Mobile stroke units can halve the time it takes a patient to get clot-busting drugs, a small German trial found.
The drugs only work if given within four and a half hours of stroke onset.
Since not all patients are suitable candidates, a rapid assessment is critical, The Lancet Neurology reports.
Clot-busting drugs (thrombolytics) can be effective if the stroke is caused by a blood clot (the cause in about 80% of cases), but not if it is due to a bleed.
The faster an eligible patient receives clot-busting treatment, the better their chances are of surviving and reducing long-term disability.Brain scan
The latest trial, which involved 100 patients in Germany, found treatment decision times were reduced by equipping ambulance staff with the necessary tools, including CT scanners, to diagnose and manage stroke.
Treating suspected stroke patients at the site of the emergency is an interesting development ”
In the study, thrombolysis was given within 35 minutes, on average, for those patients treated by mobile stroke units. In comparison, those sent to hospital for treatment in the usual way waited 76 minutes.
Patient outcomes did not differ significantly between the two groups but the researchers point out that the study was not designed to evaluate this and that the number of patients involved in their trial was small. The follow up was also short - a week.
Experts say larger studies are needed to explore what impact earlier treatment will have on prognosis, and to confirm whether mobile stroke units would also work in other geographical regions, not just in urban areas with short journey distances.
Stroke is the third biggest cause of death in the UK and the largest single cause of severe disability. Each year more than 110,000 people in England will have a stroke, which costs the NHS over £2.8bn.
In 2007 the government set out a National Stroke Strategy to improve stroke services and recommended that patients with a suspected stroke should have a brain scan as soon as possible to determine if it was caused by a blocked artery or a burst blood vessel.
A stroke can be diagnosed using "FAST":
- Facial weakness - has the person's face drooped, usually down one side
- Arm weakness - is the person able to lift both arms above their head
- Speech problems - does the person's speech sound slurred
- Time to call 999 - if one or more of these symptoms are present call 999 immediately
Only a minority of stroke patients reach hospital and undergo brain scanning within a few hours, which is necessary if these drugs are to be given.
But stroke care has been improving over recent years, audits show.
Nikki Hill of The Stroke Association said: "When a stroke strikes time lost is brain lost, meaning that getting urgent medical attention quickly is absolutely essential.
"Treating suspected stroke patients at the site of the emergency is an interesting development and it could help to speed up the whole treatment process for some patients.
"However, this research was conducted in an urban area of Germany, and so it's difficult to say whether the same method would work in the more rural areas of the UK. A lot more research is needed."
A Department of Health spokeswoman said: "The results of this study are interesting, but we would need more evidence on whether mobile stroke units would be a clinical and cost effective addition to NHS stroke services.
"In some instances, it could be just as quick or quicker to get the patient to hospital in an ambulance as it would to get a mobile stroke unit to the patient."