Published online by Cambridge University Press: 04 November 2025
For suspected acute myocardial infarction (AMI) and unstable angina patients, prehospital aspirin (ASA) administration has been the standard of care by Emergency Medical Services (EMS) field providers. Recently, Emergency Medical Dispatchers (EMDs), using Medical Priority Dispatch System (MPDS), provide telephone instructions to qualifying suspected AMI patients to take ASA, prior to EMS field provider arrival. No formal studies exist that measure time saved from earlier Dispatcher-Directed Aspirin Administration (DDAA).
The primary objectives of the study were: (1) to determine the amount of time saved, if any, using DDAA; and (2) to describe the frequency of DDAA and Field Provider-Directed Aspirin Administration (FPAA).
The retrospective study analyzed EMD and EMS data collected during a six-month period at three dispatch services and three EMS agencies in the United States. The frequency and mean (plus 95% confidence interval [CI]) time of DDAA and FPAA were calculated. Reasons why patients who qualified to take ASA per dispatch protocol but did not take it were also assessed.
A total of 108,459 EMS cases were analyzed; EMD/EMS delivered ASA to 4.0% (n = 4,113) of these patients. The most frequent primary impressions were: cardiac chest pain (angina), cardiovascular (CV)-chest pain (presumed cardiac), ST-segment elevation myocardial infarction (STEMI), and CV-chest pain – acute coronary syndrome (ACS; 50.0%). Overall, DDAA saved 13 minutes mean time (95% CI, 11.4-14.6; P < .001) (median: 12.3 minutes) from the case creation time.
It was found that DDAA provides measurable time savings in ASA delivery to patients. Further studies will need to assess if the reduction of ASA delivery time by EMDs has the potential to improve overall care and survival for patients. The study identified beneficial new knowledge for possible future enhancements to medical dispatch protocols and for EMS providers.