Research from the University of Oxford has discovered a unique way to measure the level of consciousness in anaesthetised patients. It is thought the technique could revolutionise the way anaesthetics are administered, reducing the risk of complications during surgery.
The study was carried out at Oxford’s Centre for Functional Magnetic Resonance Imaging of the Brain, and monitored patients’ brains whilst the anaesthetic propofol was gradually administered. Using functional magnetic resonance imaging (fMRI) and electroencephalography (EEG), scans showed that each patient showed common patterns of behaviour whilst losing consciousness.
The research also showed that after a certain point in loss of consciousness, higher doses of anaesthetic had no further effect on the brain. Therefore, the development allows the determination of the minimal dose of anaesthetic needed to achieve unconsciousness, reducing the dangers of anaesthetics.
Importantly, the team discovered that these patterns occurred at different time intervals in each individual. This demonstrates that the effect of an anaesthetic is unique to each patient, and gives hope for a technique to monitor consciousness throughout surgery. Not only would this ensure patients don’t wake up prematurely during surgery, but it would reduce the risk of overdosing on anaesthetics. The use of unnecessarily high doses of anaesthetic is a cause of complications and deaths in surgery, especially in elderly patients and those with cardiac and neurological problems.
Perhaps surprisingly, little is known of how anaesthetics influence the brain, and currently there is no way to directly detect if a patient is responsive. Instead, consciousness is measured indirectly, using inaccurate indicators such as heart and breathing rates. It is thought that the new technique will provide a more accurate, personalised measure of consciousness. Professor Irene Tracey, who led the study, described hope for “a much more nuanced approach,” compared to current methods.
Previous theories had believed that anaesthetics shut down communication between the cerebral cortex and the thalamus, two core regions of the brain. However, the fMRI scans showed that the thalamus continued to communicate with the cerebral cortex, suggesting that the loss of consciousness is a result of a block on messages to wider areas of the brain.
Professor Hugh Perry, from the Medical Research Council, spoke of how the work provides ‘an excellent scientific foundation for new ways of treating vulnerable patients.’ The next test for the technique is to monitor patients whilst undergoing surgery, and scientists wait in anticipation for the results.