07 August 2010

The Effect of Oxygen on the Brain.

On the back of the previous post concerning Hyperbaric Oxygen administration, perhaps we should take a look at the effect of oxygen on the brain and ask whether research should not focus upon how the oxygen is delivered.  How many of our children have suffered further brain injury through the direct administration of enriched oxygen? There is a good preventative lesson in this report.
The current practice of administering 100 percent oxygen to children, to prevent brain damage caused by oxygen deprivation, may actually inflict additional harm, researchers at UT Southwestern Medical Center have found.
Brain damage caused by oxygen deprivation, known as hypoxic-ischemic brain injury, is one of the most common causes of death and long-term neurological damage among infants and children. This can happen during birth trauma, near drowning and other crises.

The UT Southwestern researchers found that mice treated with less than a minute of 100 percent oxygen after a hypoxic-ischemic brain injury suffered far greater rates of brain-cell death and coordination problems similar to cerebral palsy than those allowed to recover with room air.

"This study suggests 100 percent oxygen resuscitation may further damage an already compromised brain,"  said Dr. Steven Kernie, associate professor of pediatrics and developmental biology and senior author of the study, which appears in the July issue of the Journal of Cerebral Blood Flow & Metabolism.

Most of the damage involved cells that create myelin, a fatty substance that insulates nerve cells and allows them to transmit electrical signals quickly and efficiently. Infants have much less myelin than adults; as myelin develops in children they become more coordinated. Areas of the brain with dense areas of myelin appear white, hence the term "white matter."
"Patients with white-matter injuries develop defects that often result in cerebral palsy and motor deficits,"  Dr. Kernie said.

Myelin comes from cells called glial cells, or glia, which reach out and wrap part of their fatty membranes around the extensions of nerve cells that pass electrical signals. The brain creates and renews its population of glial cells from a pool of immature cells that can develop into mature glia.

In their study, the researchers briefly deprived mice of oxygen, then gave them either 100 percent oxygen or room air, which contains about 21 percent oxygen, 78 percent nitrogen and 1 percent other gases.

After 72 hours, mice given 100 percent oxygen fared worse than those given room air. For example, they experienced a more disrupted pattern of myelination and developed a motor deficit that mimicked cerebral palsy. The population of immature glial cells also diminished, suggesting that the animals would have trouble replacing the myelin in the long term.

"We wanted to determine whether recovery in 100 percent oxygen after this sort of brain injury would exacerbate neuronal injury and impair functional recovery, and in these animals, it did impair recovery," Dr. Kernie said. "Our research shows even brief exposure to 100 percent oxygen during resuscitation actually worsens white-matter injuries."

Dr. Kernie said adding pure oxygen to the damaged brain increases a process called oxidative stress, caused by the formation of highly reactive molecules. The researchers found, however, that administering an antioxidant, which halts the harmful oxidation process, reversed the damage in the mice given 100 percent oxygen.

"Further research is needed to determine the best possible concentration of oxygen to use for optimal recovery and to limit secondary brain injury," Dr. Kernie said. "Research is now being done to determine the best way to monitor this sort of brain damage in humans so we can understand how it correlates to the mouse models. There are many emerging noninvasive technologies that can monitor the brain."

Interesting isn't it? I wonder if they want to know why this happens?

When we try to administer high concentrations of oxygen to the brain, we actually cut the supply of oxygen the brain actually recieves. This is because high concentrations of oxygen act to constrict the cerebral arteries and veins. Constricted veins carry less blood and as blood carries oxygen, the individual concerned, who might already be in oxygen debt, has his oxygen supply further compromised.

Exactly the same problem is seen in epilepsy, which whether caused by pathology or physiology is a reflexive response to a compromised oxygen supply. The first thing a doctor will do is to supply the individual with oxygen, which very often just produces a bigger, better and more prolonged seizure! They then have to administer massive doses of anti – epileptic medication to undo the damage they have done through administering oxygen and to bring the seizure under control.

So what should be done instead of administering oxygen?

There is a great deal of research, which suggests that carbon dioxide is a good solution to this problem. The brain reacts to higher than normal levels of CO2 by dilating the cerebral arteries and veins. Dilated arteries carry more blood and as I previously pointed out, more blood = more oxygen. Obviously the timing, level and concentration of CO2 administration would need to be carefully controlled, but there is research, particularly with regard to epilepsy that CO2 could provide answers to some serious problems. http://www.medicalnewstoday.com/articles/73558.php is a good source just for starters!

So, in summary, the evidence suggests that we should completely review our methods for delivering oxygen to the brain. The direct route of direct administration of oxygen, actually produces the opposite effect to that which is desired and can actually make oxygen deprivation worse, thereby exacerbating the potential for brain injury and worsening neurological symptoms like epilepsy. We need to devise a treatment whereby CO2 enriched air can be administered thereby helping to turn on the brain's own natural anticonvulsant systems and in turn affecting the cerebral vascular system so that it is able to deliver oxygen as necessary. In this way we could not only prevent the occurrence of some types of brain injuries, but we could help to ameliorate the symptoms of those already suffering the consequences of neurological damage.

One thing is certain though, no one should take it upon themselves to administer CO2 enriched air to their child or to anyone else. This should only be done under the guidance of someone who is suitably qualified.

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