Infection rates, survival didn't change, but more risk for low blood sugar seen in study
By Serena Gordon
FRIDAY, Sept. 7 (HealthDay News) -- Tightly controlling blood sugar levels after young children's heart surgery doesn't reduce the risk of infection, length of hospital stay or death, according to new research.
By keeping blood sugar levels in a normal range using insulin after surgery, researchers had hoped to see a reduction in infections and other complications. Instead, they saw an increased risk of dangerously low blood sugar levels.
"I think in the pediatric cardiac population, the question of whether or not tight glycemic control provides a benefit has been answered," said the study's lead author, Dr. Michael Agus, director of the medicine critical care program at Boston Children's Hospital. He said it's clear from this study that there's no statistically significant benefit to this therapy, and a clear risk from it.
Results of the study were published online Sept. 7 in the New England Journal of Medicine to coincide with a presentation at a pediatric critical care meeting in Santa Monica, Calif.
During a critical illness or a surgical procedure, blood sugar levels in the body rise, sometimes dramatically. For a long time, it was assumed this was a natural response to the stress of illness or surgery. What wasn't clear was whether these high blood sugar levels provided a benefit, such as giving the body extra fuel to fight off an infection, or if they were causing harm.
What was known was that people who had high blood sugar levels often had bad outcomes, such as higher rates of infection and death, according to Agus. In 2001, a single-center trial of people in the intensive care unit reported that lowering blood sugar levels with insulin resulted in dramatic reductions in bad outcomes, Agus said.
Since that time, larger studies have shown no benefit from lowering blood sugar levels to normal in the adult intensive care population. However, research has also shown that one group -- adult cardiac surgery patients -- do benefit from achieving more normal blood sugar levels after surgery. But, the question remained as to whether or not this benefit would be seen in pediatric heart surgery patients.
The current study included 980 children ranging from newborn to 36 months old from two medical centers. All were undergoing surgeries that required cardiopulmonary bypass, which means that the function of the heart and lungs was temporarily controlled by a machine.
Half of the children were randomly assigned to tight blood sugar (glycemic) control after surgery, and the other half were assigned to standard care. Those on tight blood sugar control had their blood sugar lowered to a target of between 80 and 110 milligrams per deciliter. The researchers used a continuous glucose-monitoring system and an insulin-dosing algorithm to reduce the risk of dangerously low blood sugar levels.
The investigators found that reducing blood sugar levels didn't reduce the rate of infections, length of hospital stay or death compared to standard care.
Three percent of the children on the tight glycemic control regimen experienced low blood sugar levels (hypoglycemia). "There's always a risk with severe hypoglycemia. We don't truly know whether or not even a short time in hypoglycemia will affect neurodevelopment," Agus said.
A major lesson from this study, Agus said, is that "pediatric cardiac surgery babies are a unique population. Any population is going to have its own unique characteristics, so we have to be responsible and conduct therapeutic trials before adopting new therapies in any population."
Another expert agreed.
"This seems to be one of the areas where children and adults are significantly different," said Dr. David Meyer, a pediatric cardiac surgeon at Steven and Alexandra Cohen Children's Medical Center of New York, in New Hyde Park. "In cardiac surgery in adults, it's important to maintain tight glycemic control after surgery, but this study shows in children, there's no particular advantage to maintaining the sugar at lower levels. There doesn't seem to be a similar benefit in children."
Learn more about heart surgery in children from the U.S. National Library of Medicine.
SOURCES: Michael S.D. Agus, M.D., director, medicine critical care program, Boston Children's Hospital, and assistant professor of pediatrics, Harvard Medical School, Boston; David B. Meyer, M.D., pediatric cardiac surgeon, Steven and Alexandra Cohen Children's Medical Center of New York, New Hyde Park, N.Y.; Sept. 7, 2012, New England Journal of Medicine, online
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