A growing awareness

Awareness during surgery on children

Despite anaesthesia, some children may be aware during surgery. A new project aims to find out how common awareness is and whether it causes psychological problems after surgery.

Going into hospital for an operation is bad enough without having the added worry that you may wake up while under the anaesthetic. Your fears are likely to be magnified when it is your child who is having the operation.

The anaesthetist may reassure you that wakefulness during anaesthesia is rare, that patients who do become responsive very rarely remember it, and that it is most often associated with cases where light anaesthesia is medically necessary – such as Caesarean sections, where it is important to avoid giving anaesthetic drugs to the baby.

Yet many studies have shown that some patients do become responsive while anaesthetised. One small study in children found that almost 20 per cent having surgery responded to a command to squeeze the researcher's fingers while supposedly anaesthetised.

Dr Jackie Andrade, Lecturer in Psychology at the University of Sheffield, has recently been awarded a grant by the Wellcome Trust to try to find out whether such high rates of awareness are commonplace in children having surgery. Her project will also be the first to investigate whether children who have periods of wakefulness during anaesthesia for surgery are more likely to form unconscious memories of surgery than children who remain anaesthetised throughout. Thirdly, she will examine how periods of wakefulness during anaesthesia affect children’s behaviour and recovery after surgery.

"We need to get a better estimate of the proportion of children who become responsive during anaesthesia," says Dr Andrade. "In addition, if we find that there is learning during anaesthesia, then it will be important for researchers to investigate ways of harnessing this ability for the patient’s benefit, perhaps by playing reassuring suggestions or relaxing music."

Anaesthesia and awareness

Almost all the studies carried out to date that have looked at awareness during anaesthesia for surgery have concentrated on adults. In the early days of anaesthesia, anaesthetists used to give very high doses of anaesthetic drugs in order to make the patient unconscious and to bring about the paralysis needed for some types of surgery. Today, much lighter doses of anaesthetics are given, and the anaesthetist induces paralysis by giving neuromuscular blockers. As a result, however, if the patient wakes up, he or she cannot move to alert the anaesthetist.

To overcome this problem, Mike Tunstall, an anaesthetist at Aberdeen Royal Infirmary, developed a technique that involves wrapping a cuff (the type used for measuring blood pressure) around the patient's forearm and then inflating it so that the paralysing drugs cannot enter the hand. Anaesthetists can then check periodically if patients are aware by asking them to squeeze their fingers. This is known as the isolated forearm technique.

"Some studies using this technique have found no responses," says Dr Andrade, "but others have reported between 44 per cent and 97 per cent of patients responding at some point. In the one study done with children, the researchers found that eight out of 41 responded to commands to squeeze the researcher’s fingers – almost 20 per cent."

Anaesthesia in children

Dr Andrade’s study will assess how common such responsiveness is in 635 children aged six to 15 years having surgery at Sheffield Children’s Hospital, using the isolated forearm technique. Children will only be entered into the study if their parents give their consent, and provided they have no hearing problems. Before their operation, they will be told that when they begin to wake up after their operation, they will be asked to move their hand so that staff know they can hear them.

Those who respond during anaesthesia will be asked to squeeze the researcher’s hand twice if they are comfortable, and then asked to squeeze twice if they are in pain. Additional anaesthetic will be given if necessary.

The design of the study puts Dr Andrade into an excellent position for studying children’s unconscious learning during anaesthesia. In particular, if such learning takes place, the study will allow her to find out if it is more likely to occur in those children who become responsive while anaesthetized for surgery.

Unconscious, or implicit, learning is the opposite of explicit learning. Someone who has an explicit memory – of a certain word, for example – is conscious of having heard it, and is aware that he or she remembers it. Implicit memories, by contrast, affect behaviour even though the person is not aware of them.

It is implicit memory that Dr Andrade will study in her research project. She has ready two lists of words that are familiar to children of five and under. Children entering the study will be played a tape of one of the lists while anaesthetised. Then, after they have come round from the anaesthetic and are able to do a memory test, they will be played the same list that they heard earlier, plus the second list, which they have not heard before.

In order to make all the words quite difficult to hear, they are played against a background of ‘white noise’. Typically, if someone has heard the words before, even if he or she has no conscious memory of having done so, they are easier for the person to pick out against a noisy background. The increased ability to detect the previously presented words gives a measure of implicit memory.

The third strand of the research project will examine the extent to which episodes of awareness during anaesthesia affect the incidence of children’s behavioural problems after surgery.

"We don’t know," says Dr Andrade, "to what extent learning during anaesthesia or awareness during anaesthesia contributes to the kinds of problems that adults have following surgery, such as depression and insomnia. But so many people have operations with general anaesthetics every year that if there are ways of bringing about even a small improvement in people’s mental health on recovery, it is important for us to know this."

To measure how the children who take part in the study are feeling in the week following their operations, Dr Andrade will ask their parents to complete a questionnaire about their offspring’s behaviour. This will endeavour to find out whether behaviours such as attention seeking, crying, temper tantrums, waking up at night, problems going to bed, and being afraid of being alone are more or less common than they were before the child went into hospital.

Dr Andrade says: "This is quite a crude measure of how an individual child is feeling but over the whole sample we hope it will give us a good indication of how children are affected by what happens to them during anaesthesia." The results will be analysed to find out if behavioural problems are more likely to occur in children who become responsive while anaesthetised.

Clinical application

The study begins in June 2002 and will run for three years. Its results could affect clinical practice or influence the direction of future research. "If we find that there is even a modest incidence of responding using the isolated forearm technique during surgery, I think this would stimulate anaesthetists to use the technique in routine practice. It is a very simple technique, and does not require any expensive equipment." Anaesthetists could then give a little bit more anaesthetic to those children who become responsive, she says.

If the study finds that implicit learning does take place during anaesthesia and that this affects children’s postoperative behaviour, then two strategies could come into play. Dr Andrade says: "Either patients could wear headphones, to play them relaxing music or possibly therapeutic suggestions, such as 'You won't be in pain when you come round'. Alternatively, operating theatre staff should be asked to be careful about what they say so that the patient does not hear them talking about the progress of the operation, for example."

Evidence that learning does take place would provide a foundation for further research into ways of improving patients’ experiences during anaesthesia, Dr Andrade concludes.

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