Shock index as a predictor for short term mortality in helicopter emergency medical services: a registry study.

Background The value of shock-index has been demonstrated in hospital triage, but few studies have evaluated its prehospital use. The aim of our study was to evaluate the association between shock-index in prehospital critical care and short-term mortality. Methods We analyzed data from the national helicopter emergency medical services database and the Population Register Centre. The shock-index was calculated from the patients' first measured parameters. The primary outcome measure was 1- and 30-day mortality. Results A total of 22 433 patients were included. The 1-day mortality was 7.5% and 30-day mortality was 16%. The median shock-index was 0.68 (0.55/0.84) for survivors and 0.67 (0.49/0.93) for non-survivors (P = .316) at 30-days. Association between shock-index and mortality followed a U-shaped curve in trauma (shock-index 1.3: odds ratio 4.4 [2.7-7.2] at 30 days). Patients with neurological emergencies with a low shock-index had an increased risk of mortality (shock-index 1.3: odds ratio 3.5 [2.3-5.4). The association was similar for all ages, but older patients had higher mortality in each shock-index category. Conclusion The shock-index is associated with short time mortality in most critical patient categories in the prehospital setting. However, the marked overlap of shock-index in survivors and non-survivors in all patient categories limits its predictive value. Editorial comment Shock in the prehospital resuscitation situation is not one specific condition, and it can be life-threatening. In this study, an initial shock-index assessment from the prehospital site showed some relation to short-term survival, but this was limited in this large group assessment. The first vital signs do not seem to be strongly predictive of how patients will respond to resuscitation and hospitalization.