When blood flow is restored to an area after being restricted like during surgery it can cause tissue damage. But a new study conducted at the University of Virginia shows how people who exercise are less susceptible to the muscle and nerve damage that can typically occur.
An ischemia-reperfusion injury can be the result of blood flowing again after being stopped for a period of time. Reperfusion or reoxygenation is the process of returning the blood to tissue after a period of ischemia or lack of oxygen.
UVA’s Dr. Zhen Yan is an expert on the cellular benefits of exercise. He and his team are conducting research to better understand how the body is damaged by the restoration of blood flow in an effort to improve outcomes for people who experience it such as surgery and trauma patients and soldiers injured in battle.
The study findings, which are detailed in the Journal of Applied Physiology, show that pre-event exercise in mice was beneficial in protecting from both muscle and nerve damage. "Exercise-trained mice had a much better recovery, evidenced by less nerve damage, less muscle damage and less reduction of contractile function (in the muscle) immediately after injury and days later," Yan said.
Doctors need to be careful to limit the amount of time blood flow is restricted because of the potential damage caused by reperfusion injury.
"There are some situations where you have to stop bleeding to save life," Yan said. "The way we often do that is by putting on a tourniquet, to completely stop the circulation until the patient can be taken to the emergency room. But there's an issue there: We cannot block it too long. The tissues will be dead. We have to restore the blood flow at some point, but it will cause reperfusion injury. There is a conundrum."
Researchers were able to measure the amount of oxidative stress to cells when blood flow was restored. They found pre-event exercise was able to reduce the muscle and nerve damage but did not appear to reduce the oxidative stress. "We know exercise made the muscle and nerve tougher," Yan said. "The protection is very clear."
Yan is hoping to come up with some type of drug to prevent ischemia reperfusion injury because he believes it will be especially beneficial to the military.
"On the battlefield, a simple thing to do is to put a bandage around the limb to block the circulation, to block the bleeding," he said. "But at a certain point, you have to re-establish circulation, and our approach could offer a way to minimize the collateral damage and get better outcomes."