Functional outcomes may not improve with mobile stroke units

Mobile stroke units may not be a successful and cost-effective way to improve functional outcomes, according to a presentation at the International Stroke Conference.

Components of mobile stroke units include imaging, imaging technician, point-of-care laboratory, telemedicine connection with a hospital, paramedic, nurse and medication such as tissue plasminogen activator (tPA) and four-factor prothrombin complex concentrate, according to Andrew W. Asimos, MD, FACEP, medical director of the stroke network at Carolinas HealthCare System in Charlotte, North Carolina, and professor in the department of emergency medicine at Carolinas Medical Center in Charlotte.

Asimos noted that Atrium Health does not have mobile stroke units, and his opinion is based on research from outside studies.

Mobile stroke units were first introduced in Germany in 2003 and first utilized in 2008, according to the presentation. By 2011, the first mobile stroke unit went into operation in Berlin.

These units were then brought to Houston in 2014. Since then, about 13 units have been deployed in the United States. The newest stroke units cost an estimated $1.2 million, which does not include the cost to operate and sustain them.

“The multimillion-dollar question is what problem are we trying to solve with this groundbreaking vehicle,” Asimos said.

Although the units can help achieve faster IV administration times, it is still unknown whether it has resulted in improved outcomes.

“If the problem that we’re trying to solve prolonged door-in/door-out times, maybe that’s what we need to focus on rather than taking the CT scanner out of the hospital and into the ambulance,” Asimos said.

Potential benefits

Intracerebral hemorrhage identification and treatment in transport is one of the appealing factors of mobile stroke units, according to the presentation.

“As an emergency medicine physician, the patients that I most commonly intubate are intracerebral hemorrhage patients, and those are the patients that typically get intubated before you can even go to the CT to secure their airway,” Asimos said. “I’ve experienced the cluster of an intubation in a CT scanner, and the only thing that would make that worse would be in a CT scanner in the back of an ambulance. There’s a cost for spending a little bit more time in the field, especially as it relates to [intracerebral hemorrhage].”

Oral anticoagulation-associated hemorrhage reversal is another potential benefit from mobile stroke units. Both SPOTLIGHT and STOP IT were negative trials showing the effects of this treatment, but the agents were administered 2 hours later, which may make it an indication for these units.

Mobile units can also bring more patients to a health care system, especially in competitive health care markets, and once patients are in a system, they are more likely to revisit it.

Cost concerns

High-technology vehicles such as medical helicopters and mobile stroke units cost a lot of money for health care systems across the country. In a study published in the Journal of NeuroInterventional Surgery in 2017, patients transported by helicopter was a negative predictor for an intervention for false-positive stroke thrombectomy.

“EMS is underfunded, but we have money to pay for these expensive things that we really don’t have compelling data to show that they resulted in improved outcomes,” Asimos said.

Scalability is another issue with mobile stroke units. A scale associated with population density must be developed, especially as dense areas often need more than one mobile stroke unit to cover the entire population, according to the presentation.

Newer mobile stroke units are not often smaller and faster. A unit that is used in Memphis weighs 14 tons, has a bigger CT scanner and gets 5 to 6 miles per gallon.

“The mantra of the mobile stroke unit community is waste gas, not brain, and I can tell you there’s plenty of gas being wasted,” Asimos said.

In Cleveland, a mobile stroke unit was deployed 317 times, and tPA was administered in 5% of the cases. Prior to the unit arriving to the site, 68% of deployments were canceled.

“This is a big problem associated with this, especially the cost of running these vehicles,” Asimos said.

Although mobile stroke units are the best examples of the “stay and play” model, it may be best to put the patient into the ambulance, go to the nearest hospital and conduct all necessary tests. If the patient must go to an endovascular center, they can go in the same ambulance they came in.

CTA imaging can be performed on the newer mobile stroke units, but transmitting 1.7 gigabytes of data to a radiologist takes about 20 minutes. On-board power generation is another issue aboard newer units, Asimos said.

Discretion needed

With a huge emphasis on time to treatment, providers must be cautious about the patients they choose to treat with IV tPA, according to the presentation. There is a link between decreasing door-to-needle times and an increased rate of stroke mimic treatment, which may be a result of early treatment for patients who are more likely to have transient ischemic attacks. Less experienced practitioners in mobile stroke units may be the ones who are making the decision to administer tPA without consulting with a neurologist.

“I’ve been doing this for 20 years now,” Asimos said. “I’ve witnessed a lot of telestroke consults in our system. There seems to be an incredibly low threshold to want to treat patients who have a high suspicion to have complicated migraines or conversion disorders with tPA.”

Three studies were performed that focused on mobile stroke units, and they did not demonstrate improved functional outcomes with mobile stroke units, according to the presentation.

Most mobile stroke units have been paid for by philanthropic grants, but a business model must be created that focuses on efficacy and cost-effectiveness, Asimos said. As there are different payers for prehospital, hospital and long-term care in the U.S., the return on investment and cost-effectiveness will vary across different practice settings, according to the presentation.

“Mobile stroke units are expensive and are likely to be financially nonsustainable,” Asimos said. – by Darlene Dobkowski

References:

Asimos AW. Session 123 – Prehospital Approaches to Maximize the Public Health Impact of tPA and Thrombectomy. Presented at: International Stroke Conference; Jan. 23-26, 2018; Los Angeles.

Yi J, et al. J Neurointerv Surg. 2017;doi:10.1136/neurintsurg-2017-013043.

Disclosure: Asimos reports he receives research grants from Stryker and VIZ.ai.

Editor’s Note: This article was updated on Feb. 16, 2018 to clarify that Dr. Asimos’ institution does not have mobile stroke units.