Prognosis improvement effects of physician staffed helicopter emergency medical service on cerebral infarction patients: registry based prospective observational study
Authors: Mashiko Kazuki , Okada Kazuhiro , Hara Yoshiaki , Yokobori Shoji , Takayama Hayato , Nakagawa Yoshihide , Kobayashi Makoto , Tsuchiya Asuka , Hayakawa Tatsuya , Noda Tatsuya , Ito Kayo , Endoh Hiroshi , Suda Takayuki , Yanagawa Youichi , Kato Seiya , Yamamori Yuji , Kanemaru Katsuhiro , Yonemori Terutake 
Published: September 2022

Abstract
Purpose This study clarifies the effectiveness of helicopter emergency medical service, widely known as “Doctor-Heli” (DH) in Japan, and its impact on the neurological outcome of cerebral infarction patients.
Materials and methods Out of 4,480 patients registered from April 2015 to August 2018 whose principal diagnosis was cerebral infarction at the fourth week of their hospitalization, discharge, or hospital transfer, we focused on 3,599 patients after excluding transferred to other than base hospitals. Among these 3,599 patients, we analyzed 1,246 cases after eliminating cardiac arrest cases that occurred at the time the ambulance crews arrived at the scene as well as cases with missing data and errors that would affect the analytical results. We examined the effect of DH transports on the illness outcome by establishing and comparing two groups, a group of helicopters that transported patients to base hospitals during the operating hours of DHs (i.e. the DH group) and a group of ground ambulances that transported patients because of bad weather, short distance, overlapping cases, etc. (i.e. the GA group). We used the Cerebral Performance Category (CPC) to evaluate the neurological outcome as a primary evaluation index and used the Overall Performance Category (OPC) as a bodily function outcome evaluation index. We also examined in-hospital mortalities of both groups.
Results/discussion A comparison of 421 cases in the DH group and 825 cases in the GA group revealed significantly negative tendencies in the Japan Coma Scale (JCS) at the time the ambulance crews made physical contact with the patients and the Glasgow Coma Scale (GCS) at the time the patients were transported. We believe that the DH group tended to transport patients with severe illnesses since it had significantly high National Institutes of Health Stroke Scale (NIHSS) scores at the time of transporting the patients. We confirmed that the DH group had significantly high rates of emergency treatment provisions such as recombinant tissue plasminogen activator (rt-PA) and interventional radiology (IVR). We found no differences in rt-PA between the two groups from the time of illness onset to the start of radical treatments. However, the DH group had significantly short onset to IVR time (167.00 min/197.50 min: p = 0.025). The DH group had poor CPC results, but we observed no difference in OPC between the two groups. We conducted a multivariate logistic regression analysis to determine the background factors because the results from the DH group indicated relatively long transport distances and short transport times. The DH group had a favorable neurologic outcome (CPC1–2) with an odds ratio of 1.38 (95% CI: 0.89–2.12, p = 0.15), a favorable bodily function outcome (OPC1–2) with an odds ratio of 2.33 (95% CI: 1.28–4.24, p = 0.01), and an in-hospital mortality odds ratio of 0.71 (95% CI: 0.29–1.74, p = 0.46). We conducted a subgroup analysis for serious cases of the illness (NIHSS > 10) and discovered that the odds ratio for CPC1–2 was 2.19 (95% CI: 1.12–4.27, p = 0.02) and that for OPC1–2 was 2.62 (95% CI: 1.27–5.42, p = 0.01).
Conclusion The DH group responded to patients who had high severity of the illness and were located in remote areas. In particular, the DH group provided emergency IVR treatment opportunities in a short time. This paper proposes possible DH transport improvements in terms of bodily function and neurologic outcomes, particularly for NIHSS > 10 cases.