A group from the FDA, Northwestern University, Washington State University and the University of Toronto wrote about their concerns Wednesday in an article in the New Journal of Medicine, one of the most influential medical journals in the world.
They said studies in a number of animal species show that the drugs used to induce unconsciousness during surgery are toxic for some brain cells — particularly in developing brains — in those animals.
But it is not known if the drugs have the same impact on the brains of babies and toddlers.
Despite the high-profile placement of their article, at least one of the authors was nervous about how the airing of these concerns would play among parents of young children who need surgical care.
Dr. Beverley Orser, an anesthesiologist at Toronto's Sunnybrook Health Sciences Centre, said if anesthesia damages the cells of developing brains, the effect is subtle. If it were profound, that would already be evident, she said.
And she noted that children who require surgery should undergo the procedures they need.
"It's important that parents don't panic," said Orser.
"Anesthetics have been used safely. Millions of children undergo anesthesia in the U.S. alone. And there are times when of course (the need for) anesthesia is life threatening or urgent. So that's an important message."
Studies in animals ranging from nematodes — a type of worm — to non-human primates suggest exposure to the chemicals used in anesthesia changes some types of cells in developing brains and that these changes seem to lead to impaired performance in behavioural tests.
Orser said the deficits appear to relate to memory and task performance.
It's not known if the drugs have the same impact on developing human brains. Some observational studies raise the possibility of an impact, but studies designed in this way can only point out correlations. They cannot prove that something causes something else.
"The data in animals is fairly concerning. Very concerning. I think the data in children are still inconclusive," said Dr. Shobha Malviya, president of the Society for Pediatric Anesthesia
Orser is on the board of an initiative called SmartTots, short for Strategies for Mitigating Anesthesia-Related Neurotoxicity in Tots. It is a public-private partnership set up in 2009 by the FDA and involves the International Anesthesia Research Society.
In 2012, the FDA, SmartTots and the American Academy of Pediatrics released a consensus statement outlining what is known about the issue and recommending, among other things, that non-essential surgeries should be avoided in children under the age of three. The group is working on an updated statement that it hopes to publish by the end of March, Orser said.
The article in the New England Journal of Medicine suggests there is enough evidence from animal studies now to warrant conducting well-designed randomized controlled trials in children.
Malviya said the need for more study has been apparent for a while, but funding commitments have been slow to materialize.
Dr. Jason Maynes, an anesthesiologist at the Hospital for Sick Children in Toronto, questioned the timing of the publication of this article, saying these concerns have been known for a number of years and there is no new evidence at present.
He also noted any decision around delaying surgeries in young children would have to weigh the potential risks from anesthesia against the problems that might arise from delaying care.
"Certainly some of the procedures we do could be delayed if there was enough evidence to do that," Maynes said.
"But we would also have to evaluate from the other end. From the other end, what would be the risks to the patient of delaying that surgery?"
Note to readers: This is a corrected story. A previous version had a wrong name for the Society for Pediatric Anesthesia