Adding Oxygen During a Stroke Can Reduce Brain Damage

Two groups of animals received either normal oxygen or pressurized oxygen while blood flow was blocked in the brain. Two other sets of rats received normal or pressurized oxygen after blood flow was restored; and a control group received no supplemental oxygen, breathing room air instead. Two days later, the researchers examined the rats' brains using a 4.7-Tesla magnetic resonance imaging (MRI) device to calculate the volume of damaged tissue. The images demonstrated the size of the infarct, representing the area of tissue susceptible to stroke damage as a result of poor oxygenation.

The images showed that the animals that received supplemental oxygen treatment while blood flow was blocked had a significantly smaller amount of tissue damage compared to the rats that received oxygen after blood flow was restored. By further examining images, the scientists determined that the supplemental oxygen during the active period of a stroke specifically reduced the death of neurons, and prevented the damage that free radicals can cause to lipids that help protect those brain cells. By comparison, more dead neurons and oxidative stress were found in the brains of rats receiving oxygen only after blood flow was restored. The study was presented at the Society for Neuroscience annual meeting, held during October 2009 in Chicago (IL, USA).

"Ultimately, the supplemental oxygen after blood flow is restored is more than the tissue can handle, and is more than it needs. Why add oxygen on top of tissue that's already oxygenated?” said study presenter and coauthor Cameron Rink, M.D., Ph.D., an assistant professor of surgery at Ohio State. "Supplemental oxygen during the blockage, on the other hand, is highly protective.”

An ischemic stroke occurs when a blood a clot is blocking blood flow in the brain, as compared to hemorrhagic stroke, which occur when blood vessels rupture in the brain.

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