Accidental awareness during general anaesthesia – a narrative review

Abstract

Summary Unintended accidental awareness during general anaesthesia represents failure of successful anaesthesia, and so has been the subject of numerous studies during the past decades. As return to consciousness is both difficult to describe and identify, the reported incidence rates vary widely. Similarly, a wide range of techniques have been employed to identify cases of accidental awareness. Studies which have used the isolated forearm technique to identify responsiveness to command during intended anaesthesia have shown remarkably high incidences of awareness. For example, the ConsCIOUS‐1 study showed an incidence of responsiveness around the time of laryngoscopy of 1:25. On the other hand, the 5th Royal College of Anaesthetists National Audit Project, which reported the largest ever cohort of patients who had experienced accidental awareness, used a system to identify patients who spontaneously self‐reported accidental awareness. In this latter study, the incidence of accidental awareness was 1:19,600. In the recently published SNAP‐1 observational study, in which structured postoperative interviews were performed, the incidence was 1:800. In almost all reported cases of intra‐operative responsiveness, there was no subsequent explicit recall of intra‐operative events. To date, there is no evidence that this occurrence has any psychological consequences. Among patients who experience accidental awareness and can later remember details of their experience, the consequences are better known. In particular, when awareness occurs in a patient who has been given neuromuscular blocking agents, it may result in serious sequelae such as symptoms of post‐traumatic stress disorder and a permanent aversion to surgery and anaesthesia, and is feared by patients and anaesthetists. In this article, the published literature on the incidence, consequences and management of accidental awareness under general anaesthesia with subsequent recall will be reviewed.

Guidelines for the safe practice of total intravenous anaesthesia (TIVA)

“…Monitoring of the effect of the anaesthetic drug on the cerebral cortex with a pEEG monitor can reduce the likelihood of awareness . The isolated forearm technique can also be used to assess conscious state in paralysed patients ; however, its use to date has largely been confined to research studies. Almost 20% of the NAP5 reports of awareness occurred after the end of surgery and these were commonly caused by neuromuscular blockade still being present when the patient regained consciousness .…”

“…This may be achieved by setting an initial propofol target of 4 μg.ml −1 and decreasing the target after the pump indicates that a 2–3 mg.kg −1 bolus has been delivered (which typically takes 60–120 s). When using an analgesic adjunct such as remifentanil or a regional block, the propofol target concentration during maintenance can be reduced by up to 50% . This is important in children aged < 12 years, as a target concentration of 5–6 μg.ml −1 soon leads to accumulation of propofol, resulting in delayed recovery after anaesthesia.…”

Pre‐operative gastric ultrasound – should we look inside Schrödinger's gut?

“…The anaesthetic technique could be better planned for such patients, such as choosing a rapid sequence induction or avoiding the use of a SAD. This may nevertheless expose the patient to a new range of risks such as failure of tracheal intubation and its sequelae and the requirement for neuromuscular blockade, which may increase the incidence of postoperative pulmonary complications and accidental awareness during general anaesthesia . Alternatively, gastric ultrasound may reveal an empty stomach despite clinical assessment suggesting otherwise, which may support the avoidance of rapid sequence induction or tracheal intubation.…”

Innovative Brain-Computer Interface based on motor cortex activity to detect accidental awareness during general anesthesia

“…During general anesthesia, the occurrence of one particular phenomenon is feared by both patients and anesthesiologists: Accidental Awareness during General Anesthesia (AAGA) [4]. This event can be defined as an unexpected awakening of the patient during a surgical procedure under general anesthesia [5].…”