Characteristics, diagnostic accuracy, and safety in patients receiving selective prehospital thrombolysis in out-of-hospital cardiac arrest: A retrospective cohort study.

Objectives: Out-of-hospital cardiac arrest (OOHCA) carries a significant mortality implication despite optimal conventional therapies. To better understand the role of prehospital thrombolysis for OOHCA, we report the clinical outcomes, safety and enhanced care team diagnostic accuracy concerning selective thrombolysis by a physician-paramedic staffed air ambulance service. Methods: A retrospective database review of electronic documentation was undertaken for all cases where thrombolysis was administered in OOHCA between January 2017 to April 2022 at Essex and Hertfordshire Air Ambulance Trust (EHAAT). Data collected included demographics, timings, pertinent clinical features, outcomes, and the treating team's suspected cause of arrest. For patients who died, cause of death was obtained from local coroners. Results: 100 patients were identified and five survived to hospital discharge. The median (IQR) time from first cardiac arrest to thrombolysis was 58.5 min (44-75). The cause of death was available for 60 patients, among these 43% had suffered either a pulmonary embolus (PE) or myocardial infarction (MI). In patients who died of MI the critical care team correctly diagnosed this in 76.9% of cases, and of those who died of PE 92.3% were correctly diagnosed. However, the positive predictive value (PPV) of clinician diagnosis overall was only 36.7%. Conclusion: Despite a high proportion of patients having a cause of OOHCA theoretically amenable to thrombolysis, survival to hospital discharge remains poor. Further work is required to better understand the future role and timing of prehospital thrombolysis in refractory OOHCA. Clinicians detected both MI and PE with high sensitivity but low PPV.