Low acuity EMS dispatch criteria can reliably identify patients without high-acuity illness or injury

This retrospective study evaluated the appropriateness of requests assigned the alpha determinant at the time of dispatch by Emergency Medical Dispatchers using the Medical Priority Dispatch System (MPDS).

The primary end point was the proportion of EMS calls assigned the alpha dispatch determinant that resulted in a high-acuity patient encounter. Patient care reports from January 1 to June 30, 2004, were eligible for inclusion; reports with known errors in data entry or those that were not the result of caller interrogation via the 9-1-1 emergency medical dispatch center (EMDC) were excluded. High-acuity patients were defined as those who met trauma triage criteria or received treatment for acute coronary syndrome, respiratory distress, altered mental status, acute stroke, allergic reaction, or abnormal vital signs. Secondary end points included call-processing time, the proportion of included patients who were transported emergently to hospital, and the adherence of the EMDC to National Academy of Emergency Dispatch (NAED) quality assurance guidelines.

There were 23,939 dispatches; 2,703 were recorded as alpha dispatches in the electronic patient care report (ECR), of which 582 were excluded. Twenty-one of 2,121 calls (<1%) meeting inclusion criteria met high-acuity criteria and were considered as inappropriate alpha dispatches. Fourteen of 2,121 (<1%) were transported emergently to the hospital, eight of whom also met the high-acuity criteria. The call-processing time at the 90th percentile was 2 minutes and 29 seconds. The EMDC demonstrated 99% compliance with NAED quality assurance standards.

The use of standard MPDS protocols can successfully identify patients who do not demonstrate high-acuity illness or injury more than 99% of the time.