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Brainstorming in Dr. Andrew Baker’s lab

Toronto, March 10, 2014

By Leslie Shepherd

Dr. Andrew Baker prepares to set off a controlled experimental blast in the “Baker Blast Device” to test treatments aimed at reducing brain injury in soldiers.
Dr. Andrew Baker prepares to set off a controlled experimental blast in the “Baker Blast Device” to test treatments aimed at reducing brain injury in soldiers. (Photo by Katie Cooper)

What do angioplasty patients from the 1990s, some elite Canadian swimmers and rats in Dr. Andrew Baker’s lab have in common?

They’ve all been exposed to something called pre-conditioning.

The general idea of pre-conditioning is that exposing a patient to a minor injury, such as ischemia, make them better able to tolerate the real injury they receive later.

Cardiologists discovered this long ago when they would partially inflate a balloon into a patient’s blocked artery for a few minutes, blocking blood flow to the heart (ischemia), and then deflate it. The heart then tolerated the full angioplasty procedure better. With newer techniques, this is no longer done, but researchers wondered whether the same principle could be applied elsewhere.

For example, a doctor at SickKids is studying whether he can use preconditioning to improve the performance of some of Canada’s top swimmers. Even though these athletes have superb cardiovascular fitness and their hearts provide maximal oxygenated blood flow, their performance is limited by just how much oxygen can be used by their muscles. Using preconditioning, can he increase the muscles’ ability to use oxygen efficiently and so squeeze a little more work out of them giving the athletes an edge?

In yet-to-be-published research, he induced ischemia in their skeletal muscles by putting swimmers though four, five-minute sustained inflation cycles of a blood pressure cuff before practice. At a later practice, he measured such things as their speed, blood lactate levels (an indication of the efficiency with which the muscles use the available oxygen), heart rate and breathing frequency, and compared them to swimmers who had less-than-full inflations of the blood pressure cuffs.

Taking the preconditioning concept one step forward, Dr. Baker is studying whether ischemia of the limbs could also be used to lessen traumatic brain injuries, such as blast injuries experienced by soldiers.

In his lab in the Keenan Research Centre for Biomedical Science, Dr. Baker applies tourniquets to the rats’ legs and then induces TBI. Rats that had ischemia have different responses to the blast than those who did not.

Dr. Baker has also just received a $100,000 grant from the Canadian Institutes for Health Research to develop a blood-based test to determine whether a person exposed to a blast has suffered mild traumatic brain injury.

“Imagine, eventually, if a soldier stationed in Afghanistan put a blood pressure cuff on in the morning before going out on patrol and possibly suffering a blast injury?” asked Dr. Baker, who is also head of critical care.

At the same time, Dr. Baker is studying whether there are any drugs that can lessen the impact of TBI and has found one possibility. He’s still a longshot, but he explains why he’s excited:

“It is so important that we look for ways to treat the underlying biology of these blast-induced brain injuries. It may seem like a long shot, but even though experimentally we have to give the treatment in advance, we have at least shown that we can now improve the biology of the brain’s response to blast injury. Sure it may be a long way from application, but the fact that we can demonstrate in principle that it can be done is extremely exciting. It means that we are on the way.”

About St. Michael's Hospital

St. Michael’s Hospital provides compassionate care to all who enter its doors. The hospital also provides outstanding medical education to future health care professionals in 27 academic disciplines. Critical care and trauma, heart disease, neurosurgery, diabetes, cancer care, care of the homeless and global health are among the hospital’s recognized areas of expertise. Through the Keenan Research Centre and the Li Ka Shing International Healthcare Education Centre, which make up the Li Ka Shing Knowledge Institute, research and education at St. Michael's Hospital are recognized and make an impact around the world. Founded in 1892, the hospital is fully affiliated with the University of Toronto.

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