Very-low-birth-weight (VLBW) babies who undergo major surgery appear to have an increased risk of death or subsequent neurodevelopmental impairment, according to a new study published June 16 in the journal JAMA Pediatrics.

Major surgeries are procedures that require general anesthesia, and some animal studies have suggested that general anesthesia can increase the risk for neurocognitive or behavioral deficits.

The new retrospective study, which is the largest of its kind to date, looked at the risks associated with surgery by comparing outcomes in 12,111 very low birth-weight infants enrolled in the Eunice Kennedy Shriver National Institute of Child Health and Human Development Neonatal Research Network Generic Database from 1998 through 2009. In the study, surgery was classified as major if it was expected to require general anesthesia or minor if it could have been done with nongeneral anesthesia. A total of 2,186 infants underwent major surgery, 784 had minor surgery, and 9,141 had no surgery.

Overall, surgery increased the risk of death and of neurodevelopmental impairment in VLBW infants who survived to 18 to 22 months. Any type of surgery increased the risk of death or neurological impairment by about 30 percent compared to infants who did not have surgery, and the risk was 50 percent higher for VLBW babies undergoing major surgery compared to VLBW infants who had no surgeries.

In addition, multiple surgeries further increased the risk of death or neurological damage in these infants.

"Our analysis supports the concern that major surgery with general anesthesia increased the risk for these very low birth weight infants during this vulnerable period in their lives," says senior study author Frank Morriss, a neonatologist with University of Iowa Children's Hospital and a professor of pediatrics at the UI Carver College of Medicine. "We need to learn more about this window of vulnerability to determine if we might delay some surgeries until after the window closes or if there are ways to reduce the risks for those babies who have to have surgeries during this time."

Infants born with very low birth weight (between 401 g or 14 oz. and 1500 g or 53 oz.) are very vulnerable. Many don't survive (approximately 30 percent) and those who do have a greater risk than term infants of neurological problems including cerebral palsy, cognitive deficits, and vision and hearing impairment.

Despite the concerns that major surgery under general anesthetic may be harmful to VLBW infants, up to 25 percent of these infants have at least one surgery, which often are necessary to save the baby's life.

One encouraging finding from the study according to Morriss was that procedures classified as minor surgery (likely done without general anesthetic) did not appear to increase the risk of death or neurological impairment in the infants.

Further analysis of the data also found that a small subset of surgeries used to correct certain gastrointestinal problems did not appear to increase the infants' risk of death or neurological problems.

"The anesthesiology, surgical and neonatology communities are aware that general anesthesia might be harmful to these very low birth weight infants," Morriss says. "This type of study helps us learn which babies are most at risk from major surgery, and which surgical procedures might be particularly risky and helps us figure out what we can do about it."

Other UI neonatologists involved in the study were Edward Bell, and Tarah Colaizy. The study also involved researchers from institutions around the country that participate in the Neonatal Research Network—a consortium of 22 neonatal intensive care units nationwide specializing in caring for newborns, especially those born too early or with very low birth weight. The network aims to find evidence-based approaches to improve both survival and outcomes for these infants.

The study was funded by grants from the National Institutes of Health.