Noninvasive Versus Invasive Brain Temperature Measurement During Targeted Temperature Management: A Preclinical Study in a Swine Cardiac Arrest Model.

We aimed to evaluate correlation and agreement between noninvasive brain temperature (T BN ) and invasive brain temperature (T BI ) measurement during targeted temperature management (TTM) in a swine cardiac arrest model. Defibrillation attempts were provided after 5 minutes of ventricular fibrillation and 12 minutes of cardiopulmonary resuscitation in five pigs. After return of spontaneous circulation, TTM was provided with induction and maintenance phases with a target temperature of 33°C for 6 hours and a rewarming phase with a rewarming rate of 1°C/h for 4 hours. T BN and T BI were measured using a double sensor method and an intracranial catheter, respectively. Pulmonary artery temperature (T P ), esophageal temperature (T E ), and rectal temperature (T R ) were measured. Primary outcomes were correlation and agreement between T BN and T BI and secondary outcomes were correlation and agreement among T BN and other temperatures. The Pearson correlation coefficient (PCC) between T BN and T BI was 0.95 ( p  < 0.001) during the whole TTM phases. PCCs between T BN and T BI during the induction, maintenance, and rewarming phases were 0.91 ( p  < 0.001), 0.88 ( p  < 0.001), and 0.94 ( p  < 0.001) and 95% limits of agreement (LoAs) between T BN and T BI were (-0.27°C to 0.78°C), (-0.18°C to 0.54°C), and (-0.93°C to 0.88°C), respectively. Correlation between T BN and T BI during the maintenance phase was higher than correlation between T BN and T E (PCC = 0.74, p  < 0.001) or T P (PCC = 0.81, p  < 0.001). The 95% LoAs were narrowest between T BN and T P in the induction phase (-0.58 to 0.11), between T BN and T BI in the maintenance phase (-0.54 to 0.18), and between T BN and T R in the rewarming phase (-0.96 to 0.84). Noninvasive brain temperature showed good correlation with invasive brain temperature during TTM in a swine cardiac arrest model. Correlation was highest during the rewarming phase and lowest during the maintenance phase. Agreement between the two measurements was not clinically acceptable.