Incidence of accidental awareness during general anaesthesia in obstetrics: a multi-centre, prospective cohort study

Summary
General anaesthesia for obstetric surgery has distinct characteristics, which may contribute towards
a higher risk of accidental awareness during general anaesthesia. The primary aim of this study was
to investigate the incidence, experience and psychological implications of unintended conscious
awareness during general anaesthesia in obstetric patients. From May 2017 to August 2018, 3115
consenting patients receiving general anaesthesia for obstetric surgery in 72 hospitals in England
were recruited. Patients received three repetitions of standardised questioning over 30 days, with
responses indicating memories during general anaesthesia verified using interviews and record
interrogation. A total of 12 patients had certain/probable or possible awareness; an incidence of 1 in
256 (95%CI 1 in 149 – 1 in 500) for all obstetric surgery. The incidence was 1 in 212 (95%CI 1 in 122 –
1 in 417) for caesarean section surgery. Distressing experiences were reported by seven (58.3%)
patients; paralysis by five (41.7%), paralysis with pain by two (16.7%) reported. Accidental
awareness occurred during induction and emergence in nine (75%) patients. Factors associated with
AAGA were high BMI (25-30 kg.m-2
), low BMI (<18.5 kg.m-2
), out-of-hours surgery and use of
ketamine or thiopental for induction. Standardised psychological impact scores at 30 days were
significantly higher in awareness patients (median (IQR [range]): 15 (2.75 – 52 [2 – 56]) than in
patients without awareness: 3 (1 – 9 [0 – 64]; p = 0.010). Four patients had a provisional diagnosis of
post-traumatic stress disorder. We conclude that direct postoperative questioning reveals high rates
of accidental awareness during general anaesthesia for obstetric surgery, which has implications for
anaesthetic practice, consent and follow-up.