Streamlining a Thrombectomy Candidate’s Care Outside the Hospital District of a Comprehensive Stroke Centre: Focus on the Emergency Call and Expedited Transportation with Helicopter Emergency Medical Services

Ischemic stroke causes marked morbidity and mortality in Western societies. Consequences are particularly severe when the stroke is due to a large vessel occlusion (LVO): the occlusion occurs in the internal carotid artery, middle cerebral artery, or basilar artery. Intravenous thrombolysis is rather ineffective in these cases. State-of-the-art treatment is the mechanical removal of the occlusion, i.e., mechanical thrombectomy. The odds of returning to independent living depend mainly on the time between the onset of stroke symptoms and restoration of circulation to the occluded artery. Only neurointerventionalists in university hospitals perform mechanical thrombectomies in Finland. Prehospital care of a patient with an LVO stroke far from a thrombectomy centre has been debated.

This thesis aims to streamline the care of a patient with an LVO stroke. We studied the contents of emergency calls for paramedic-suspected thrombectomy candidates and determined whether identifying a thrombectomy candidate during the emergency call was possible by asking about conjugate eye deviation (CED) away from the paretic side. We examined if a helicopter emergency medical services (HEMS) unit could expedite transporting a thrombectomy candidate and how this affects the regional ambulance preparedness near the primary stroke centre.

Study I was a retrospective review of the dispatch information and medical records of patients with suspected stroke dispatches and dispatcher-suspected CED in Tampere between 13 February 2019 and 31 October 2020. In Study II, we listened to recorded emergency calls for 157 paramedic-suspected thrombectomy candidates. The keywords and symptoms mentioned were studied. We particularly concentrated on how the question concerning CED was placed and answered.

In Study III, the on-call HEMS unit in the Tampere University Hospital area was dispatched to continue the thrombectomy candidates’ transports from the South Ostrobothnia Hospital district. We reviewed the prehospital timeline of these patients until the arterial occlusion’s removal. Study IV approximated the return of the ambulances in Study III to their station.

Study I included 1913 suspected stroke dispatches, of which 81 (4%) had a “yes” answer marked to the CED question in the dispatch report. The paramedics could verify CED in nine (11%) callouts. Only two of these 81 patients were finally treated with mechanical thrombectomy. During the same study period, 19 other patients from Tampere were treated with mechanical thrombectomy.

The callers in Study II mentioned typical stroke symptoms: speech disturbance, facial asymmetry, and one-sided motor difficulty. The dispatcher used a non-stroke dispatch code in 69 (44%) cases; hence, CED was not inquired about in those emergency calls. In the suspected stroke dispatches (n=88), CED was asked about 50 (57%) times. CED’s direction was asked correctly 13 (26%) times. CED’s presence was verified in 12 (7.6%) emergency calls. Ten of these 12 patients were diagnosed with an LVO.

The median (Q1–Q3) transport time from the primary stroke centre to the thrombectomy centre was 109 (104–116) minutes in an ambulance and 84 (82–86) minutes (p<0.001) when the HEMS unit continued the transport. When the primary stroke centre was bypassed, the ambulance transport took 97 (91–108) minutes; with a helicopter it took 93 (80–102) minutes (p=0.28). The percentages of patients returning to independent living were equal between different transport modalities.

The returning ambulance’s median driving time (Q1–Q3) to its station was approximated to last 53 (38–68) minutes when the HEMS unit continued the transport. The median return time from the thrombectomy centre to its base was approximately 145 (117–153) minutes (p<0.001). The HEMS unit was occupied in the mission for a median of 136 (127–148) minutes.

In conclusion, the dispatch protocol for suspected strokes did not discriminate between LVO and non-LVO strokes. An LVO patient’s time to definitive care decreased with a helicopter transport. Additionally, thrombectomy candidates’ HEMS transports might increase the number of vacant ambulances near a primary stroke centre.