10. HYDROGEN and HELIUM and some other gases
Hydrogen. H2. A colourless odourless tasteless gas; highly flammable; the lightest of the elements; forms 3/4 of the mass of the Universe.
Helium. He. A colourless odourless tasteless gas; non- flammable; formed by the fusion of two hydrogen molecules; the second lightest element; forms more than 1/5 of the mass of the Universe, but is rare on Earth.
Nitrogen. N2. A colourless odourless tasteless gas; chemically inactive; forms approximately 4/5th of the earth’s atmosphere.
Argon. Ar. & Xenon. Xe. ‘Inert’ or ‘noble’ gases; colourless, odourless and tasteless; present in air at concentrations of 0.93% and 0.086 ppm respectively.
Putney, London
I was nearly three when the Hindenburg airship exploded in a ball of fire as it came into land in New Jersey, killing the thirty five passengers and crew on board. Of course, I was too young to be aware of the disaster at the time, but in later years I have been greatly moved by the recording of Herb Morrison’s eye-witness account, as no doubt you will have been too, if you have heard it.
To-day dirigibles are lifted not by hydrogen, but by helium, which is non-flammable, but very expensive. Whilst hydrogen has only very weak anaesthetic properties, helium under high pressure will reverse anaesthesia[1,2].
A.D. 1939
The first balloon I was given that floated to the ceiling when I let go of the string was not filled with helium from a cylinder, but with ordinary ‘gas’ from a gas tap in the house, which was (in those days) about 50% hydrogen and 30% methane. As it also contained between 8 and 18% carbon monoxide it was pretty dangerous stuff.
Still I was pleased enough to have the balloon. It stayed up at ceiling level for three days, shrivelling slowly like an over-sized plum.
A.D. 1946
Harrow, Middlesex
‘Have you ever seen a mercury heart?’
‘A mercury heart? What’s that?’
‘I’ll ask Daddy to show you.’
We were visiting some distant cousins whose father was a schoolmaster. He was a most interesting man.
‘Will you make a mercury heart for us, Dad? Pleeease.’
He said he would.
So we all went to the garden shed and waited while he collected the necessary equipment. He arrived a few minutes later carrying a shallow glass dish, a piece of insulated wire about two foot long, a small bottle with mercury in it, another bottle with some acid in it, and a battery from bicycle lamp.
He put the shallow dish on the table and poured some mercury into it so that it formed a shiny grey puddle in the middle of the dish. Then he poured some of the acid into the dish till it covered the mercury completely. Next he took the piece of wire and stripped a short length of the insulation off the ends, not much, just so that there was a bit of shiny metal exposed. Now he put one end into the mercury and the other end into the acid close to the mercury but not quite touching it.
‘This is like a battery,’ he said. ‘Two different metals dipped in an acid always acts like a battery.’
‘Is that why mummy can’t suck acid drops?’ I asked. ‘She’s got some silver fillings and some gold ones. She says they give her electric shocks if she sucks an acid drop.’
‘I’ve never heard of anything like that, but it certainly makes sense. Silver fillings are made from mercury, of course, not from silver; your Dad will tell you about that. Anyway, although this is a battery it is too weak for the job I want it to do, so I am going to fix this proper battery into the middle of the wire, like this.’
He held the middle of the wire, cut it, stripped some more of the insulation and fixed the new ends of shiny wire to the terminals of the battery, twisting them tightly so that the connections were firm.
‘Now watch,’ he said, and he moved the end of the wire that was lying free in the acid back and forth. ‘I’m trying to find just the right distance between this end of the wire and the mercury.’
Soon he good it just right. The blob of mercury suddenly bunched itself up so that it became a smaller but deeper puddle and then after a moment it fell back again to its original flatter and wider shape. Then it bunched itself up again, and collapsed, and bunched, and on and on. It was fascinating.
‘Why it is doing that?’ I asked.
‘It’s because the two different metals are acting as electrodes and they repel each other, but it is only the mercury that can move. When it bunches up like that is trying to get as far away as it can from the wire, and then it gets to the point where the weight of the mercury is greater than the electrical force and it flops down again.’
We watched for several minutes, hardly able to believe our eyes. After a while we noticed tiny bubbles appearing on the wire that was lying free in the acid solution.
‘Those are bubbles of hydrogen. We will have to shake them off in a minute if we want it to carry on working. It’s a bit fiddly.’
He paused briefly as we watched the bubbles appearing from nowhere, as if by magic. Then he said
‘Hydrogen is what the sun is made of, you know.’
I laughed. I thought he must be joking.
