Mobile stroke units decrease global disability at 3 months vs. conventional ambulance

The dispatch of mobile stroke units resulted in lower global disability at 3 months compared with conventional ambulances among patients who experienced an acute ischemic stroke, according to findings published in JAMA.

“Mobile stroke units (MSUs) are ambulances equipped with a CT scanner designed to allow thrombolysis prior to hospital arrival,” the researchers wrote. “Mobile stroke units shorten the time to treatment, increase thrombolysis rates and improve prehospital triage. However, potential effects of MSUs on functional outcomes after stroke are uncertain.”

Martin Ebinger, MD, PhD, member of the Center for Stroke Research Berlin and chief neurology physician at Medical Park Berlin, and colleagues performed a prospective, nonrandomized, controlled intervention study in Berlin between February 1, 2017, to October 30, 2019. The study protocol involved the dispatch of both a conventional ambulance and an MSU, when available, for emergency calls that aroused suspicion of stroke. The researchers compared functional outcomes in patients who received a final confirmed diagnosis of acute cerebral ischemia who were eligible for thrombolysis or thrombectomy according to the initial dispatch — both MSU and conventional ambulance (n = 749) or conventional ambulance only (794).

The distribution of modified Rankin Scale (mRS) scores, a disability score ranging from 0 (no neurological deficits) to 6 (death), at 3 months served as the primary outcome. Ebinger and colleagues used three-tier disability scale (none to moderate disability, severe disability or death), with tier assignment according to mRS scores if they were available or place of residence if they were not, at 3 months as the coprimary outcome. The researchers calculated ORs to examine the link between exposure and outcome, with values less than 1 denoting a “favorable shift in the mRS distribution and lower odds of higher levels of disability,” according to the study results.

The adjusted primary analysis included 1,543 patients (mean age, 74 years; 47% women). Of these, 1,337 (87%) had mRS scores available and 1,506 patients (98%) had the three-tier disability scale assessment available.

Ebinger and colleagues observed lower median mRS scores at month 3 in patients for whom an MSU was dispatched (1; interquartile range [IQR], 0-3) compared with patients who did not have an MSU dispatched (2; IQR, 0-3), resulting in a common OR for worse mRS of 0.71 (95% CI, 0.58-0.86). Patients for whom an MSU was dispatched also experienced lower 3-month coprimary disability scores: 586 patients (80.3%) were classified as having none to moderate disability; 92 patients (12.6%) had severe disability; and 52 (7.1%) died. This was compared with patients for whom an MSU was not dispatched: 605 (78%) of those patients had none to moderate disability; 103 (13.3%) had severe disability; and 68 (8.8%) died (common OR for worse functional outcome, 0.73; 95% CI, 0.54-0.99).

Thrombolysis treatment was administered in 451 patients (60.2%) for whom an MSU was dispatched and in 382 patients (48.1%) who did not receive an MSU dispatch (adjusted OR [aOR], 1.62; 95% CI, 1.32-2). Median times from dispatch to start of thrombolysis for patients with an MSU dispatch was 50 minutes (IQR, 43-64 minutes) and 70 minutes (IQR, 59-86 minutes) for patients without an MSU dispatch (mean difference in percentage based on log-transformed values, 27%; 95% CI, 31% to 22%).

Symptomatic secondary intracranial hemorrhage occurred in 24 patients (3.2%) who received an MSU dispatch and in 22 patients (2.8%) without an MSU dispatch (aOR, 1.2; 95% CI, 0.66-2.19). The researchers reported 13 deaths (1.7%) within 7 days among patients who received an MSU dispatch and 24 deaths (3%) among patients who did not (aOR, 0.54; 95% CI, 0.26-1.12).

“In this prospective, nonrandomized, controlled intervention study of patients with acute ischemic stroke in Berlin, Germany, the dispatch of [MSUs], compared with conventional ambulances alone, was significantly associated with lower global disability at 3 months,” the researchers wrote. “Clinical trials in other regions are warranted.”