Long-term survival after drowning-related cardiac arrest

Background: Long-term outcomes after drowning-related cardiac arrest are not well characterized. Objective: Our aims were to estimate long-term survival and identify prognostic factors in a large, population-based cohort of drowning victims with cardiac arrest. Methods: We conducted a population-based prospective cohort study (1974-1996) of Western Washington Drowning Registry (WWDR) subjects with out-of-hospital cardiac arrest and attempted professional resuscitation. The primary outcome was long-term survival through 2012. We tabulated Utstein-style exposure variables, estimated Kaplan-Meier curves, and identified prognostic factors with Cox proportional hazard modeling. Results: Of 2824 WWDR cases, 407 subjects (median age 17 years [interquartile range 3-33 years], 81% were male) were included. Only 54 (13%) were still alive after 1663 person-years of follow-up. Most deaths occurred after termination of initial resuscitation or during initial hospitalization. Risk of subsequent death after hospital discharge was 9.6 (95% confidence interval [CI] 5.7-15.9) per 1000 person-years. Long-term survival differed by Utstein variables (older age, illicit substance use, pre-drowning activity, submersion duration, cardiopulmonary resuscitation duration, intubation, defibrillation, and medications) and inpatient markers of illness severity (vital signs, Glasgow Coma Scale, laboratory values, shock). In adjusted analyses, older age (hazard ratio [HR] 1.01; 95% CI 1.01-1.02), epinephrine administration (HR 1.92; 95% CI 1.31-2.80), antiepileptic administration (HR 0.53; 95% CI 0.35-0.81), initial arterial pH (HR 0.49; 95% CI 0.26-0.92), and shock (HR 2.19; 95% CI 1.16-4.15) were associated with higher risk of death. Conclusions: Most cases of drowning-related cardiac arrest were fatal, but survivors to hospital discharge had a low risk of subsequent death that was independently associated with older age and clinical evidence of shock.