Tracheal temperature for monitoring body temperature during mild hypothermia in pigs

Aim of the study: Out-of-hospital induction of mild therapeutic hypothermia after cardiac arrest needs easy to use and accurate body temperature monitoring. The aim of the study was to evaluate the best temperature probe position on a specially designed tracheal tube, as compared to pulmonary artery temperature (Tpa) during cooling to mild hypothermia in pigs. Methods: Eight swine (29-38 kg) were anesthetized and intubated with an endotracheal tube with three temperature probes: T1 was attached to the wall of the tube, 1 cm proximal to the cuff-balloon, without contact to the mucosa; T2 and T3 were placed on the cuff-balloon with tight contact to the mucosa, T3 was covered by a small plastic tube to protect the mucosa against mechanical alterations. Body temperature was measured with a pulmonary artery catheter. Pigs were cooled from Tpa 38.5 to 33.0 degrees C with fast surface and slow endovascular cooling in a crossover design. To assess hysteresis, areas under the curve (AUC) were compared. Data are presented as mean and 95% confidence intervals. Results: Temperatures were not different either during fast surface (T1-Tpa: 0.1[-0.3 to 0.5]degrees C, T2-Tpa: 0.2[0.0 to 0.4] degrees C, T3-Tpa: 0.4[0.1 to 0.7] degrees C) or slow endovascular (T1-Tpa: -0.3[-0.5 to 0.2]degrees C, T2-Tpa: -0.1[-0.3 to 0.0]degrees C, T3-Tpa: -0.1 [-0.5 to 0.3]degrees C) cooling. There was no difference in hysteresis related to the location of the temperature probes. Faster surface cooling correlated with a larger but not significantly different hysteresis between the probes. Conclusions: Tracheal temperature is an accurate surrogate for body temperature during fast and slow cooling to mild hypothermia in pigs and regardless of the location of the temperature probe on the tube. (C) 2009 Elsevier Ireland Ltd. All rights reserved.