UBC Theses and Dissertations
Emergency medical services design and response : the role of chain-of-survival clinical interventions on survival following out-of-hospital cardiac arrest Andrusiek, Douglas Lorne
Out-of-hospital cardiac arrest (OHCA) resuscitation is guided by a set of published guidelines that includes several interventions based on the organizing framework known as the chain-of-survival. The aim of the studies in this dissertation was to examine the effects of these interventions in improving survival following non-traumatic adult OHCA. Data for this purpose was obtained from two multi-centre studies carried out in the United States and Canada. Analysis methods included multivariable logistic regression and matched propensity score analysis. The first study was an analysis of a cohort of 12,821 OHCA cases that showed that younger age, public location, shorter response time, initial rhythm of ventricular fibrillation/tachycardia, and advanced airway management were associated with improved survival, while epinephrine administration was associated with a reduction in survival. Specialized post-arrest care appeared to be associated with improved survival but the magnitude of this was attenuated in analyses of cases transported to hospital. There was a non-significant association between advanced airway management and reduced survival (adjusted odds ratio (AOR) 0.82, 95% confidence interval (CI) 0.59–1.14) and a substantial reduction in survival among those who received epinephrine (AOR 0.13, 95% CI 0.10–0.17). The second study was based on a cohort of 14,673 non-traumatic OHCA cases and showed that initial rhythm modified the effect of prehospital epinephrine administration: asystole was associated with a 14-fold decrease in the adjusted odds of survival if epinephrine was administered, while ventricular fibrillation/tachycardia was associated with a 5.8-fold decrease in the adjusted odds of survival if epinephrine was administered (p-value for interaction < 0.01). The third study used propensity score matching and showed that epinephrine was negatively associated with return of spontaneous circulation (ROSC; AOR 0.50, 95% CI 0.42–0.60) and survival (AOR 0.15, 95% CI 0.11–0.19), while tracheal intubation was positively associated with ROSC (AOR 2.31, 95% CI 1.92–2.77) and survival (AOR 1.97, 95% CI 1.62–2.40). These findings raise concerns regarding the efficacy of some commonly used interventions in OHCA. Some interventions, such as epinephrine, may potentially compromise survival at least in some subgroups, and should to be more rigorously studied through randomized controlled trials.
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