Accuracy of skin temperature over carotid artery in estimation of core temperature in infants and young children during general anaesthesia.

Background and Aims: Core temperature monitoring is essential in children under general anaesthesia as they are more susceptible to hypothermia. We aimed to use skin temperature over the carotid artery (Tsk -carotid) with correction factors (Cf) to estimate core temperature. Primary outcome measure was to assess the sensitivity of Tsk -carotid with Cf for detecting hypothermia. Secondary outcome measure was to assess the specificity of Tsk -carotid with Cf for detecting hypothermia.

Methods: First consecutive 50 patients fulfilling the inclusion criteria were included in modelling group and next 60 in the validation group. In the modelling group, average estimation error between Tsk -carotid and Tnaso was calculated and Cf was derived by multiple regression analysis (body surface area to mass ratio, body fat %, room temperature, relative humidity and warm Gamgee). In the validation group, Cf derived was used to predict Tnaso using Tsk -carotid by the formula: Tnaso-predicted = Tsk -carotid + Cf. Bland-Altman plots were used to assess the agreement between Tsk -carotid with Cf and Tnaso in the validation group.

Results: The sensitivity for detecting hypothermia with the use of Tsk -carotid and Cf was 100%. The final Cf derived was 0.064 × (room temperature) -2.65. Most of the measurements fell within 95% confidence limit of Bland-Altman plot; 95% confidence interval (0.504-[-0.451]). The specificity of this method was 11%.

Conclusion: This method overestimated hypothermia in most cases and cannot be accurately used as a measure of core temperature monitoring perioperatively.