General anaesthesia – questions and answers

by Margo White / 25 August, 2012
All you wanted to know (but were probably too afraid to ask) about being given a general anaesthetic.
General anaesthesia - Dr Aidan O'Donnell

Having a general anaesthetic is one of the most common procedures of modern medicine, one that allows us to snooze our way through the most invasive operations. Yet the idea of this medically induced state of consciousness still gives us the creeps, and myths and misconceptions about “going under” abound. This is what prompted Dr Aidan O’Donnell, lead obstetric anaesthetist at Waikato Hospital, to write Anaesthesia: A Very Short Introduction. As he explains, there’s nothing that mysterious about it.

Has general anaesthesia changed?
Enormously. I remember getting gas in the dentist’s chair as a child, the horrible smell, the anaesthetist telling my mum, ‘He won’t remember this’, and I remember thinking, ‘I bloody well will, you bastard.’ And then I woke up with my mouth full of blood, feeling woolly headed, my mouth was sore. I felt queasy and unwell for some days afterward. The anaesthetist didn’t do anything wrong … that’s the treatment people got. But now we’ve achieved safe anaesthesia, we’re aiming for pleasant anaesthesia. The anaesthetic agents wear off much more quickly, there is much better pain relief and we are much better at treating nausea. It’s much more comfortable than it was a generation ago.

You note in your book that to prove the first inhaled anaesthetic actually worked, surgeons had to stage an operation?
For centuries people believed that surgery without pain was an unattainable goal, so when we fi nally got something that would work, which was ether, it had to be publicly demonstrated before people would believe it was possible. Even afterward, there were a few surgeons who thought, ‘I don’t want it for my patients, because it might kill them, and at least they’ll remain alive even if they’ll be in agony as I’m hacking their leg off.’ So it did meet with some resistance. But the introduction of anaesthesia was one of three or four developments that made modern surgery possible.

Is it true that anaesthesia is holding a patient in a suspended state between life and death?
That’s a somewhat dramatic interpretation. There’s a continuum from being fully awake to being a little bit drowsy through to being unrousable through to death. General anaesthesia happens at the safe end of that continuum … we don’t bring the patient close to death by any reasonable standards. General anaesthetic agents push the “pause button” on the conscious mind only, interrupting the formation of perception and stopping the formation of memories of those perceptions. We generally leave everything else alone. We’re very fortunate that our nervous systems are designed in such a way that the automatic stuff, like breathing and our hearts beating, carries on under general anaesthesia.

How do the general anaesthetic agents work?
There is a signalling chemical in your brain called GABA, which switches off neuronal activity. All the general anaesthetic agents we use (and a few others like alcohol) bind to one particular type of receptor, the GABAA receptor, which enhances the brain’s own switching-off mechanisms.

How is the sleeping state different from the anaesthetised state?
If you study the brain of someone asleep, you can see that sleep is a highly structured physiological process that takes place in a series of sleep cycles that alternate between light sleep and deep sleep. But even when you are deeply asleep, you’ll still be aware of the things that go on around you; if there was an intruder in your bedroom and you heard the fl oor creak, you’d be wide awake in an instant. In general anaesthesia, the cortical activity that generates sleep cycles is suppressed. And although you might look as if you are asleep, you are unrousable.

What made you become an anaesthetist?
I was a physician originally, and hated it; I was given far too much work, far too much responsibility and not enough support. A post came up in anaesthesia and I took it in desperation. And I immediately loved it. With anaesthesia, I can devote my entire clinical energy to one patient, all the way through the anaesthetic care until he or she is awake and in recovery. And anaesthesia is about relieving suffering. You go home feeling like you’ve helped make an improvement in someone’s life. It’s morally and intellectually satisfying. It’s also very technically satisfying. I love my job.

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ANAESTHESIA: A VERY SHORT INTRODUCTION, by Dr Aidan O’Donnell (Oxford University Press, $21).


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