Children 'more aware' under surgery
Four-year-old Minh Nguyen goes under anaesthetic at the Royal Children's Hospital. Research suggests that, as a child, he is more likely to be aware of the experience than an adult is.
Awareness under anaesthetic is far more common in children than adults, a Victorian study has found.
It affects about eight in 1000 children, compared with one or two in 1000 adults.
Researchers at the Murdoch Children's Research Institute and the Royal Children's Hospital interviewed 864 children aged five to 12 after surgery under routine anaesthetic. They found seven were aware at some point during their operations.
The patients reported hearing noises such as an orthopedic saw, suction or medical staff talking. One also felt a metal object being put in her mouth while she had her tonsils removed.
Despite these experiences, anaesthetist and lead researcher Andrew Davidson said there was little evidence of distress among the children with awareness, with only half reporting mild pain.
This contrasts sharply with adult experiences, which are often horror stories of feeling pain or discomfort but being paralysed and unable to communicate.
In children, the muscle relaxants that paralyse a person are used in only about 15 per cent of operations.
"In adults, it's much more common for awareness to be associated with the use of muscle relaxants," Dr Davidson said.
This led him to conclude that awareness is probably caused by a different mechanism in children, who are more likely to be aware because their brains are more active.
Before this study, children's awareness under anaesthetic was little researched, Dr Davidson said. Even though those in his study did not seem particularly distressed by the experience, there was no doubt that "for some children it's a very significant event".
Children also appear to be vivid dreamers under anaesthetic, which is thought to be related to awareness. The study found that 11 per cent of the children recalled dreaming during surgery, experiencing a mixture of good and bad dreams, Dr Davidson said.
The research, which was part of a larger study examining children's behaviour after surgery, also found that 15 per cent had a change in their behaviour a month after their operations.
Despite the high incidence of awareness in children, Dr Davidson said there was not enough evidence to show the effectiveness among children of the bispectral index (BIS) machine, which uses electrodes to monitor brain activity and interpret the level of consciousness.
"We find it works in older children, but in very small children (under two) it doesn't work," he said.
Researchers first needed to work out what caused awareness in children and to conduct proper trials using BIS to check its effectiveness, he said.