Mobile Stroke Treatment Unit Cuts Time to Thrombolysis

Pauline Anderson

March 16, 2017

A mobile stroke treatment unit outfitted with a computed tomography (CT) scanner and portable laboratory equipment, and with telemedicine capability, shaves 38.5 minutes off the typical time from a stroke call to delivery of thrombolysis, a new study found.

The time to thrombolysis with tissue plasminogen activator (tPA) is a crucial factor for favorable outcome after acute ischemic stroke.

"Every minute, every second, counts," said study author Muhammad S. Hussain, MD, Cleveland Clinic, Ohio, adding that without treatment, stroke patients lose an estimated 2 million neurons per minute. "So saving about 40 minutes in terms of time to treatment translates into a huge benefit."

Dr Muhammad S. Hussain

Research shows that reducing time to treatment by about 15 minutes means that 5% more patients go home from the hospital and 3% more patients are able to walk, said Dr Hussain.

The study was published online March 8 in Neurology.

For every potential stroke call, the Cleveland emergency medical services (EMS) dispatch center simultaneously sends both an EMS squad and the Cleveland Clinic mobile stroke treatment unit (MSTU). If stroke is suspected, the EMS transitions care to the MSTU team, which includes a registered nurse, paramedic, emergency medical technician (EMT), and CT technologist who is also trained as an EMT.

The MSTU team initiates vital sign monitoring, completes a quick assessment, performs head CT, and transmits the CT images to a neuroradiologist for interpretation. A vascular neurologist conducts a National Institutes of Health Stroke Scale assessment via telemedicine.

Mobile stroke treatment unit. Courtesy of The Cleveland Clinic

After testing, treatment is initiated and the MSTU transports the patient to an appropriate destination. MSTU transfer sites include 3 comprehensive stroke center hospitals and 11 primary stroke centers or stroke-certified hospitals. Cleveland has a population of almost 400,000 and spans some 216 kilometers.

Preliminary Diagnosis

The study included the first 100 patients for whom the MSTU was deployed from 8 am to 8 pm between July 18 and November 1, 2014, and for whom a diagnosis of stroke was likely. The vascular neurologist made a preliminary diagnosis of probable acute ischemic stroke in 33% of patients, possible acute ischemic stroke in 30%, and transient ischemic attack in 4%.

Researchers compared data on various time points for these patients with that collected on 53 control patients. The controls presented to hospital emergency departments directly through the Cleveland EMS during the same operating hours as the study group but between January 1 and December 31, 2014.

Only those who had a stroke alert activated within 30 minutes of arrival to the emergency department were included in the control cohort.

Mobile stroke treatment unit. Courtesy of The Cleveland Clinic

The median age was similar for the MSTU group (62 years) and the control group (63.4 years), as were sex, race, and stroke severity on presentation.

Of the 100 MSTU patients, 16 received thrombolysis. From the time of symptom onset, patients evaluated in the MSTU received this treatment 25.5 minutes earlier than control patients (median, 97 minutes vs 122.5 minutes; P = .0485).

From the alarm time (time of the stroke call), the MSTU patients received thrombolysis 38.5 minutes sooner than the control patients (median, 55.5 minutes vs 94 minutes; P < .0001).

While 25% of the MSTU group received thrombolysis within an hour of symptom onset, none in the control group received the treatment within this time frame.

Treatment within the first hour of symptom onset — often referred to as the "golden hour" — is very difficult in the traditional system, said Dr Hussain. "In the mobile unit, we are getting to see the patients a lot earlier after their symptom onset where tPA is probably a lot more effective."

The team was deployed 317 times to get the 16 cases of tPA, which meant that there were several cancellations. Dr Hussain recognized that this might have taken the unit away from pressing stroke cases.

This issue may be addressed with additional training "at the front end" to more effectively screen for stroke, he said. "Perhaps working on some of the algorithms that dispatchers use might be the next step."

