Early warning scores and critical care transfer – patient heterogeneity, low sensitivity, high mortality

Abstract

Background: Emergency warning systems (EWS) are becoming a standard of care, but have unproven screening value in early critical illness. Similarly, emergency response team (ERT) care is of uncertain value. These questions are most controversial in mixed patient populations, where screening performance might vary, and intensivist-led ERT care might divert resources from existing patients. Aims: To examine triggering events, disposition and outcome data for an intensivist-staffed EWS-ERT system. Methods: We analysed process and outcome data over three years, classing EWS-triggered patients into three categories (non-escalated, escalated ward care and critical care transfer). The relationships between EWS data, pre-triggering clinical data, and patient disposition and outcome were examined. Results: There were 1675 calls in 1190 patients. Most occurred later during admission, with critical care transfer in a minority; the rest were followed by escalated or non-escalated ward care. Patients transferred to critical care had high mortality (40.3%); less than half of patient transfers occurred following triggering EWS score predicted overall hospital mortality, but not mortality after critical care. Conclusions: In a diverse hospital population, most triggering patients did not receive critical care and most critical care transfers occurred without triggering. Triggering was an insensitive screening measure for critical illness, followed by poor outcome. Higher scores predicted higher probability of transfer, but not later mortality, suggesting that EWS is being used as a decision aid but is not a true severity of illness score. Other, non-EWS data are needed for earlier detection and for prioritizing access to critical care.