Mobile Stroke Unit Cuts Time to Treatment

Pauline Anderson

April 11, 2012

April 11, 2012 — Using a mobile stroke unit (MSU) equipped with a computed tomography (CT) scanner, laboratory, and telemedicine connection cuts "door to needle" time in half, a new study shows.

"There is much clinical and experimental evidence showing that the earlier thrombolysis treatment starts, the better the outcome, the 'time is brain' concept," study author Klaus Fassbender, MD, PhD, Department of Neurology, University of the Saarland, Homburg, Germany told Medscape Medical News. "Thus, if the delay until treatment can be halved by pre-hospital stroke diagnosis and treatment, outcome is considered to be better."

Dr. Klaus Fassbender

Dr. Fassbender pointed out that thrombolysis is underused, with only 2% to 5% of patients receiving it, mostly because of delays in accessing it within the first crucial hours after symptom onset. "So every effort should be made to accelerate stroke management. Pre-hospital stroke treatment is the now the fastest solution."

The study was published online April 11 in Lancet Neurology.

Specially Equipped Ambulance

For the study, all emergency calls to the central emergency medical service (EMS) coordinating office from a region of up to 30 km around Saarland University Hospital were assessed for reporting of stroke symptoms. Patients aged 18 to 80 years who had at least 1 stroke symptom that had started within the previous 2 to 5 hours were considered for the study.

Mobile stroke unit

Patients entered into the study within a particular week received the same procedure — either MSU or control. "It was a randomized study because the 'MSU' or 'control' weeks were determined by chance through a computer program," said Dr. Fassbender. "For medical and ethical reasons it was not blinded."

The MSU team included a paramedic, a stroke physician, and a neuroradiologist. The team undertook a neurologic examination, CT, and laboratory examination in their specially equipped ambulance and, if the patient was eligible, gave thrombolysis directly at the emergency site.

Patients in the control group received optimized conventional stroke management that included point-of-care laboratory testing instead of testing by the centralized hospital lab. Thrombolysis was given in accordance with criteria for the approval of alteplase.

The study was stopped early after 100 of 200 planned patients (53 in the MSU and 47 in the control groups) when the predefined interim analysis showed the prespecified superiority (P = .0015) in the primary endpoint, time from alarm to therapy decision.

Median times from alarm to arrival at the scene were 12 minutes for the MSU group and 8 minutes in the control group. However, the MSU approach roughly halved the time from alarm to therapy decision compared with the time in the control group, with a median of 35 minutes vs 76 minutes.

Inside the mobile stroke unit

Time Savings

Other time-related aspects of stroke management were also substantially reduced. For example, the MSU strategy reduced the median time from symptom onset to therapy decision (56 minutes vs 104 minutes) and from symptom onset to intravenous thrombolysis (72 minutes vs 153 minutes). Median times were also shorter in the MSU group for alarm to end of CT (34 minutes vs 71 minutes).

The MSU did not significantly increase the proportion of patients who received thrombolysis (12 of 53 vs 8 of 47 in the control group).

However, neurologic outcomes did not differ substantially between the 2 groups. At 7 days, 21 were dead or dependent in the MSU group compared with 20 in the control group. Three patients in the MSU group and no patients in the control group died.

Dr. Fassbender noted that the study was not statistically powered to show significant differences in clinical outcome. "For showing differences in clinical endpoints, studies that are 10-fold larger and multicenter would be required for statistical reasons."

Asked whether the MSU approach would be useful only in densely populated urban areas, Dr. Fassbender said his study, which was performed in a mixed urban and rural region, found advantages in timing of stroke management in both settings. He noted that efficiency in "crucial interfaces" between the relevant healthcare professionals was also improved. "It might be helpful in big cities with many patients but also in rural regions which are currently not covered with stroke units," he said.

The question of whether the MSU strategy is cost-effective still needs to be addressed, said Dr. Fassbender. Further research is also needed on triaging patients with suspected stroke by the MSU to determine the most appropriate hospital, he said.

Proof of Concept

The research is kind of a "proof of concept" study, commented Alastair M. Buchan, professor, Nuffield Department of Medicine, Oxford University, United Kingdom, who along with Peter M. Rothwell, also of Oxford University, wrote an editorial accompanying the study.

"It proves that they could get to the patients and scan them and therefore intervene more quickly," Dr. Buchan said in an interview with Medscape Medical News. "So it was a proof of principle; it wasn't a randomized test of efficacy. But that's great; it's proof that you can actually do this, particularly in places where it would make sense."

The MSU approach makes sense in an urban, densely populated setting but may make less sense in areas that are more spread out, said Dr. Buchan. "In rural areas, you need to get the patients as quickly as you possibly can to a stroke center rather than sending an ambulance out which adds to the delays," he said. "It's faster to get local ambulance to bring in the patient."

Dr. Buchan noted that although the study was not powered to demonstrate superiority in neurologic outcomes from a mobile stroke unit, one way to demonstrate a surrogate benefit would be to show that scanning patients earlier leads to healthier brains.

"I always regard the ASPECT [Alberta Stroke Program Early CT' score as the ECG [electrocardiogram] for the brain, and the CT scan as the cardiogram of the brain," said Dr. Buchan. "To be able to get it in a mobile setting is fantastic and whether you can do this in a way that's cost-effective and reproducible will, I think, require some further developments to the technology to make it really, really simple."

Science Fiction

Asked to comment on the study, Ralph L. Sacco, MD, chief of neurology, Jackson Memorial, Miller School of Medicine, University of Miami, said it demonstrates that the MSU strategy can substantially reduce delays to treatment decisions for stroke, something that was only recently considered something of a pipe dream.

"Not too many years ago, we would show these cartoons of a mobile stroke unit and talk about it like it was science fiction," he told Medscape Medical News.

"Just as telemedicine is helping to bring acute stroke expertise to low-access areas, a mobile stroke unit may help reduce treatment delays in the right settings," said Dr. Sacco.

Prototype mobile units in the United States as well as Europe are equipped with CT scanners and other diagnostic testing to expedite the treatment of stroke, he added.

However, he agreed that cost issues need further evaluation. "More studies are needed to evaluate cost-efficacy to determine where such innovative units could have their biggest impact."

The study was funded by the Ministry of Health of the Saarland, Germany, the Werner-Jackstädt Foundation, the Else-Kröner-Fresenius Foundation, and the Rettungsstiftung Saar. Dr. Fassbender has disclosed no relevant financial relationships. Dr. Rothwell and Dr. Buchan have disclosed no relevant financial relationships.

Lancet Neurol. Published online April 11, 2012. Abstract

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