Further confirmation of the compelling health and economic benefits of mobile stroke units. Results of a German study, with a robust sample size, published a couple of days ago.
This is very important as it is consolidating the evidence base for substantial take up of point of care stroke imaging for the long term.
The metrics, surely, will be even more compelling for small footprint devices such as EMV's.
Mobile Stroke Units Improve Outcomes
Feb 3, 2021 Ambulances equipped with CT scanners allow thrombolysis before hospital arrival
Mobile stroke units (MSUs) — ambulances equipped with CT scanners to allow thrombolysis before hospital arrival — were associated with lower global disability at three months in acute ischemic stroke patients, a prospective study in Germany showed.
“The absolute differences of 8.6% for survival without any disability (modified Rankin Scale (mRS) 0-1) and 4% for survival without moderate to severe disability (mRS 0-3) are clinically relevant,” wrote Heinrich Audebert, MD, of Charite–Universitatsmedizin in Berlin, and co-authors in JAMA.
Between Feb. 2017 and Oct. 2019, both conventional ambulances and, when available, mobile stroke units were dispatched for calls suggesting stroke. Audebert and colleagues studied patients with a final diagnosis of ischemic stroke who were eligible for thrombolysis or thrombectomy, comparing those whose response included MSU with those whose response did not. MSUs provided CT with or without angiography, laboratory testing, and thrombolysis.
For the primary outcome at 3 months, the analysis included 749 patients whose response included the mobile stroke unit and 794 whose response did not. Median 3-month mRS scores were 1 for the MSU group versus 2 for those with conventional ambulance only (OR for worse outcome 0.71 favoring the MSU group (95% CI 0.58-0.86, P< 0.001).
At 3 months, patients with and without MSU response had 80.3% and 78% rates of moderate disability, respectively. Severe disability rates were 12.6% versus 13.3%, and rates of death were 7.1% versus 8.8%.
“The rate of thrombolysis was higher and the median dispatch-to-thrombolysis time was lower among patients with an MSU dispatch than among patients without an MSU dispatch,” Audebert and colleagues wrote. “The combined effect of these parameters may explain the better outcomes in the MSU group.”
Evidence like this is “crucial for improving future use of MSUs for out-of-hospital treatment of patients with stroke and planning of new sites for MSU implementation, whether in metropolitan areas like Berlin, or rural locations with long distances and scattered populations,” noted Kristi Bache, PhD, of the Norwegian Air Ambulance Foundation and the University of Oslo, and James Grotta, MD, of Memorial Hermann Hospital-Texas Medical Center, in an accompanying editorial.
Time-dependent benefits of acute treatment for ischemic stroke have motivated attempts to render treatment closer to onset of symptoms with the use of MSUs, whose capabilities have evolved to include CT angiography. A 2018 study suggested pre-hospital thrombolysis was associated with better clinical outcomes, as did a 2020 study. That study compared door-to-puncture times for thrombectomy patients seen prior to (2014-2018) and after (2018-2019) CT angiography was added to MSUs. They found median door-to-puncture time was 53.5 minutes shorter with onboard CT angiography (41 versus 94.5 minutes, respectively) and associated with more improvement of National Institutes of Health Stroke Scale (NIHSS) score.
“Most guidelines do not explicitly comment on the use of MSUs, in part due to sparse evidence,” Audebert and co-authors noted.
Of 1,543 patients included in the present study’s adjusted primary analysis, mean age was 74 years and 47% were women. Median NIHSS (which ranges from 0-42, with higher scores indicating greater deficit) was 4 at the first assessment in both groups.
Time from dispatch to hospital arrival was median 67 minutes with MSU dispatch and 37 minutes without.
For patients receiving thrombolysis (60% of those with MSU dispatch and 48% of those without), post-hoc analysis found shorter onset-to-treatment times were associated with good outcome (mRS 0-1). Compared with times from 181 to 270 minutes, the adjusted ORs for good outcome were 3.25 (95% CI 1.72- 6.13) for times of 60 minutes or less, 2.54 (95% CI 1.44-4.49) for 61 to 120 minutes, and 2.11 (95% CI 1.12-3.94) for 121 to 180 minutes.
Symptomatic secondary intracranial hemorrhage occurred in 24 patients (3.2%) with an MSU dispatch and 22 patients (2.8%) without (adjusted OR 1.20, 95% CI 0.66-2.19).
For patients receiving thrombectomy, time from dispatch to start of procedure was not significantly different for those with and without MSU (137 versus 125 minutes, respectively). This contrasts with recent reports from other MSU sites, the authors noted.
“Although MSU staff did notify the hospital teams en route if the CT angiographic scan taken aboard the MSU demonstrated the need for endovascular treatment, patients underwent another scan in most emergency departments,” they wrote. “The main reason was that interventionalists requested imaging of the aortic arch and the proximal carotid arteries that were not covered by the small MSU CT scanner.”
“With every MSU project, unforeseen new opportunities emerge,” Bache and Grotta observed. “The data from this study identify two such areas: the need to make EMS dispatch algorithms more precise so the MSU will not be occupied on a futile call when it is needed for a patient who experiences a stroke and the opportunity to speed endovascular thrombectomy by onboard CT angiography, and better communication between MSU and endovascular thrombectomy teams.”
“The next steps, as noted by the authors, should be aimed at undertaking confirmatory trials that could increase knowledge about cost-effectiveness, implementation strategies, and generalizability of MSU models,” they added.
Limitations of the study include a non-randomized intervention. Also, documentation of neurological deficits on EMS arrival was 9% higher in the MSU group.
Mobile stroke units (MSUs) — ambulances equipped with CT scanners to allow thrombolysis prior to hospital arrival — were associated with lower global disability at three months in acute ischemic stroke patients, a prospective study in Germany showed.
Confirmatory trials that could increase knowledge about cost-effectiveness, implementation strategies, and generalizability of MSU models are needed, the authors and editorialists suggested.
Paul Smyth, MD, Contributing Writer, BreakingMED™
The study was funded by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation); te registry was funded by the Federal Ministry of Education and Research via the Center for Stroke Research Berlin.
Audebert reported receiving personal fees from Bayer Vital, Boehringer Ingelheim, Bristol Myers Squibb, Novo Nordisk, Pfizer, and Sanofi.
Grotta is a principal investigator of a randomized trial of mobile stroke units funded by the Patient-Centered Outcomes Research Institute, receives grant support in the form of tPA from Genentech; and serves as a consultant for Frazer Ltd, a manufacturer of mobile stroke units. Bache is a principal investigator of a controlled trial of mobile stroke units in Norway funded by the Norwegian Air Ambulance Foundation.
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