Effects of adding links to "the chain of survival" for prehospital cardiac arrest: A contrast in outcomes in 1975 and 1995 at a single institution

Study objective: The concept of a "chain of survival" to improve outcome from prehospital cardiac arrest has been defined and promulgated over the last two decades. The purpose of this study was to compare outcomes of prehospital cardiac arrest in 1975 and 1995 at a single institution. Methods: This longitudinal, before-after study compares published data collected at our municipal, tertiary care in 1974-1975 with data collected prospectively in 1995. The 1975 study group served as control subjects (n=120). We enrolled an equal number of consecutive patients who met inclusion criteria in the 1995 cohort (consecutive patients who experienced prehospital arrest and who received prehospital Advanced Cardiac Life Support (ACLS) measures during the two study periods). Patients younger than 18 years or with posttraumatic arrest were excluded. Between 1975 and 1995 the following "links" in the "chain of survival" were added to the prehospital care system: (1)911 access and dispatch, (2) paramedic endotracheal intubation, (3) EMT automated defibrillation, (4) standing out-of-hospital orders before hospital radiotelemetry contact, and (5) introduction of American Heart Association ACLS algorithms. Results: The following significant differences (chi(2)) were observed between the study periods: prevalence of ventricular fibrillation or tachycardia (42% in 1975 versus 28% in 1995, P=.021), prevalence of asystole or pulseless electrical activity as the first documented rhythm (58% versus 72%, P=.021), survival to hospital discharge (22% versus 9%, P=.007), and percent of survivors of ventricular fibrillation or tachycardia (30% versus 0%, P=.004). Eighty-six percent of the 1995 cohort had advanced chronic disease and 29% experienced cardiopulmonary arrest in a nursing home. Conclusion: Survival decreased dramatically during the 20-year study period. This may be because of the high incidence of chronic disease, the greater frequency of asystole and pulseless electrical activity, and the inclusion of patients with "end-of-life" arrests in which ACLS protocol was initiated in the 1995 cohort. The patient population in which ACLS is initiated is the weakest link in the "chain of survival."