The Cleveland Clinic currently has just the one mobile unit, which can serve up to about 500,000 people. As the MSTU catchment area expands to include the city's suburbs, another unit will probably be needed, said Dr Hussain.

Mobile stroke units require wireless networks to transmit images, and in some rural areas, access to such coverage may be difficult. However, said Dr Hussain, new technology is increasingly addressing this issue.

Cost-Effectiveness

Not only might this new mobile treatment approach improve stroke outcomes, but it could prove cost-effective. "The more we can reduce disability, the more we are going to save in terms of healthcare costs as a whole," said Dr Hussain.

It costs $750,000 to $1 million to convert an ambulance to a mobile stroke treatment unit and $500,000 to $700,000 in annual operational expenses, said Dr Hussain.

"Based on our calculations, if you treat about 50 people on the unit with IV [intravenous] tPA, you basically cover the first year's cost of running the vehicle."

Making MSUs multipurpose vehicles might further enhance cost-effectiveness, Andrew M. Southerland, MD, Departments of Neurology and Public Health Sciences, University of Virginia Health System, Charlottesville, told Medscape Medical News.

"In an EMS network served by a mobile stroke unit, portable CT angiography would enable prehospital confirmation of large vessel occlusions and selective routing to an endovascular-capable center."

Dr Southerland and Ethan S. Brandler, MD, Department of Emergency Medicine, SUNY Stony Brook Medicine, New York, wrote an editorial that accompanied the study.

CT Angiography

The Cleveland MSTU already has the capability to perform CT angiography, and the triage algorithm takes this into account, said Dr Hussain. "If the CT angiogram shows a large vessel that's occluded, or if there's bleeding into the brain, we will actually take the patient to a comprehensive stroke center right away rather than going to the closest stroke center."

Avoiding patient transfer from one hospital to another saves precious time. "It doesn't take much time to get to the first hospital, but getting from the first hospital to a second hospital takes about 3 hours," said Dr Hussain.

By augmenting the portable CT scanner to include body imaging, MSTUs could support prehospital management of acute trauma and other non-neurologic emergency conditions, Dr Southerland and Dr Brandler write in their editorial.

Dr Hussain, too, sees the usefulness of this approach. "There potentially can be a lot of other applications for a specialized unit like this one, for example, head trauma," where patients can be quickly diverted to the appropriate treatment center.

To determine cost-effectiveness, more data are needed to show benefits of MSTUs in terms of clinical outcomes, said Dr Southerland.

He pointed to a recent analysis of the PHANTOM-S Observational Registry Study, which estimated that for every 1000 patients treated with thrombolysis in a mobile stroke unit vs emergency department, 182 would be less disabled (number needed to treat, 5.5) and 58 more would be free from disability altogether.

"While these numbers suggest the possibility of substantial clinical benefit compared to conventional emergency stroke care, the data are limited by the observational nature of the registry, and questions remain regarding generalizability, cost, and efficiency for health systems to consider prior to investing in a mobile stroke unit."   

There's hope that future trials will demonstrate that mobile stroke units improve outcomes by treating patients more quickly and effectively, Dr Southerland and Dr Brandler conclude in their editorial.

"In the meantime, ongoing efforts are needed to streamline [MSTU] cost and efficiency before achieving road-readiness for widespread health system deployment."

The Cleveland Clinic and the Milton and Tamar Maltz Family Foundation support the MSTU project. The study authors have disclosed no relevant financial relationships. Dr Southerland reports provisional US Patent 61/867,477; research support from the Health Resources and Services Administration and the Virginia Alliance of Emergency Medical Education and Research; and travel reimbursement and honoraria from the American Heart Association. Dr Southerland also serves as deputy section editor for the Neurology p odcast. Dr Brandler reports research support from the National Institutes of Health/National Institute of Neurological Disorders and Stroke, Northeast Cerebrovascular Consortium, Perseus Science Group LLC, and Janssen Research & Development LLC.

Neurology. Published online March 8, 2017. Abstract, Editorial

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