Mobile stroke units may “result in lower rates of disability”

James C Grotta

A late-breaking abstract presented at the International Stroke Conference (ISC) 2021 (17 –19 March, online) has presented evidence that patients who received care from a mobile stroke unit (MSU) were less likely to have a disability three months after their stroke than those taken to the emergency department by a standard ambulance. 

“Our goal in this study was to treat patients on the mobile stroke unit within an hour of the onset of their stroke symptoms, and we were gratified that one-third of the patients were actually treated within that time frame,” said James C Grotta, lead study author and director of stroke research at the Clinical Institute for Research and Innovation at Memorial Hermann—Texas Medical Center, Houston, USA. “Our study confirmed that patients who are treated early benefit from a complete reversal of stroke symptoms and avoidance of disability. This suggests that in the first hour after a stroke occurs, the brain is not yet irreversibly damaged and is very amenable to effective treatment.”

According to researchers, MSUs are special ambulances equipped to diagnose and treat stroke quickly. The team on board the mobile stroke unit can treat the patient right away with a clot-dissolving medication called tissue plasminogen activator (tPA).

Houston mobile stroke unit

This study is a phase III, alternating week, cluster-controlled trial, and is part of the ongoing BEST-MSU study. Due to local limitations, researchers were not able to randomise patients so instead alternated weeks the MSU was in service; in the off week, there would be standard medical management. Across both weeks, patients were adjudicated for tPA treatment by a blinded adjudicator, a vascular neurologist. If they were deemed eligible, this patient was included in the study.

The primary outcome for this study was patient utility-weighted modified Rankin Scale (mRS) at three months. Assessments carried out at 90 days were performed by an investigator blinded to treatment assignment.

Investigators examined data from 1,047 patients who suffered an ischaemic stroke and who were eligible for tPA treated at seven US centres (Houston, Aurora, New York City, Indianapolis, Los Angeles, Memphis, and Burlingame) between 2014 and 2020. Researchers compared outcomes of stroke patients brought to the emergency department by a mobile stroke unit versus those who arrived by standard emergency medical services (617 patients via mobile stroke unit, and 430 patients via standard ambulance).

Overall, 97% of eligible patients transported by a mobile stroke unit received tPA, compared to 80% of those brought to the emergency department by a regular ambulance. One-third of the patients treated by a mobile stroke unit were treated within one hour after the onset of stroke symptoms, compared to only 3% of patients transported by a standard ambulance. A total of 53% of the patients treated by a mobile stroke unit made a complete recovery from the stroke after three months, while 43% of the patients treated by a standard ambulance achieved a full recovery.

For their primary outcome, researchers found that the utility weighted mRS had a mean of 0.726 for the MSU, and a mean of 0.657, giving a difference of 0.069. According to Grotta, this difference is statistically significant at a p value of 0.002.

When looking at the population of the study, Grotta noted that the groups were “very well compared” on baseline characteristics. Additionally, he commented that their population was diverse, with equal representation of men and women; around 40% of patients were Black, approximately 17% were Hispanic or Latino, and 20% had a baseline mRS greater than two, meaning they had some pre-existing disability.

“Our results mean that, on average, for every 100 patients treated on a mobile stroke unit rather than standard ambulance, 27 will have less final disability and 11 of the 27 will be disability-free,” Grotta said.

“More widespread deployment of mobile stroke units may have a major public health impact on reducing disability from stroke,” he added. “Although mobile stroke units are costly to equip and staff, they reduce the time to treatment. We also expect that more treatment via mobile stroke units can reduce the need for downstream utilisation of long-term care.”


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