Concordance of Brain and Core Temperature in Comatose Patients After Cardiac Arrest

Comatose patients after cardiac arrest should receive active targeted temperature management (TTM), with a goal core temperature of 32-36°C for at least 24 hours. Small variations in brain temperature may confer or mitigate a substantial degree of neuroprotection, which may be lost at temperatures near 37°C. The purpose of this study was to define the relationship between brain and core temperature after cardiac arrest through direct, simultaneous measurement of both. We placed intracranial monitors in a series of consecutive patients hospitalized for cardiac arrest at a single tertiary care facility within 12 hours of return of spontaneous circulation to guide postcardiac arrest care. We compared the absolute difference between brain and core (esophageal or rectal) temperature measurements every hour for the duration of intracranial monitoring and tested for a lag between brain and core temperature using the average square difference method. Overall, 11 patients underwent simultaneous brain and core temperature monitoring for a total of 906 hours of data (Median 95; IQR: 15-118 hours per subject). On average, brain temperature was 0.34C° (95% confidence interval [CI] 0.31-0.37) higher than core temperature. In 7% of observations, brain temperature exceeded the measured core temperature ≥1°C. Brain temperature lagged behind core temperature by 0.45 hours (95% CI = -0.27-1.27 hours). Brain temperature averages 0.34°C higher than core temperature after cardiac arrest, and is more than 1°C higher than core temperature 7% of the time. This phenomenon must be considered when carrying out TTM to a goal core temperature of <36°C.