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

Abstract

We aimed to evaluate correlation and agreement between noninvasive brain temperature (TBN) and invasive brain temperature (TBI) 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. TBN and TBI were measured using a double sensor method and an intracranial catheter, respectively. Pulmonary artery temperature (TP), esophageal temperature (TE), and rectal temperature (TR) were measured. Primary outcomes were correlation and agreement between TBN and TBI and secondary outcomes were correlation and agreement among TBN and other temperatures. The Pearson correlation coefficient (PCC) between TBN and TBI was 0.95 (p < 0.001) during the whole TTM phases. PCCs between TBN and TBI 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 TBN and TBI 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 TBN and TBI during the maintenance phase was higher than correlation between TBN and TE (PCC = 0.74, p < 0.001) or TP (PCC = 0.81, p < 0.001). The 95% LoAs were narrowest between TBN and TP in the induction phase (−0.58 to 0.11), between TBN and TBI in the maintenance phase (−0.54 to 0.18), and between TBN and TR 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.