The association between vital signs and mortality in a retrospective cohort study of an unselected emergency department population

BACKGROUND: Vital signs are widely used in emergency departments. Previous studies on the association between vital signs and mortality in emergency departments have been restricted to selected patient populations. We aimed to study the association of vital signs and age with 1-day mortality in patients visiting the emergency department. METHODS: This retrospective cohort included patients visiting the emergency department for adults at Södersjukhuset, Sweden from 4/1/2012 to 4/30/2013. Exclusion criteria were: age < 18 years, deceased upon arrival, chief complaint circulatory or respiratory arrest, key data missing and patients who were directed to a certain fast track for conditions demanding little resources. Vital sign data was collected through the Rapid Emergency Triage and Treatment System – Adult (RETTS-A). Descriptive analyses and logistic regression models were used. The main outcome measure was 1-day mortality. RESULTS: The 1-day mortality rate was 0.3 %. 96,512 patients met the study criteria. After adjustments of differences in the other vital signs, comorbidities, gender and age the following vital signs were independently associated with 1-day mortality: oxygen saturation, systolic blood pressure, temperature, level of consciousness, respiratory rate, pulse rate and age. The highest odds ratios was observed when comparing unresponsive to alert patients (OR 31.0, CI 16.9 to 56.8), patients ≥ 80 years to <50 years (OR 35.9, CI 10.7 to 120.2) and patients with respiratory rates <8/min to 8–25/min (OR 18.1, CI 2.1 to 155.5). DISCUSSION: Most of the vital signs used in the ED are significantly associated with one-day mortality. The more the vital signs deviate from the normal range, the larger are the odds of mortality. We did not find a suitable way to adjust for the inherent influence the triage system and medical treatment has had on mortality. CONCLUSIONS: Most deviations of vital signs are associated with 1-day mortality. The same triage level is not associated with the same odds for death with respect to the individual vital sign. Patients that were unresponsive or had low respiratory rates or old age had the highest odds of 1-day mortality.