Drugs used regularly to anaesthetise children for surgery have been found to cause brain damage in rats, research has claimed.

The American researchers go as far as suggesting postponing operations early in life that are not life-threatening.

But they point out that anaesthetics are needed where surgery is the only option for children with potentially fatal conditions.

The research team also found that the signs of damage were only detected when specific brain tests were carried out on the rats.

For the study, published in the Journal of Neuroscience, researchers gave seven-day-old rats a combination of midazolam, nitrous oxide and isoflurane.

Cell death

The medication is commonly used to put children to sleep for operations.

The rats were divided into three groups before examination at the Washington University School of Medicine in St Louis, USA.

One group was killed the next day and the rats’ brains examined, the second group were allowed to grow to a month old, while the third progressed to adulthood.

The rats were given the drugs during a brain growth spurt period called synaptogenesis which lasts for the first few weeks of a rat’s life.

The same spurt in humans goes from the later stages of pregnancy until about the age of three.

Nerve cells in the brain make connections with each other during this time and form what are called networks. But these cells destroy themselves if something happens to interfere with the connection process.

In the study the researchers found moderately severe cell death had occurred in several regions of every rat brain studied.

Those that had been anaesthetised performed worse that the rest in when tested in mazes designed to measure learning and memory.

Abnormally high

The rats appeared to behave normally in most other ways and there were no outward signs of brain damage, the researchers found.

Senior investigator John W Olney, a professor of neuropsychopharmacology, said: “That’s important because if similar brain damage had occurred in a human infant it appears there would not be any overt signs that would alert you to it.”

A child starts life with an excess number of nerve cells and it is normal to have some cell death in the developing brain.

What the study found was that in the rats, when drugs interfered with the cell while it was trying to make connections, the self destruction rate rose to abnormally high proportions.

Professor Olney said surgery is the only option for some children with life-threatening conditions and it can only be carried out with an anaesthetic.

“But some paediatric surgery is elective,” he said. “In light of these findings I would recommend that if surgery really does not have to be performed early in life, it would be prudent to postpone it.”