Value Utilization of Emergency Medical Services Air Transport in Acute Ischemic Stroke

Determining whether a patient has a time-critical medical condition requiring helicopter Emergency Medical Services (HEMS) transportation is a challenge with acute ischemic stroke (AIS). Although HEMS is largely accepted as improving outcomes in time-sensitive conditions, overtriage of patients ineligible for acute stroke therapies places patients and providers at unnecessary risk and wastes limited health care resources.

We sought to identify how accurate our triage system was at identifying high-yield EMS transfers. A better triage system would decrease the volume of low flight value HEMS transfers.

We conducted a retrospective study during a 1-year period. Low flight value was defined by acute therapy eligibility and presenting medical status.

Of 141 AIS patients transferred by HEMS, 23 (16%) were deemed of low flight value; 14 (61%) were outside the acute treatment time window for either intravenous tissue plasminogen activator or endovascular therapy (EVT); 5 patients (22%) were ineligible for EVT (National Institute of Health Stroke Scale < 6); 2 patients (9%) were ineligible for EVT (Modified Rankin Scale ≥ 3); and 2 patients (9%) were flown despite negative angiographic studies performed at transferring institution. Thirteen (57%) of the patients were interfacility transfers as opposed to direct HEMS transport from the field.

HEMS transport for AIS patients plays a crucial role in delivering the best evidence-based care. However, a significant percent of patients did not meet criteria for its optimal utilization, most commonly due to expired treatment windows. Furthermore, low flight value transfers were initiated in spite of physician evaluation > 50% of the time. These results represent a unique opportunity to coordinate education and build effective triage paradigms across a system of stroke care.