Consequences of awareness
Andrew Davidson
Department of Anaesthesia, Royal Children's Hospital, Melbourne
Awareness may have consequences for the anaesthetist and the patient. Keeping a patient unconscious is a fundamental role of the anaesthetist. An anaesthetist may be reluctant to accept that they have failed in this role, even when presented with the evidence. The effect of an awareness event on the anaesthetist is an interesting and unexplored area.
The most important consequences are for the patient. The consequences of awareness range in degree of severity. Some patients report no distress or psychological morbidity associated with their awareness 1. In contrast several studies have reported that awareness was the patient's worst hospital experience 2. In one study four of the eight awareness cases were distressed after the surgery and a further two were sufficiently anxious to need ongoing treatment 3. Patients who have been aware may describe difficulty sleeping and reluctance to undergo further anaesthesia 4-6.
Of greater concern are those who develop severe disorders such as post-traumatic stress disorder (PTSD) 7. PTSD consists of elevated autonomic arousal, intrusive and distressing thoughts and avoidance of cues or circumstances that may prompt the memory. PTSD may be preceded by a dissociate state where the memory is fragmented and the patient is unable to give a coherent account of their experience. Patients in a dissociate state appear zombie-like and may be misdiagnosed as lethargic or over sedated.
The true incidence of the severe complications after awareness is controversial. Self-reporting studies, studies from closed claimed analysis and studies based on referrals, will all have a selection bias 4,8. Closed-claims analyses suggest a high incidence of distress and morbidity associated with awareness including a 10% incidence of PTSD 9. Schwender et al reported three cases of PTSD amongst 45 cases that responded to newspaper advertisements 6. In another study by Osterman, also relying on newspaper advertisement recruitment, nine of 16 awareness cases met criteria for PTSD 10.
One prospective study with a 2-year follow-up found a significant incidence of psychological morbidity 11. This study was a follow-up 2 years after these patients had been identified as awareness cases in another study 12. In the initial identification 11 of 18 cases had described anxiety during the awareness and four had described symptoms of sleep disturbance and anxiety in the early post-operative period. All four described a resolution of their symptoms within 3 weeks and did not request follow-up or help. It is of considerable interest that, in spite of their apparent resolution, 2 years later several of these people described significant psychological symptoms. Two years later only nine of the original 18 could be interviewed, but four of these nine fulfilled diagnostic criteria for PTSD 11. None of the patients who described awareness without paralysis developed PTSD.
In contrast, in a prospective audit and follow-up to 6 months, Ranta et al reported no patients with PTSD amongst ten patients with awareness 5. Similarly, Wennervirta et al found that two of 11 patients with awareness had sleep disturbance early after the event, and only one had signs of persistent psychological disturbance at 23 months 13.
Although the small numbers restrict the confidence of any conclusions, it is likely that significant distress is associated with awareness that included memories of severe pain and paralysis 1,2,4,12. This may be due to "inescapable stress" - the inability to escape a stressful event by fight or fight responses. Inescapable stress is associated with the development of PTSD 7. There are no reports of significant psychological morbidity in patients who aware and not paralysed. Poor management of an awareness event by medical staff after the event may also predispose to an increased psychological morbidity 7,8.
In children awareness is more common but is usually not distressing, and is not associated with behavioural disturbance. This is consistent with the observation that awareness occurs more frequently in non-paralyzed children.
In summary awareness is associated with significant psychological morbidity in some cases. In many cases there are no consequences. Significant consequences occur only in paralysed patients. Three long-term prospective studies found incidences of significant consequences in 0%, 9% and 44% of paralysed cases.
Time of Presentation
Sunday 8 May 2005 - 1330-1500
References
1. Miller DR, Blew PG, Martineau RJ, Hull KA. Midazolam and awareness with recall during total intravenous anaesthesia. Can J Anaesth 1996;43(9):946-53.
