Trends in the incidence and outcomes of cardiopulmonary resuscitation-induced consciousness in out-of-hospital cardiac arrest: a retrospective study

OBJECTIVE: To examine the incidence, trends, characteristics, and patient outcomes associated with cardiopulmonary resuscitation induced consciousness (CPRIC) in out-of-hospital cardiac arrest (OHCA). METHODS: We conducted a retrospective cohort study of adult (≥16 years) OHCA events between 1st January 2008 and 31st December 2024. Patients with CPRIC were identified from prehospital patient care records and linked to data from the Victorian Ambulance Cardiac Arrest Registry (VACAR). Poisson regression was used to assess temporal trends in CPRIC incidence and multivariable logistic regression to examine the association between CPRIC and survival to hospital discharge. RESULTS: Among 43,402 OHCA events, 1438 patients (3.3%) experienced CPRIC. The annual incidence of CPRIC increased over time in the overall cohort (IRR 1.083, 95% CI 1.07-1.10) and across all arrest rhythms (p < 0.001 for all). Factors independently associated with CPRIC included younger age, calendar year, cardiac aetiology, public location, witnessed arrest, initial shockable rhythm and use of mechanical CPR. In adjusted analysis, CPRIC was independently associated with improved survival to hospital discharge (OR 2.71, 95% CI: 2.38-3.09), with similar findings for both interfering (OR 2.36, 95% CI: 2.04-2.74) and non-interfering phenotypes (OR 4.09, 95% CI: 3.17-5.29). CPRIC was also associated with return of spontaneous circulation and survival to hospital admission. CONCLUSION: Over the 16-year study period, the annual incidence of CPRIC increased, and patients with CPRIC found to have better OHCA survival outcomes. CPRIC may help identify patients with favourable physiology and is associated with improved survival outcomes.