Importance Comatose survivors of out-of-hospital cardiac arrest experience high rates of death and severe neurologic injury. Current guidelines recommend targeted temperature management at 32 °C to 36 °C for 24 hours. However, small studies suggest a potential benefit of targeting lower body temperatures. Objective To determine whether moderate hypothermia (31 °C), compared with mild hypothermia (34 °C), improves clinical outcomes in comatose survivors of out-of-hospital cardiac arrest. Design, Setting, and Participants Single-center, double-blind, randomized, clinical superiority trial carried out in a tertiary cardiac care center in eastern Ontario, Canada. A total of 389 patients with out-of-hospital cardiac arrest were enrolled between August 4, 2013, and March 20, 2020, with final follow-up on October 15, 2020. Interventions Patients were randomly assigned to temperature management with a target body temperature of 31 °C (n = 193) or 34 °C (n = 196) for a period of 24 hours. Main Outcomes and Measures The primary outcome was all-cause mortality or poor neurologic outcome at 180 days. Neurologic outcome was assessed using the Disability Rating Scale, with poor neurologic outcome defined as a score greater than 5 (range, 0-29, with 29 being the worst outcome [vegetative state]). There were 19 secondary outcomes, including mortality at 180 days and length of stay in the intensive care unit. Results Among 367 patients included in the primary analysis (mean age, 61 years; 69 women [19%]), 366 (99.7%) completed the trial. The primary outcome occurred in 89 of 184 patients (48.4%) in the 31 °C group and in 83 of 183 patients (45.4%) in the 34 °C group (risk difference, 3.0% [95% CI, 7.2%-13.2%]; relative risk, 1.07 [95% CI, 0.86-1.33]; P = .56). Of the 19 secondary outcomes, 18 were not statistically significant. Mortality at 180 days was 43.5% and 41.0% in patients treated with a target temperature of 31 °C and 34 °C, respectively (P = .63). The median length of stay in the intensive care unit was longer in the 31 °C group (10 vs 7 days; P = .004). Among adverse events in the 31 °C group vs the 34 °C group, deep vein thrombosis occurred in 11.4% vs 10.9% and thrombus in the inferior vena cava occurred in 3.8% and 7.7%, respectively. Conclusions and Relevance In comatose survivors of out-of-hospital cardiac arrest, a target temperature of 31 °C did not significantly reduce the rate of death or poor neurologic outcome at 180 days compared with a target temperature of 34 °C. However, the study may have been underpowered to detect a clinically important difference. Trial Registration ClinicalTrials.gov Identifier: NCT02011568.

中文翻译：

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中度与轻度治疗性低温对院外心脏骤停昏迷幸存者死亡率和神经系统结局的影响：CAPITAL CHILL 随机临床试验。

重要性 院外心脏骤停的昏迷幸存者经历了高死亡率和严重的神经损伤。当前指南建议在 32 °C 至 36 °C 下进行 24 小时的有针对性的温度管理。然而，小型研究表明针对较低体温的潜在好处。目的 确定中度低温 (31°C) 与轻度低温 (34°C) 相比是否能改善院外心脏骤停昏迷幸存者的临床结局。设计、设置和参与者 在加拿大安大略省东部的一个三级心脏护理中心进行的单中心、双盲、随机、临床优势试验。2013 年 8 月 4 日至 2020 年 3 月 20 日期间，共有 389 名院外心脏骤停患者入组，最终随访时间为 2020 年 10 月 15 日。干预 患者被随机分配到温度管理组，目标体温为 31 °C（n = 193）或 34 °C（n = 196），持续 24 小时。主要结果和测量 主要结果是 180 天时的全因死亡率或不良神经系统结果。使用残疾评定量表评估神经系统结果，不良神经系统结果定义为分数大于 5（范围，0-29，其中 29 为最差结果 [植物人状态]）。有 19 项次要结局，包括 180 天死亡率和重症监护病房住院时间。结果 在纳入主要分析的 367 名患者（平均年龄 61 岁；69 名女性 [19%]）中，366 名（99.7%）完成了试验。主要结局发生在 31 °C 组 184 名患者中的 89 名（48.4%）和 183 名患者中的 83 名（45.5%）。4%）在 34 °C 组（风险差异，3.0% [95% CI，7.2%-13.2%]；相对风险，1.07 [95% CI，0.86-1.33]；P = .56）。在 19 项次要结局中，18 项无统计学意义。目标温度为 31 °C 和 34 °C 治疗的患者在 180 天的死亡率分别为 43.5% 和 41.0% (P = .63)。31 °C 组在重症监护病房的中位住院时间更长（10 天 vs 7 天；P = .004）。在 31 °C 组和 34 °C 组的不良事件中，深静脉血栓形成分别为 11.4% 和 10.9%，下腔静脉血栓分别发生在 3.8% 和 7.7%。结论和相关性 在院外心脏骤停的昏迷幸存者中，与 34°C 的目标温度相比，31°C 的目标温度并没有显着降低 180 天时的死亡率或不良神经系统预后。然而，该研究可能不足以检测临床上重要的差异。试验注册 ClinicalTrials.gov 标识符：NCT02011568。