Before the advent of anesthesia, surgical procedures were almost universally horrific, so it's pretty hard to argue with the idea that anesthesia has vastly improved medicine. And yet, few surgeons would call it perfect. Some people don't react very well to the drugs employed, for instance, and there are accounts of people waking up during surgery and being unable to alert doctors of their situation. But now, a new study suggests that children who are anesthetized before their first birthday experience problems with short-term memory later in life — and these problems may influence reading comprehension, classroom learning, and a child's ability to recall details about their life.

"anesthesia in kids is not harmless."

"Up until a few years ago we thought that anesthesia in kids was perfectly safe," says Greg Stratmann, an anesthesiology professor at the University of California San Francisco and lead author of the study. But in the last few years, some researchers have found that anesthesia might increase a child's risk of experiencing developmental disorders and ADHD-like symptoms. Clearly, Stratmann says, "anesthesia in kids is not harmless."

In the study, published today in Neuropsycopharmacology, Stratmann and his team investigated the recollection abilities of 28 kids, age 6 to 11, who had undergone anesthesia before the age of one. Each child was matched with another kid of the same age and gender that had never been anesthetized. To test their recognition abilities, both groups of children were shown 80 drawings with varying border colors and locations on a computer screen. Five minutes later, the kids were asked to point out the drawings they had seen from a set of 160 drawings in which the border colors had been removed and locations had been changed. If they could remember the drawing, they were also asked to recall the color and the original location of the drawing.

"We found that for color details, anesthetized kids scored 20 percent less correct answers than unanesthetized kids," Stratmann says, even though the two groups of kids did not differ in intelligence or behavior. And in the spatial-recognition task, anesthetized kids scored 21 percent lower than kids who didn't undergo anesthesia at all.

the recollection impairment was stronger in rats

The researchers also examined what effect anesthesia has on odor recollection in rats. As with the human study, one group of rats had been anesthetized and the other had not, but to ensure that the experiment also accounted for any variables that a surgery might introduce, half of the anesthetized rats also underwent "tail clamping" — a procedure that Stratmann says is "at least as severe as surgical tissue injury." Regardless of the tissue injury, however, the overall effect of the anesthesia was similar to the one recorded in human infants: "anesthetized rats had less recollection than unanesthetized rats," Stratmann says. But the effect was far stronger in the rat experiment, as half of all anesthetized rats had zero recollection, whereas only two out of 17 rats in the control group had problems remembering odors.

When combined, the rat and the human experiments suggest that "general anesthesia in infancy impairs recollection later in life," the researchers write in the study. And in rats, "this effect is independent of underlying disease or tissue injury."

unmeasured differences may have also played a role

Caleb Ing, an anesthesiologist at Columbia University who was not involved in the study, said in an email to The Verge that the study's findings are valuable. "This builds on other work showing that children exposed to surgery and anesthesia at an early age may have an increased risk of specific cognitive deficit compared to children who were unexposed." But even though Stratmann's team tried to account for numerous other variables, such as family income and age, it's possible that unmeasured differences between the groups contributed to the effect, he said. Parents should therefore make sure that they "speak to their physicians before canceling or postponing surgical procedures."

The researchers now plan to compare the recall abilities of children who have undergone general anesthesia with those who have experienced local anesthesia. This may help rule out the possibility that the kids' surgical procedures are contributing to the deficit. They also hope to determine when children stop being vulnerable to these long-term memory effects.

this probably won't change pediatric surgery

This study is the first to find that anesthesia can cause recall problems in humans, so researchers will need to replicate it multiple times before they can make any firm conclusions. Performing the study on a larger group of children, for example, would go a long way toward validating the results. But the truth is that unless researchers figure out exactly what mechanisms are triggering these memory impairments, the findings are unlikely to change the way doctors approach pediatrics surgery.

"If a child needs a surgical procedure, that child will also need an anesthetic — there is nothing you can do about that," Stratmann says. But children are sometimes given anesthetics to prevent them from moving during nonsurgical procedures, such as MRI scans. When those situations arise, he says, "doctors need to consider [these effects] when thinking about the risk-benefit ratio of procedures requiring general anesthesia."

As for parents who might be worried about possible memory effects, Stratmann says that they may be reversible. "I derive this hope from a study in animals that we did a few years back." In the study, Stratmann's team found that increasing a rat's level of exercise and social interaction, as well as increasing the complexity of the environment in which it dwells, reverses the cognitive effects of anesthetics. So "it's conceivable that such lifestyle changes could do the same in humans," he says, "and help compensate for anesthesia­-induced cognitive problems."