'Time Is Brain': How Mobile Stroke Units Are Saving Lives

Andrew N. Wilner, MD


July 09, 2018

While attending the American Academy of Neurology 2018 Annual Meeting, Medscape contributor Andrew N. Wilner, MD, interviewed Andrei V. Alexandrov, MD, about the world's first mobile stroke unit with advanced imaging capabilities. Alexandrov is a professor and the chair of the Department of Neurology at the University of Tennessee Health Science Center.

A Newer, Better Mobile Stroke Unit

Wilner: You launched the stroke ambulance system here in Memphis. We all know that time is brain, and the minutes tick away while you're waiting to give tissue plasminogen activator (tPA) or perform thrombectomy. What has been your experience with mobile stroke units?

Alexandrov: We were fifth in the nation to acquire a mobile stroke unit, but the first in the world to develop one that has a state-of-the-art CT scanner capable of full CT angiography of the head and neck, similar to CT scanners found in stroke centers. The key difference in the technology is that our ambulance has a moving entry, so the patient is scanned exactly the same way they are scanned in radiology departments.

The time acquisition is only 3.5 minutes, and we have a 16-slide CT. Full CT angiography of the head and neck can be performed in these 3.5 minutes. We can do it in the field within minutes of arriving on the scene. As a result, our median time from arrival on the scene to administration of tPA in the field is 13 minutes.

Wilner: Thirteen minutes. Is mobile CT done elsewhere?

Alexandrov: Yes. The first center in the United States was in Houston, which was followed by Cleveland, Denver, Toledo, and Memphis. At least 9 or 10 of these units are currently in operation.

Wilner: Do you anticipate expansion of these mobile stroke units?

Alexandrov: Some of these units are currently operating on a 1-week-on/1-week-off schedule as part of a multicenter study aiming to demonstrate that mobile stroke units treat patients faster and are as safe as hospitals, with possibly better outcomes. We already know that we are getting to patients faster and treating them earlier. We already know that we are safe. We just need to demonstrate to our peers and third-party payers that faster treatment in the field results in better outcomes.

Another benefit of having the technology that allows us to perform CT angiography in the field is that we remove the uncertainties of patient triage to a primary stroke center versus a comprehensive stroke center. If we see a large-vessel occlusion, the patient goes directly to the cath lab. The need for clinical scales is removed because we actually see on imaging why the patient needs to be taken to the comprehensive stroke center.

Engaging With Legislature

Alexandrov: The reason for testing all of this technology in a clinical trial is because, until recently, there was no place for the technology to be identified as place of service. Doctors do not ride in ambulances in the United States, tPA is not given to outpatients or in the field, and CT scans are not performed in ambulances. This is a marriage of the emergency medical services (EMS) system and the stroke team.

When we first approached the Centers for Medicare & Medicaid Services (CMS), they congratulated us on creating the box outside all boxes. Until recently, we could not charge for any of what we were doing except basic transportation fees for the ambulance. We learned that we need to engage with legislature to create that place of service, to create a mandate for CMS to consider this.

And just about a month ago, the first bill was passed on Capitol Hill, thanks to Senator Lamar Alexander of Tennessee, who is a vocal advocate of our work. Two things were included in the bill. First was the provision of telemedicine services, including teleneurology, which should boost all the telemedicine networks nationally. Also included in the bill was the recognition of mobile stroke units—sophisticated ambulances with some elements of hospital treatments (such as tPA and CT scans) and the presence of a teleneurology doctor or a fellowship-trained healthcare provider who understands stroke and makes decisions in the field. We are one step away from being sustainable in terms of providing this operation because the bill is going to be initiated in 2019.

Training and Qualifications

Wilner: Do the technicians in the mobile stroke units require special training?

Alexandrov: Yes. The personnel on ambulances include the EMT driver and a paramedic capable of critical care to operate the ambulance, such as a regular EMS; a radiologic technologist to operate the CT scanner; and a person to help with telemedicine, such as a nurse. In our case, we have a stroke fellowship-trained nurse practitioner or a stroke fellowship-trained physician on board because we do not rely on telemedicine yet.

Wilner: Who reads the CT scans?

Alexandrov: We have neurologists who are trained in neuroimaging and board-certified in reading MRI and CT scans, so they are read by our own neurology faculty. However, as with any acute stroke treatment, it's a two-step process.

The first step is to evaluate the CT scan as it is being acquired by the stroke team, similar to what happens every day in every emergency department. The stroke team member looks at the CT scan as it is being acquired and makes a quick decision. Bleeding or no bleeding? Yes or no to tPA? That decision is made by a stroke team member aboard the ambulance exactly the same way it is made in the hospital.

The images are then uploaded into the system and later officially read for the record. In the future, an ideal system would allow us to integrate that scan into the electronic medical record. We are working on developing a system that would allow us to upload the image from the ambulance into the destination hospital's picture archiving and communication system.

Wilner: It sounds like you've accomplished a great deal. What was the response of the EMS when you approached them? Did they think this was a good idea?

Alexandrov: The main criticism is that mobile stroke units are expensive. More than $1 million for an ambulance such as ours is a lot of money spent to benefit a few. However, when we started operating in Memphis, the emergency physicians were relieved because patients who were brought in from the field would already have an National Institutes of Health Stroke Scale score and a completed CT angiography. We were essentially delivering patients on a silver platter with a definitive assessment.

More important, patients who were treated with tPA or required thrombectomy were directly admitted to stroke teams, bypassing the emergency department. Emergency physicians were relieved to hear that the most difficult patients were going directly to the stroke team. It is less pressure on emergency physicians and better for patients to be treated early, brought in with tPA dripping, and registered as an inpatient. So, locally, we have had very positive responses from most of the emergency department physicians.

When Will We See the Data?

Wilner: When will we see the outcomes data to know whether this is really saving lives and saving brains?

Alexandrov: Our clinical trial of the mobile stroke unit is actively recruiting. We expect to acquire the full sample within 2 years. The aim of this trial is to demonstrate the effectiveness of this approach. In parallel, there is a more proximal need to properly triage stroke patients to comprehensive stroke centers, particularly those who have a large-vessel occlusion and require thrombectomy.

We believe that our technology is ideally positioned to remove all the guesswork from the process. Even if that is the only benefit of mobile stroke units, their use will be worthwhile, because the benefit of thrombectomy would be negated if a patient with a large-vessel occlusion stops at the primary stroke center to be assessed for the need for tPA and then spends an additional 100+ minutes being transferred to the comprehensive stroke center. These 100+ minutes reduce the benefit of thrombectomy. If we can eliminate the unnecessary stop at the primary stroke center, that in itself would be a great enough benefit of this technology.

Our plan for the Memphis area, regardless of whether we are effective in giving superb resolution with tPA, is to deploy enough of these mobile stroke units so that instead of bringing patients to the nearest hospital, the paramedic and CT angiography will determine whether the patient should go to the comprehensive stroke center versus the primary stroke center.

Wilner: Thank you for explaining this new approach to ensuring rapid and effective treatment for stroke.


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