Association of ambulance and helicopter response times with patient survival: A systematic literature review. Meta-data from Covidence.

ABSTRACTBackground: Only sparse scientific evidence supports the notion that the shortest possible response time relates to improved patient outcomes in acute conditions, other than out-of-hospital cardiac arrest and trauma. Confounders such as bidirectional causality and confounding by indication may influence patient-centered outcomes, which may prevent actionable conclusions from literature reviews. The purpose of the systematic literature review was to assess current evidence on association, if any, between ambulance and helicopter response times and survival in all patient categories treated by ambulance or helicopter services. Methods: The systematic search was conducted in MEDLINE, Cochrane Library, EMBASE, CINAHL, Scopus, and Clinical Trial Registries. No time language or language limitations were imposed to avoid missing relevant literature. All study designs and settings identified as relevant to the topic were eligible. We retrieved data from a predefined template. Two reviewers worked independently, and conflicts were resolved by a third reviewer. The researchers used PRISMA guidelines for abstracting data and GRADE methodology for assessing data quality and validity. Data were pooled using a random-effects model. As per study protocol, the primary study outcome was patient survival, and the main measurement was response time for emergency medical services vehicles. Results: We included 115 studies that in total included 691,056 patients, ranging from 64 til 182,895 patients in the individual studies. The overall median survival rate was 11.5% (IQR 5.2; 25.8). Response time varied between 1.10 and 48.62 minutes. The predefined domains and items of interest were accounted for in 46.7% of the included literature. Certainty of evidence was very low as per GRADE methodology.Conclusions: The main finding of this literature review was indicative of no statistically significant association between ambulance and helicopter response times and patient survival, as the studies addressed the topic very diversely. We found substantive research and knowledge gaps and very low certainty of evidence. Therefore, no actionable conclusions can be made from this systematic review.摘要： 背景：除院外心脏骤停与创伤患者外，仅有少量科学证据支持“最短响应时间与急性病患者的更佳预后相关”这一观点。双向因果关系、指征混杂偏倚等混杂因素可能影响以患者为中心的结局，进而导致系统综述无法得出可付诸实践的结论。本系统综述的目的为评估现有证据中，救护车与直升机响应时间与所有接受急救医疗服务的患者生存率之间的关联（若存在此类关联）。 方法：系统检索了MEDLINE、考克兰图书馆（Cochrane Library）、EMBASE、护理及相关健康文献累积索引（CINAHL）、Scopus以及临床试验注册库（Clinical Trial Registries）。为避免遗漏相关文献，未对检索时间与语言设置限制。所有与本主题相关的研究设计与研究场景均符合纳入标准。研究数据通过预设模板提取。由两名评价员独立开展评价，意见分歧由第三名评价员协调解决。研究人员采用系统综述与元分析优先报告条目（PRISMA）指南进行数据提取，并使用建议分级、评估、制定与评价（GRADE）方法评估数据质量与有效性。采用随机效应模型对数据进行合并分析。根据研究方案，本研究的主要结局为患者生存率，核心测量指标为急救医疗服务车辆的响应时间。 结果：本研究共纳入115项研究，合计纳入691056名患者，单项研究的纳入患者数量介于64至182895名之间。总体中位生存率为11.5%（四分位数间距（Interquartile Range，IQR）：5.2；25.8）。响应时间的分布区间为1.10至48.62分钟。纳入的文献中仅有46.7%覆盖了预设的研究领域与关注条目。根据GRADE方法评估，本研究的证据确定性等级极低。 结论：本系统综述的主要发现显示，救护车与直升机的响应时间与患者生存率之间不存在统计学意义上的显著关联——这是因为各项研究对该主题的研究设计差异极大。本研究发现存在大量的研究与知识空白，且证据确定性等级极低。因此，本系统综述无法得出可付诸实践的结论。