Oxygen is vital for life—without it, severe brain damage may ensue in as little as three minutes. So doctors routinely treat traumas such as heart attack or stroke by providing victims with more oxygen. Mounting evidence suggests, however, that resuscitating with too much of the gas may actually have a harmful effect. The culprit in brain damage may not be a lack of oxygen but rather its reintroduction into the body.

Researchers at the University of Texas Southwestern Medical Center at Dallas reported in the Journal of Cerebral Blood Flow and Metabolism on March 12 that resuscitating baby mice with pure oxygen caused more brain damage and cerebral palsy–like coordination problems, as compared with mice that breathed air during resuscitation.

“Our results are counterintuitive,” says developmental biologist Steven Kernie, lead author of the study. “Many think oxygen doesn’t hurt and you can give as much as possible to make up for a deficiency. Our study shows this notion is wrong.”

Although Kernie’s study does not exactly mimic patient care—physicians usually administer slightly above air’s 21 percent oxygen and rarely more than 60 percent—it raises the important possibility that doctors are treating patients the wrong way, says Lance Becker, professor of emergency medicine at the University of Pennsylvania School of Medicine and director of its Center for Resuscitation Science*, who similarly showed in 2004 that cells were much more likely to die after being reexposed to oxygen than they were when deprived. In fact, Becker explains, physicians do not know how much is too much or whether administering extra amounts actually benefits patients at all.

So why would treating injuries with a molecule that fuels life actually do the reverse? Evidence suggests that pumping in too much oxygen too quickly can strip the molecule of a single electron, creating a free radical. Free radicals, linked to rapid aging, are highly reactive with other molecules, including vital DNA and proteins, the destruction of which can damage or kill cells.

Treating with too much oxygen, therefore, could increase the production of free radicals and make a bad situation even worse. The key is to find that “sweet spot,” Becker says—the optimal amount to give a person so he or she can recover with minimal damage.

A Chilly Solution
How can doctors avoid the toxic effects of reintroducing oxygen to the body after a trauma? Hypothermia therapy—lower­ing a patient’s body temperature to decrease metabolic rate and thus the need for oxygen—may be a solution, according to Hasan Alam, a trauma surgeon at Massachusetts General Hospital who established that the therapy worked in critically wounded Yorkshire pigs. The technique is popular for preserving transplant organs and reducing the need for oxygenated blood during heart surgery, but it has not been widely tested in trauma patients. De­spite its high-profile use on profes­sion­al football’s Kevin Everett after his paralyzing spine injury in September 2007, hypothermia treatment remains controversial, and studies of its ef­fec­tiveness are inconclusive.

Note: This article was originally printed with the title, "The Oxygen Dilemma".

*Erratum (10/28/08): Lance Becker was originally identified as the director of emergency medicine at the University of Pennsylvania School of Medicine.

This article was originally published with the title The Oxygen Dilemma.

7 Comments

1. 1. jean 01:43 AM 10/15/08

   The difference between drug and poison is a matter of dose.... so in case of Oxygen ...it maybe possible. For Biology is "MAYBE".......

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2. 2. xponen 02:39 AM 10/15/08

   I have a question: do cell really need oxygen to survive? I thought cell can still convert glucose to lactic acid for energy. Is brain cell any different than muscle cell, or were lactic acid kills??

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3. 3. HARMIT RANHOTRA in reply to xponen 11:40 AM 10/15/08

   Neurons cannot utilize lactic acids to generate ATP molecules which is critical for brain's high energy requirements

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4. 4. Boris 10:16 PM 10/15/08

   From my understanding our oxygen saturation in the blood is over 95% anyways and it is very difficult to "sat" someone to 100% so i have a problem understand why re-"sat"-ing someone after trauma would pose a problem.
   On the other hand reperfusion of highly oxygenated blood after hypoxic injury do cause cell death in the heart and brain.

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5. 5. Dr. Riyashat Kazmi 03:02 PM 10/18/08

   Xponen,
   
   Cells do require oxygen in order to survive. Cells recieve energy in the form of ATP via the process of cellular respiration, which involves the breakdown of glucose to (ultimately provide ATP). The ATP that cells use is derived from a process known as Oxidative Phosphorylation which (as the name implies) requires oxygen.
   
   Oxidative Phosphorylation is a part of cellular respiration and is reponsible for creating the most ATP from one molecule of glucose. In this process, the oxygen is highly electronegative and binds to all of the electrons from the reduced electron carriers which oxidizes (extracts electrons) from glucose, pyruvate, and citric acid which are respectively components from glycolysis, the PDC, and the Krebs Cycle.
   
   Without the oxygen to oxidize the electron carriers, the full energy from glucose cannot be obtained and the processes of the PDC, Krebs Cycle, and Oxidative Phosphorylation may stop.
   
   And besides, a cell is only able to make use of lactic acid for energy for a transitory amount of time. Think about it, how long can muscles sustain the culminating amount of acidity from the lactic acid while using aneobic respiration?
   
   As for the comment made by Harmit, that's a very interesting point.

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6. 6. AlexFekken 08:56 PM 10/20/08

   Many think oxygen doesnt hurt": Many what?
   
   Every since Lavoisier it has been known that oxygen is a highly reactive and corrosive element. Consensus is that life on earth couldn't even have started if it had been present in any substantial amounts.
   
   So if this really is the first time somebody took a good look at this, or if any scientist claims that the results are "counterintuitive", then I think we should be very concerned about the state of medical research.
   
   Or is this just "obligatory hype" to sell the research or the article? No wonder science is getting a bad name then.

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7. 7. discgolfer 03:16 AM 11/24/09

   you are correct sounds more like "obligatory hype to sell research, thats what over half the research is now days. Its sad, hope the scientific community changes

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