To print: Select File and then Print from your browser's menu --------------------------------------------------------------------------------------- Title: Room Air Appears To Do Less Brain Damage Than Pure Oxygen URL: http://www.pslgroup.com/dg/B01A6.htm Doctor's Guide September 18, 1998
BALTIMORE, MD -- Sept. 18, 1998 -- When a person's heart stops, standard resuscitation includes treatment with 100 percent oxygen. Now researchers at the University of Maryland School of Medicine and George Washington University School of Medicine and Health Sciences report that regular air -- which is 21 percent oxygen -- may be a better choice in some cases, helping prevent neurological damage that can occur after the brain is deprived of oxygen. A study conducted by Gary Fiskum, PhD, University of Maryland professor of anesthesiology and Robert Rosenthal, MD, professor of emergency medicine at George Washington, is the first research to look at chemical changes in the brain during restoration of blood flow after cardiac arrest and the neurological damage that can follow. They reported their findings in the August issue of the medical journal Stroke. Much of the brain damage that occurs after the heart stops pumping is what doctors call reperfusion injury. That means it occurs while the blood flow is being restored to the brain. Fiskum said it is caused by the toxic effects of free radicals, which are by-products of the process of oxidation. Fiskum and Rosenthal compared levels of oxidation of brain lipids -- fatty acids and fat-like substances that maintain vital metabolic functions -- in animal models resuscitated after 10 minutes of cardiac arrest. In those given 100 percent oxygen, free-radical levels were significantly higher than in those resuscitated using the oxygen ratio found in room air. When neurological deficits were measured, the animals resuscitated with 21 percent oxygen showed less brain damage than those resuscitated with 100 percent oxygen, the researchers report. "It was reasonable to expect that pure oxygen would be good for a brain that has been deprived of oxygen," Fiskum said. "But we found that was not necessarily the case. After oxygen levels reached normal levels in the blood, continuing to administer pure oxygen actually was damaging the metabolic mechanism in the brain." Further studies are needed to understand the precise mechanisms of oxidative injury to the brain, Fiskum said. That understanding could help medical science develop more effective therapies to improve neurological outcomes after heart attacks, strokes and head injuries, he explained. Meanwhile, the researchers said the neurological and neurochemical results of their study raise questions about the appropriateness of current resuscitation guidelines that call for pure oxygen for undefined lengths of time during and after cardiac arrest. "We are not saying to stop using 100 percent oxygen and to start using only room air," Fiskum explained. "We are saying to monitor oxygen levels in the blood more closely and not to use pure oxygen if the oxygen level already is at or above normal." Related Links: Stroke --------------------------------------------------------------------------------------------- Copyright © 1999 P\S\L Consulting Group Inc. All rights reserved. Republication or redistribution of P\S\L content is expressly prohibited without the prior written consent of P\S\L. P\S\L shall not be liable for any errors, omissions or delays in this content or any other content on its sites, newsletters or other publications, nor for any decisions or actions taken in reliance on such content. --------------------------------------------------------------------------------------------- This news story was printed from *Doctor's Guide to the Internet* located at http://www.docguide.com --------------------------------------------------------------------------------------- Return to News Story Page This site is maintained by webmaster@pslgroup.com Please contact us with any comments, problems or bugs. All contents Copyright (c) 1998 P\S\L Consulting Group Inc. All rights reserved.