Anesthesia exposure may alter emotional behaviour in infants

Repeated exposure to anesthesia early in life causes alterations in emotional behaviour that may persist long-term, a new study on rhesus monkeys suggests.

The study is the first to address the question of whether repeated postnatal anesthesia exposure caused long-term behavioural changes in a highly translationally relevant rhesus monkey model.

The stage of neurodevelopment of rhesus monkeys at birth is more similar to that of human infants compared to neonatal rodents; with respect to brain growth, a six-week-old rhesus monkey corresponds to a human in the second half of his or her first year of life.

The study was conducted in the absence of a surgical procedure, co-morbidities that may necessitate surgical intervention or the psychological stress associated with illness, researchers said. "The major strength of this study is its ability to separate anesthesia exposure from surgical procedures, which is a potential complication in the studies conducted in children," said Mark Baxter, professor in the Departments of Neuroscience and  Anesthesiology at the Icahn School of Medicine at Mount Sinai.

"Our results confirm that multiple anesthesia exposures alone result in emotional behaviour changes in a highly translational animal model," Baxter said. "This raises concerns about whether similar phenomena are occurring during clinical anesthesia exposure in children," he said.

Specifically, the study team exposed 10 rhesus monkeys to a common pediatric anesthetic called sevoflurane for a comparable length of time required for a significant surgical procedure in humans (four hours).

They were exposed to the anesthetic at postnatal day seven and then again two and four weeks later, because human data indicate that repeated anesthesia results in a greater risk of learning disabilities relative to a single anesthetic exposure.

Researchers evaluated the socioemotional behaviour of exposed subjects compared with that of healthy controls at six months of age using a mild social stressor (an unfamiliar human). They found the anesthesia-exposed infants expressed significantly more anxious behaviours compared with controls.

"The task we used is designed to be similar to the task used for assessing dispositional anxiety and behavioural inhibition in children, thus increasing the study's applicability to humans," said first author Jessica Raper, research associate at Yerkes National Primate Research Centre at Emory University. The study results also demonstrate that alterations in emotional behaviour persist at least five months after anesthesia exposure, suggesting long-term effects.

The study was published in the journal Anesthesiology.