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Implications of pre-alerts in emergency medical dispatch


In emergency dispatching, pre-alerts are used to send responders to calls prior to getting a final dispatch code. Some studies have showed that pre-alerts can effectively reduce dispatch time for out-of-hospital cardiac arrests, potentially improving overall patient outcome. However, there is also a potential risk in running lights-and-siren on non-fully triaged calls. Although pre-alerts have been used for several years, no research studies have demonstrated its benefit, in general.

The goal of this study was to determine the implications of pre-alerts for medical emergency calls, with regard to dispatch priorities, response units, and call cancellation and call downgrading.

This retrospective, descriptive study analyzed de-identified dispatch and EMS data from two emergency communications centers in the USA: Johnson County Emergency Communications Center (ECC), Kansas, and Guilford County Emergency Services, North Carolina. Results: A total of 139,815 calls were included in the study, of which 73,062 (52.3%) were downgraded, and 7,189 (5.1%) were cancelled. This indicates a waste of valuable resources and an implied increase in cost and risk. Additionally, in 20.0% of the calls, at least one response unit was cancelled, while only 1.12% were transported with high priority (lights-and-siren). A median elapsed time (-14 sec) from pre-alert to ProQA launch indicates that calls sat in the queue for median time of 14 seconds before first units were assigned.

The study found a significant number of cancelled units and downgraded calls. In addition, the very small percentage of calls where patients were transported with high priority indicates unnecessary pre-alerts for non-critical patients. Study findings demonstrated that calls spent a substantial amount of time in queue, and units were sent without safety/final coding information. To better establish the positive and negative impacts of pre-alerting, a controlled study should be done to compare with findings from agencies that do not pre-alert calls.


Faudere, D., Hutchens, J., Olola, C., Scott, G., Broadbent, M., & Gardett, I. (2018). Implications of Pre-Alerts in Emergency Medical Dispatch.Annals of Emergency Dispatch and Response, 6(3), pp. 10-14.

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Last Updated: 12/12/23