Validation of the National Early Warning Score in the prehospital setting

Abstract

Background: Early intervention and response to deranged physiological parameters in the critically ill patient improves outcomes. A National Early Warning Score (NEWS) based on physiological observations has been developed for use throughout the National Health Service (NHS) in the UK. Although a good predictor of mortality and deterioration in inpatients, its performance in the prehospital setting is largely untested. This study aimed to assess the validity of the NEWS in unselected prehospital patients.

Methods: All clinical observations taken by emergency ambulance crews transporting patients to a single hospital were collated along with information relating to hospital outcome over a two month period. The performance of the NEWS in identifying the endpoints of 48h and 30 day mortality, intensive care unit (ICU) admission, and a combined endpoint of 48h mortality or ICU admission was analysed.

Results: 1684 patients were analysed. All three of the primary endpoints and the combined endpoint were associated with higher NEWS scores (p<0.01 for each). The medium-risk NEWS group was associated with a statistically significant increase in ICU admission (RR=2.466, 95% CI 1.0-6.09), but not in-hospital mortality relative to the low risk group. The high risk NEWS group had significant increases in 48h mortality (RR 35.32 [10.08-123.7]), 30 day mortality (RR 6.7 [3.79-11.88]), and ICU admission (5.43 [2.29-12.89]). Similar results were noted when trauma and non-trauma patients were analysed separately.

Conclusions: Elevated NEWS among unselected prehospital patients is associated with a higher incidence of adverse outcomes. Calculation of prehospital NEWS may facilitate earlier recognition of deteriorating patients, early involvement of senior Emergency Department staff and appropriate critical care.

Keywords: National Early Warning Score; Prehospital; Risk stratification.