Bystander CPR Technique and Outcomes for Cardiac Arrest With and Without Opioid Toxicity

Importance Previous studies support bystander provision of chest compression–only cardiopulmonary resuscitation (CC-CPR) for out-of-hospital cardiac arrest (OHCA). However, it is unknown whether OHCA secondary to opioid toxicity may benefit from chest compression plus ventilation CPR (CCV-CPR). Objective To examine the association between bystander CPR technique and outcomes among both opioid-associated OHCA (OA-OHCA) and otherwise undifferentiated OHCA. Design, Setting, and Participants This cohort study (performed from August 1, 2023, to December 31, 2024) analyzed cases of adult emergency medical services–treated OHCA that occurred from December 1, 2014, to March 31, 2020, as identified through the British Columbia Cardiac Arrest Registry. Exposures Cases were classified as OA-OHCA based on positive postmortem toxicologic investigations, death certificates, or opioid-specific hospital-based diagnoses. All other cases were classified as undifferentiated OHCA. Main Outcomes and Measures Favorable neurologic outcome at hospital discharge (cerebral performance category ≤2). A multivariable Utstein-adjusted logistic regression model of complete cases was used to assess the association between bystander CPR technique (CC-CPR [reference] vs both CCV-CPR and no CPR individually) with outcomes. An interaction term between the OA-OHCA and bystander CPR technique was used to estimate associations among OA-OHCA and undifferentiated OHCA cases separately. Results The study included 10 923 OHCAs. After removing 24 cases only treated with ventilatory support, there were 1343 OA-OHCAs (median [IQR] patient age, 40 [31-50] years; 1015 [76%] male) and 9556 undifferentiated OHCAs (median [IQR] patient age, 70 [58-81] years; 6636 (69%) male). In the OA-OHCA group, bystander CCV-CPR was associated with an increased odds of a favorable neurologic outcome (adjusted odds ratio [AOR], 2.85; 95% CI, 1.21-6.75) when compared with CC-CPR. No association was detected with favorable neurologic outcome (AOR, 1.52; 95% CI, 0.82-2.82) when no CPR was compared with CC-CPR. Among undifferentiated OHCAs, no association was detected with a favorable neurologic outcome (AOR, 1.16; 95% CI, 0.80-1.67) when CCV-CPR was compared with CC-CPR. No CPR was associated with a decreased odds of a favorable neurologic outcome (AOR, 0.69; 95% CI, 0.55-0.87) when compared with CC-CPR. The interaction term was statistically significant ( P for interaction = .04). Conclusions and Relevance In this cohort study of OHCA, bystander CCV-CPR (compared with CC-CPR) was associated with improved outcomes in opioid-associated OHCA; however, this association was not observed among undifferentiated cardiac arrests. These results suggest that the optimal bystander CPR technique for OA-OHCA and undifferentiated OHCA may differ and that ventilations may improve outcomes in OA-OHCA resuscitation.