Outcomes after cancelled helicopter emergency medical service missions due to concurrencies: a retrospective cohort study

Background Appropriate dispatch criteria and helicopter emergency medical service (HEMS) crew decisions are crucial for avoiding over-triage and reducing the number of concurrencies. The aim of the present study was to compare patient outcomes after completed HEMS missions and missions cancelled by the HEMS due to concurrencies. Methods Missions cancelled due to concurrencies (AMB group) and completed HEMS missions (HEMS group) in Western Norway from 2004 to 2013 were assessed. Outcomes were survival to hospital discharge, physiology score in the emergency department, emergency interventions in the hospital, type of department for patient admittance, and length of hospital stay. Results Survival to discharge was similar in the two groups. One-third of the primary missions in the HEMS group and 13% in the AMB group were patients with pre-hospital conditions posing an acute threat to life. In a sub group analysis of these patients, HEMS patients were younger, more often admitted to an intensive care unit, and had an increased survival to discharge. In addition, the HEMS group had a greater proportion of patients with deranged physiology in the emergency department according to an early warning score. Conclusion Patients in the HEMS group seemed to be critically ill more often and received more emergency interventions, but the two groups had similar in-hospital mortality. Patients with pre-hospital signs of acute threat to life were younger and presented increased survival in the HEMS group.