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WASHINGTON -- Infants exposed to prolonged sedation during surgery to repair gastrointestinal congenital abnormalities may be at higher risk of brain abnormalities compared with babies who don't have surgery, researchers reported here.

In a small study, infants exposed to prolonged anesthesia had more MRI findings indicative of brain atrophy than healthy controls, Dusica Bajic, MD, PhD, of Harvard Children's Hospital in Boston, and colleagues reported at the Society for Neuroscience (SfN) meeting.

"Our preliminary findings suggest that children who have prolonged sedation during surgery have more signs of brain atrophy," Bajic said during an SfN press briefing.

Her group studied nine infants who had prolonged sedation during surgery to fix GI congenital abnormalities, including repair of long-gap esophageal atresia. Though some work has suggested that prolonged sedation is associated with long-term outcomes, they couldn't exclude other possible causes such as prematurity or heart problems, which is why the researchers focused on full-term GI surgical patients.

"Parents always ask doctors, 'What is the effect of prolonged sedation on the baby's brain and development?,'" Bajic said. "Honestly, the answer is, 'We don't really know.'"

In looking at MRI data from these nine infants, they saw a constellation of signs of brain atrophy, including increased fluid in and around the brain, a widening of the space between brain lobes, and a thinning of the white matter tracts that connect the two brain hemispheres. They also had clinically significant findings, including old venous hemorrhagic strokes and subdural hematoma.

When they compared those findings with MRI findings from 12 healthy controls, they saw significantly more signs of brain atrophy in surgical patients. The proportion of fluid in and around the brain was approximately 4% greater in surgical infants, and their brain growth was slower than that of healthy babies.

However, they eventually did have an increase in total brain volume, Bajic said. "It's a good sign; it means that even despite [prolonged sedation], the brain continues to grow," she noted.

In further analyses, the authors found a positive correlation between hours of anesthesia exposure and the total number of MRI findings. They also saw a positive correlation between the length of sedation and the number of findings, which was significant for both morphine and midazolam.

Bajic strongly cautioned that the findings are very preliminary, and that larger studies with more infants need to be done. Research also needs a better control group, "My control group is healthy infants with no exposure to any kind of treatment, so they're not really the ideal control. Future research needs to include a surgical control group; kids who have similar surgeries but in the absence of prolonged sedation," she explained.

"There's a lot of work to be done with respect to saying that this has to do with sedation, versus surgery on its own," she added.

There are also outstanding questions as to whether these babies who have prolonged sedation for surgical procedures are just born with these abnormalities. Future studies should perform brain MRI before the infant is ever exposed to anesthesia, Bajic said.

Similarly, sicker infants will have more anesthesia, as well as potentially more surgical complications, more antibiotics, and other comorbidities. And the effect of parenteral nutrition and its role in brain development needs to be assessed, she said.

Finally, neuroplasticity needs to be taken into account. "Despite [early] detrimental findings, will plasticity lead to positive adaptations in the brain that can overcome this initial insult?," Bajic stated.

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