Objective: To determine the effect of different case and survival definitions of out-of-hospital cardiac arrest on survival rate calculations.
Design: A 22-month case series of nontraumatic, out-of-hospital cardiac arrests.
Setting: Southwestern city (population, 400,000; area, 390 km2) with a two-tiered emergency response system consisting of emergency medical technicians and paramedics.
Patients: A consecutive sample of 372 patients found without palpable pulse of spontaneous respiration.
Main outcome measures: Survival rate after cardiac arrest was calculated using three case definitions of arrest and two definitions of survival.
Results: Twenty percent of all patients survived to hospital admission and 6% survived to hospital discharge. Twenty-six percent of adults whose collapse was witnessed survived to hospital admission, and 10% survived to hospital discharge. Patients whose collapse was witnessed and who experienced initial ventricular fibrillation survived to hospital admission in 38% and to hospital discharge in 15% of cases.
Conclusions: The survival rate after out-of-hospital cardiac arrest varies widely depending on the case and survival definitions selected. To facilitate intersystem comparison and assessment of interventions designed to improve outcome, the Utstein Consensus Conference recommended that case and survival definitions should be adopted by all prehospital emergency systems.