Multiple anaesthetic exposures may impair memory in infants

A study, done on baby monkeys, discovered that anaesthesia-exposed infants exhibited major damage to memory after the first year of life. A recent study has revealed that frequent exposure to a common anaesthesia drug very early in life results in visual recognition memory impairment, which occurs after the first year of life and may be long lasting.

The study from the Icahn School of Medicine at Mount Sinai is among the first to focus on repeated postnatal anaesthesia exposure, in and of itself, causing memory impairment in a highly translationally relevant rhesus monkey model.

Rhesus monkeys at birth are at a stage of neurodevelopment that is more like that of human infants than are neonatal rodents; with respect to brain development, a six-week-old rhesus monkey tallies with a human 6 to 12 months of age.

As these kinds of controlled experiments cannot be approved for humans, it is essential to use a similar animal model to discover if anaesthesia is disturbing the brain. Unlike previous research, the study was done in the absence of a surgical procedure, co-morbidities that may compel surgical intervention, or the psychological stress linked with illness.

“The major strength of this study is its ability to separate anaesthesia exposure from surgical procedures, which is a potential complication in the studies conducted in children,” said researcher Mark Baxter. “Our results confirm that multiple anaesthesia exposures alone result in memory impairment in a highly translational animal model. Interestingly, the anaesthesia-exposed group had normal visual memory at six months of age. Visual memory impairment didn’t emerge until the second year of life, corresponding roughly to the age of three to six years old in humans.”

Particularly, the study team exposed 10 non-human primate subjects to a common paediatric aesthetic called sevoflurane for four hours, the time required for a major surgical procedure in humans. They were exposed to the aesthetic at postnatal day 7 and it was repeated two and four weeks later, as human data indicates that repeated anaesthesia causes a greater risk of cognitive disability as compared to a single anaesthetic exposure.

They found the anaesthesia-exposed infants displayed no damage to memory when tested at 6-10 months, but showed major memory impairment (reduced time looking at the novel image) after the first year of life as compared with the control group.

This primate model may be used by researchers for future studies to develop a new anaesthetic agent or prophylactic treatment to counter the effect of anaesthesia on behaviour in children. The findings also imply that more work is needed to identify the ways by which anaesthetics may cause long-term changes in central nervous system function that influence behaviour.

The study is published in The British Journal of Anaesthesia.