Abstract Body: Background:
Overdose continues to be a major public health problem. High potency fentanyl and derivatives as well as other substances and adulterants are present in varying degrees across the U.S. This study aims to describe the substances associated with overdose-associated cardiac arrest (OA-OHCA) compared to a population of persons with substance use disorder.

Methods:
This is a secondary analysis of a cohort of patients enrolled in a large U.S. cardiac arrest clinical trial at Yale New Haven Hospital in New Haven CT. The study cohort were patients with an out-of-hospital cardiac arrest who were resuscitated by EMS and survive to Emergency Department (ED) presentation and presumed to be caused by overdose or poisoning. This cohort was compared to a cohort of patients that were enrolled in a study of ED initiated buprenorphine for opiate use disorder. The primary objective was to analyze the difference in substances contained in the urine toxicologic screen between a cohort of patients with presumed overdose-associated cardiac arrest versus a cohort of patients with opiate use disorder (OUD) in the ED.

Results:
Thirteen patients with presumed overdose-associated cardiac arrest were included in this study, however, one patient had incomplete toxicologic data and was therefore, not analyzed. Of these, 6 (50%) were female and 3 (25%) had experienced an ED presentation in the month prior to arrest for an overdose. Two patients had an initial shockable rhythm and 6 (50.0%) survived to hospital discharge. The most common substances were fentanyl (50%, n = 6), benzodiazepines (50%, n = 6), and cannabis (33%, n = 4). (Table 1) Compared to patients with OUD, patients with OA-OHCA had a higher proportion of cocaine (67% vs. 36%) and benzodiazepines (50% vs. 15%). Polysubstance abuse was common among patients with OA-OHCA; the median [interquartile range] of substances was 3 [1.7,3]. All 6 patients with fentanyl had additional substances present. The median [interquartile range] of substances in patients with substance use disorder was 3 [2,4].

Conclusion:
In this descriptive secondary analysis of a cohort of patients with documented OA-OHCA, cocaine and benzodiazepines are more prevalent when compared to a cohort of ED patients with OUD. Notably, all patients who tested positive for fentanyl had co-involved substances, and fentanyl in isolation was not identified on screening.