Assessing psychological impact in anaesthetic awareness claims

Millions of patients undergo surgical procedures requiring a general anaesthetic (GA) each year. While the overall risks associated with GA have progressively decreased, the precise mechanism by which anaesthetic drugs act on the body remains poorly understood. Furthermore, like all medications, adverse events can occur. One of these is accidental awareness during general anaesthesia (AAGA), defined as the unexpected and explicit recall by patients of events that occurred during anaesthesia (1).

Estimates of the incidence of AAGA vary widely (2) and depend on many factors, such as the population sample, time of investigation, definition of awareness and method of identifying events (3). The generally accepted incidence rate is in the region of 1 or 2 cases per 1000 patients (1, 2, 4). Factors that increase the likelihood of AAGA include the use of neuromuscular blocking agents during anaesthesia (1, 2, 5), female gender (4), young age, drug resistance and substance abuse, and a history of difficult intubation or previous awareness events (1). Certain procedures are also associated with a higher incidence of AAGA, including cardiac surgery, caesarean section and trauma surgery (1, 6), possibly due to an association with comorbidities or other factors that affect the choice of drugs used (6).

The sensations reported by patients during AAGA events vary widely and can include one or more of the following: hearing voices or noises associated with equipment, touch without pain, awareness of tracheal intubation, pain, an inability to breathe or feeling of suffocation, being moved and visual sensations (1-3). Many patients also report an inability to move or communicate. Paralysis appears to be commonly experienced, independent of whether the AAGA event occurs during induction of anaesthesia, during surgery or at emergence. Auditory sensations are most common during induction, while pain is most likely to be reported if the AAGA event occurs during the surgical procedure (2).

Memories of AAGA may not emerge immediately (1). Around half of all cases are reported directly post-anaesthesia, but a similar proportion are not recalled until 7–14 days after surgery. This may be due to delayed recall or a reluctance to report the event, possibly due to fear of not being believed or because the patient does not wish to relive the experience (2).

The reasons why AAGA occurs are not fully understood and may be multifactorial (1). This is compounded by the current lack of clinical or other measurements that can reliably determine whether an anaesthetised patient is fully unconscious (1, 5). Furthermore, episodes of awareness have occurred without abnormal physical changes being evident (1, 7). AAGA events may be due to patient factors such as comorbidity or genetic variation in the response to the anaesthetic drugs, or failings on the part of the anaesthetist, such as medication errors or inadequate training or experience (1-3, 7). Sometimes the exact cause is never identified. However, it has been reported that around 75% of AAGA events are preventable, as human error is far more likely to be the cause than equipment failure (5).

While some patients are relatively unconcerned by AAGA, others find it a terrifying experience (1, 2). During the incident, patients may become anxious because things have gone wrong, or they fear that things will get worse. Many feel powerless because they cannot alert medical personnel to their predicament. Preoperative concern about AAGA can cause additional anxiety, and a failure to discuss the issue during the consenting process may increase the tendency for the patient to negatively interpret the experience (2). 

Around half of all cases of AAGA result in distress to the patient, and this is more likely if the sensations reported include paralysis, particularly if this is accompanied by pain (2, 5). Paralysis appears to be the primary driver of patient distress at the time of the event. However, it is also associated with longer-term psychological harm, the likelihood of which is significantly increased if the patient perceives there is a threat to life (2). This is dependent on the patient’s understanding and interpretation of the events they are experiencing and may be significantly worsened by neuromuscular paralysis. The inability to move tends to lead to increased feelings of helplessness and a more catastrophic interpretation (2, 5).

Over half of patients who report paralysis, with or without pain, go on to develop moderate-to-severe long-term harm, compared to only 25% of those with only auditory or tactile sensations. However, there is no clear relationship between the precise experience and the long-term impact, so a particular sensation is not necessarily predictive of an adverse long-term outcome. Likewise, the duration of the event does not predict its impact. The factor that appears to be most influential is the patient’s level of distress at the time of the AAGA, and even brief experiences can be severely disturbing (2).  

Not surprisingly, post-traumatic stress disorder (PTSD) has been reported in patients who have experienced AAGA (1, 5), but it is unclear how common this condition is. Rates vary from 0% up to 70% of patients, with a pooled incidence rate of around 15% being estimated (2-4). Even without AAGA, hospital admission, surgery and anaesthesia can result in adverse experiences for patients, so disentangling the effects of AAGA becomes even more complex. However, it is clear that awareness during surgery carries its own risk of PTSD over and above that of routine surgery, with the rates being more than doubled in patients who have experienced AAGA compared to the general post-surgical population. Cognitive appraisal at the time of the trauma is thought to be central to the development of PTSD and thus there may be a link with catastrophic interpretation of an AAGA event (2).

As well as PTSD, patients who report AAGA are more likely to suffer from depression or phobias (1-3, 5). In addition, some patients re-live the event through flashbacks and nightmares, experience hyperarousal in the form of increased anxiety and sleep disturbance, or use avoidance behaviour (1-3).

Many minor surgical procedures are carried out under sedation rather than general anaesthesia. During sedation, the patient is relaxed and sleepy but remains conscious. Under these circumstances, AAGA events would not be expected but are actually reported by a significant proportion of patients (5). Furthermore, the levels of distress and psychological harm associated with these reports is high and may even exceed those reported for anaesthesia-associated AAGA events.

This suggests that patients do not understand the distinction between sedation and anaesthesia; many patients interpret sedation or light anaesthesia as being unconscious and free from pain and recall (2). This is important because the mismatch between patient expectation and reality may give rise to litigation, and it is therefore vital that during the consenting process patients are made fully aware of the difference between sedation and full anaesthesia (2, 5). A clear explanation of the possibility of recall following sedation may reduce the risk of panicking and distress in lightly sedated patients (5), thus reducing the likelihood of long-term adverse sequelae.

As distress at the time of the AAGA event appears to be critical in the development of long-term psychological harm, efforts to reassure the patient and increase their understanding and acceptance of their experience should help to reduce the likelihood of an adverse outcome. All reports of AAGA should be taken seriously, as all have the potential for serious long-term psychological damage. Where possible, there should be a discussion between the patient and anaesthetist to explore possible reasons for the event as well as reassurance that recurrence during future procedures is unlikely (1).

While it might be expected that litigation would inevitably follow an incidence of AAGA, statistics suggest that this is not necessarily the case (2, 5), although there is some evidence that AAGA events are increasingly leading to claims for negligence (7). Even if the number of cases is small, settlement is almost always in favour of the patient and the damages awarded can be significant (2). 

Thus, it might appear that any claim relating to AAGA cannot be defended, but in reality, this is not necessarily the case. The lack of a reliable form of monitoring to determine unconsciousness means that a standard of care is difficult to define (2); therefore, an occurrence of AAGA does not necessarily signify negligence (1). Between-patient variability in response to anaesthetic drugs, masking of signs of awareness either by pathology or medication, and the possibility of equipment failure mean that an assumption of fault should not be automatic (5). Even so, meticulous record-keeping will be needed to demonstrate that a good standard of care was provided to the patient. A compassionate approach to patients who report AAGA, as well as the prompt provision of appropriate support (1, 5), may lessen the effects of this potentially traumatic experience and reduce the chances of future litigation.

References: