I am frightened that I may be aware during an operation. Is that possible?

This experience, known as "awareness", is one of the biggest concerns for patients about to undergo surgery. Though it may worry patients, this condition can be almost entirely eliminated by the anaesthetist, with fewer than 1 in a 1000 patients remembering any part of their operation and most of these not recalling any pain.

Conscious awareness without recall of pain is more common; it has been estimated at 0.1 to 0.7 per cent of cases (1 in 142 to 1 in 1000).

Some operations are associated with a higher risk of awareness than others. They include cardiac surgery, emergency surgery, surgery associated with significant blood loss and caesarean section.

Specialised monitoring equipment is available to assist anaesthetists to assess the depth of anaesthesia. Such equipment includes processed electro-encephalography such as Bispectral Index Scale (BIS) and Entropy, which record electrical wave patterns in the brain and assign a score which reflects the depth of unconsciousness. These monitors have been shown to reduce the incidence of awareness, particularly in high-risk cases.


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