Objectives: We investigated whether comorbidity burden of comatose survivors of out-of-hospital cardiac arrest (OHCA) affects outcome and if comorbidity modifies the effect of target temperature management (TTM) on final outcome.
Design: The TTM trial randomized 939 patients to 24 h of TTM at either 33 or 36 °C with no difference regarding mortality and neurological outcome. This post-hoc study of the TTM-trial formed a modified comorbidity index (mCI), based on available comorbidities from the Charlson comorbidity index (CCI).
Results: Bystander cardiopulmonary resuscitation (CPR) decreased with higher comorbidity group, p = 0.01. Comorbidity groups were univariately associated with higher mortality compared to mCI0 (HRmCI1: 1.55, CI: 1.25-1.93, p < 0.001, HRmCI2: 2.01, CI: 1.55-2.62, p < 0.001, HRmCI ≥ 3: 2.16, CI: 1.57-2.97, p < 0.001). When adjusting for confounders there was a consistent, nonsignificant association between level of comorbidity and mortality (HRmC11: 1.17, CI: 0.92-1.48, p = 0.21, HRmCI2: 1.28, CI: 0.96-1.71, p = 0.10, HRmCI ≥ 3: 1.37, CI: 0.97-1.95, p = 0.08). There was no interaction between comorbidity burden and level of TTM on outcome, p = 0.61.
Conclusion: Comorbidity burden was associated with higher mortality following OHCA, but when adjusting for confounders, the influence was no longer significant. The association between mCI and mortality was not modified by TTM. Comorbidity burden is associated with lower rates of bystander cardiopulmonary resuscitation after OHCA.
Keywords: Out-of-hospital cardiac arrest; comorbidity; neurological outcome; target temperature management.