Children younger than two who have had multiple surgeries with general anesthesia may be at increased risk of learning difficulties, though doctors say the findings should not change surgery decisions for young children.

Children receive general anesthesia for procedures ranging from ear surgery to hernia repair.

The study in Monday's online issue of the journal Pediatrics looked at medical and educational records of 1,050 children born between 1976 and 1982 in Rochester, Minn.

The clinical significance of toxic effects of anesthesia on the brain is controversial. (iStock)

"The major finding of this study is that, after adjustment for health status and matching for other factors associated with learning disabilities, exposure to anesthesia/surgery before the age of two was a risk factor for the development of learning disabilities and the need for an individualized education program for speech/language impairment in children with multiple, but not single, exposures," the study's authors concluded.

"At this point we cannot exclude the possibility that multiple exposures to anesthesia/ surgery may adversely affect neurodevelopment."

The study's lead author, Dr. Randall Flick, a pediatric anesthesiologist at the Mayo Clinic, said the findings should not change decision making related to surgery for young children, since researchers don't have enough information to change practice and avoid problems that may occur from delaying needed procedures.

Delaying ear surgery for children with repeated ear infections, for example, might cause hearing problems that could create learning difficulties later in school, Flick said.

In the study, 350 children who had surgeries with general anesthesia before their second birthday were matched with 700 children who did not undergo a procedure with anesthesia.

The two groups were matched for gender, birth weight, gestational age, mother's education level and birth date.

Learning disabilities developed by age 19 in:

• 21.3 per cent of those who weren't exposed to anesthesia by age two.
• 23.6 per cent of those exposed once.
• 36.6 per cent of the 64 children exposed at least twice.

The risk of dyslexia or any other learning disability doubled to 2.12 times with multiple surgical anesthesia exposures, the researchers reported.

Older anesthetic

Children repeatedly exposed to anesthesia early in life also scored lower on achievement tests.

The study's authors tried to take into consideration how sick the children were by reviewing all medical charts, but they acknowledged they could not distinguish between the effects of anesthesia per se and surgery.

Another drawback of the study is that it included children given the anesthetic halothane, which is no longer in widespread use. Also, previous effects such as hypoxia (low oxygen conditions) might have occurred before more modern methods were develop to monitor patients' oxygen levels during surgery.

Most of the participants were white children from families earning more than the average U.S. national income, which could limit how the findings might apply to other groups.

"The clinical significance of anesthetic neurotoxicity is controversial and under heated debate," Dr. Robert Williams of the departments of anesthesia and pediatrics at the University of Vermont in Burlington said in a journal commentary.

Williams said it is reassuring that the researchers could find no clinical effects after a single exposure to anesthetic, noting few children have more than one surgical procedure in the first few years of life.

None of the authors or commentators said they had any conflicts of interest.

The study was funded by the U.S. Food and Drug Administration.