Abstract 182: Medical Comorbidities and Age Both Predict Neurological Outcomes in Survivors of Cardiac Arrest Treated With Hypothermia

Abstract

Introduction: Age is a known predictor of outcome in comatose survivors of out of hospital cardiac arrest (OHCA), but it is unknown whether this is inherent or because age is a marker for overall health status. In a cohort treated with hypothermia, we hypothesized that age and pre-arrest comorbidities would both contain unique neurological prognostic information. Methods: We conducted a retrospective cohort study, reviewing electronic medical records of all patients treated with mild therapeutic hypothermia (MTH) in the University of Michigan Emergency Department for OHCA. We categorized patients’ past medical history into a Charlson Comorbidity Index (CCI). Age was analyzed by decade. Neurologic outcomes were determined 6-12 months post-discharge by Cerebral Performance Category (CPC). Logistic models were evaluated by c-statistics and likelihood ratio tests. Trends were evaluated using one-sided Cochrane Armitage tests. Results: After exclusions, 123 patients received MTH between 7/1/2006 and 9/14/2012. Favorable neurological outcomes in patients with CCI 0, 1-2, 3-4, and ≥5 are shown (figure). Odds ratio (95% confidence intervals) by CCI category were 1 (ref), 0.4 (0.1-1.0), 0.5 (0.2-1.7), and 0.2 (0.03-0.9) (c = 0.65, p for trend=0.04). Combined Charlson-age index had slightly higher predictive ability (c=0.71, p=0.0004). CCI added significant predictive ability when added onto a model containing only age (c-statistic increased from 0.71 to 0.78; likelihood ratios p=0.0073). Similarly, age added significant predictive ability when added onto a model containing CCI alone (c-statistic increased from 0.65 to 0.78; p=0.0001) Conclusions: Both age and pre-arrest comorbidities are associated with outcome in comatose survivors of cardiac arrest, but the former appears to be a stronger predictor. This may reflect limitations of the health index used, but more likely that age is an independent predictor of prognosis rather than a marker for comorbidity.