Prehospital mortality in an EMS system using medical priority dispatching: a community based cohort study

This study was planned to record prehospital death rates in four medical priority categories (A, B, C and D) and to evaluate if deaths in lower urgency categories C and D (target response times 20 and 90 min) could have been avoided by a faster ambulance response.

The design was a community based cohort study including an expert panel evaluation of the deaths. The study was conducted in the Emergency Medical Services in Helsinki, Finland. All consecutive ambulance calls excluding interhospital patient transfers between 1 January 1999 and 31 December 2002 were included. Prehospital mortality and avoidability of prehospital deaths by a faster ambulance response (maximum 8 min) were used as main outcome measures.

A total of 151928 calls were prioritized in the dispatching centre (category A 8677 calls, B 41005, C 71991 and D 30255). Prehospital death occurred 451 times in category A, 468 times in category B, 73 times in category C and 8 times in category D calls. Respectively, the prehospital death rates per 1000 calls were 52.0 (A), 11.4 (B), 1.0 (C) and 0.3 (D) (P < 0.0001). The expert panel judged that 1 (1.3%) of category C deaths would have been avoidable, 24 (32.9%) potentially avoidable and 48 (65.8%) not avoidable by a more rapid ambulance response. The corresponding figures for category D deaths were 0 (0%), 5 (62.5%) and 3 (37.5%), respectively.

The use of medical priority dispatching was associated with very low prehospital mortality in lower urgency categories C and D. Approximately, one-third of those deaths could probably be prevented by a faster ambulance response but the price would be a three-fold increase in calls with blue lights and siren. Further studies are needed to find out if our results are applicable to other types of EMS systems.