Expert Conversations: Evolution of Mobile Stroke Units and Pre-Hospital Care

In part one of this series, Section Editor Amrou Sarraj, MD, discusses the core concepts of mobile stroke units as well as findings from recent clinical trials with James Grotta, MD, Director of Stroke Research, Clinical Institute for Research and Innovation, Memorial Hermann Hospital– TMC; Director, Mobile Stroke Unit Consortium as well as Geoffrey Donnan AO, and Stephen Davis AM, Professors of Neurology and Translational Neuroscience at the University of Melbourne and Co-Chairs of the Australian Stroke Alliance.

Read the Transcript: 

Dr. Amrou Sarraj:  Hello, this is Amrou Sarraj, I am the Stroke and Vascular Editor at Neurology Learning Network with a podcast on the "Mobile Stroke Unit and Prehospital Care." I have three of the original stroke trialists and major contributors to the field for a long time and with a wealth of experience on the subject, specifically on the Mobile Stroke Unit and Prehospital Care.

We have Professor Stephen Davis, Professor of Neurology at the University of Melbourne, and the Co-Chair of the Australian Stroke Alliance. Professor Geoffrey Donnan, the Professor of Neurology at the University of Melbourne and the Co-Chair of the Australian Stroke Alliance.

We have Dr. Jim Grotta, the former director of the Stroke Program at UT Houston and previous chair of the Department of Neurology at University of Texas in Houston and the medical director of the Houston Mobile Stroke Unit at Memorial Hermann Hospital. Thank you all for joining us for this podcast.

We will talk about the prehospital care and the mobile stroke unit. We'll tackle the subject from the core concept. From the beginning, how did this idea come about and how it progressed from just an idea to all of the excellent data that we have from multiple recent clinical trials.

Then, what are the implications of these findings on our clinical practice, the implications on thrombolysis and thrombectomy for acute stroke management. What are the future directions as well as the challenges of this approach?

We'll also tackle the cost effectiveness of the mobile stroke unit, not only improving patients' clinical care, but as well, being cost effective from a health economics standpoint.

We'll start with an open question and ask our guests to tell us about the core concept of the mobile stroke unit, and mix it with the history. How did this idea come about and progress until it got here?

Let's go ahead, Dr. Grotta, on the core concept and history.

Dr. James Grotta:  You’ve got three guys on the call here who are roughly the same age. What you probably don't know is that we all actually came from the same source. We all did our fellowship in Mass General (Massachusetts General Hospital) in internal blood flow and metabolism where we were first, among the first, to see in patients, the fact that brain tissue was still viable on the first minutes after a stroke.

That's what got us, at least me and I think I could speak for Geoff and Steve, interested in acute stroke therapy. For years, we've known that time is brain.

I think that really what is the hallmark of the mobile stroke unit is that the time of the first hour is never before been possible outside of the laboratory, the animal lab, where we were able to work on it and see that we could almost totally reverse strokes if we could recanalize within the first hour in animal models. That's not possible in real life.

It was Klaus Fassbender who was the person who refocused attention on this with doing the first Mobile Stroke Unit in Homburg. We continue to take the lessons we learned in our fellowship 40 to 50 years ago and applied them on this ambulance.

Dr. Stephen Davis:  Amrou, the basic concept is moving the emergency department to the patient. That's been proven in many, many studies to save time, save brain, improve clinical outcomes.

Now we have two phase 3 trials -- one from Europe, and one from Houston, and other centers by Jim Grotta, and Heinrich Audebert in Germany -- that show conclusively that mobile stroke units improved clinical outcomes.

Dr. Geoffrey Donnan:  It might be worth, while we're going down memory lane as well, Jim and Steve, to remember when the NIMS trial, the first thrombolytic trial to be positive, was published. You would always notice that there are no patients during the first hour.

Jim, you mentioned the first hour. The whole idea of the mobile stroke ambulance it's to start treating people for the first time during that period.

Our knowledge of the pathophysiology of stroke, as you're alluding to, Jim, Steve and I and you worked on back in the early '80s. We all always understood, because of transient ischemic attacks, that the brain could recover very quickly if you got there early enough.

