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The largest ever study of awareness during obstetric general anaesthesia shows around 1 in 250 women may be affected, and some may experience long-term psychological harm.

Accidental awareness occurs when a patient is temporarily conscious during a general anaesthetic and can remember things that happened during surgery, perhaps feeling pain or being unable to move. More commonly however, awareness occurs during the transition at the very start or end of a general anaesthetic (i.e. before and after surgery), as the patient is going to sleep or waking up. Although accidental awareness during general anaesthesia is rare, and the experiences usually only lasted for a few seconds or minutes, the complication remains an important concern for both patients and anaesthetists.

A new study co-authored by Professor Jaideep Pandit and published in Anaesthesia, shows that 1 in 256 women undergoing pregnancy-related surgery, including caesarean section, under general anaesthesia experienced awareness – a figure much higher than reported before. A recent national audit into accidental awareness (NAP5 - of which Professor Pandit is the lead author) indicated that approximately 1 in every 19,000 patients undergoing general anaesthesia spontaneously reported accidental awareness to medical staff. Although this incidence varied for different types of surgery and patient subgroups, the infrequency of reports was reassuring.

This project takes forward previous research findings.The issue of consent is especially important, as the incidence we find is similar to that for other complications which we would normally warn patients about. - Professor Jaideep Pandit

This new research was driven by the suggestion from NAP5 that women having caesarean section, or other surgery at childbirth, may have a higher incidence of awareness. The researchers studied over 3,000 women having general anaesthesia for obstetric procedures in 72 NHS hospitals in England and found 12 reports of awareness: seven (58%) patients were distressed and five (42%) felt paralysed (that they were unable to move, which may occur due to the common use of drugs to relax muscles during general anaesthesia for pregnant women). Two women (17%) felt paralysis with pain. Other sensations included tugging, stitching, feelings of dissociation and being unable to breath. Longer term psychological harm often included features of post-traumatic stress disorder.

Dr Peter Odor, Project Lead and Consultant Anaesthetist at University College Hospital in London, explained: 'This research is patient-focussed throughout. We identified a complex range of risk factors for awareness, including drug types and variations in practice. Although the incidence of awareness during caesarean section is much higher than that in the general surgical population, it is important to emphasise that general anaesthesia remains safe and around half the patients that experienced awareness did not find it distressing. Although we have provided many answers, questions remain as to exactly why awareness is more common in pregnant women; our next steps are to apply the lessons learned from this study to help reduce risk in the future.'

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