Intraoperative zero-heat-flux thermometry overestimates esophageal temperature by 0.26 °C: an observational study in 100 infants and young children

Abstract

In pediatric anesthesia, deviations from normothermia can lead to many complications, with infants and young children at the highest risk. A measurement method for core temperature must be clinically accurate, precise and should be minimally invasive. Zero-heat-flux (ZHF) temperature measurements have been evaluated in several studies in adults. We assessed the agreement between the 3M Bair Hugger™ temperature measurement sensor (TZHF) and esophageal temperature (TEso) in children up to and including 6 years undergoing surgery with general anesthesia. Data were recorded in 5 min-intervals. We investigated the accuracy of the ZHF sensor overall and in subgroups of different age, ASA classification, and temperature ranges by Bland–Altman comparisons of differences with multiple measurements. Change over time was assessed by a linear mixed model regression. Data were collected in 100 children with a median (1st–3rd quartile) age of 1.7 (1–3.9) years resulting in 1254 data pairs. Compared to TEso (range from 35.3 to 39.3 °C; median 37.2 °C), TZHF resulted in a mean bias of +0.26 °C (95% confidence interval +0.22 to +0.29 °C; 95% limits of agreement −0.11 to +0.62 °C). Lin’s concordance correlation coefficient was 0.89. There was no significant or relevant change of temperature over time (0.006 °C per hour measurement interval, p = 0.199) and no relevant differences in the subgroups. Due to the mean bias of +0.26 °C in TZHF, the risk of hypothermia may be underestimated, while the risk of hyperthermia may be overestimated. Nevertheless, because of its high precision, we consider ZHF valuable for intraoperative temperature monitoring in children and infants.

Modeling iatrogenic intraoperative hyperthermia from external warming in children: A pooled analysis from two prospective observational studies

“…For this reason, the pediatric care warming strategy is still aggressive and aims at preventing hypothermia rather than hyperthermia, resulting in unintended iatrogenic hyperthermia in up to 26.5% of cases among children between 1 and 2 years of age 8 . This finding is supported by two recent prospective observational studies conducted by our study group, 12,13 leading us to investigate whether and how the warming strategy currently used could contribute to a steady increase in core temperature over time.…”

Perioperative Hypothermia in Children

“…On the other hand, some studies demonstrate that with an adequate protocol, hypothermia rates can be below 10% [ 14 , 15 , 16 , 17 ], even in preterm infants [ 18 ]. Thus, it seems that the rate of perioperative hypothermia depends more on the actual warming strategy, and less on patient factors, regardless of age or surgical procedure.…”

“…Ideally, a non-invasive, quick to apply measurement system would be preferable, which could be used in the entire perioperative period [ 17 ]. Presently, several non-invasive thermometers are available, and are gaining more and more interest in children’s medicine [ 17 , 72 , 73 ]. However, to date, neither technique has been evaluated thoroughly in children [ 74 ].…”

“…This would correspond to an infusion rate of about 700 mL/h in an adult weighing 70 kg, and several guidelines for the prevention of perioperative hypothermia [ 1 , 77 ] recommend infusion warming in adults for high infusion rates of >500 mL/h. However, many paediatric anaesthesiologists do not use infusion warming for the background infusion and do not have high hypothermia rates [ 17 , 81 , 82 , 88 , 89 ]. The continuous heat losses from the maintenance infusion can usually be offset by forced-air warming.…”

“…Especially during longer-lasting operations in small children, forced-air warming can lead to overheating [ 17 , 81 , 82 , 88 , 112 ]. Intraoperative hyperthermia has been associated with SSI in neonates and infants [ 57 ] and is generally undesirable.…”