Background and importance 

There has been much discussion of the results of the PARAMEDIC2 trial, as resuscitation outcome rates are considerably lower in this trial than in country-level registries on out-of-hospital cardiac arrest (OHCA). Here, we developed a statistical framework to investigate this gap and to examine possible sources for observed discrepancies in outcome rates.

Design 

Summary data from the PARAMEDIC2 trial were used as available in the publication of this study. We developed a modelling framework based on logistic regression to compare data from this randomized controlled trial and registry data from the German Resuscitation Registry (GRR), where we considered 26 019 patients treated with epinephrine for OHCA in the GRR. To account and adjust for differences in patient characteristics and baseline variables predictive for outcomes after OHCA between the GRR cohort and the PARAMEDIC2 study sample, we included all available variables determined at the arrival of EMS personnel in the modelling framework: age, sex, initial cardiac rhythm, cause of cardiac arrest, witness of cardiac arrest, CPR performed by a bystander, and the interval between emergency call and arrival of the ambulance at the scene (baseline model). In order to find possible explanations for the discrepancies in outcome between PARAMEDIC2 and GRR, in a second (baseline plus treatment) model, we additionally included all available variables related to the interventions of the EMS personnel (type of airway management, type of vascular access, and time to administration of epinephrine).

Main results 

A patient cohort with baseline variables as in the PARAMEDIC2 trial would have survived to hospital discharge in 7.7% and survived with favourable neurological outcome in 5.0% in an EMS and health care system as in Germany, compared with 3.2 and 2.2%, respectively, in the Epinephrine group of the trial. Adding treatment-related variables to our logistic regression model, the rate of survival to discharge would decrease from 7.7 (for baseline variables only) to 5.6% and the rate of survival with favourable neurological outcome from 5.0 to 3.4%.

Conclusion 

Our framework helps in the medical interpretation of the PARAMEDIC2 trial and the transferability of the trial’s results for other EMS systems. Significantly higher rates of survival and favourable neurological outcome than reported in this trial could be possible in other EMS and health care systems.

中文翻译：

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PARAMEDIC2 和德国复苏注册中心之间的结果差异：与注册数据相比的随机对照试验的二次分析

背景和重要性 

人们对 PARAMEDIC2 试验的结果进行了很多讨论，因为该试验的复苏结果率远低于国家级院外心脏骤停(OHCA) 登记处的结果。在这里，我们开发了一个统计框架来调查这一差距并检查观察到的结果率差异的可能来源。

设计 

本研究的出版物中使用了 PARAMEDIC2 试验的总结数据。我们开发了一个基于逻辑回归的建模框架，以比较该随机对照试验的数据和德国复苏登记处 (GRR) 的登记数据，其中我们考虑了 GRR 中因 OHCA 接受肾上腺素治疗的 26 019 名患者。为了解释和调整 GRR 队列和 PARAMEDIC2 研究样本之间患者特征和预测 OHCA 后结果的基线变量的差异，我们在建模框架中纳入了 EMS 人员到达时确定的所有可用变量：年龄、性别、初始心脏病节律、心脏骤停的原因、心脏骤停的目击者、旁观者进行的心肺复苏以及紧急呼叫和救护车到达现场之间的时间间隔（基线模型）。为了找到 PARAMEDIC2 和 GRR 之间结果差异的可能解释，在第二个（基线加治疗）模型中，我们另外纳入了与 EMS 人员干预相关的所有可用变量（气道管理类型、血管通路类型） ，以及肾上腺素的给药时间）。

主要结果 

PARAMEDIC2 试验中具有基线变量的患者队列存活出院的比例为 7.7%，在德国的 EMS 和医疗保健系统中存活并获得良好神经学结果的比例为 5.0%，而在德国，这一比例分别为 3.2% 和 2.2%。试验的肾上腺素组。将治疗相关变量添加到我们的逻辑回归模型中，出院生存率将从 7.7（仅对于基线变量）下降到 5.6%，神经学结果良好的生存率将从 5.0% 下降到 3.4%。

结论 

我们的框架有助于 PARAMEDIC2 试验的医学解释以及试验结果向其他 EMS 系统的可转移性。在其他 EMS 和医疗保健系统中，存活率和良好的神经系统结果可能比本试验中报告的要高得多。