Two posts in one day!! Thought I might as well post about this whilst it was back in my brain.
On June 7 Richard Fidler conducted an interview on ABC local radio, on the topic of consciousness and anaesthesia.
Two patients asked me about it within 24 hrs of it airing……
One, who had listened to it on the day of his procedure, was mildly terrified by the interview ( I hadn’t heard it at that stage, but did my best to reassure him).
I listened to the interview on my walk in to work the following morning.
The first patient of the day mentioned the interview to me. She was fascinated! She had me repeat a random word to her throughout the case to see if she could recall it after the event – she couldn’t! [although I didn’t hypnotise her]
It came to mind today as I was listening to one of my favourite podcasts, Chat10Looks3 , where the interview is discussed again.
It is worth listening to. Make up your own minds about it. It is always good to be cognisant of the information out patients are receiving about our specialty – the information doesn’t always come from us…..
Although a unique EEG “neural correlate of consciousness” has not yet been identified, drugs that induce anaesthesia do have characteristic effects on the spontaneous EEG. However, it is important to note that these effects are not the same for different drugs, even though they may produce a similar clinical endpoint. Appreciating these differences is the key to understanding why commercial EEG monitoring devices may give misleading results when certain drugs are used.
T / F The EEG during sevoflurane anaesthesia has less “randomness” than when awake.
T / F Propofol causes burst-suppression of the EEG at levels which have little effect on spinal reflexes.
T / F When burst-suppression is induced by propofol, total brain oxygen consumption is reduced by up to 90%.
T / F Nitrous oxide causes similar changes to the EEG compared to sevoflurane.
T / F Electrocortical silence cannot be produced with ketamine.
This is the first of three posts on the EEG – 1) the basic physiology, 2) how drugs affect the EEG, and 3) quantitative EEG monitors.
Inferring the state of consciousness by analysing electrical voltages on the surface of the forehead may seem a bit like trying to see who is winning the football by holding a voltmeter up to the TV screen. However, as reversible obliteration of consciousness is our core business, and the electroencephalogram (EEG) is one of the few ways to observe the effect of drugs on the brain, it is important to understand some basics of the EEG, in part so that the various claims made for quantitative EEG devices can be assessed critically.
Useful resources include the 8th Ed of Miller, especially Chapter 17, which is available online from the ANZCA website.
T / F The frontal EEG is a mixture of electrical signals derived from the cerebral cortex as well as sub-thalamic structures and the limbic system.
T / F An “activated” EEG means that the amplitude of the EEG waveform is reduced.
T / F The amplitude of an awake EEG is about the same as the p-wave on a standard ECG.
T / F The amplitude of the EEG decreases with age.
T / F “Burst suppression” is defined as periods of electrical activity alternating with periods of isoelectric EEG.
Following my blunder this morning, I went looking for an LO related to memory – there isn’t one.
I found this one instead
BT_PO 1.99 Outline the pharmacology of anti-depressant, anti- psychotic, anti-convulsant, anti-parkinsonian and anti- migraine medication
The link above is a little misleading as the top of the two LOs ( BT_PM 1.9) is actually something you need to know in detail.
I also thought I would show you a bit of art from a Japanese artist, Yayoi Kusama, now in her 90s, who has lived voluntarily, since 1977, in a psychiatric hospital. The piece below was created last year- “All the eternal love I have for pumpkins”
Fluoxetine significantly inhibits cytochrome P450 enzymes T/F
Nortriptyline is usually better tolerated in the elderly than amitriptyline T/F
There is a significant risk of serotinergic syndrome when SSRIs are given with tapentadol T/F
Chronic lithium therapy has no effect on MAC of inhaled anaesthetics T/F
Haemodyalisis is effective in the treatment of tricyclic antidepressant toxicity T/F