‘No, it is, really; and the hydrogen in the sun is turning into another gas called helium, and it gives off heat as it does so. It’s a good job too that it does, or we would all freeze to death.’
Freeze to death? That did not sound very nice!
A.D. 1948
Epsom, Surrey
As I have said before, chemistry lessons were great fun. I particularly enjoyed making hydrogen by pouring an acid onto granules of zinc in a test tube. The mixture fizzed delightfully, and if after a few minutes you put a match to the open end of the tube the hydrogen exploded with a splendidly satisfying high-pitched pop; or you could put a paper bag over the top of the tube and after a while the bag would float up to the ceiling just like the Hindenburg airship.
A.D. 1957
Guy’s Hospital, London
The poor lady was obviously very distressed. She was struggling to breathe through her clenched teeth, her lips pulled away from her mouth in a bizarre grimace, and there was a husky stridor in her throat. The right side of her neck was very swollen and she looked very ill.
‘What’s the matter with her?’, I asked the casualty officer.
‘I think she’s got a quinsy and it is causing her severe trismus.’
‘What’s a quinsy?’ I asked. ‘And what is trismus?’
‘Oh, a quinsy is a peritonsillar abscess,’ he replied, ‘and trismus is spasm of the masseter muscle which makes it difficult for her to open her mouth. Apparently she has had a sore throat for two weeks and it’s been getting worse each day till now her neck is very swollen at the side here and it seems to be tracking upwards and giving her trismus. Her airway is partly obstructed by the abscess and all the swelling around it, and the fact that she can’t open her mouth doesn’t help. I’ve asked the surgical registrar and the anaesthetist to come, but I think we should give her some helium and oxygen in the meantime. She’ll find that easier to breathe till we can get her mouth open and drain the pus out.’
‘Helium and oxygen? I’ve not heard of that before. How does it help?’
‘Oh, helium is a very light gas, and a mixture of oxygen and helium is easier to breathe than air, which is oxygen and nitrogen, of course. Anyway we’ll give it a go.’
He disappeared for a moment and then came back pulling a trolley with a tall cylinder which looked like an oxygen cylinder in that the body was black, but the shoulder of the cylinder was marked out in four segments which were brown and white alternately. It was labelled HELIUM 79% OXYGEN 21%.
‘Try breathing this, Mrs Carter, ‘ he said, holding a mask to her face and turning the cylinder on.
I watched her closely. I noticed the noise of her obstructed breathing become eerily high-pitched, and, yes, she did seem to be breathing this more easily, though she still looked distressed.
A few minutes later the surgeon and the anaesthetist arrived.
The surgeon felt the front of her neck.
‘It’s not too swollen here,’ he said. ‘If I need to do a tracheostomy it shouldn’t be too difficult. The infection seems to have tracked up the neck rather than round to the front, which is why she has the trismus.’
‘I’m not too keen on giving her a general anaesthetic unless we can open her mouth a bit more than this.’ Turning to the patient he said
‘ Mrs Carter, just see if you can open your teeth a bit and I’ll put this wedge between them. That’s good,’ he said. She had opened her mouth about 1/4 inch and he thrust a slim wooden wedge firmly between her back teeth.
'Now let’s see if you can open just a bit wider and I’ll push this in again.’
An 1/8 inch only this time, and he pushed the wedge a little bit further between her back teeth. But that was it. She could not open her mouth any wider, even when he tapped on the end of the wooden wedge with a patella hammer[1] and put a metal mouth gag with a ratchet mechanism between her molars on the other side.
‘Mrs Carter, have this to breathe again if it helps,’ he said, putting the mask back on her face. ‘I am going to inject some local anaesthetic into this muscle here,’ he continued, touching her right masseter lightly. ‘It ought to relieve the spasm and let you open your mouth better.’
It worked brilliantly. Five minutes after he had finished infiltrating the muscle with Xylocaine she could open her mouth widely, though her breathing was not greatly improved by this.
‘I think it will be OK now to anaesthetise her,’ the anaesthetist said to the surgeon. ‘I’ll give her some oxygen with a little cyclopropane and see if I can pop a nasopharyngeal tube past the obstruction. It often works like magic when there are swollen tonsils, as long as it doesn’t make the nose bleed.’
And so it proved. Once the tube was in place just above the larynx all was well. Everyone breathed a sigh of relief. The anaesthetist increased the cyclopropane concentration, taking her deeper so that now he could pass a longer tube blindly into her trachea. This was a plain uncuffed tube so that they still had to tip her head down with a pillow under her shoulders before the surgeon plunged the sinus forceps into the swelling and let out half a cupful of thick yellow pus.
