Mobile Stroke Units: Weighing the Conflicting Arguments

In just five years the United States has expanded from its first mobile stroke ambulance in 2014¹ to roughly a dozen mobile stroke units (MSUs) now spanning from California to New York City. Whether MSUs are an effective and efficient means of prehospital care, however, continues to generate a great deal of debate. 

Through analysis of current evidence, it is clear MSUs give first responders a tool that can lessen the time to administer interventions to stroke patients. Skepticism persists, though, over the notable cost, potentially minimal benefit, and overall allocation of resources.

Time Savings

Ambulances designed for prehospital stroke care are typically equipped with a mobile CT scanner and an array of personnel that may include critical care nursing staff, a paramedic, and an imaging technologist. The unit’s delivery of care reduces the interval for stroke patients to receive intravenous interventions and diagnostic testing. 

The ideal scenario for this unit begins with the 9-1-1 dispatcher identifying a potential stroke patient. After dispatching the MSU, the process to treat patients who are candidates for stroke interventions is streamlined into an efficient sequence of events: A CT scanner sends imaging to a radiologist to determine the type of stroke (and ultimate intervention needed). The rapid turnaround time to determine the nature of the stroke allows for a notably faster time frame for patients to receive pharmacological intervention such as tPA (if they are experiencing an ischemic stroke). 

The ability to save in some cases upward of 30 minutes toward interventions for stroke cases appears to be a groundbreaking advance. However, the idea also has its shortcomings. 

Though an evident efficiency comes with the utilization of MSUs, there is skepticism as to whether their benefits outweigh those of other potential uses of the funds. 

First, more data must be collected to better define how much time is actually saved by these units compared to traditional care. A 2014 JAMA article noted that “Compared with usual care, the use of ambulance-based thrombolysis resulted in decreased time to treatment without an increase in adverse events. Further studies are needed to assess the effects on clinical outcomes.”² 

To date there’s been a wide range of estimated time savings through MSUs. This data begins with an initial study from the world’s first mobile stroke unit out of Germany. That unit produced a 30-minute reduction in time to provide tPA to patients compared to the existing standard of care.³ The Cleveland Clinic notes in a promotional publication a time reduction of approximately 90 minutes with mobile stroke operations. This is nearly three times what was seen in Europe.⁴ 

Reducing the time to administer stroke care by an hour would dramatically improve the efficiency of care—that’s a third of the entire window in which interventions must be provided following a stroke.

Outcomes and Cost

While mobile stroke units have been shown to get tPA to ischemic patients faster, they are not yet shown to improve patient outcomes. 

The German analysis mentioned above is one of the most reputable sources of evidence on this subject. This study, coined PHANTOM-S (for Pre-hospital Acute Neurological Therapy and Optimization of Medical Care in Stroke Patients Study), used a patient population of roughly 300 treated by conventional transport and roughly 300 who received care from an MSU.

Ultimately the median time from stroke onset to thrombolysis was 112 minutes for the standard group, compared to 73 minutes for MSU patients. However, no significant difference was found in outcomes between the populations. 

Another barrier is cost. Initial costs are estimated to be approximately $1 million per mobile stroke unit. In addition, there is an annual operating cost of roughly $950,000 to $1.2 million. Over 10 years, a total financial impact of nearly $15 million for one of these units raises serious questions as to their value. Could more lives be saved by directing those resources elsewhere?

However, a study of the cost-effectiveness of mobile stroke units concluded based on a one-year benefit-cost analysis that prehospital treatment of acute stroke is highly cost-effective in a diverse assortment of environments. Interestingly, cost-effectiveness is most profound when staffing on the MSU is reduced by practices such as telemedicine support from neurologists and similar providers.⁵ 

Conclusion

Getting care to stroke patients faster would seem to have intuitive benefit. However, evidence-informed conclusions cannot yet be made until we see a more definitive body of literature.   

References

1. Parker SA, Bowry R, Wu T, et al. Establishing the First Mobile Stroke Unit in the United States. Stroke, 2015; 46: 1,384–91.

2. Ebinger M, Winter B, Wendt M, et al.; STEMO Consortium. Effect of the use of ambulance-based thrombolysis on time to thrombolysis in acute ischemic stroke: a randomized clinical trial. JAMA, 2014 Apr 23–30; 311(16): 1,622–31.

3. ClinicalTrials.gov. PHANTOM-S: The Pre-Hospital Acute Neurological Therapy and Optimization of Medical Care in Stroke Patients—Study, https://clinicaltrials.gov/ct2/show/NCT01382862?term=PHANTOM-S&rank=1.

4. Cleveland Clinic. Cleveland Clinic Mobile Stroke Treatment Unit. YouTube, https://www.youtube.com/watch?v=3ZW5AWeinEM.

5. Dietrich M, Walter S, Ragoschke-Schumm A, et al. Is prehospital treatment of acute stroke too expensive? An economic evaluation based on the first trial. Cerebrovasc Dis, 2014; 38(6): 457–63.

Sidebar: Mobile Stroke Ambulances—What Does the Evidence Say?

Reduced call-to-tPa-decision time by 41 minutes (100 patients)

—No difference in neuro outcomes (Walter, et al., 2012)

Call to tPa time on average 4 minutes faster (152 patients)

—Data regarding neurologic outcomes purposefully obscured (Weber, et al., 2012)

~30% of patients administered tPa within 60 minutes vs. 1% in general population (24 patients)

—No neurological outcomes analyzed (Parker, et al., 2015)

~15-minute reduction in call-to-tPa time (6,182 patients)

—No significant benefit in number of patients discharged home (Parker, et al., 2015)

Christopher Gaeta is a student at Swarthmore College, Swarthmore, Pa.