OBJECTIVES: 

The no-flow time (NFT) can help establish prognosis in out-of-hospital cardiac arrest (OHCA) patients. It is often used as a selection criterion for extracorporeal resuscitation. In patients with an unwitnessed OHCA for whom the NFT is unknown, the initial rhythm has been proposed to identify those more likely to have had a short NFT. Our objective was to determine the predictive accuracy of an initial shockable rhythm for an NFT of 5 minutes or less (NFT ≤ 5).

DESIGN: 

Retrospective analysis of prospectively collected data.

SETTING: 

Prehospital OHCA in eight U.S. and three Canadian sites.

PATIENTS: 

A total of 28,139 adult patients with a witnessed nontraumatic OHCA were included, of whom 11,228 (39.9%) experienced an emergency medical service-witnessed OHCA (NFT = 0), 695 (2.7%) had a bystander-witnessed OHCA, and an NFT less than or equal to 5, and 16,216 (57.6%) with a bystander-witnessed OHCA and an NFT greater than 5.

INTERVENTIONS: 

Sensitivity, specificity, and likelihood ratios of an initial shockable rhythm to identify patients with an NFT less than or equal to 5 minutes.

MEASUREMENTS AND MAIN RESULTS: 

The sensitivity of an initial shockable rhythm to identify patients with an NFT less than or equal to 5 was poor (25% [95% CI, 25–26]), but specificity was moderate (70% [95% CI, 69–71]). The positive and likelihood ratios were inverted (negative accuracy) (positive likelihood ratio, 0.76 [95% CI, 0.74–0.79]; negative likelihood ratio, 1.12 [95% CI, 1.10–1.12]). Including only patients with a bystander-witnessed OHCA improved the sensitivity to 48% (95% CI, 45–52), the positive likelihood ratio to 1.45 (95% CI, 1.33–1.58), and the negative likelihood ratio to 0.77 (95% CI, 0.72–0.83), while slightly lowering the specificity to 67% (95% CI, 66–67).

CONCLUSIONS: 

Our analysis demonstrated that the presence of a shockable rhythm at the time of initial assessment was poorly sensitive and only moderately specific for OHCA patients with a short NFT. The initial rhythm, therefore, should not be used as a surrogate for NFT in clinical decision-making.

中文翻译：

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初始心律预测院外心脏骤停中短无流量时间的准确性

目标： 

无血流时间 (NFT) 有助于确定院外心脏骤停 (OHCA) 患者的预后。它经常被用作体外复苏的选择标准。对于患有无人见证的 OHCA 且 NFT 未知的患者，建议采用初始节律来识别那些更有可能发生过短 NFT 的患者。我们的目标是确定 NFT 为 5 分钟或更短（NFT ≤ 5）的初始可电击节律的预测准确性。

设计： 

对前瞻性收集的数据进行回顾性分析。

环境： 

美国八个和加拿大三个地点的院前 OHCA。

患者： 

总共纳入了 28,139 名目睹非创伤性 OHCA 的成年患者，其中 11,228 名 (39.9%) 经历过紧急医疗服务见证的 OHCA (NFT = 0)，695 名 (2.7%) 经历过旁观者见证的 OHCA，以及 NFT小于或等于 5，以及 16,216 (57.6%) 具有旁观者见证的 OHCA 且 NFT 大于 5。

干预措施： 

用于识别 NFT 小于或等于 5 分钟的患者的初始可电击心律的敏感性、特异性和似然比。

测量和主要结果： 

初始可电击心律识别 NFT 小于或等于 5 的患者的敏感性较差 (25% [95% CI, 25–26])，但特异性中等 (70% [95% CI, 69–71]) ]）。阳性和似然比倒置（阴性准确度）（阳性似然比，0.76 [95% CI，0.74–0.79]；阴性似然比，1.12 [95% CI，1.10–1.12]）。仅包括旁观者见证的 OHCA 患者，将敏感性提高至 48% (95% CI, 45-52)，阳性似然比提高至 1.45 (95% CI, 1.33-1.58)，阴性似然比提高至 0.77 (95 % CI，0.72–0.83），同时将特异性略微降低至 67%（95% CI，66–67）。

结论： 

我们的分析表明，对于 NFT 较短的 OHCA 患者，初始评估时存在可电击心律的敏感性较差，并且只有中等特异性。因此，在临床决策中，初始心律不应被用作 NFT 的替代指标。