According to the NewScientists, anaesthesia wears off in about 0.02% of surgeries worldwide. In 2008, a study conducted by Washington University School of Medicine in St. Louis found that around 30,000 Americans a year awaken during surgical procedures, more often in children, sometimes experiencing intense pain and terror.
Researchers at the Massachusetts Institute of Technology (MIT) led by Emery Brown used an EEG cap with 64 electrodes to keep track of patients' brain activity across multiple brain regions as unconsciousness was induced using general anaesthetic. The team identified patterns related to consciousness and unconsciousness, and were thereby able to determine when a patient was waking up.
In the UK, about 2 % of hospitals do EEG monitoring during surgery, but only 3 or 4 electrodes are used. It only monitors one region of the brain, but the MIT team’s 64-electrode cap could bring new insight into patients’ levels of awareness during surgery, although it requires patients to shave their heads and EEG measurements are very sensitive to mechanical and electrical interference. The technique is not yet available in clinical settings.
Source: Consciousness signature warns of awareness during surgery. New Scientists, March 2013
Fewer patients awake during surgery
A new report published by the Royal College of Anaesthetists found that 153 cases of accidental awareness reported in 2011 across the UK, about 1 in every 15,000 general anaesthetics, a lot less than had been thought. Previous study found that about 1 in 500 patients were aware or awake under general anaesthetics. However, the leader of the new report, Professor Jaideep Pandit, says that under-reporting is possible partly because anaesthetists do not routinely see patients after an operation, so may not be aware of the awareness report. Sometimes patients do not report the incident.
Pandit says brain monitoring systems are available in about two-thirds of UK hospitals, but most anesthesiologists do not use them and there is a debate over how useful the monitors are. He is planning more research to focus on patient experience.
Source: Pandit JJ, Cook TM, Jonker WR, et al. A national survey of anaesthetists (NAP5 Baseline) to estimate an annual incidence of accidental awareness during general anaesthesia in the UK. British Journal of Anaesthesia. Published online March 13 2013
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