Emerging on the scene in the past few years, Mobile Stroke Units (MSU) are specially designed emergency vehicles deployed to answer emergency calls for patients who may be having strokes. Originally launched in Germany in 2008, MSUs have been deployed in more than a dozen U.S. cities including Houston (the nation’s first in 2014), Cleveland, Los Angeles, and New York, among others.
In acute stroke management, MSUs address the “time is brain” concept, a forward-looking strategy to improve clinical outcomes, that focuses on the swift delivery of treatment to the patient rather than the conventional approach of waiting for a patient to arrive at the hospital. Restoring blood flow in an obstructed blood vessel(s) is most beneficial when performed within 60 minutes and up to a maximum of 4.5 hours of initial symptom onset. In reality, most patients arrive at a hospital too late, often resulting in only a limited number of those patients (5-10%) receiving treatment that can prevent disability or even death.
Three studies have proven MSU care delivery achieves faster time to treatment, but similar to medical helicopters, they are expensive to put into operation and maintain, and so far have not resulted in compelling data for improved outcomes.
How Mobile Stroke Units treat patients
MSUs are hyper-customized ambulances equipped with standard EMS tools plus all the custom devices necessary for the hyperacute time-sensitive treatment of stroke patients. Much like an ambulance, they are deployed by emergency services to patients who require immediate aid with the key difference being they are deployed specifically for patients who may be having a stroke.
On arrival, paramedics load a patient into the vehicle and MSU staff, which usually includes a nurse, CT technician, a paramedic, and a neurologist, as well as a hospital physician via telemedicine, takes over. Evaluation on-board the MSU includes a CT scan, point-of-care laboratory testing, and a high-fidelity audio-visual teleconference with an experienced stroke physician to determine if the patient is having a stroke and, if so, the stroke type (ischemic, transient, or hemorrhagic). Patients determined to be having an ischemic stroke that meets inclusion criteria and do not have any contraindication(s) to treatment receive the "clot-busting" medication, tPA and four-factor prothrombin complex concentrate.
Observations of faster times to early treatment include a risk for increasing the rate of stroke mimic treatment for patients experiencing transient events, as well as complications with intubation for hemorrhagic stroke in a mobile CT apparatus. Mobile tech challenges include the time, capacity and power resources required to transmit large CT data files.
Specialized care, faster decisions
With specialized equipment and staff, MSUs can make accurate triage decisions about the most appropriate hospital based on the patient’s needs: a primary versus a comprehensive stroke center, which is a hospital equipped with specialized facilities for endovascular or neurosurgical protocols. This type of destination targeting alone has been shown to reduce critical delays.
Geographical benefits of on-site MSUs may be particularly helpful in ultra-rural and heavy traffic urban areas. Small towns can be located a half hour or more from the nearest hospital. In large urban areas like Los Angeles, the traffic can triple the drive time of only a few miles.
Scaling a fleet of 14-ton vehicles that get 5 or 6 miles per gallon of gas to accommodate densely populated cities or far-flung sparsely inhabited communities gets expensive quickly when half or more of the emergency stroke deployments are canceled before the MSU arrives.
Still, every minute a stroke victim is untreated they lose two million brain cells. Time spent driving back to the hospital without initiating treatment could lead to debilitating side effects for the rest of their life, including paralysis and loss of speech or comprehension, or even death.
The financial burden for a patient disabled by a stroke because of a delay in treatment could be lifelong. Direct and indirect medical costs of an individual unable to care for themselves or work, along with health insurance expenses for the rest of that person’s life would be astronomical.
Measuring improvements, future possibilities
Current research on the sustainability and efficacy of MSUs revolve around whether the potential benefits (reduced treatment time, improved clinical outcomes, reduced disability and economic burden for both patient and healthcare system) outweigh the financial costs of deploying and maintaining an MSU fleet.
A large randomized trial is being conducted through the Patient-Centered Outcomes Research Institute (PCORI), with participation by MSU programs in Houston, Memphis, Denver, L.A., and soon New York to study cost-effectiveness. If proven, MSU accessibility is expected to expand and change the infrastructure of prehospital care.
Increasing patient volume is also a consideration. Given the competitive environment that many hospitals face, MSUs may help grow patient volume for health systems. The hypothesis is that patients who arrive at a hospital via MSU might stay and return in the future due to the improved likelihood of a favorable outcome.
In addition to clinical outcomes, MSUs hold the potential to unlock research advances in prehospital stroke management. MSUs can feature in the investigation of novel diagnostic treatments, such as biomarkers and automated imaging evaluation, as well as therapeutic options including neuroprotective drugs, differential blood pressure management, reversal of warfarin effects in hemorrhagic stroke, and management of cerebral emergencies other than stroke.
For the first time, the field of stroke is ahead of the rest of the medical world in trying to speed treatment given the extremely time-sensitive nature of this disease. Some medical experts suggest prioritizing EMS funding and training over implementing pricey and largely unproven high tech services like medical helicopters and MSUs. Others believe adding additional diagnostic equipment monitored by telemedicine specialists could expand the MSU concept to make it much more cost-effective and spur wider adoption by EMS.
- Mobile stroke units for prehospital thrombolysis, triage, and beyond: benefits and challenges. The Lancet. http://www.thelancet.com/journals/laneur/article/PIIS1474-4422(17)30008-X/fulltext Accessed 3.28.2018
- Mobile stroke unit brings hospital to patients – and could save lives. Fox News. http://www.foxnews.com/health/2018/01/26/mobile-stroke-unit-brings-hospital-topatients-and-could-save-lives.html Accessed 3.28.2018
- Mobile Stroke Units: A Device in Search of an Indication. Journal of Emergency Medical Services. http://www.jems.com/articles/2017/01/mobile-stroke-units-a-device-in-search-of-an-indication.html?c=1 Accessed 3.28.2018
- Functional outcomes may not improve with mobile stroke units. Healio. https://www.healio.com/cardiology/stroke/news/online/%7B43576221-a11c-4469-b0ce-34abd86c77e5%7D/functional-outcomes-may-not-improve-with-mobile-stroke-units Accessed 3.28.2018
- Mobile stroke units designed to quickly reach, treat patients. American Heart Association. https://news.heart.org/mobile-stroke-units-designed-quickly-reach-treat-patients/ Accessed 3.28.2018
- As drug fails to stop bleeding strokes, brain scan advance proves its worth. American Heart Association. https://news.heart.org/as-drug-fails-to-stop-bleeding-strokes-brain-scan-advance-proves-its-worth/ Accessed 4.3.2018
- Prove It: Mobile stroke care improves patient outcome. EMS1.com. https://www.ems1.com/mobile-stroke-unit/articles/204219048-Prove-It-Mobile-stroke-care-improves-patient-outcome/ Accessed 4.3.2018
- Lansberg, M. G., Schrooten, M., Bluhmki, E., Thijs, V. N., & Saver, J. L. (2009). Treatment time-specific number needed to treat estimates for tissue plasminogen activator therapy in acute stroke based on shifts over the entire range of the modified Rankin Scale. Stroke, 40(6), 2079-2084. doi:10.1161/STROKEAHA.108.540708 https://www.ncbi.nlm.nih.gov/pubmed/19372447 Accessed 4.3.2018
- Mobile Stroke Unit Project Receives $6.8 Million from PCORI to Expand Research in Houston and Beyond. Memorial Hermann Hospital. http://www.memorialhermann.org/news/mobile-stroke-unit-project-receives-$6-8-million-from-pcori-to-expand-research-in-houston-and-beyond/ Accessed 4.3.2018