Major medical events in patients with acute coronary syndrome during helicopter emergency medical service operations.

Abstract

Background: Acute coronary syndromes (ACS) are a leading cause of helicopter emergency medical services (HEMS) operations in Germany. Complications that arise during HEMS operations are challenging due to limited resources. However, the National Advisory Committee for Aeronautics (NACA) score and National Early Warning Score (NEWS) provide potential for risk stratification. Nevertheless, there is an absence of data concerning the incidence and risk of medical events (e.g. malignant arrhythmia, cardiac arrest, cardiogenic shock) in ACS patients during HEMS operations. The objective of this study is to evaluate the incidence of medical events and to assess risk stratification using scoring systems.

Methods: This retrospective observational cohort study analyzed prehospital records from 38,473 HEMS operations with "ACS" coding conducted between 2012 and 2024 in Germany. Routine data were systematically recorded using a standardized digital form that captured patient demographics, clinical presentation, and medical interventions. Major medical events (MME) were defined using surrogate markers, including defibrillation, resuscitation, airway management, ventilation, and new ST-elevation myocardial infarction (STEMI) findings. Scores (NACA, NEWS, and a combined MME-score) were calculated, with the MME-score integrating NACA and NEWS. Ethical approval was obtained from the Albert-Ludwigs-University Freiburg Ethics Committee (No: 24-1082-S1, 25 April 2024).

Results: MME occurred in 8.8% of the 38,473 HEMS operations. They occurred more frequently during secondary missions (interfacility transports) (11.8%) than primary missions (6.7%), and at night (15.3%) than during the day (8.2%) (both p < 0.001). The NACA, NEWS, and MME-scores were significantly higher in cases with medical events (p < 0.001). The risk stratification exhibited areas under the curve in the receiver operating characteristics (ROC) curve, with values of 0.831 for NACA, 0.866 for NEWS, and 0.895 for the MME-score.

Conclusion: The incidence of MMEs is subject to variation depending on the operational context. Established scoring systems such as the NACA and NEWS are available for the purpose of risk stratification of medical events in patients with ACS during air rescue operations. The combination of these scores may indicate potential for improved risk stratification.