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Br J Anaesth. 2014 Oct;113(4):549-59. doi: 10.1093/bja/aeu313. Epub 2014 Sep 9.

5th National Audit Project (NAP5) on accidental awareness during general anaesthesia: summary of main findings and risk factors.

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Nuffield Department of Anaesthetics, Oxford University Hospitals NHS Trust, Oxford, UK
Department of Psychology, School of Psychology and Cognition Institute, Plymouth University, Plymouth, UK.
Department of Anaesthesia, Nottingham University Hospitals NHS Trust, Nottingham, UK.
Member Royal College of Anaesthetists' Lay Committee, London, UK.
Department of Anaesthesia, Intensive Care and Pain Medicine, Sligo Regional Hospital, Sligo, Ireland.
Department of Anaesthesia, Northwick Park Hospital, Harrow, Middlesex, UK.
Department of Anaesthesia, Papworth Hospital, Cambridge, UK.
Department of Anaesthesia, Royal Infirmary of Edinburgh, Edinburgh, UK.
Bristol School of Anaesthesia, Bristol, UK.
Department of Anaesthesia, St James Hospital, James Street, Dublin, Ireland.
Adult Intensive Care Unit, Royal Brompton Hospital, London, UK.
Department of Anaesthesia, Salford Royal Hospital, Salford, UK.
Department of Anaesthesia, Imperial College NHS Trust, London, UK.
Department of Neuroanaesthesia, National Hospital for Neurology and Neurosurgery, Queen Square, UK.
Department of Anaesthesia, Great Ormond Street Hospital NHS Foundation Trust, London, UK.
Bradford Teaching Hospitals NHS Foundation Trust, Bradford, UK.
University of Leicester, Leicester, UK.
Leicestershire Partnership NHS Trust, Leicester, UK.
Department of Anaesthesia and Intensive Care Medicine, Royal United Hospital, Bath, UK.


We present the main findings of the 5th National Audit Project (NAP5) on accidental awareness during general anaesthesia (AAGA). Incidences were estimated using reports of accidental awareness as the numerator, and a parallel national anaesthetic activity survey to provide denominator data. The incidence of certain/probable and possible accidental awareness cases was ~1:19,600 anaesthetics (95% confidence interval 1:16,700-23,450). However, there was considerable variation across subtypes of techniques or subspecialities. The incidence with neuromuscular block (NMB) was ~1:8200 (1:7030-9700), and without, it was ~1:135,900 (1:78,600-299,000). The cases of AAGA reported to NAP5 were overwhelmingly cases of unintended awareness during NMB. The incidence of accidental awareness during Caesarean section was ~1:670 (1:380-1300). Two-thirds (82, 66%) of cases of accidental awareness experiences arose in the dynamic phases of anaesthesia, namely induction of and emergence from anaesthesia. During induction of anaesthesia, contributory factors included: use of thiopental, rapid sequence induction, obesity, difficult airway management, NMB, and interruptions of anaesthetic delivery during movement from anaesthetic room to theatre. During emergence from anaesthesia, residual paralysis was perceived by patients as accidental awareness, and commonly related to a failure to ensure full return of motor capacity. One-third (43, 33%) of accidental awareness events arose during the maintenance phase of anaesthesia, mostly due to problems at induction or towards the end of anaesthesia. Factors increasing the risk of accidental awareness included: female sex, age (younger adults, but not children), obesity, anaesthetist seniority (junior trainees), previous awareness, out-of-hours operating, emergencies, type of surgery (obstetric, cardiac, thoracic), and use of NMB. The following factors were not risk factors for accidental awareness: ASA physical status, race, and use or omission of nitrous oxide. We recommend that an anaesthetic checklist, to be an integral part of the World Health Organization Safer Surgery checklist, is introduced as an aid to preventing accidental awareness. This paper is a shortened version describing the main findings from NAP5--the full report can be found at


National Audit Project; accidental awareness; awareness

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