Theoretically, that graph we see with thrombolysis where there's nothing in the first hour, but then, from the first hour onwards, a slow decrement in the ability for people to get up and walk home.

Theoretically, if you went back to the vertical axis, it could go asymptotically back to almost full recovery if you get people early enough. In fact, that's proving in some ways to be true.

Dr. Sarraj:  Very well. As you all said, it is taking the emergency room to the patient. It's cutting on the time that transportation is needed, registration of the patients in the emergency room. Taking this smaller emergency room to the patient and saving on the time, we need means in order to do that.

This mobile stroke unit is equipped with the means to do that with the CT scan, with the necessary laboratory tests to be done, delivering the thrombolysis or diagnosing the patient with acute intracerebral hemorrhage, and transferring them to the hospital to save on the time and the logistics associated with that.

Definitely, it made sense that it saved time. The first trial was to cut on the time.

When did we start seeing results of that time saving to be associated with improving the clinical outcome, all the way until we got the randomized evidence that it definitely does?

Dr. Grotta:  Years ago, when we were doing, right after the NIMS Trial, we monitored every patient in real time with transcranial doppler and could see the clots dissolving with tPA in relationship to the time when we treated them.

I was late for this podcast because we just treated a patient with a carotid occlusion or extracranial carotid occlusion 47 minutes after symptom onset. It was proven on a CT angio on the mobile stroke unit. By the time the patient got to the emergency room, it was getting better. The carotid had re-catalyzed.

It's not just that the brain is less damaged when we treat them early, but the clot is easier to dissolve when we treat it earlier. Alex Czap showed this at the stroke meeting. In her abstract, 28 percent of the patients with documented large vessel occlusion on the mobile stroke unit, the clot disappears after tPA when they're treated within the first hour.

So, it's not just that the brain is less damaged, it’s that the clot is easier to dissolve when we treat it earlier. We can see it right in front of us.

Dr. Davis:  These are treatment units, they’re diagnostic and treatment units. The first breakthrough was giving tPA earlier. The other evidence that's come out is that thrombectomy is facilitated by diagnosis using CT angiography on the unit and in triage, very rapidly, through a catheter-equipped center.

In fact, in our Melbourne Mobile Stroke Unit, the biggest cost savings came out of facilitated thrombectomy. Also, cerebral hemorrhage, which remains a treatment challenge, there's still a lot we can do on a mobile stroke unit.

We can lower blood pressure. We can reverse anticoagulation. We can treat seizures. We can triage to an appropriate center. The benefits are now well beyond thrombolysis.

Dr. Sarraj: Recently, we had, as you mentioned. Dr. Davis, two phase 3 randomized trials showing improving the clinical outcomes apart from the time saved, one from Europe and one from the United States in Houston with Dr. Grotta and the other centers.

How would that translate to the clinical practice? The neurologists and the hospital directors across the country that listen to this, how do they utilize this in deploying a mobile stroke unit? What is the usual catchment area of these mobile stroke units? How do they logistically operate? How can that be integrated into the current clinical practice?

Dr. Davis:  We now have level one evidence from two phase 3 trials and Jim should comment because he ran BEST-MSU. The other one is B_PROUD from Germany. There's level one evidence that this principle of prehospital emergency onsite stroke care works and it's highly clinically effective.

Now, they're going to stroke guidelines, Jim can comment on that, and become part of standard practice. I hope there will be time also, Geoff and I are interested in, rural and remote applications of this principle. But we should first talk about guidelines.

Dr. Sarraj:  Dr. Grotta and Dr. Donnan, how do we see the evidence from B_PROUD and the BEST-MSU translating into the guidelines and integrating into our clinical practice?

Dr. Donnan:  It went back, you were asking before, when it started. The initial evidence was provided by the German group in the PHANTOM-S study. Martin Ebinger was the first author. I was just looking before we started, the original protocol was published in "International Journal of Stroke" in 2013. It goes back quite a way.

What they showed importantly, we showed, and Jim, you showed the same thing, the surrogate endpoints of improved treatment times was universally demonstrated across all of these three centers. Of course, showing that treatment times are improved doesn't necessarily mean that patient outcomes are improved.

