October 23, 2013

expert reaction to new research into anaesthesia and consciousness

Researchers publishing in Science Translational Medicine showed that measuring slow-wave activity in an individual’s brain while they are under anaesthetic offers the clearest picture yet of degrees of perceptual awareness in the brain during the period of anaesthesia. 

Dr Robert D Sanders, Honorary Lecturer, University College London Hospital, said:

“This study provides significant scientific insights into propofol-induced anaesthesia using sophisticated technology, electroencephalography (the electrical signals in the brain) and magnetic resonance imaging (the structure and activity patterns in the brain). It shows that when the human brain is in a maximally “slow wave” electrical pattern it is poorly receptive to external sensory information such as sounds or pain. An exciting proposal is that achieving this slow electrical pattern may prevent awareness of surgery during general anaesthesia. However this is a laboratory study and, as yet, we are unsure whether this state can be achieved and maintained in the operating room, or whether surgical stimulation will wake the brain from this slow electrical state or whether this will work for all patients or all anaesthetic drugs and combinations. Nonetheless despite these remaining questions, this is an exciting study that may have significant impact on the care of patients undergoing general anaesthesia.”

Cathy McKenzie, Royal Pharmaceutical Society expert on propofol & a consultant pharmacist in intensive care, said:

“This is a very interesting study. There are clearly lots of limitations as the authors describe, e.g. age factors on EEG. Nevertheless, this is a step in the direction of measuring consciousness during intravenous sedation in surgery. The authors suggest it may be useful in limiting awareness during surgery. I rather think it may have a future in reducing over-sedation. Although propofol has quite ‘clean’ pharmacokinetics and no active metabolites, patients often report feeling ‘sluggish’ up to 48 hours after surgery and can be ‘slow to wake’. There may also be potential for use in the intensive care unit, where surrogate markers like sedation scores are often used. Techniques like this may revolutionise our assessment of sedation.”

‘Slow-Wave Activity Saturation and Thalamocortical Isolation During Propofol Anesthesia in Humans’ by Tracey et al. published in Science Translational Medicine on Wednesday 23 October.