Mobile Stroke Units Drive Better Functional Outcome

Damian McNamara

March 03, 2020

LOS ANGELES ― The availability of mobile stroke units (MSUs), specially equipped ambulances that enable patients who are experiencing an acute stroke to be scanned and treated before they arrive at the hospital, was associated with better functional recovery in a new prospective study.

Disability and death rates were 26% lower in an adjusted comparison between people who received treatment in the prehospital setting vs those who received standard treatment upon arrival at an emergency department in Berlin.

Dr Heinrich Audebert

"MSUs were associated with higher rates of thrombolysis, reduced time to treatment, and [improved] functional outcomes at 3 months in patients with acute cerebral ischemia," lead study author Heinrich J. Audebert, MD, said here during a late-breaking abstract session at the 2020 International Stroke Conference (ISC).

"Just waiting until the patient arrives at the hospital is not enough anymore," he said.

Previous research shows that MSUs equipped with CT and staffed by first responders who can administer thrombolysis can be beneficial in this very time-sensitive scenario.

"From several studies, we know we can save time to treatment, but so far it has really been unclear if MSUs improve functional outcomes," said Audebert, who is senior physician in the Department of Neurology and Experimental Neurology, the Center for Stroke Research Berlin, Charité Berlin, in Germany.

Mobile stroke unit in Berlin.

Researching Real-World Recovery

The investigators conducted the Berlin Pre-hospital or Usual Care Delivery (B_PROUD) trial to compare 3-month functional outcomes among 749 adults who underwent treatment when an MSU was available with outcomes for 794 adults who received usual care. The mean age of the patients was 74 years, and 47% were women.

All patients who were included in the study had experienced an ischemic stroke within 4 hours of ambulance dispatch call within one of three MSU service areas. The MSUs operated from 7:00 AM to 11:00 PM 7 days a week.

Three neurologists who were blinded to type of ambulance transport assessed outcomes. They called patients and families to gauge function using the modified Rankin Scale (mRS). The investigators added a coprimary endpoint during the trial "because we felt we would not get mRS information [by telephone] for all of our patients," Audebert said. In these cases, they relied on information from registration offices to calculate mRS scores; 1506 patients were included in this analysis.

The availability of MSU transport significantly reduced rates of disability and death at 3 months in the primary outcome (adjusted odds ratio [aOR], 0.72; 95% confidence interval [CI], 0.60 – 0.87).

Thrombolysis rates were higher in the cohort for which MSU was availabile, at 60% vs 48% in the standard-care group (P < .001).

In addition, median alarm-to-treatment times were shorter in the MSU cohort, at 50 minutes (interquartile range [IQR], 43 – 64) vs 70 minutes in the standard-care group (IQR, 59 – 85). This difference also was significant (P < .001).

"This resulted in three times more patients receiving tPA [tissue plasminogen activator] within 60 minutes," at 4% vs 13%, Audebert said.

"We were not overoptimistic to see positive results," Audebert said. "Fortunately, we did see very clearly benefit for those on MSU dispatch across a full range of modified Rankin Scale scores."

In contrast, coprimary outcomes did not differ significantly between groups (aOR, 0.80; 95% CI, 0.61 – 1.06). The odds ratio for the coprimary endpoint was very similar odds ratio, at 0.75, but the confidence intervals were wider.

"mRS and QOL [quality of life] were clearly better in the MSU-available group," Audebert said.

For the secondary outcome of symptomatic hemorrhage, proportions were low in both groups, at 3.6% in the MSU group vs 2.6% in the standard-care group. There was also a trend toward lower mortality at 7 days in the MSU group, at 1.7% vs 3.0%. In addition, the percentage of patients who were discharged home was higher in the MSU group, at 61% vs 56%.

The researchers found no significant differences in other secondary outcomes, including the thrombectomy rate or time from alarm to thrombectomy.

Earlier and more frequent thrombolytic treatment was primarily responsible for the majority of beneficial effects observed in the study, Audebert said, "but other effects may have contributed."

Earlier neurologic assessment, continuous monitoring, and management of complications during the prehospital phase likely made a difference, but he noted that patients also underwent a second medical assessment upon arrival at the hospital.

The study was conducted in the Berlin metropolitan area, which could limit generalizability to other settings. Another limitation, he added, was the "high number of MSU dispatches relative to the number of treatment candidates, so there is clearly room for improvement of stroke identification at the dispatch center."

"A Really Exciting Development"

"We know that we can get to people sooner and treat them sooner with the mobile stroke units, but there hasn't been a lot of head-to-head comparison of standard therapy allowing people to get to the emergency room and get treated there vs treating them in the mobile stroke unit," Mitchell S. V. Elkind, MD, president-elect of the American Heart Association and professor of neurology and epidemiology at Columbia University in New York City, said in a video commentary that accompanied the study.

"What makes the B_PROUD study so exciting is that they were able to do just that," he said.

"They found that in fact, bringing the ambulance to the patient, doing the imaging, and treating them shaves about 20 minutes off the time that people get tPA," he said. "A much higher proportion of patients got treated with tPA using the mobile stroke unit than without it."

The functional benefits make the findings "a really exciting development" as well, Elkind added.

The considerable expense of MSUs is a potential limitation. "Not every municipality can afford to have there's always the concern that these will lead to an increase in disparities, for example, and who can get treated and where," he said.

The research, he said, "confirms what many of us have thought for a long time, which is that getting treatment to patients sooner is going to lead to better outcomes."

The study was funded by the German Research Foundation and the German Federal Ministry for Research and Education. Audebert receives research grants from Pfizer, Stiftung Deutsche Schlaganfall-Hilfe, Bundesministerium für Bildung und Forschung (BMBF), and the Deutsche Forschungsgemeinschaft, Innovationsfonds des Gemeinsamen Bundesausschusses and honoraria from Pfizer, Bristol-Myers Squibb, Bayer Vital, Boehringer Ingelheim, Takeda, and Novo Nordisk. Elkind has disclosed no relevant financial relationships.

International Stroke Conference (ISC) 2020: Late-breaking abstract 5. Presented February 20, 2020.

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