Every surgery poses risk, as doctors will inform you, but in most cases, it's a necessary one. The benefits of going under the knife frequently outweigh the risks of infection or complications, or the dangers associated with anesthesia.
But balancing benefits and risks is more difficult when the patients are babies, the most fragile population. Now a new study from the Mayo Clinic, published on March 24 in the journal Anesthesiology, finds a link between exposure to anesthesia during surgery in infancy and learning disabilities later in life the first such study to do so in humans making the decision to operate even more fraught for both parents and doctors. (See TIME's Year in Medicine 2008, from A to Z.)
Studying a group of more than 5,000 children born between 1976 and 1982 in Olmstead County, Minn., researchers tracked the number of operations each youngster underwent before age 4, as well as his or her scores on reading, writing and math tests, administered once a year from elementary school through high school. Infants who had just one exposure to anesthesia showed no greater risk of having learning problems by age 19, but those with two or more exposures had a 60% increased chance of developing a learning disability compared with babies who had not had any operations. Three or more exposures to anesthesia by age 3 doubled children's risk of having difficulty in thinking, speaking, spelling or performing math calculations by the end of high school. (See 9 kid foods to avoid.)
The results reignite a long-standing controversy over the impact of anesthesia on still developing minds and bodies. The hazards were documented in earlier studies of animals: for example, rat studies have repeatedly shown that animals exposed to anesthesia drugs in the first seven days of life when nerve cells are forming and connecting to the larger neural network develop problems performing maze exercises, which require memory and reasoning skills. In the 1960s, based on similar concerns over possible injury to a baby's immature nervous system, doctors advocated only light anesthesia or none at all for infants undergoing surgery. Some experts believed babies did not have sufficiently developed neural connections to even feel any pain. "There was a whole series of papers showing that [giving anesthesia] was a bad thing to do," says Dr. Robert Wilder, a co-author of the Mayo Clinic study. "One thing that is very clear is that kids who have surgery without the appropriate anesthetic have higher degrees of morbidity and, in some cases, even mortality associated with surgery compared to kids who have gotten the appropriate anesthetic." (Read a TIME cover story on children.)
But that anesthesia may also put babies at greater risk for cognitive problems later in life, according to Wilder's latest findings. The author is quick to point out, however, that the data are preliminary and do not necessarily suggest a direct or definitive causal link between anesthesia and learning disabilities, only an association. "We clearly have not demonstrated that anesthetics are the cause of learning disability," says Wilder. "We don't want this to alarm the public to the point they aren't giving children appropriate medical care." It could be dangerous to deny children surgery to spare them the anesthesia, Wilder says, since in most cases of pediatric surgery, the procedure is a necessary and potentially lifesaving one that cannot be avoided or postponed.
Wilder and his colleagues are also cautious about their results because the data do not make clear whether it was the anesthesia that contributed to the children's learning deficits or whether it was an underlying condition that may have required surgery and precipitated the learning problems. Of the more than 5,000 babies studied, 593 needed at least one surgery and just over 100 infants needed more than two before age 3. There may have been something unusual about this population of children that made them vulnerable to learning problems and required them to undergo surgery and anesthesia. "The data we have are very preliminary," says Dr. Randall Flick, Wilder's co-author at the Mayo Clinic. "It really doesn't prompt me or any of my colleagues to say we should change the way we practice."
Not yet, perhaps. But it does highlight the need for future research. While the study does not establish a direct link between anesthesia and learning disabilities, it doesn't rule one out. The babies who underwent surgery in the Mayo study were treated for a wide range of conditions, few of which were brain-related. By far, the most common procedure performed on the infants involved the insertion of tubes in the ears to remove fluid to prevent hearing loss and potential delays in speech and language skills; 26% of the babies undergoing surgery fell into this category. One-quarter of the infants needed general surgery, while 13% required some type of orthopedic procedure. Only 1% of the infants who had surgery needed a neurological procedure. That suggests that some aspect of the operation or anesthesia and not the condition that required surgical treatment could have influenced the babies' cognitive development. (See TIME's Pictures of the Week.)
What's more, the Mayo researchers found hints of a dose-dependent effect: the longer infants stayed under anesthesia, the greater their chance of developing later problems reading, writing and doing math.
Still, experts are not willing to say that babies should never be given anesthesia. "We don't want to delay surgery or withhold surgery for the kids who need it," says Dr. Sulpicio Soriano, an anesthesiologist at Harvard Medical School and Children's Hospital in Boston. "But we need more research and clinical investigation to find new drugs and new combinations of drugs that can attenuate or mitigate the cognitive effects."
Already, the Food and Drug Administration is supporting further study of the connection between anesthesia and cognition to find such alternatives. Meanwhile, says Flick, "it's just not time yet to make any recommendations about changing practices."