Author Response: “A Transfer Strategy Utilizing a Helicopter and a Ground Ambulance Together Does Not Prolong Door-In-Door-Out Times in Thrombectomy Patients: A Retrospective Analysis”

We appreciate the interest of Un Nisa et al. in our study “A Transfer Strategy Utilizing a Helicopter and a Ground Ambulance Together Does Not Prolong Door-In-Door-Out Times in Thrombectomy Patients: A Retrospective Analysis” [1] and their insightful comments regarding potential additional analyses and perspectives.

First and foremost, we wish to highlight the most important conclusion in our study: a thrombectomy candidate in a primary stroke center (PSC) should not remain waiting for a prolonged time the information whether the air transfer is available. The transfer should commence as soon as possible by ground and a helicopter emergency medical service (HEMS) unit should join the mission and continue the air transfer on route when suitable. Wong et al. [2] showed that air transfer increases the DIDO and is feasible only when the travel distance exceeds 250 km. Our transfer protocol had no impact on the DIDO and decreased the travel time when the driving distance from the PSC to our endovascular center was circa 180 km [3].

We agree with Un Nisa et al.: patients with large vessel occlusion are not interested in one detail of the care pathway such as door-in-door-out time. Only their functional outcome matters. Since our previous study [3] already reported the outcomes and travel times of the patients from South Ostrobothnia, we wanted this study to concentrate solely on investigating the change the transfer protocol modification caused to the in-hospital workflow. To overcome the possibility of the Hawthorne effect, we decided to compare DIDOs from two similar PSCs.

Which minutes are worth saving? The costs of helicopter emergency services units are mostly fixed. Adding a few flight hours causes only minimal increments to the costs. Implementing helicopter transports to stroke care pathway is a feasible solution to improve cost-effectiveness [4]. Naturally, a pragmatic local assessment needs to be done when an air transfer protocol for stroke patients is considered. One must keep in mind that local ambulance preparedness is preserved when the ground EMS is able to return earlier to their own station after patient handover to HEMS [5].

Why we were not able to replicate the expediting effect of thrombolysis on DIDO? [2, 6, 7] Similarly to our results, Choi et al. [8] showed equivalent DIDOs in patients treated with thrombolysis and in patients with a contraindication for it. The studies showing faster DIDOs with thrombolysis present markedly slower DIDOs than ours or the ones published by Choi et al. We encourage PSCs to collaborate with local EMS to revise the thrombectomy candidates' transfer protocol thoroughly with and without thrombolysis.

Pauli Vuorinen: conceptualization, writing – original draft, writing – review and editing. Joonas Kiili: conceptualization, writing – review and editing. Markku Grönroos: conceptualization, writing – review and editing. Ilkka Virkkunen: writing – review and editing. Heini Huhtala: writing – review and editing. Piritta Setälä: conceptualization, writing – review and editing. Sanna Hoppu: conceptualization, writing – review and editing.

The authors declare no conflicts of interest.

This is a linked article to Un Nisa et al. ‘Letter to the Editor: A Transfer Strategy Utilizing a Helicopter and a Ground Ambulance Together Does Not Prolong Door-In-Door-Out Times in Thrombectomy Patients: A Retrospective Analysis.’ To view this article, visit https://doi.org/10.1111/ene.70306.