Increased Heat Generation in Postcardiac Arrest Patients During Targeted Temperature Management Is Associated With Better Outcomes

Objectives: Assess if amount of heat generated by postcardiac arrest patients to reach target temperature (Ttarget) during targeted temperature management is associated with outcomes by serving as a proxy for thermoregulatory ability, and whether it modifies the relationship between time to Ttarget and outcomes. Design: Retrospective cohort study. Setting: Urban tertiary-care hospital. Patients: Successfully resuscitated targeted temperature management–treated adult postarrest patients between 2008 and 2015 with serial temperature data and Ttarget less than or equal to 34°C. Interventions: None. Measurements and Main Results: Time to Ttarget was defined as time from targeted temperature management initiation to first recorded patient temperature less than or equal to 34°C. Patient heat generation ("heat units") was calculated as inverse of average water temperature × hours between initiation and Ttarget × 100. Primary outcome was neurologic status measured by Cerebral Performance Category score; secondary outcome was survival, both at hospital discharge. Univariate analyses were performed using Wilcoxon rank-sum tests; multivariate analyses used logistic regression. Of 203 patients included, those with Cerebral Performance Category score 3–5 generated less heat before reaching Ttarget (median, 8.1 heat units [interquartile range, 3.6–21.6 heat units] vs median, 20.0 heat units [interquartile range, 9.0–33.5 heat units]; p = 0.001) and reached Ttarget quicker (median, 2.3 hr [interquartile range, 1.5–4.0 hr] vs median, 3.6 hr [interquartile range, 2.0–5.0 hr]; p = 0.01) than patients with Cerebral Performance Category score 1–2. Nonsurvivors generated less heat than survivors (median, 8.1 heat units [interquartile range, 3.6–20.8 heat units] vs median, 19.0 heat units [interquartile range, 6.5–33.5 heat units]; p = 0.001) and reached Ttarget quicker (median, 2.2 hr [interquartile range, 1.5–3.8 hr] vs median, 3.6 hr [interquartile range, 2.0–5.0 hr]; p = 0.01). Controlling for average water temperature between initiation and Ttarget, the relationship between outcomes and time to Ttarget was no longer significant. Controlling for location, witnessed arrest, age, initial rhythm, and neuromuscular blockade use, increased heat generation was associated with better neurologic (adjusted odds ratio, 1.01 [95% CI, 1.00–1.03]; p = 0.039) and survival (adjusted odds ratio, 1.01 [95% CI, 1.00–1.03]; p = 0.045) outcomes. Conclusions: Increased heat generation during targeted temperature management initiation is associated with better outcomes at hospital discharge and may affect the relationship between time to Ttarget and outcomes. This study was performed at Beth Israel Deaconess Medical Center, Boston, MA. Supplemental digital content is available for this article. Direct URL citations appear in the printed text and are provided in the HTML and PDF versions of this article on the journal's website (https://ift.tt/29S62lw). Ms. Uber disclosed she is a fellow supported by the Sarnoff Cardiovascular Research Foundation. Dr. Cocchi is supported by the American Heart Association (15SDG22420010). Dr. Donnino received support for article research from the National Institutes of Health (1K24HL127101) and is supported by the American Heart Association (14GRNT20002). The remaining authors have disclosed that they do not have any potential conflicts of interest. For information regarding this article, E-mail: aj.uber@gmail.com Copyright © by 2018 by the Society of Critical Care Medicine and Wolters Kluwer Health, Inc. All Rights Reserved.

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