The big step that we're all waiting for was to see, in phase 3 studies, whether these improved treatment metrics across the globe as I was saying, actually translate into improved outcomes.

This is where, as Steve was saying, these two phase 3 studies have been so absolutely pivotal, and no doubt are going to change guidelines around the world. Jim has got the personal experience with the phase 3 studies, and I'm sure would give a real insight into how he conducted his study.

Dr. Sarraj:  Thank you, Dr. Donnan and Dr. Grotta, tell us about the results of the mobile stroke unit and how this translates to the clinical practicing guidelines.

Dr. Grotta:  First of all, the results were consistent between the Berlin study and ours, that about 11 percent absolute increase in the percentage of patients completely recovering, driven mainly by the patients treated early. Almost 70 percent of patients treated in the first hour, completely recovered back to normal.

Then there was also a shift downstream in patients who started off disabled returning to their baseline. Not only that, not only did we treat patients faster and their outcomes better, but more patients got treated because on the mobile stroke unit, you have the expertise, so a higher percentage of patients get treated.

I think the one thing that is true, and I think Steve and Geoff would attest to this, is that mobile stroke units actually run pretty smoothly. It's pretty logical. Once you get one on the road, and you integrate it with the fire department, it's not rocket science to have a mobile stroke unit run out, evaluate patients, and treat them. It's just the same exact thing that we do in the emergency room.

You asked about application and how this is going to be translated. The fact is that it's pretty straightforward to do it from a technical standpoint. The real trick is in any community getting it to interact with the fire department and the first responders and build a communication system so that mobile stroke units get alerted and work with all the EMS agencies in the city.

In some cities where there are multiple EMS agencies, you may only get alerted by one of the EMS agencies, in which case then you don't see all the other patients in the city. Similarly, if your mobile stroke unit operates out of one hospital and can't deliver patients to another hospital, then you're not going to be able to treat as many patients.

It really requires an integration of all the stroke centers and all EMS agencies in a particular area, and now that we have the data, it's going to be hard not to do that. It's going to be hard in a city to say, "OK, we're not going to cooperate with this mobile stroke unit because it's run by another hospital," for instance, or it's run by this other EMS agency.

Now that we have the data, I think it's going to be easier to accept the concept, at least in cities.

Dr. Donnan:  It might be worth describing how it works practically, and Steve will back me up on this, I'm sure. How it works in Melbourne is, we have a so-called dual response, and I think you have the same, Jim, but let us know. When a stroke call comes through the emergency service, the standard ambulance gets called, and at the same time we get called.

Steve and I and Jim go out on our ambulances. Both ambulances head off into the community. More often than not, the standard ambulance arrives first, and they might go, and they might examine the patient and find it's not a stroke at all. In which case, they'd let us know, and we'd turn back.

Often, we continue on, and they then do a quick handover, and then we take over from there, and usually we would then transport the patient back to the hospital after we've treated them that Jim was describing earlier.

This dual response model is very common around the world, particularly it was pioneered with micro ambulances, ambulances for heart attacks. That's worked so well so we follow exactly the same model.

I think, Jim, you do the same.

Dr. Grotta:  The rendezvous, so to speak, model that the first responders get, and the mobile stroke units get with them or meet at a certain point if not at the patient's house to get on time.

Dr. Davis:  Actually, I think what Geoff described is true, and that's the most common dispatch where someone calls in, and the dispatch people think it's a stroke, the 9-1-1 who handled the call, and they dispatch both at the same time. Today's case, for instance, an alert patient had a stroke far out on the southwest side of town and was not initially thought to be a stroke.

The medic arrived on scene and recognized a stroke and called for us, and in that case, we did rendezvous. We met them halfway, which bespeaks the utility of mobile stroke units, not just in the center of a city but even in suburban areas where the patient has to come a while. That's different than in a rural area behind Steve and Geoff, you see a real rural area on their picture.

It remains to be seen how well this is going to work and if it can work in very rural areas. I would like to hear their plans, but definitely in a city. I think we really just need 350,000 to 500,000 people to have enough stroke calls to keep one mobile stroke unit sufficiently busy to be cost effective.

Dr. Sarraj:  Yeah, and we will talk about the cost effectiveness concept.

Hear more in part two of this series.