during hypothermia below 32°C.