THE screaming headlines were enough to strike fear in anyone awaiting even the most minor surgery: âHalf of patients âawake during surgeryâ.â But for anaesthetists they were yet another painful reminder of the most difficult and controversial problems in their profession. What does it mean to be âawakeâ under anaesthetic? How aware must a patient be to run the risk of long-lasting trauma from surgery? And how can anaesthetists improve the way they monitor patients?
Michael Wang, the clinical director of the psychology department at the University of Hull and his colleague Ian Russell, a consultant anaesthetist, made those headlines after claiming that almost half of their patients are sufficiently awake during anaesthesia to respond to yes or no questions about how they feel by opening and closing their fingers.
Their paper, presented at this yearâs meeting of the British Psychological Society in April, looked like a head-on challenge to research published in the British Journal of Anaesthesia last year. This showed that only about 1 patient in 10 000 wakes up during surgery conscious of pain but unable to move because of the paralysing muscle relaxants they are given to make the surgeonâs job easier, and that the number who recall being conscious during surgery yet feeling no pain could be up to forty times as high. Wang and Russell believe these figures are not the whole story.
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Balancing act
Wang says that a patientâs level of consciousness depends on the balance between the depressant effects of anaesthesia and the simulating effects of painful surgery. Even if the former is monitored closely, the latter can fluctuate wildly throughout a single operation. Anaesthetists, he argues, should be more aware of the risks of traumatising patients who seem to be unconscious and cannot remember anything about their surgery. âI donât think itâs reasonable to assume, as many medics do, that if people donât have any postoperative recollection of a traumatic event then it doesnât matter,â says Wang.
Wang and Russell have been accused of alarmism by other researchers. Some, including Gareth Jones, an anesthetist at the University of Cambridgeâs department of anaesthesia, object to Wangâs assertion that patients able to respond to voices under general anaesthetic might suffer psychological aftereffects. In a letter to The Times, Jones points out that practitioners widely accept that a combination of general anaesthetic drugs will produce a state of complete indifference to pain and loss of memory of events within a few seconds. âMany anaesthetists,â he concludes, âwould regard this state as ideal for most surgery and certainly not a ticket for the psychiatristâs couch.â
These are difficult waters because people respond differently to anaesthesia depending on factors such as their age and state of health. And, given that our ideas about what it is to be conscious are sketchy in the extreme, it is hardly surprising that anaesthetists cannot reach a consensus about exactly what happens when they sedate their patients.
The assumption anaesthetists make every time they put someone to sleep is that the drugs will block the neural pathways in the nervous system involved in creating the sensation of pain as well as those through which we are aware of our surroundings, our bodies and our minds. According to Susan Greenfield, a neuroscientist at the University of Oxford, evidence from decades of clinical practice have lead anaesthetists to believe that pain is the first sensation lost as a patient âgoes underâ.
But in a study dating back to the early 1970s, David Scott, a consultant anaesthetist at Whiston Hospital in Lancashire found that under general anaesthetic vision is lost first, followed by discomfort, pain and finally hearing. His findings were based on a reanalysis of hundreds of studies. But, as with any research of this kind, he had to rely on patientsâ recall and since anaesthetic drugs are known to disrupt long-term memory, the results are at best inconclusive.
Most experts do agree, however, that there is no on/off switch separating consciousness from unconsciousness. During anaesthesia, as in natural sleep, there is a gradual slide into oblivion. Greenfield likens the process to a dimmer switch. The level of consciousness described by Wang and Russell, she says, is at the darker end of the spectrum. According to Greenfield, being conscious enough to respond to voices under anaesthesia does not automatically put a patient in danger of feeling pain. For Wang and Russell this is not the point. They argue that surgery can leave psychological scars for many reasons.
Stitched up
Evidence about the kind of events that traumatise patients seems to support this view. At one end of the spectrum are the rare cases where patients are awake but unable to move throughout their surgery. Take the case of a 41-year-old nurse who woke up during a hysterectomy: âI came out of the anaesthetic as they were stitching me up. I felt acute burning pain every time the needle went in and could tell which type of stitching they were doing. I tried to move or yell, but could not flicker an eyelid. I could feel the warmth of the lights and hear the click of instruments and low voices.â
Another woman recalls how she came round during a tonsillectomy to feel âa large spoon-shaped object gouging fleshâ from her throat. Now in her 70s, she remembers with perfect clarity the operation 50 years ago.
More benign events can also leave psychological scars. In 1993, Nelly Moerman of the Academic Medical Centre at the University of Amsterdam interviewed 26 patients who recalled waking up during surgery. Only 40 per cent of these patients claimed to have experienced pain, but almost 90 per cent of them remembered hearing sounds or voices while under anaesthetic. Moerman found that half of them had developed a persistent fear of anaesthesia, and a quarter suffered from disturbed sleep, nightmares, anxiety and mental distress.
And other studies suggest that even when patients do not have explicit memories of their surgery they can be traumatised. The experiences of a 19-year-old female college student were reported in the Medical Journal of Australia in 1987. After getting counselling for obesity and shyness, she began to lose weight and appeared much happier. But two weeks after a minor operation under general anaesthetic, she reported that she felt very depressed and had gone back to binge eating. She was unable to remember anything that had happened to her during surgery, but under hypnosis she recalled the surgeon making disparaging remarks about her size.
