Ever since the first reports of spontaneous awakenings during what was presumed to be general anaesthesia, 'awareness' has been an elusive concept in anaesthesia. Awareness is said to have taken place if and when patients have memories, spontaneous or otherwise, of intraoperative events after general anaesthesia. These memories mostly relate to episodes of auditory perception, but other sensations (sight, smell, pain) may also be involved.
Various percentages of occurrence of awareness have been reported, ranging from nil to over 40% in special circumstances, but only few attempts have been made to document its exact incidence. In general, the latest figures with large patient samples indicate an estimated incidence of 0.2%, but this is probably higher in particular patient groups. Patients undergoing Caesarean section or cardiac surgery, or those with alcohol or drug abuse, or obesity, are reported to be more prone to awareness than others. Nevertheless, clinical case studies have shown that unexpected awakening and subsequent emotional symptoms can occur without a clear cause.
Many will agree that being aware during a period of alleged general anaesthesia can be a horrific experience, leaving its psychological traces for an unknown period of time. Especially when sensations of paralysis have been present, patients describe their emotions as extreme fear and anxiety over what in their mind's eye was evidently going wrong. Postoperative distress, anxiety, restlessness, anger towards doctors and recurring nightmares are among the first symptoms postoperatively. Intrusive thoughts, phobic reactions, avoidance, sleep disturbances, persistent avoidance of associated stimuli, numbing of general responsiveness and persistent symptoms of increased arousal are symptoms that may last for longer periods of time. In some cases, patients develop a posttraumatic stress disorder as a consequence of an awareness episode.
Some have argued that awareness cases can easily be overlooked. This 'tip of the iceberg' phenomenon is based on the fact that patients are often reluctant to discuss their experiences with their anaesthetists, for fear of being disbelieved or dismissed. Also, because few patients know that awareness may sometimes take place, patients have frequently doubted their own experiences and attributed their symptoms to other causes. It is a common misunderstanding that absence of spontaneous recall in patients after general anaesthesia equals absence of periods of awareness. Experience shows that some patients only remember episodes of inadvertent awakening after some time, for instance after a dream, or upon repeated questioning. One patient described in the literature did not come up with memories of the surgical episode until 8 days postoperatively. Others have been awakened for surgical reasons, as in the case of incontinence surgery where tests had to be carried with the conscious patient. Despite clear evidence of consciousness during the surgical procedure, exemplified by the patient's ability to read out loud a two-digit figure, many patients denied any recall of the episode afterwards.
Systematic investigations into documented cases of awareness have been undertaken in the past years, which have led to more specific details of the experiences patients with awareness go through. It has mainly been the (lack of) empathic reactions of doctors and nurses that determined the severity of problems patients had as a consequence of an awareness episode.
Can awareness be detected on-line, for instance by close inspection of the anaesthetic record and haemodynamic parameters? Without the help of sophisticated monitors, which have been and are being developed, the human eye - and mind - of the anaesthetist is probably not able to do so. We asked trained anaesthetists to inspect closely the anaesthetic records of patients who had and who had not been aware. They were first asked to identify any records that, in their opinion, might indicate periods of awareness. Next, we collected, in the hospital archives, two records of patients who closely matched the patients in whom awareness had occurred on relevant variables such as age, weight, type of surgery, type of anaesthesia, et cetera. Our anaesthetic judges were then provided with bunches of three records and told that one of each three records belonged to a patient who had been through an episode of awareness. In neither of the judging procedures were the anaesthetists able to detect the awareness cases at a level above chance. Nevertheless, close inspection of the awareness records revealed that an increased heart rate (>30 bpm) and blood pressure (>30 mmHg) was present in 67% of the awareness cases, whereas this was so in only 21% of the matched controls. Presumably, both values were considered to be within a normal range of values, by our judges.
As a matter of course, awareness may take place if and when there is an equipment failure, when syringes have been swapped, with empty vaporizers, infusion errors, or when muscle relaxants have been substituted for induction agents. Nevertheless, awareness may be caused by reasons beyond our comprehension.
What can be done in cases of awareness? Main advice is to acknowledge the patient's story, without any signs of dismissal or disbelief, and to reassure the patient that a note will be made in the hospital record. Be sure to give a full account of the interview in the clinical notes. Obviously, some patients may have taken their dreams or fantasies for auditory or visual perceptions, but in all cases patients should be treated with care. Take the time that is necessary for the patient's story to be told, and be sure to do appropriate follow-ups, in person. Explain what may have been the case, and do not hesitate to apologise where appropriate. Consider psychotherapeutic or psychiatric help in cases where patients have severe and/or prolonged symptoms, or when symptoms of a posttraumatic stress disorder are present. These are persistent reexperiencing of the traumatic event, eg, intrusive recollections, nightmares, intense distress, persistent avoidance of associated stimuli, numbing of general responsiveness, and symptoms of increased arousal, with a duration of symptoms > 1 month.
Beside an overview of awareness studies some case studies will
be presented in some detail.