Cardiac arrest during interfacility transport with emergency medical services: a preliminary nationwide cross-sectional study

OBJECTIVES: We aimed to provide the first national study of out-of-hospital cardiac arrests (OHCA) witnessed by emergency medical services (EMS) during interfacility transport (IFT). METHODS: We used a nationwide prehospital patient care report dataset from 2023 to complete a cross-sectional observational study of EMS encounters for IFT during which OHCA occurred. Descriptive statistics were computed, stratified by level of EMS care provided. Multivariable logistic regression analysis was completed to evaluate factors associated with return of spontaneous circulation (ROSC) at the end of the IFT encounter upon transfer of care to the receiving facility. Finally, we completed a similar multivariable logistic regression analysis restricted to the subgroup of patients with an unshockable initial rhythm. RESULTS: A total of 1,466 OHCA incidents occurred during an IFT with EMS: 7.5% with basic life support (BLS), 53.6% with advanced life support (ALS), and 38.9% with critical care transport (CCT). Among these incidents 11.8% were associated with trauma, 9.2% involved cardiopulmonary resuscitation (CPR) prior to EMS unit arrival, 14.7% involved a mechanical device to perform CPR, 22.2% had a shockable initial rhythm, and 58.1% were transported via ground as opposed to air. At the conclusion of the IFT EMS encounter, 50.3% had sustained ROSC. Geriatric age (aOR 0.64, 95%CI 0.44-0.94), BLS care (aOR 0.45, 95%CI 0.22-0.90), and ground transport (aOR 0.58, 95%CI 0.38-0.89) were associated with worse outcomes on adjusted analysis, whereas shockable initial rhythm (aOR 3.86, 95%CI 2.42-6.36) and CCT care (aOR 2.21, 95%CI 1.42-3.48) were associated with better outcomes. The sub-analysis for OHCA during IFT with an unshockable initial rhythm also showed greater odds of ROSC when managed by CCT relative to ALS (aOR 2.65, 95%CI 1.64-4.33) while adjusting for other key factors. CONCLUSIONS: Using a large nationwide sample of OHCA incidents that occurred during IFT, we found that higher level of EMS care was associated with superior short-term outcomes while controlling for other key factors. These findings underscore the importance of accurate patient triage at sending facilities and the value of CCT for high-risk patients.