Background and Purpose Survival from out-of-hospital cardiac arrest (OOHCA) is less than 10% in most communities. A better understanding of prognostic factors may help explain disparity in outcome and ultimately guide resuscitation. Most prognostic studies of OOHCA have focused on circumstances (ie, witness status) or health services factors (ie, CPR, response interval of emergency services). Little is known about how chronic health conditions prior to arrest influence outcome. A single study reported an inverse association, indicating lower likelihood of survival with increasing number of chronic conditions prior to the arrest. This study, however, was resource intensive and required family member and if possible patient interviews. The study objective was to determine whether chronic conditions as determined by emergency medical services (EMS) reports were associated with survival.
Study Design and Methods This investigation was a retrospective cohort study of EMS-treated cardiac arrest cases that occurred between January 1, 1999 and December 31, 2003 in King County, Washington. EMS reports for 1,768 cases of cardiac arrest were reviewed using a standardized data collection form to determine patient chronic conditions and symptoms prior to the arrest. Descriptive statistics were used to assess the proportion of cardiac arrest victims said to have had various chronic conditions and symptoms prior to arrest. Total number of medications for each case were also tallied. Logistic regression was used to evaluate the association between survival and number of chronic conditions, symptoms, and medications.
Results Using EMS ascertainment, approximately two-thirds were reported to have a chronic health condition and half specifically were said to have a form of heart disease. Increasing count of chronic conditions is associated with several characteristics: older age, more medications, residential location, and a smaller proportion with VF rhythm. Survival to hospital discharge is significantly associated with chronic condition count. For each additional chronic condition, the odds ratio of survival decreases by 0.85 (0.74, 0.96) after adjusting for other factors.
Conclusion Increasing count of chronic conditions as determined by EMS reports is associated with a lower odds of survival to hospital discharge following OOHCA even after accounting for other prognostic factors. Preexisting chronic conditions may help explain differences in outcomes between individuals, populations, or EMS systems and may enable a better assessment of care and outcome following cardiac arrest.
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