Validation of the naloxone cardiac arrest decision instrument for identifying opioid-associated cardiac arrests.

Abstract

Up to fifteen percent of out-of-hospital cardiac arrests (OHCAs) are precipitated by occult drug overdose - cases without history or evidence of drug use that are often attributed to a non-overdose cause. The NAloxone Cardiac ARrest Decision Instrument (NACARDI) was derived to help emergency medical service (EMS) providers rapidly identify patients at higher risk of occult opioid-associated (OA)-OHCAs during resuscitation. In this analysis we externally validate NACARDI in an independent cohort of OHCA patients. We conducted a retrospective validation using data from EMS-attended OHCA patients and coroner records in Ontario, Canada between 2020-2021. Inclusion criteria were age ≥18 years and OHCA death with a coroner record. Exclusion criteria were EMS-suspected drug overdose or known cause of the OHCA. NACARDI consists of two criteria: patient age and unwitnessed cardiac arrest. Two cut-offs for patient age were assessed for this validation: <50 years (NACARDI-50) and <60 years (NACARDI-60). The primary outcome was coroner adjudicated cause of death. We calculated screening characteristics and receiver operating characteristic (ROC) curves using standard formulae. Of 2904 OHCA cases without an obvious cause, 791 had coroner evaluations and 121 (15.3 %) were adjudicated as occult OA-OHCA. NACARDI-60 had: sensitivity 82.6 % (95 %CI 74.9-88.4 %), specificity 77.1 % (95 %CI 73.8-80.1 %), negative predictive value 96.1 % (95 %CI 94.1-97.4 %), and positive predictive value 39.4 % (95 %CI 33.6-45.5 %). NACARDI-50 had: sensitivity 63.6 % (95 %CI 54.4-72.2 %), specificity 89.3 % (95 %CI 86.7-91.5 %), negative predictive value 93.2 % (95 %CI 90.9-95.0 %), and positive predictive value 51.7 % (95 %CI 43.4-59.9 %). ROC curves for both NACARDI-50 and NACARDI-60 demonstrated excellent discrimination for occult OA-OHCA. In this external validation cohort, NACARDI had a sensitivity and specificity sufficiently high to aid in the real-time identification of occult OA-OHCA in the field. NACARDI has the potential to guide targeted interventions for OA-OHCA.