Mobile stroke treatment needs more evidence

Treating stroke patients in specialised ambulances en route to hospital could boost the number of patients who receive life-saving therapy, BBC News has today reported.

The news is based on a small but well-conducted study looking at whether the time taken to assess and treat stroke patients could be reduced using special “mobile stroke units”, which are vehicles kitted out with a mobile brain scanner, lab and experts in assessing strokes. Compared with traditional testing in a hospital, researchers found that being able to scan patients at the site of their stroke roughly halved the time taken to decide on an appropriate treatment. Since (in the case of most strokes) the earlier treatment is given the better the outcome, this study is important.

However, the study was not designed to find out if mobile stroke units improve important outcomes such as the long-term outlook for stroke patients, or their chances of disability or death. A larger study is required to assess whether this approach can improve clinical outcomes in stroke patients. Furthermore, the research was conducted in an urban area of Germany with short journey distances, and more research would need to test whether mobile stroke units have benefits in more remote settings.

In the UK, stroke experts have drawn up standards for good stroke care, including rapid response to a 999 call, prompt transfer to hospital, urgent brain scan and immediate access to a specialised stroke unit. If you suspect that you or someone else is having a stroke, call 999 immediately. The sooner you get help, the greater the chance of recovery.

Where did the story come from?

The study was carried out by researchers from the John Radcliffe Hospital in Oxford, Saarland University Hospital and several other centres in Germany. It was funded by the Ministry of Health of the Saarland and several other German organisations. The study was published in the peer-reviewed medical journal Lancet Neurology.

It was reported accurately by the BBC, which also included interviews with independent UK experts.

What kind of research was this?

Having a stroke is a life-threatening condition where the blood flow to the brain is interrupted, either through a blockage in the blood vessels supplying the brain or due to a bleed in them. Strokes caused by a blockage are known as “ischaemic”, while those caused by a bleed are termed “haemorrhagic”. Around 80% of strokes are ischemic.

Whatever the cause of a stroke, it is vital that treatment is given as soon as possible to prevent a lack of blood and oxygen damaging the brain or even causing death. This was a randomised controlled trial to investigate whether specially equipped mobile stroke units (MSUs) could reduce the time taken for suspected stroke patients to be diagnosed and treated where appropriate, compared with conventional treatment in hospital. An RCT is the best type of study design to compare different treatment interventions.

The authors pointed out that the majority of strokes are due to blood clots in the brain. They can be treated using a “clot-busting” medicine called alteplase which dissolves blood clots (thrombolysis), but to be effective this has to be given within 4.5 hours of the onset of a stroke – the earlier the better. The authors said this is often difficult to achieve because various tests and examinations are needed to rule out another type of stroke (called a haemorrhagic stroke, caused by bleeding in the brain) and to ensure patients are suitable for thrombolysis. It could be dangerous to give thrombolysis drugs to stroke patients with a bleed, therefore it can’t be prescribed as a matter of course. The researchers pointed out that less than 15%-40% of patients with acute stroke currently arrive at hospital early enough to receive “clot-busting” treatment and only 2%-5% of patients actually receive it.

What did the research involve?

Between 2008 and 2011, the researchers recruited patients aged between 18 and 80 who had one or more stroke symptoms that had started within the previous 2.5 hours. Patients experiencing a stroke were randomly selected to receive either:

• pre-hospital stroke treatment at the site of the emergency in a specialised MSU equipped with a CT scanner, mobile laboratory and online medical systems
• conventional hospital-based treatment, transporting patients to hospital and carrying out similar treatments there

The MSU team included a paramedic, a stroke physician and a neuroradiologist (an X-ray doctor trained to operate the CT scanner), while the conventional emergency medical service (EMS) included an emergency doctor. The MSU team obtained the patient’s history, undertook a neurological examination, CT scan and laboratory examinations and, if the patient was eligible, gave thrombolysis directly at the site of the stroke. The EMS patients received what is currently considered to be the best conventional stroke care plan, which included assessment and appropriate treatment in hospital.

With both groups, the researchers monitored the time it took from the first emergency call for help until a medical decision was made about treatment. They also compared the intervals between the emergency call and the end of CT scanning and the end of the laboratory analysis. In addition, they compared the numbers of patients in each group who received thrombolysis, the time between the emergency call and thrombolysis and the outcome that treatment had on the patients’ brains. They also looked at other results, including survival rates seven days after the stroke.

What were the basic results?

The researchers had planned to include 200 patients but stopped the trial after analysing results on the first 100 (53 in the pre-hospital stroke treatment group, 47 in the control group). They found that  compared with standard hospital treatment, the pre-hospital stroke treatment:

• reduced the time from the first call for help to a decision about treatment, from 76 to 35 minutes on average (median difference 41 minutes, 95% CI 36 to 48 minutes)
• reduced the average time between the first call for help and the end of CT scan
• reduced the average time between the first call for help and the end of laboratory analysis
• reduced the average time between the first call for help and the start of intravenous thrombolysis for eligible ischaemic stroke patients

There was no substantial difference in the number of patients in each group who received intravenous thrombolysis or in their neurological outcomes. Survival rates seemed similar across the two groups.

How did the researchers interpret the results?

The researchers concluded that mobile stroke units offer a potential solution to the problem of most stroke patients arriving at hospital too late for treatment.

Conclusion

This small study found that using specialised mobile stroke units to assess and treat suspected stroke patients at the site of the emergency roughly halved the time taken for doctors to decide on the appropriate treatment. Since, in the case of most strokes, the earlier thrombolytic treatment is given the better the outcome, this is important. As the authors pointed out, stroke is a medical emergency where time is critical for saving the brain, and patients’ lives.

However, it’s important to note that although researchers looked at patient outcomes seven days later, the study was not designed in a manner to assess fully whether MSUs would enable more patients to benefit from thrombolysis, would save brain tissue or reduce disability or death in these patients. Arguably all of the time-based measures assessed in the study would come secondary to these key considerations of whether MSUs would allow more patients to survive, and whether the quality of patients’ life and health would improve if they did survive.

The authors of the study also raised some of the study’s other limitations, such as the doctors assessing the patients after treatment being aware (unblinded) of the treatment that patients had received. This means that their knowledge of what treatment was received may have subconsciously influenced their assessments. The authors also noted a potential for bias in the way patients were randomised, as all stroke patients treated within a particular week received one form of treatment, and patients treated the next received the opposing treatment.

As an accompanying editorial points out, the study was set in an urban area of Germany where the average distance from the patient to the hospital was 7km. Whether an MSU could provide assessment and treatment more quickly would depend on the setting. For example, an MSU might work less well in rural areas, where local ambulance services might get patients to hospital just as fast as a hospital-based MSU could get out to the patient. Equally, in built-up cities where there are numerous hospitals the journey to hospital in a conventional ambulance might be particularly quick.

MSUs, unsurprisingly, are extremely expensive, with the researchers estimating a cost of about €300,000 (£247,000) for the equipment alone. They are also likely to be resource-intensive in terms of the dedicated trained staff required to operate them.

While the idea of mobile stroke units is an exciting prospect, there is still more research and planning needed to tell if they actually do provide the best option for treating patients. A larger study is needed to look at whether they can improve the medical outcomes stroke patients experience and whether the costs involved would be better spent on other, less expensive measures. These could include further specialised training of ambulance crews, additional specialised stroke centres (already operating with some success within the NHS), greater availability of scanners within hospitals or simply increasing the public’s awareness of the need to seek treatment early and ways to cut their stroke risk.