Simple technique may reduce severity of stroke
Use of standard blood-pressure cuff recommended
An international team led by University of Toronto medical professors Andrew Redington and Cecil Hahn (Department of Paediatrics), based at The Hospital for Sick Children, has found a new potential treatment to help reduce the severity of acute stroke.
The new potential treatment involves the use of an ordinary blood-pressure cuff and a technique called remote ischemic per-conditioning. The method is both simple and inexpensive. It can also be delivered anywhere. Remote ischemic per-conditioning, which involves intermittently pumping up a blood-pressure cuff to temporarily restrict blood supply to a limb and then releasing it, caused a 40 per cent reduction in the size of stroke in animal models, which mimic stroke in humans. The advance online edition of the study was published in August in Stroke.
The current study follows last year’s major breakthrough by the same research team. The scientists reported in The Lancet that a similar technique, using a regular blood-pressure cuff in patients with an acute heart attack, reduced the size of their heart attacks by up to 50 per cent.
“It is not surprising that such a similar method is also showing promising results, as the stroke study is basically the brain equivalent of our heart attack research,” said senior investigator Andrew Redington, who is also division head of crdiology and a senior associate scientist at SickKids.
Ischemic conditioning is a powerful innate mechanism the body uses to protect all its tissues from the effects of lack of blood flow. Reducing the blood flow in a limb sends a warning message to the body and other organs—in this case, the brain—by releasing substances in the blood that protect the body and the brain from subsequent injury.
A stroke occurs when blood supply to the brain is interrupted. If any part of the brain loses blood flow for longer than a few seconds, then brain cells in that area cannot get oxygen and may die, resulting in permanent damage. The size and location of the stroke determine how much damage is done.
The current study measured the size of strokes using animal models designed to mimic acute stroke in humans. The 39 animals were randomly assigned to three groups that received the ischemic conditioning stimulus at different times: before the onset of stroke (preconditioning), after the onset of stroke (per-conditioning) and a control group that received no therapy. The per-conditioning group, which is also the most clinically relevant, had the largest reduction in stroke size.
“The timing of stroke is almost always unpredictable, so we need therapies that can be given after the onset of stroke and before blood supply returns to the brain,” said Hahn, lead author of the study and a staff neurologist and associate scientist at SickKids. In this study, the per-conditioning stimulus was more effective than the preconditioning stimulus, which was surprising.”
Redington suggests the difference lies in the timing of the delivery of the technique. Unlike in the heart attack study, where the whole episode lasted about an hour, the stroke study looks at a three-hour time period. The preconditioning would take place much earlier and “presumably is wearing off by the time the brain gets its blood flow back, so the protection is limited. With per-conditioning, you’re actually delivering the protection much closer to the time that the brain gets its blood flow back,” he said.
“The beauty of this technique is that it doesn’t require highly specialized care,” says Hahn. “It is very simple and can be done by anyone, anywhere. More research is required to determine how well this technique works in humans. If it’s found to be safe and effective in people with acute stroke, this method may eventually be used in both adults and children in developed and developing countries.”
Redington and colleagues are also working on developing an automated blood-pressure cuff that would make it easier and more efficient for health-care workers to deliver the therapy. SickKids has licensed intellectual property and is working with a Canadian company to develop the product.