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Air Med J. 2018 Mar - Apr;37(2):108-114. doi: 10.1016/j.amj.2017.11.015. Epub 2018 Jan 12.

Canceled to Be Called Back: A Retrospective Cohort Study of Canceled Helicopter Emergency Medical Service Scene Calls That Are Later Transferred to a Trauma Center.

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Sunnybrook Health Sciences Centre, Toronto, Ontario, Canada. Electronic address:
St. Michael's Hospital, Toronto, Ontario, Canada.
Sunnybrook Health Sciences Centre, Toronto, Ontario, Canada.



In our trauma system, helicopter emergency medical services (HEMS) can be requested to attend a scene call for an injured patient before arrival by land paramedics. Land paramedics can cancel this response if they deem it unnecessary. The purpose of this study is to describe the frequency of canceled HEMS scene calls that were subsequently transferred to 2 trauma centers and to assess for any impact on morbidity and mortality.


Probabilistic matching was used to identify canceled HEMS scene call patients who were later transported to 2 trauma centers over a 48-month period. Registry data were used to compare canceled scene call patients with direct from scene patients.


There were 290 requests for HEMS scene calls, of which 35.2% were canceled. Of those canceled, 24.5% were later transported to our trauma centers. Canceled scene call patients were more likely to be older and to be discharged home from the trauma center without being admitted.


There is a significant amount of undertriage of patients for whom an HEMS response was canceled and later transported to a trauma center. These patients face similar morbidity and mortality as patients who are brought directly from scene to a trauma center.

[Indexed for MEDLINE]

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