Retrospective observational cohort study of out-of-hospital cardiac arrest outcomes in Tasmania 2010-2014.

Objective: This study aims to present overall survival rates to hospital discharge for out-of-hospital cardiac arrest (OHCA) in Tasmania and to identify predictors of survival.

Methods: A retrospective observational cohort study was undertaken from 1 January 2010 to 31 December 2014. A probabilistically linked data set was created from paramedic electronic medical records and hospital patient records. Logistic regression was used to assess factors associated with survival of OHCA.

Results: During the study, 2949 incidents of OHCA were reviewed and 1146 had emergency management provided, with an overall survival rate to hospital discharge of 135 (12%). A number of independent factors are associated with improved outcomes including if the initial presenting cardiac rhythm was either ventricular fibrillation or ventricular tachycardia (adjusted odds ratio [OR] 8.75, 95% confidence interval [CI] 5.15-14.89) (P < 0.0001) relative to those who were found in a non-shockable rhythm. Another factor was age group (overall P < 0.001). Those aged 85+ years had a reduced overall survival rate (2.9%), which was lower than those <16 years of age (OR 0.37, 95% CI 0.07-1.94; adjusted OR 0.38, CI 0.03-1.00) (P < 0.001). The odds of surviving OHCA decreased by 9% for every minute defibrillation of a shockable rhythm was delayed were witnessed by a bystander (OR 0.90, 95% CI 0.85-0.95).

Conclusion: Time to defibrillation for witnessed arrests, other than paramedic witnessed arrest was associated with better overall survival rates than unwitnessed OHCA. Further factors such as the event being of cardiac aetiology, bystander cardio-pulmonary resuscitation performed, initial presenting cardiac rhythm of ventricular fibrillation or ventricular tachycardia and decreasing age were all associated with increased probability of survival.