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If you have a stroke within about 3 miles of Memorial Hermann-Texas Medical Center in Houston, you might end up in the first mobile stroke unit in the U.S., which is scheduled to begin treating patients within weeks.
The unit -- a standard ambulance equipped with a CT scanner and stocked with clot-busting tissue plasminogen activator (tPA) -- overcomes the limitation of having to wait until a patient arrives at the hospital to confirm that the stroke is ischemic, which can drastically delay administration of the proven treatment.
The hope is that bringing the imaging and the tPA to the point of first medical contact out in the field will restore blood flow to the brain faster, save neurons, and ultimately improve patient outcomes, according to , director of stroke research for the Clinical Institute for Research & Innovation at Memorial Hermann-Texas Medical Center.
"My prediction is that 10 years from now every city in the country will have imaging on their ambulances," he told 番茄社区 at the International Stroke Conference in San Diego. "If not every ambulance, then a certain percentage of their ambulances that get dispatched for certain conditions, including stroke."
Taking the Hospital to the Patient
The idea of mobile medical imaging isn't new. In fact, and drove them to the front lines during World War I.
But the -- about a decade ago by , now of the University Hospital of the Saarland in Germany, and colleagues. Data since published by his group has shown that taking stroke treatment into the field can be done and can cut treatment times -- a finding that caught the eye of stroke neurologists like Grotta.
Both animal and human studies have demonstrated that much of the beneficial action of tPA comes in the first few hours after the onset of stroke, and clinicians and researchers have had their sights on ways to treat patients within the first 60 minutes -- the "golden hour".
After observing the German experience, Grotta decided to make a push to get a mobile stroke unit in Houston, pointing to the "pretty aggressive" stroke program and the close relationship with the paramedics.
"If anybody can do it, we can do it, so why shouldn't we do it?" he said.
Grotta became so committed to the idea that he stepped down as chairman of the neurology department at the University of Texas Health Science Center at Houston (UTHealth) Medical School -- which has partnered with Memorial Hermann-Texas Medical Center on the mobile stroke unit -- to focus on the effort full-time. He'll be the neurologist riding in the unit as it starts rolling.
"This is something I really believe in that could make a big difference, so I decided this will be my second career," he said.
Getting Started
Grotta said that the National Institutes of Health -- which would normally be looked to for funding -- doesn't generally cover costs for equipment, which left him with the problem of paying for the unit itself. That obstacle was removed when he was approached at a fundraiser by the owners of Frazer, a company that builds emergency vehicles. The company agreed to donate an ambulance.
The ambulance itself is not all that different from a regular one, Grotta said. The door is a bit bigger than normal to allow for the CT scanner to be placed inside. The CT scanner is the same portable type found in many intensive care units.
The cost to get the project going was roughly $1 million -- about $500,000 in equipment and supplies (including the CT scanner) and about $500,000 for the staff to operate the unit. The funding came from other local businesses and philanthropists.
"A million dollars is a million dollars, but it's not terribly expensive to get something like this up and running," Grotta said.
With those logistics out of the way, Grotta and his team started testing out the unit -- without patients -- earlier this month.
"When you get delivered an airplane, you don't fly it with passengers until you've learned how to land it and take it off and know that you can do that a few times without crashing it," he said.
After fixing some minor issues -- for example, getting the side door of the unit to open wider so the computer can be mounted on the door without impeding the ability to get in and out of the ambulance, and installing an awning to block the sun from the monitor -- the team should be able to start treating patients next month.
How It Will Be Deployed
Eventually, the mobile stroke units -- if shown to be beneficial and embedded within a fleet of ambulances -- will be staffed by regular paramedics, who can handle patients who are not having strokes. But because the idea has not yet been proven to help patients, Grotta and his team have to do things differently.
Initially, when a 911 call comes in and stroke is suspected, the mobile stroke unit will be dispatched along with a regular ambulance. In order to not delay the patient's arrival at the hospital, the stroke unit needs to arrive on the scene when the paramedics in the other ambulance are still on site. Since paramedics are on site for an average of 15 or 20 minutes, Grotta said, that means that the stroke unit can only respond to calls within a radius of 3 or 4 miles -- a distance that would take around 15 minutes to travel.
If the evaluation indicates that the patient is having a stroke, then he or she will be placed in the CT and scanned on site. If an ischemic stroke is confirmed, then the team will administer a bolus of tPA and then continue to infuse the drug on the way to the hospital.
According to the German experience, about 30% of patients receive tPA within an hour of stroke onset using the mobile stroke unit. Grotta said that currently no patients with ischemic stroke in Houston are getting treated that fast.
But in addition to getting more patients treated within the golden hour, the system is expected to get treatment to more patients who normally wouldn't have been eligible for tPA at all because they got to the hospital later than 4.5 hours after stroke onset, Grotta said.
"By having greater awareness in the ambulance and earlier recognition, you're going to get at patients a lot faster, even when they get to the emergency department," he said.
What's the Benefit?
Grotta acknowledged, however, that it remains to seen whether getting more patients treated in the first hour after stroke will improve outcomes, and if it does improve outcomes whether the gain is enough to justify the cost of the mobile stroke unit.
"If it's just a little bit more benefit, it's not going to be worth the cost," he said. "If it's a lot more benefit, then it would be worth the cost."
To find out, Grotta's team will be conducting a trial in which the outcomes of patients with ischemic stroke will be compared between weeks when the mobile stroke unit is operating and weeks when it isn't. In order to get a sample size big enough to detect clinically meaningful differences in outcomes, Grotta expects that they'll need about 300 patients total, which could take several years to enroll.
He said his team will be trying to find ways to tweak the dispatch method to make sure they can target as many actual strokes as possible.
The time to complete the study could also be reduced if other communities across the country raise the funding needed to put a mobile stroke unit on the road.
But whenever the results come, Grotta expects them to show that using the mobile stroke unit is beneficial and cost-saving.
He pointed out that the additional cost for the unit itself -- on top of a regular ambulance -- is the $400,000 for the CT scanner.
Each stroke costs the healthcare system an estimated $200,000, which includes costs related to acute care, rehabilitation, and nursing home care.
So if the mobile stroke unit can reverse two strokes during its entire lifespan, it will have paid for CT scanner. Even if you assume that the neurologist on board will eventually be replaced by a driver and telemedicine capabilities -- which would require an off-site neurologist who could handle ambulances in several cities -- that might only add up to another $200,000 per year. Those costs could be offset by reversing just one more stroke, he said.
"To me, it's a no-brainer that this would be cost-effective based on the back-of-the-envelope calculations," Grotta said.
The trial is expected to begin next month.
From the American Heart Association: