Effect of Body Temperature on Cerebral Autoregulation in Acutely Comatose Neurocritically Ill Patients

Objectives: Impaired cerebral autoregulation following neurologic injury is a predictor of poor clinical outcome. We aimed to assess the relationship between body temperature and cerebral autoregulation in comatose patients. Design: Retrospective analysis of prospectively collected data. Setting: Neurocritical care unit of the Johns Hopkins Hospital. Patients: Eighty-five acutely comatose patients (Glasgow Coma Scale score of ≤ 8) admitted between 2013 and 2017. Interventions: None. Measurement and Main Results: Cerebral autoregulation was monitored using multimodal monitoring with near-infrared spectroscopy–derived cerebral oximetry index. Cerebral oximetry index was calculated as a Pearson correlation coefficient between low-frequency changes in regional cerebral oxygenation saturation and mean arterial pressure. Patients were initially analyzed together, then stratified by temperature pattern over the monitoring period: no change (< 1°C difference between highest and lowest temperatures; n = 11), increasing (≥ 1°C; n = 9), decreasing (≥ 1°C; n = 9), and fluctuating (≥ 1°C difference but no sustained direction of change; n = 56). Mixed random effects models with random intercept and multivariable logistic regression analysis were used to assess the association between hourly temperature and cerebral oximetry index, as well as between temperature and clinical outcomes. Cerebral oximetry index showed a positive linear relationship with temperature (β = 0.04 ± 0.10; p = 0.29). In patients where a continual increase or decrease in temperature was seen during the monitoring period, every 1°C change in temperature resulted in a cerebral oximetry index change in the same direction by 0.04 ± 0.01 (p < 0.001) and 0.02 ± 0.01 (p = 0.12), respectively, after adjusting for Paco₂, hemoglobin, mean arterial pressure, vasopressor and sedation use, and temperature probe location. There was no significant difference in mortality or poor outcome (modified Rankin Scale score of 4–6) between temperature pattern groups at discharge, 3, or 6 months. Conclusions: In acute coma patients, increasing body temperature is associated with worsening cerebral autoregulation as measured by cerebral oximetry index. More studies are needed to clarify the impact of increasing temperature on cerebral autoregulation in patients with acute brain injury.