Supplementary Material for: Evaluation of physiological variables determining time to mortality after stroke-associated pneumonia

Introduction
Stroke-associated pneumonia (SAP) frequently complicates stroke and is associated with significant mortality. Clinicians often use physiological variables within the National Early Warning Score (NEWS) when diagnosing and prescribing antibiotics for SAP, but little is known of its association with mortality. We investigated the relationship of the NEWS 2 score and its components (respiratory rate, heart rate, temperature, oxygen requirement, oxygen saturation and alertness level) prior to antibiotic initiation, with time-to-mortality in SAP.
Methods
We included patients with SAP (n=389) from a single hyperacute stroke unit. Diagnosis of SAP was made if pneumonia occurred within 7 days of hospital admission. Kaplan-Meier survival curves were generated to assess NEWS 2 parameters influencing survival at pre-defined time periods (1 year and 5 years). The association of these parameters on time-to-mortality were analysed using multivariable Cox regression models to account for a set of pre-specified potential confounders.
Results
The median age was 80y (71y-87y) and median NIHSS was 7 (IQR 4-17). Mortality within 1 year was 52.4% and 65.8% within 5 years. In the multivariable analyses, time-to-mortality was independently associated with respiratory rate (HR 1.04, 95% CI 1.01 to1.08, p=0.009) and total NEWS 2 score (HR 1.13, 95% CI 1.06 to 1.21, p=<0.001).
Conclusions
In patients with SAP, higher respiratory rate and total NEWS 2 score prior to antibiotic initiation were independently associated with time-to-mortality. Further studies are warranted to identify potential opportunities for intervention and ultimately guide treatment to improve outcomes in SAP patients.

引言
卒中相关性肺炎（Stroke-associated pneumonia, SAP）常作为卒中的并发症出现，且与较高的死亡率密切相关。临床医师在诊断卒中相关性肺炎并为其开具抗生素处方时，常参考国家早期预警评分（National Early Warning Score, NEWS）所涵盖的生理学变量，但目前对于该评分与死亡率的关联尚不清楚。本研究旨在探讨抗生素启用前的国家早期预警评分2（National Early Warning Score 2, NEWS 2）及其各组成项（呼吸频率、心率、体温、氧需求、血氧饱和度及意识水平）与卒中相关性肺炎患者至死亡时间的关联。

方法
本研究纳入来自单个超急性卒中单元的389例卒中相关性肺炎患者。若患者于入院7天内发生肺炎，则确诊为卒中相关性肺炎。通过生成Kaplan-Meier生存曲线，评估预设时间段（1年及5年）内影响患者生存的NEWS 2相关参数。采用多变量Cox回归模型分析上述参数与至死亡时间的关联，以校正一系列预先设定的潜在混杂因素。

结果
本研究队列的中位年龄为80岁（四分位数间距：71岁~87岁），中位美国国立卫生研究院卒中量表（National Institutes of Health Stroke Scale, NIHSS）评分为7（四分位数间距：4~17）。患者1年内死亡率为52.4%，5年内死亡率为65.8%。多变量分析结果显示，至死亡时间与呼吸频率（风险比（Hazard Ratio, HR）1.04，95%置信区间（95% confidence interval, 95% CI）：1.01~1.08，p=0.009）及总NEWS 2评分（HR 1.13，95%CI：1.06~1.21，p<0.001）独立相关。

结论
在卒中相关性肺炎患者中，抗生素启用前更高的呼吸频率及总NEWS 2评分与至死亡时间独立相关。未来需开展进一步研究以明确潜在的干预靶点，并最终指导治疗以改善卒中相关性肺炎患者的临床结局。