(290) Emergency Medical Service Use and In-Hospital Mortality in Patients With Substance Misuse

Introduction: Patients with substance misuse disproportionately utilize emergency medical services (EMS) and have higher mortality due to a variety of diseases. This study aims to better understand the association between in-hospital mortality in these patients and the frequency of EMS use in the 30 days prior to hospitalization.

Methods: We conducted a retrospective analysis of the electronic health records (EHR) of adult emergency room and hospitalized patients at the University of Wisconsin (UW) between 2017 and 2021 with an International Classification of Disease (ICD) code for substance misuse. EHR data were linked with the Wisconsin Ambulance Run Data System using privacy-preserving record linkage software. The primary outcome was in-hospital mortality. The primary exposure was the number of EMS incidents in the 1-30 days prior to hospitalization, categorized into (0, 1, or > 1). Patients with an admission in the prior 30 days from the index hospitalization were excluded. Unadjusted and adjusted logistic regression models were used to examine the association between EMS incidents and the outcome of in-hospital death.

Results: Among 24,015 patient admissions, 568 (2.4%) died in-hospital. In the 1-30 days before hospitalization, 21,517 (89.6%) encounters were not preceded by an EMS incident, 1,758 (7.3%) encounters were preceded by 1 EMS incident, and 740 (3.1%) encounters had >1 EMS incidents. The mean age was 47 years (SD 17) and 9,178 (38.2%) of the encounters were female. Patients with only alcohol misuse represented 12,122 (50.5%) encounters, only opioid misuse was 3,472 (14.5%), and polysubstance or other misuse was 8,421 (35%).

In unadjusted analysis, patients with 1 or > 1 EMS incidents were associated with increased risk of in-hospital mortality, compared to admissions without preceding EMS incidents (1 EMS incident OR 1.63 (95% CI: 1.24-2.12); >1 EMS incident OR 2.22 (95% CI: 1.53-3.11)). The association persisted after adjusting for age, sex, comorbidities, means of arrival to the hospital and type of substance misuse (1 EMS incident OR 1.36 (95% CI: 1.02 – 1.77); > 1 EMS incident OR 1.76 (95% CI: 1.21 – 2.50).

Conclusions: Increased utilization of EMS within 30 days of hospitalization is associated with higher in-hospital mortality among patients with substance misuse.