Infants who are put under for surgery more than once before the age of 2 may be at increased risk of learning disabilities later in life, according to research from the Mayo Clinic in Rochester, Minn.
The use of general anesthesia in infants undergoing surgery is currently considered very safe, but mounting evidence, first in animals and more recently in humans, suggests that repeated exposure to anesthetics in the first few years of life could cause brain damage if carried out during certain key developmental periods.
The Mayo Clinic study, published Monday in the journal Pediatrics, tracked the medical and school records of a thousand children born between 1976 and 1982 in Rochester, Minn., 350 of which were given general anesthesia at least once in the first two years of life.
Among infants who had had more than one surgery during those years, almost 37 percent experienced a learning disability later in life, compared with only 21 percent in the children who did not undergo surgery. Even for those children who had only one surgery during infanthood, the rate of learning disability was slightly higher, at 24 percent. Learning disabilities seemed to center on speech and language difficulties, says Dr. Randall Flick, Mayo Clinic pediatric anesthesiologist and lead author of the study.
Researchers controlled for characteristics that might also affect development later in life such as birth weight, gestational age and maternal education level, by matching each of the 350 study subjects to two control children in the same population who shared similar characteristics.
"Kids who were exposed were three times as likely to later need a special education program to address speech and language difficulties than kids who weren't exposed to anesthesia," he says.
The research is preliminary, and shouldn't change surgical protocol at this time, the authors say. But even the possibility that anesthesia is damaging to infants' brains is disquieting for physicians and parents, especially because infant surgery is so seldom elective -- surgery in infants is almost always medically necessary.
These findings may be enough to discourage using anesthesia in infants if it is avoidable, such as when heavy sedatives or anesthesia is used to faciliate diagnostic testing in infants, says Dr. Michael Roizen, chief wellness officer at the Cleveland Clinic and head of SmartTots, a partnership between the Food and Drug Administration and the International Anesthesia Research Society which investigates the potential danger of using anesthesia in children.
"In the instances that you can delay surgery, you probably want to. This is something the parent should discuss with the physician," he says.
Other physicians believe it's still too early to call for even that:
"Clearly these findings raise some concerns, but surgery on infants addresses pressing medical issues. Until more is understood about the Mayo findings, we should [not be] raising red flags," says Dr. Elliot Krane, professor of Pediatrics and Anesthesia at Stanford University.
Millions of children are exposed to anesthetic drugs each year, but for decades no connection was ever made between anesthesia exposure and learning disabilities.
"It might seem that if this was a problem, we would have noticed it by now, but that may not be true," says Flick. "The time lag between the event, the anesthesia exposure, and the outcome on development, may be years long so it would be quite difficult to connect those two things," he says.
The link was original suggested in the late 1990s when research in animals showed that animals that were put under with anesthesia many times showed brain cell death -- "regression of the brain, if you will," says Roizen.
Since then, further animal studies in rodents and monkeys consistently show that repeated exposure to anesthesia cause irreversible loss of brain cells and developmental issues.
In monkey models, even one episode of exposure to anesthesia during important periods of brain growth early in life resulted in deficiencies in memory and learning difficulties later," Roizen says.
"Really this points to how much we need more research," he says. "Because the data is very suggestive that this is a problem, but we don't know for sure. We also don't know if there is something protective we can give alongside the anesthetic to block this effect."