Trends in presumed drug overdose out-of-hospital cardiac arrests in San Francisco, 2015-2023

Evaluating the accuracy of surrogate markers for identifying opioid-associated out-of-hospital cardiac arrests

BACKGROUND

Previous studies have used emergency medical services (EMS) naloxone administration and EMS overdose impression as surrogate markers to identify opioid-associated (OA) out-of-hospital cardiac arrests (OA-OHCA). We evaluated the accuracy of these two surrogate markers using medical examiner post-mortem toxicology data in OHCA patients who died.

METHODS

We conducted a retrospective cohort study of all adult (≥18) non-traumatic OHCA patients treated by Milwaukee County EMS between January 1st, 2015 to December 31st, 2016. EMS naloxone administration and EMS impression of cardiac arrest etiology were used to classify expired patients into 2 groups: (1a) Received ≥1 Naloxone (1b) No Naloxone, and (2a) EMS-impression overdose, (2b) Not EMS-impression overdose. Milwaukee County Medical Examiner (MCME) opioid toxicology data was used as the reference standard and matched to EMS-treated OHCA patients that expired to determine the sensitivity (SN), specificity (SP), positive predictive value (PPV), and the negative predictive value (NPV) of both surrogate markers.

RESULTS

1,654 OHCA cases were included; 112 (6.8%) received ≥1 Naloxone and 1,542 (93.2%) received No Naloxone; 60 (3.6%) were EMS-impression overdose and 1,594 (96.4%) were not EMS-impression overdose. Of the 525 opioid-associated deaths in the MCME Drug-related Death Database, 150 (28.6%) were OA-OHCA cases treated by EMS. The SN, SP, PPV, and NPV for EMS naloxone administration was 39%, 96%, 52%, and 94% respectively. The SN, SP, PPV, and NPV for EMS-impression overdose was 27%, 99%, 68%, and 93% respectively.

CONCLUSION

EMS naloxone administration and EMS- impression overdose had limited sensitivity for identifying OA-OHCA in expired patients in this large urban EMS system. Prehospital and public health researchers should identify improved methods for accurately classifying this OHCA subpopulation.

Neurological Injury in Comatose Patients Following Substance-Use-Related Out-of-Hospital Cardiac Arrest: A Retrospective Cohort Study in a Safety Net Hospital

BACKGROUND

Substance-use-related cardiac arrest (SURCA) is a public health crisis, contributing to high mortality and severe neurological disability, particularly affecting young adults. This study aims to characterize the demographic and multimodal neurological prognostication features of patients with SURCA.

METHODS

This retrospective study included patients with out-of-hospital cardiac arrest who presented to an urban academic safety net hospital between July 2016 and April 2022 and were comatose on admission. Patients with SURCA were identified through toxicology screening. Data on demographics, cardiac arrest characteristics, and multimodal neurological prognostication were collected. Poor neurological outcome was defined as a Cerebral Performance Category score of 3-5 at hospital discharge. Logistic regression was used to identify factors associated with poor neurological outcomes.

RESULTS

Among 253 patients, 99 (39%) were classified as having SURCA, with 67 testing positive for stimulants and 56 testing positive for opioids. Patients with SURCA were younger (49 vs. 66 years, p < 0.001), less likely to have a witnessed cardiac arrest (56% vs. 71%, p = 0.01), and more likely to present with nonshockable rhythms (88% vs. 73%, p < 0.001). Electroencephalogram (EEG) monitoring in the SURCA cohort revealed a higher incidence of generalized periodic discharges (54% vs. 35%, p = 0.02) and electrographic seizures (28% vs. 13%, p = 0.02). Outcomes were similar between SURCA and non-SURCA groups; 86% of patients with SURCA had poor neurological outcomes, with 67% not surviving to discharge, compared to 88% and 69% of patients with non-SURCA, respectively. Nonshockable rhythms and older age were associated with poor neurological outcomes, but SURCA was not.

CONCLUSIONS

SURCA is common and is frequently associated with poor neurological outcomes despite affecting younger patients. A higher incidence of seizures and generalized periodic discharges on EEG was observed with SURCA; therefore, validation of this finding in larger multicenter cohorts is warranted. Public health interventions to improve bystander resuscitation education in populations at risk for SURCA may improve outcomes in this vulnerable population.

Naloxone and Patient Outcomes in Out-of-Hospital Cardiac Arrests in California

Importance

The incidence of opioid-associated out-of-hospital cardiac arrest (OA-OHCA) has grown from less than 1% of OHCA in 2000 to between 7% and 14% of OHCA in recent years; American Heart Association (AHA) protocols suggest that emergency medical service (EMS) clinicians consider naloxone in OA-OHCA. However, it is unknown whether naloxone improves survival in these patients or in patients with undifferentiated OHCA.

Objective

To evaluate the association of naloxone with clinical outcomes in patients with undifferentiated OHCA.

Design, Setting, and Participants

Retrospective cohort study of EMS-treated patients aged 18 or older who received EMS treatment for nontraumatic OHCA in 3 Northern California counties between 2015 and 2023. Data were analyzed using propensity score-based models from February to April 2024.

Exposure

EMS administration of naloxone.

Main Outcomes and Measures

The primary outcome was survival to hospital discharge; the secondary outcome was sustained return of spontaneous circulation (ROSC). Covariates included patient and cardiac arrest characteristics (eg, age, sex, nonshockable rhythm, any comorbidity, unwitnessed arrest, and EMS agency) and EMS clinician determination of OHCA cause as presumed drug-related.

Results

Among 8195 patients (median [IQR] age, 65 [51-78] years; 5540 male [67.6%]; 1304 Asian, Native Hawaiian, or Pacific Islander [15.9%]; 1119 Black [13.7%]; 2538 White [31.0%]) with OHCA treated by 5 EMS agencies from 2015 to 2023, 715 (8.7%) were believed by treating clinicians to have drug-related OHCA. Naloxone was administered to 1165 patients (14.2%) and was associated with increased ROSC using both nearest neighbor propensity matching (absolute risk difference [ARD], 15.2%; 95% CI, 9.9%-20.6%) and inverse propensity-weighted regression adjustment (ARD, 11.8%; 95% CI, 7.3%-16.4%). Naloxone was also associated with increased survival to hospital discharge using both nearest neighbor propensity matching (ARD, 6.2%; 95% CI, 2.3%-10.0%) and inverse propensity-weighted regression adjustment (ARD, 3.9%; 95% CI, 1.1%-6.7%). The number needed to treat with naloxone was 9 for ROSC and 26 for survival to hospital discharge. In a regression model that assessed effect modification between naloxone and presumed drug-related OHCA, naloxone was associated with improved survival to hospital discharge in both the presumed drug-related OHCA (odds ratio [OR], 2.48; 95% CI, 1.34-4.58) and non-drug-related OHCA groups (OR, 1.35; 95% CI, 1.04-1.77).

Conclusions and Relevance

In this retrospective cohort study, naloxone administration as part of EMS management of OHCA was associated with increased rates of ROSC and increased survival to hospital discharge when evaluated using propensity score-based models. Given the lack of clinical practice data on the efficacy of naloxone in OA-OHCA and OHCA in general, these findings support further evaluation of naloxone as part of cardiac arrest care.