The use of extracorporeal membrane oxygenation during cardiac arrest (extracorporeal cardiopulmonary resuscitation (ECPR)) has increased in recent years [1] after evidence emerged that it was associated with better outcomes than conventional CPR for in-hospital cardiac arrest [2–4]. This success led some clinicians to attempt ECPR in highly selected patients who suffered out-ofhospital cardiac arrest (OHCA), often cannulating them on arrival in the emergency department [5]. One key determinant of the likelihood of survival in ECPR patients is the duration of CPR prior to cannulation [2, 3, 6, 7], so investigators inferred that the outcomes for OHCA patients might be improved by cannulation in the field (prehospital ECPR), thereby reducing the period of inadequate circulation. However, the logistic barriers to prehospital ECPR are formidable, including the difficulties inherent to undertaking complex medical procedures in a field setting, minimizing delays in cannulation without being indiscriminate about patient selection, as well as the resource consumption. Nonetheless, some hospital networks have created mobile intensive care units with prehospital ECPR capabilities [5]. The largest study to date on the use of ECPR for OHCA was recently published, shedding new light on the effectiveness of this approach. Bougouin et al. [8] reported on 13,191 OHCA cases in metropolitan Paris. Of the 12,396 patients managed with conventional CPR, 1061 (8.6%) survived to hospital discharge, compared with 44 (8.4%) of 523 ECPR patients. ECPR was attempted but failed in 58 (11%) patients. Factors associated with survival in the ECPR group included an initial shockable rhythm and transient return of spontaneous circulation (ROSC) prior to ECPR. Of note, prehospital ECPR was associated with both higher survival and more favourable neurological outcomes (OR 2.9, 95%CI 1.5–5.9, p = 0.002, and OR 2.9, 95%CI 1.3–6.4, p = 0.008, respectively) than in those patients receiving ECPR after arrival to hospital, only 7% of whom survived compared to 15% of prehospital ECPR patients. This study represents a significant setback to enthusiasts looking to use mechanical circulatory support as a means of addressing the poor outcomes seen in patients suffering from OHCA. The fact that there were no statistically significant differences in hospital mortality between those treated with ECPR and those treated with conventional CPR mandates a reappraisal of ECPR in OHCA patients. The study had a number of strengths, including its sheer size, the practical experience of these teams in facilitating rapid deployment ECPR [5], and its multicentre observational design, providing ‘real-world’ data. However, there were limitations to the study, most notably the selection bias. ECPR was not initiated per protocol but rather at the discretion of individual clinicians, and therefore influenced by both known and unknown confounders. This was reflected in the difference in baseline characteristics of the ECPR patients, who were younger and more likely to receive bystander CPR (81% vs 49%, p < 0.001) yet, importantly, were also more likely to have CPR duration exceed 30min (99% vs 77%, p < 0.001). The authors attempted to control for known confounders but were unable to demonstrate that ECPR was associated with improved hospital survival either on multivariate analysis (OR 1.3, 95%CI 0.8–2.1, p = 0.24) or propensity matching (OR 0.8, 95%CI 0.5–1.3, p = 0.41). There were a number of different groups in the

中文翻译：

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院外心脏骤停的 ECPR：需要更多证据

近年来，有证据表明体外膜肺氧合在心脏骤停（体外心肺复苏 (ECPR)）期间的使用有所增加 [1]，因为有证据表明它比传统 CPR 治疗院内心脏骤停的结果更好 [2-4]。这一成功促使一些临床医生尝试对经过严格挑选的院外心脏骤停 (OHCA) 患者进行 ECPR，通常在他们到达急诊室时对其进行插管 [5]。ECPR 患者生存可能性的一个关键决定因素是插管前 CPR 的持续时间 [2, 3, 6, 7]，因此研究人员推断，OHCA 患者的结果可能会通过现场插管（院前 ECPR）得到改善，从而减少循环不足的时期。然而，院前 ECPR 的后勤障碍是巨大的，包括在现场环境中进行复杂的医疗程序所固有的困难，最大限度地减少插管延迟，而不是不加选择地选择患者，以及资源消耗。尽管如此，一些医院网络已经创建了具有院前 ECPR 功能的移动重症监护室 [5]。迄今为止，关于将 ECPR 用于 OHCA 的最大研究最近发表，揭示了这种方法的有效性。布古恩等人。[8] 报道了巴黎大都市的 13,191 例 OHCA 病例。在接受常规 CPR 治疗的 12,396 名患者中，1061 名 (8.6%) 存活出院，而 523 名 ECPR 患者中有 44 名 (8.4%)。58 名 (11%) 患者尝试了 ECPR，但失败了。ECPR 组中与生存相关的因素包括初始可电击节律和 ECPR 前自主循环 (ROSC) 瞬时恢复。值得注意的是，与入院前 ECPR 相比，院前 ECPR 与更高的生存率和更有利的神经学结果相关（分别为 OR 2.9, 95%CI 1.5–5.9, p = 0.002 和 OR 2.9, 95%CI 1.3–6.4, p = 0.008）入院后接受 ECPR 的患者中，只有 7% 存活，而院前 ECPR 患者存活率为 15%。这项研究对希望使用机械循环支持作为解决 OHCA 患者不良结果的手段的爱好者来说是一个重大挫折。接受 ECPR 治疗的患者和接受常规 CPR 治疗的患者在住院死亡率方面没有统计学上的显着差异这一事实要求重新评估 OHCA 患者的 ECPR。该研究有许多优势，包括其庞大的规模、这些团队在促进快速部署 ECPR 方面的实践经验 [5]，以及提供“真实世界”数据的多中心观察设计。然而，该研究存在局限性，最显着的是选择偏倚。ECPR 不是按照协议启动的，而是由个别临床医生自行决定的，因此受到已知和未知混杂因素的影响。这反映在 ECPR 患者基线特征的差异上，他们更年轻，更有可能接受旁观者 CPR（81% 对 49%，p < 0.001），但重要的是，也更有可能使 CPR 持续时间超过 30 分钟（99% 对 77%，p < 0.001）。作者试图控制已知的混杂因素，但无法证明 ECPR 与多变量分析（OR 1.3，95%CI 0.8-2.1，p = 0.24）或倾向匹配（OR 0.8，95%CI）改善医院生存相关0.5–1.3，p = 0.41）。有许多不同的群体