Can emergency medical dispatch systems safely reduce first-responder call volume?

Emergency medical dispatch (EMD) protocols are intended to match response resources with patient needs. In a small city that previously sent a first-responder basic life support (BLS) engine company lights-and-siren response to every emergency medical services (EMS) call, regardless of nature or severity, an EMD system was implemented in order to reduce the number of such responses. The study objectives were to determine the effects of the EMD system on first-responder call volume and to assess the safety of the system.

This was a prospective, before-after trial. Using computer-assisted dispatch (CAD) records, all EMS calls in the 120 days before implementation of the EMD protocol and the 120 days after implementation were identified (excluding a one-month wash-in period). In the "after" phase, patient care reports of a random sample of cases in which an ambulance was dispatched with no first responders was manually reviewed to assess whether there might have been any benefit to first-responder dispatch. Given the lack of accepted clinical criteria for need for first responders, the investigators' clinical judgment was used. Paired t-tests were used to compare groups.

There were 9,820 EMS calls in the "before" phase, with 8,278 first-responder engine runs (84.3%), and 9,943 EMS calls in the "after" phase, with 3,804 first-responder engine runs (39.1%). The first-responder companies were dispatched to a median of 5.65 runs/day (range 1.1-12.7) in the "before" phase, and 3.17 runs/day (range 0.6-5.0) in the "after" phase (p = 0.0008 by paired t-test). Review of 1,816 "after" phase ambulance-only patient care reports (PCRs) found ten (0.55%) in which first-responder dispatch might have been beneficial, but review of EMS and emergency department (ED) records found no adverse outcomes in these ten patients.

This study suggests that a formal EMD system can reduce first-responder call volume by roughly one-half. The system appears to be safe for patients, with an undertriage rate of about one-half of one percent.