The validity of recovered memories such as this is hotly contested, but a 30-year-old study â which would surely be considered unethical today â provides strong evidence for this phenomenon. The experiment, published in the British Journal of Anaesthesia, involved a dental operation during which the anaesthetist staged a crisis, exclaiming that the patient was turning blue. He then hyperventilated the patientâs lungs before giving the all clear so that the operation could continue.
A month later, interviews with the ten patients who took part revealed that none of them remembered their surgery. But under hypnosis, four repeated the anaesthetistâs words almost exactly, four remembered hearing something, became anxious and woke from hypnosis, and two remembered nothing. âBefore that everybody thought of the patient as an inert lump of meat on a table,â says Wang. âThere is accumulating evidence that that is incorrect.â
One practical outcome of this new view is that more anaesthetists are keen to monitor the mental state of their patients. Indeed, the findings of Wang and Russell stem from just such research with a technique that allows them to communicate directly with their anaesthetised patients. Until quite recently, however, most anaesthetists have relied on indirect, crude measures of awareness such as heart rate, pulse, sweating and tear production â all of which typically fall as a patient âgoes underâ.
Arm signals
The method Wang and Russell are investigating is called the isolated forearm technique. It works by preventing the paralysing muscle relaxants flowing into a patientâs forearm by applying a tourniquet. So far, they have only used the technique during gynaecological surgery where they found that 44 per cent of patients were aware enough to signal how they were feeling by moving their fingers in response to questions. The method is simple but, according to Wang, it has advantages over the alternatives â sophisticated monitoring of brain activity. The benefit of the isolated forearm technique, he claims, is that it measures consciousness directly because patients can signal if they are in distress. âMost patients donât realise that they wouldnât be able to move if they woke up during an operation,â says Wang.
Critics of the technique, however, argue that it is ineffective because some movements of the arm are reflex actions in response to surgical stimulation rather than genuine responses to questions and it can be difficult to distinguish between the two. Jones points out there are also practical difficulties. For example, after 20 minutes there is a risk of damage to the arm due to lack of blood supply. Wang says this risk can be avoided by releasing the tourniquet for a few minutes and reinflating it before more muscle relaxant is pumped in. With Russell, he has successfully used this approach in operations lasting up to three hours.
But the most common criticism of the isolated forearm technique turns on the problem of judging what level of consciousness is safe for surgery. âIt tells you what you donât want to know â that the patient is already awake,â says Douglas Newton, a consultant anaesthetist at the Clinical Research Centre at Northwick Park Hospital in Harrow. Wang and Russell accept that the technique is most effective in operations where the level of anaesthesia is light â it was developed almost 20 years ago to monitor women undergoing caesarean sections which are notorious for wakefulness because the doses of anaesthetic are kept low to protect the unborn baby.
It could also, they believe, be ideal for cardiac surgery and for operations on children, both of which use anaesthetic drugs sparingly. But, argue, Wang and Russell, even in operations where high doses of anaesthetic drugs are normal, the isolated forearm technique could be used effectively as a last line of defence against those rare occasions when a patient starts to become conscious of pain. It is also far cheaper than high-tech monitors.
In Britain, which leads the field in this type of research, the mainstream way of monitoring awareness during surgery is with sophisticated machines that measure brain activity. But this approach has one major problem. âA leap has to be made from the patientâs responses with these various methods to deciding whether or not the patient is asleep,â admits Jones who is himself developing a monitor based on the âauditory evoked responseâ. He uses an electroencephalograph (EEG) to record the brainâs response to clicks played at different frequencies over headphones worn by anaesthetised patients. The EEG recordings suggest that a low level of auditory processing continues throughout anaesthesia.
According to Jackie Andrade, a psychologist at the Medical Research Councilâs Applied Psychology Unit in Cambridge who has worked with Jones, fluctuations in patientsâ responses to auditory signals correlate with their performance on tests of comprehension and memory. âHowever, it is a big step from measuring fluctuations in awareness to determining the point at which awareness ceases,â she says.
Despite this problem, the monitoring of auditory evoked EEG responses seems to have one big advantage. Unlike many of the other measures of brain activity under anaesthetic, it gives fairly consistent readings with a variety of anaesthetic drugs and from patient to patient. So promising is this approach that Gavin Kenny, an anaesthetist at Health Care International in Glasgow, is leading the development of a closed-loop computerised system in which the EEG will be linked to a machine that alters the amount of drug it delivers depending on the patientâs fluctuating auditory evoked response (Technology, żìĂš¶ÌÊÓÆ”, 29 January 1994). This will not, however, be available for a decade, says Kenny. But a less sophisticated system could be on the market by 1998.
Meanwhile, another new monitoring system is already undergoing clinical trials at Manchester Royal Infirmary and in hospitals in Belgium and California. Designed by Chris Pomfrett, a neurophysiologist at the University of Manchesterâs department of anaesthesia, and his colleagues, âFathomâ works by measuring variations in heart rate. At the University of Californiaâs department of anaesthesiology at Irvine researchers are testing Fathom in conjunction with PET scans of brain activity and have found good correlation between the two measurements. If all goes well the system could be widely available next year.
For Wang and Russell, this flurry of activity is all to the good. There is still no room for complacency, they believe. âIâm questioning the criteria that anaesthetists have used and continue to use,â says Wang. He sees an encouraging trend. âIncreasingly, psychologists as well as anaesthetists are asking what it means to be adequately anaesthetised.â