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OBJECTIVES: The optimal target temperature during targeted temperature management for patients after cardiac arrest remains under debate. The aim of this study was to evaluate the association between targeted temperature management at lower target temperatures and the neurologic outcomes among patients classified by the severity of postcardiac arrest syndrome. DESIGN: A multicenter observational study from the out-of-hospital cardiac arrest registry of the Japanese Association for Acute Medicine, which is a nationwide prospective registry of out-of-hospital cardiac arrest patients. SETTING: A total of 125 critical care medical centers or hospitals with an emergency care department across Japan. PATIENTS: A total of 1,111 out-of-hospital cardiac arrest patients who had received targeted temperature management. MEASUREMENTS AND MAIN RESULTS: We divided all 1,111 postcardiac arrest syndrome patients treated with targeted temperature management into two groups: those who received targeted temperature management at a lower target temperature (33–34°C) and those who received targeted temperature management at a higher target temperature (35–36°C). In regard to classification of the patients, we divided the patients into three categories of severity (low, moderate, and high severities) using the risk classification tool, post-Cardiac Arrest Syndrome for Therapeutic hypothermia, which was previously validated. The primary outcome was the percentage of patients with a good neurologic outcome at 30 days, and the secondary outcome was the survival rate at 30 days. Multivariate analysis showed that targeted temperature management at 33–34°C was significantly associated with a good neurologic outcome and survival at 30 days in the moderate severity (odds ratio, 1.70 [95% CI, 1.03–2.83] and 1.90 [95% CI, 1.15–3.16], respectively), but not in the patients of low or high severity (pinteraction = 0.033). Propensity score analysis also showed that targeted temperature management at 33–34°C was associated with a good neurologic outcome in the moderate-severity group (p = 0.022). CONCLUSIONS: Targeted temperature management at 33–34°C was associated with a significantly higher rate of a good neurologic outcome in the moderate-severity postcardiac arrest syndrome group, but not in the low- or high-severity group.

Introduction: There are no established risk classification for post-cardiac arrest syndrome (PCAS) patients at the Emergency Department (ED) undergoing targeted temperature management (TTM). The aim of this study was to externally validate a simplified version of our prognostic score, the "post-Cardiac Arrest Syndrome for Therapeutic hypothermia score" (revised CAST [rCAST]) and estimate the predictive accuracy of the risk classification based on it. Methods: For the external validation, we used data from an out-of-hospital cardiac arrest (OHCA) registry of the Japanese Association for Acute Medicine (JAAM), which is a multicenter, prospective registry of OHCA patients across Japan. Eligible patients were PCAS patients treated with TTM at 33ºC-36ºC between June 2014 and December 2015. We validated the accuracy of rCAST for predicting the neurological outcomes at 30 and 90 days. Results: Among the 12,024 OHCA patients, the data of 460 PCAS patients treated by TTM were eligible for the validation. The areas under the curve of rCAST for predicting the neurological outcomes at 30 and 90 days were 0.892 and 0.895, respectively. The estimated sensitivity and specificity of the risk categories for the outcomes were as follows: 0.95 (95% CI: 0.92-0.98) and 0.47 (0.40-0.55) for the low (rCAST: ≤5.5), 0.62 (0.56-0.68) and 0.48 (0.40-0.55) for the moderate (rCAST: 6.0-14.0), and 0.57 (0.51-0.63) and 0.95 2 (0.91-0.98) for the high severity category (rCAST: ≥14.5). Conclusions: The rCAST was useful for predicting the neurological outcomes with high accuracy in PCAS patients, and the three grades was developed for a risk classification based on the rCAST.