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Hypoglycemia in Newborns Might Be Linked to Brain Damage

But critic claims animal study doesn't make definitive connection

THURSDAY, Feb. 14, 2002 (HealthDayNews) -- Infants born with hypoglycemia, or low blood sugar levels, might face a greater risk of brain damage.

So says a new animal study that was funded by the National Institutes of Health and appears in the February issue of Brain Research.

The potential connection is via a brain receptor known as NMDA, which is one of the many biochemical links that influence communication between brain cells. When sugar levels are low, a change in the way these receptors respond occurs, and the researchers say that creates a potential pathway for brain damage.

"The effects of hypoglycemia on an infant's brain has been a subject of some debate, with some researchers believing that it has no detrimental effects. Obviously, we don't see it that way," says Dr. Jane McGowan, the study author and a neonatologist at Johns Hopkins Children's Center in Baltimore.

McGowan believes that when an infant's sugar levels are too low, subsequent changes in brain receptors might affect the brain's ability to develop normally.

The study, which used piglet brains, shows one of the ways in which these important changes might happen, she says.

A neonatal expert, however, thinks there's a long way to go before the studies are clinically relevant.

"Because it is an animal study, I feel the finding does not have direct clinical application to human babies at the present time," says Dr. Richard Polin, director of neonatal intensive care at Children's Hospital of New York-Presbyterian.

But he adds, "The study implicates the NMDA receptor in the pathophysiology of brain injury, and I think that this is an interesting concept. It may be important as a mechanism, and it may point the way to other ways of preventing brain injury if it turns out to be a real mechanism in [human] infants with hypoglycemia."

Although hypoglycemia can occur in almost any newborn, it is most often seen during specific scenarios. Those include when a baby is born premature or born to a mother who developed diabetes during her pregnancy.

Regardless of why and when it happens, experts say treatment is usually available right away.

"Because we give these babies adequate intravenous glucose almost from birth (followed by enteral feedings), it's a relatively uncommon problem," Polin says.

However, McGowan is quick to add that getting that treatment right is not always easy. Therefore, problems like the kind found in her study can still crop up, she says.

"I think it is somewhat of a controversy over how best to treat these babies -- we question how much [glucose] to give them, and if we are giving too much or not enough. It's very difficult to tell," McGowan says.

Polin adds this explanation: "Treatment depends on the etiology of the hypoglycemia, whether the baby is symptomatic or asymptomatic, and a whole host of other variables. The treatment of infants with hypoglycemia is controversial. Even the level of blood sugar that needs treatment is controversial," he says.

That, counters McGowan, is precisely her point: Although treatment may be available, conflicting thoughts on how best to dispense that care may leave infants wide open for the potential brain damage her study describes.

That research involved six piglets that were three to six days old. They were given insulin injections to artificially sustain a low blood sugar level for two hours. Researchers then extracted brain tissue from the six piglets, along with equal portions of tissue from six piglets that had normal blood sugar levels.

They isolated the area of the brain that housed the receptors in question, and tested them for their ability to bind to certain brain chemicals.

The result: The NMDA receptors taken from brain cells that were "bathed" in low blood sugar behaved differently than those exposed to normal sugar levels, binding to a greater amount of a substance called glutamate.

McGowan admits the finding does not prove that brain damage did occur-- or even could occur. And, she adds, she doesn't know what, if any, long-term effects these changes may represent.

However, "our findings suggest that changes are taking place in the brains of infants with hypoglycemia, indicating a need for further research to see if these changes have any long-lasting or permanent effects on brain development," McGowan says.

Polin suggests the research be kept in context.

"It's a study looking at a mechanism for hypoglycemia, but it does not say that all hypoglycemia injures babies by any means," he says.

What To Do

To learn more about hypoglycemia in infants, visit emedicine journal.

For a good overview of hypoglycemia in newborns, plus important information on breast-feeding, visit La Leche League.

SOURCES: Interviews with Jane McGowan, M.D., associate professor, pediatrics-neonatology, and neonatologist, Johns Hopkins Children's Center, Johns Hopkins University, Baltimore; Richard Polin, M.D., director, neonatal intensive care, Children's Hospital of New York-Presbyterian; February 2002 Brain Research
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