Tiny `Metabolic Engines' Rev Up Preemies' Glucose Production

Tiny premature newborns can rev up their "metabolic engines" to produce their own blood glucose using components of the intravenous solution they receive during the first days of life, says a scientist at the USDA/ARS Children's Nutrition Research Center at Baylor College of Medicine.

"Our findings indicate that the amount of glucose in the intravenous feedings could safely be reduced, cutting the risk of high blood glucose levels, or hyperglycemia, without increasing the risk of too low blood glucose concentrations or hypoglycemia," says Dr. Agneta Sunehag, a research neonatologist and an assistant professor of pediatrics at Baylor.

Once the umbilical cord is cut, healthy full-term babies are able to breakdown their glycogen, fat and protein stores to make glucose to feed the brain. But, very premature infants are born before these stores develop. So nutrition must be provided immediately after birth.

Because these tiny babies are unable to suckle or digest food, they are routinely given relatively high concentrations of intravenous glucose to prevent a brain-damaging drop in their blood glucose levels and to meet their energy needs.

But, this approach can present problems for some infants.

"Many premature newborns develop high blood glucose concentrations because they cannot handle large intravenous doses of glucose. When this happens, they lose precious sugar, water and salts through the urine, putting them at risk for dehydration and electrolyte imbalances," Dr. Sunehag says.

Excess glucose can also affect the amount of carbon dioxide premature infants produce, exacerbating problems for those with lung disorders.

Dr. Sunehag believes that hyperglycemia could be prevented if premature infants were capable of regulating their own glucose levels, making glucose out of other intravenous fuels like protein and fat when necessary.

In her study, Dr. Sunehag cut the intravenous glucose infusion rate in 20 very premature, 5-day-old infants by 75 percent while providing an intravenous solution of amino acids and a fat emulsion to test their metabolic capacity. Blood glucose levels were closely monitored and non-radioactive "tracers" tracked the source of glucose circulating in the infants' blood.

Despite lower glucose infusion rates, the blood glucose levels remained in the normal range for all infants throughout the eight- to 12-hour study period. Tracer results revealed that the majority of the glucose the infants produced was derived from the fat and amino acids in the intravenous solution. These findings confirmed that newborn premature infants could use their own metabolic pathway to make glucose when needed.

Dr. Sunehag is now working to determine the optimal mix of glucose, fat and amino acids in intravenous feedings. Finding the optimal mix could help decrease the number and severity of complications, helping premature infants leave the hospital sooner.

"Just 10 years ago, little thought was given to the nutritional needs of the tiniest of premature infants because so few of them survived. Now, 90 percent do survive. So, we must think how to best manage their care not only to help them survive, but to thrive and grow healthy and strong," Dr. Sunehag says.

(Editor's note: These findings were recently presented at the annual meeting of the Society for Pediatric Research in Boston.)

- JOAN CARTER, R.D./L.D, M.B.A.

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©2006 Texas Medical Center

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