Intraoperative zero-heat-flux thermometry overestimates nasopharyngeal temperature by 0.39 °C: an observational study...

During surgery for congenital heart disease (CHD) temperature management is crucial. Vesical (T_ves) and nasopharyngeal (T_NPH) temperature are usually measured. Whereas T_ves slowly responds to temperature changes, T_NPH carries the risk of bleeding. The zero-heat-flux (ZHF) temperature monitoring systems SpotOn™ (T_SpotOn), and Tcore™ (T_core) measure temperature non-invasively. We evaluated accuracy and precision of the non-invasive devices, and of T_ves compared to T_NPH for estimating temperature. In this prospective observational study in pediatric and adult patients accuracy and precision of T_SpotOn, T_core, and T_ves were analyzed using the Bland-Altman method. Proportion of differences (PoD) and Lin´s concordance correlation coefficient (LCC) were calculated. Data of 47 patients resulted in sets of matched measurements: 1073 for T_SpotOn vs. T_NPH, 874 for T_core vs. T_NPH, and 1102 for T_ves vs. T_NPH. Accuracy was - 0.39 °C for T_SpotOn, -0.09 °C for T_core, and 0.07 °C for T_ves. Precisison was between - 1.12 and 0.35 °C for T_SpotOn, -0.88 to 0.71 °C for T_core, and - 1.90 to 2.05 °C for T_ves. PoD ≤ 0.5 °C were 71% for T_SpotOn, 71% for T_core, and 60% for T_ves. LCC was 0.9455 for T_SpotOn, 0.9510 for T_core, and 0.9322 for T_ves. Temperatures below 25.2 °C (T_SpotOn) or 27.1 (T_core) could not be recorded non-invasively, but only with T_ves. Trial registration German Clinical Trials Register, DRKS00010720.