PATIENTS describe it as like being buried alive. The worse part is not the pain, they say, although that can be excruciating, but the horror of being paralysed, unable to talk and yet totally aware of what the surgeon is doing to you.
Suffering like this could be greatly reduced. A large international trial has proved that a simple 鈥渁wareness鈥� device, called a BIS monitor, can cut the number of cases of awareness during surgery by 80 per cent. The device is already used to monitor the depth of anaesthesia in some hospitals in the US, but few anaesthetists in the UK or Australia use it.
The trial was run by Paul Myles of the Alfred Hospital in Melbourne, Australia, and Kate Leslie of the Royal Melbourne Hospital. Leslie says that the evidence is so compelling that BIS monitoring should always be used during the 5 per cent or so of operations where there is a high risk of awareness. Myles goes further, arguing that it should be used for the 50 per cent of operations where there is a chance of awareness occurring.
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Other anaesthetists argue that the BIS monitor and others like it need to be more accurate before they are routinely employed. Disturbingly, though, it seems that many anaesthetists do not even recognise the need for a monitor because they grossly underestimate the likelihood of patients becoming aware.
Awareness during surgery is not as rare as those about to go under the knife might hope. After around 1 in a 1000 operations done under a general anaesthetic, a patient will have some recollection of the operation. For many, the experience will be fleeting and not even particularly disturbing. But up to half will have crystal clear awareness of the surgeons鈥� conversations, the procedure and even the pain. For some, the experience can be devastating (see 鈥淒own, not out鈥�).
The BIS monitor is a kind of electroencephalogram (EEG) that detects electrical activity in the brain via a single electrode on the forehead. This activity depends on metabolism, memory function and the state of consciousness, which are all affected by anaesthetics.
The raw readout is a complex mixture of different brain waves. The BIS monitor uses a routine mathematical method for studying complex waveforms, called bispectral analysis, to produce an index of awareness: 100 is wide awake, and between 40 and 60 is the recommended score for anaesthesia.
BIS monitoring has been used in the US since 1996, mainly to work out depth of anaesthesia to ensure that patients do not receive too much anaesthetic. Last year, the company that makes the device, Aspect Medical Systems of Boston, won approval from the US Food and Drug Administration to market it to prevent awareness during operations too, based partly on the results of the trial.
In the trial, Myles and Leslie followed 2500 patients undergoing surgery in 24 hospitals in Australia, New Zealand, the UK and Hong Kong. All the patients were considered to have a high risk of awareness during surgery, either because they had experienced it before, or because they were undergoing procedures where light anaesthesia is preferable, such as heart surgery or a Caesarean section. The patients were randomly assigned to either BIS monitoring or routine care, where anaesthetists try to spot awareness by looking out for sweating, movement and increases in blood pressure and heart rate.
At 4 hours, one day and 30 days after surgery, each patient was interviewed. The team defined awareness as verifiable recall of events 鈥� memory of surgeons鈥� conversations, for example. The evidence had to satisfy three independent adjudicators. Aspect helped fund the trial, but was not involved in its design, running or analysis.
Eleven patients in the routine care group experienced awareness, compared with two in the BIS group, the team found. Myles and Leslie have yet to publish the full analysis, which is expected to appear in The Lancet soon, but many anaesthetists have seen the preliminary findings, which have been presented at conferences in Melbourne and San Francisco.
鈥淭hey demonstrate the technique鈥檚 potential 鈥� we should see more of this sort of monitoring,鈥� says Rolf Sandin of the Karolinska Institute in Stockholm, who has also tested BIS monitoring with encouraging results. 鈥淏ut before we recommend they be used on every patient, we need an improvement in sensitivity and specificity.鈥� Many patients remain unaware even with BIS scores over 60, Sandin says, suggesting that if a BIS monitor is routinely used to manage anaesthesia, many patients would be given more anaesthetic than necessary. That could put undue strain on those with serious conditions.
But Myles counters that his trial found that the BIS-monitored patients woke up faster than the routine care patients, suggesting that they were actually given less anaesthetic. What鈥檚 more, they fared just as well in terms of death rates and post-operative complications.
There is also a less rational reason why anaesthetists may decide not to use BIS monitoring. According to a 2003 survey by Myles and Leslie, most anaesthetists in New Zealand and Australia believe that awareness occurs only a fifth as often as it actually does 鈥� despite widespread reporting of three recent studies from the US, Australia and Sweden that put the incidence at 1 in 1000. They also think that the incidence of awareness in their own practice is half of that of other anaesthetists (Anaesthesia, vol 58, p 11). 鈥淪o they think they are 10 times better than they are. It鈥檚 classic human psychology, and it contributes to the nihilism about ever solving the problem,鈥� says Myles.
In the end, the decision about BIS monitoring may be taken out of anaesthetists鈥� hands. Now that a monitor is available, and has been proven to reduce awareness during surgery, the fear of litigation may force its use in many countries.
Down, not out
鈥淚t was like torture. You know what鈥檚 coming next but there is nothing you can do about it,鈥� says Karen Rowan, a doctor who lives in London, Ontario. Rowan experienced awareness under anaesthesia four years ago during a gall bladder operation done in Auckland, New Zealand.
鈥淭he worse part was the fear. I didn鈥檛 know whether it was possible to survive an operation if you could feel all the pain. The pain of the probe inside was the worst. It was a far deeper pain than you usually experience.鈥�
Linda McDougall, 49, who lives in Melbourne, Australia, experienced awareness 17 years ago during a Caesarean section. 鈥淚 felt the cutting. It was like a burning feeling 鈥� excruciating. I couldn鈥檛 move or flinch or anything, but my heart was beating so fast I thought I was going to have a heart attack. When they pulled Daniel out, I heard the doctor say, 鈥楨very birth is a miracle. We have a beautiful baby boy.'鈥�
The problem is not new. Gilbert Abbott, who was given ether via a handkerchief during the first public demonstration of a general anaesthetic in Boston in 1846, also experienced awareness, but at the time it was considered far better than no anaesthetic at all.
Awareness during surgery became more common in the late 1930s with the introduction of muscle relaxants that paralyse patients. These drugs are a boon for safety because they relax a patient鈥檚 muscles without the need for massive doses of the sedating anaesthetics, which can suppress the brain centres that control breathing and heart rate.
But by paralysing patients, the relaxants also remove some of the clearest clinical signs that the anaesthesia is too light 鈥� movement and a patient calling out. 鈥淎naesthetists can closely monitor about 30 different aspects of a patient鈥檚 health, everything from blood oxygen levels to heart rate. But one thing that they haven鈥檛 been able to check until now is whether or not the patient is actually asleep,鈥� says Paul Myles, an anaesthetist at the Alfred Hospital in Melbourne.
People experience awareness for a variety of reasons. They may be peculiarly insensitive to the anaesthetic: just as sensitivity to alcohol varies between people, so does the sensitivity to anaesthetic drugs. Anaesthetists also use a light anaesthetic during Caesarean sections to protect the baby, or when the patient has a weak heart or has lost a lot of blood. In Rowan鈥檚 case, a technical failure was to blame: a faulty pump meant she received the paralysing relaxant, but not the sedating drug.
Like many other patients who have had an anaesthetic failure, Rowan admits she is very wary about submitting to medical procedures. But after 17 years, McDougall is less affected. 鈥淔or the first couple of years, it was frightening. Now I just get a bit teary when I talk about it.鈥�
For some the effects are more severe. A recent Swedish study suggests that up to half the victims develop long-term problems, including depression and post-traumatic stress disorder.