Anaesthetic Dose – `Marsh Model’
According to new research from the University of Cambridge, the difficult pattern of chat between various areas of an individual’s brain when they are awake could be helpful to doctors in tracking as well as predicting their response to general anaesthesia. This would help in identifying the amount of anaesthetic that would be necessary. Presently patients who have to undergo surgery are administered a dose of anaesthetic depending on the `Marsh model’ that tends to use factors like individual’s body weight in predicting the amount of drug that may be essential.
As the patient `go under’, their levels of awareness tends to be monitored comparatively in a simple way. If they tend to be still awake, they are given more anaesthetic, but general anaesthetics could be risky especially if the individual seems to have some underlying health issues like a heart disorder. Areas of the brain tend to communicate with each other and provide tell-tale signs which can give an indication of how conscious a person is. These networks of the brain activity is measured through electroencephalogram - EEG that measures the electric signs as the brain cells tend to talk to each other.
Propofol – Commonly Utilised Anaesthetic
Researchers from Cambridge had earlier shown that the network signatures could be seen in some individuals who had been in vegetative state and could help doctors identify patients who are aware inspite of being incapable of communicating. These discoveries have been built on advances in science of network in order to tackle the challenge of comprehending as well as measuring human consciousness.
A study published recently in the open access journal PLOS Computational Biology, funded by the Wellcome Trust, the researchers had studied how these signals tend to change in healthy participants when they received an infusion of propofol which is a commonly utilised anaesthetic.
Twenty individuals comprising of 9 males and 11 females had received a steadily increasing amount of propofol all of the same limit at the time of undergoing a task which involved pressing one button if they heard a `ping’ and different button if they heard a `pong’. The researchers, at the same time tracked their brain network activity utilising the EEG.
Brain Network Activity – Delta-Alpha Coupling
When they had reached the maximum limit of the dose, some of them were still awake and were in a position to carry out the task while there were others who were unconscious. The researchers analysed the readings of the EEG and found clear differences between those who had responded to the anaesthetic and those who were capable of carrying on with the task.
This `brain signature’ had been apparent in the network of communication between areas in the brain carried by alpha waves, - brain cell oscillations in the frequency range of 7.5-12.5Hz, which is the normal range of electrical activity ofthe brain in conscious and relaxed state. The researcher had also measured the propofol levels in the blood in order to know if this could be used as a measure of how conscious a person would be.
Having found little correlation with the alpha wave readings, they found a correlation with certain form of brain network activity known as delta-alpha coupling which could be capable of providing a useful, non-invasive measure of the level of drug that could be present in the blood.