When she woke up she found she could breathe easily without needing the helium and oxygen mixture.
A.D. 1960
Wheatley, Oxford
‘It’s time you started swotting for your exam, John.’
‘Yes, my love, I know it is. I’ll get down to it after supper. I don’t feel like it at the moment.’
I was always one to leave everything to the last few days, and this was no exception. Still the Diploma of Anaesthetics of the Royal College of Surgeons of London and the Royal College of Physicians of England had the reputation of being a fairly straightforward affair even if it did have a long name; straightforward, that is, if one had actually held down a busy SHO job in anaesthesia as I had, and a locum registrar post too. The exam was designed to make sure the candidate knew enough to be able to give a safe anaesthetic; it concentrated on theory only where this was important to understand the practical aspects of the art of anaesthesia. Of course, when it came to the vivas they could ask you anything they liked, so it was best to read the whole book through, including the esoteric bits, just to be sure.
We were enjoying ourselves greatly at Wheatley. The work at the hospital was very interesting as I had not been involved with neurosurgery before. The married quarters were extremely pleasant and there was a good community spirit, and some gossip too.
Isabel had had an exciting day: Tim had somehow wriggled out of his pram and Doreen, from next door, had heard him screaming in the garden and had found him dangling by his harness over the side of the pram; David, in the next house, had broken a window by throwing a brick over the roof with a wire tied to it - he had been trying to fix up an aerial so that he could listen to the big fight which was to be broadcast direct from the USA at three in the morning. The big question was whether Sugar Ray Robinson would win in the third or the fourth round?
We had delicious home-made steak and kidney pie for supper, one of my favourite meals. After a nice big mug of coffee I settled down to my studies. I planned to finish reading the chapter on Gases Used In Association With Anaesthesia.
I had already studied the section on oxygen the night before and had almost finished reading about carbon dioxide. I knew that a short section on nitrogen came next. What, I wondered, would be left to read when I had finished with nitrogen? I flipped the page over: there were just a few short paragraphs on the page, headed, in turn, Helium, Xenon, and Other Gases.
As I often did I started at the end:
ARGON: is reported to have mild anaesthetic properties, as is also sulphur hexafluoride.
Well, that was short enough! I knew about argon, of course, but what on earth was sulphur hexafluoride? It sounded strange and rather unlikely. I turned the page back again and read the section on nitrogen:
NITROGEN: First isolated by Rutherford in 1772
Rutherford, eh? I thought he was the man who had split the atom in this century. Perhaps this Rutherford was one of his ancestors.
Preparation: 1. fractional distillation of air. 2. Heating ammonium nitrite.
Properties: Molecular weight 28... chemically inert and will not support combustion or combine with water, but is dissolved in body tissues from which it is displaced slowly.
I did not think that was very clear. He must have meant it was displaced slowly, when you gave someone a nitrogen-free gas mixture to breathe.
Solution in plasma is the sole method of transport of nitrogen in the blood, unlike oxygen which combines with haemoglobin, and carbon dioxide which forms carbamino compounds, and combined with base is carried as bicarbonate...’
I know all this, I said to myself. Let’s jump on a bit.
The elimination of nitrogen from the lungs, breathing pure oxygen... takes about 2 minutes... Nitrogen diffuses from an isolated lung lobule, whose bronchus is tied, in 16 hours. Oxygen, under similar conditions, diffuses in 15 minutes.’
So that’s why lung alveoli collapse when the ‘nitrogen scaffold’ is removed. Now what does it say about helium:
HELIUM: Isolated by Ramsay in 1895.
Yes, but discovered in the sun’s atmosphere many years before; during an eclipse in India. When would it have been? About thirty years earlier, I thought.
Because it its low density the gas will flow through an orifice three times as fast as air, so in patients with partial respiratory obstruction, 20% oxygen and 80% helium will enable more oxygen to get to the alveoli with the same effort, or the same ventilation will take place with less effort than when air is inhaled.
I remembered the patient with the quinsy at Guy’s, it had seemed to help her breathe more easily though she had not gone pink until they had changed it to oxygen.
It decreases resistance to breathing and so is used with oxygen in the treatment of asthma and respiratory obstruction.
Asthma, eh? I had not seen it used for that. Well, it was another thing to add to the unusual treatments I had seen for asthma, which already hypnosis, ether and stellate ganglion block.
If fed through a nitrous oxide flowmeter the reading must be multiplied by 3.3 to get the approximate rate of flow in litres a minute.
Curious, that. Now for xenon.
XENON: First used in anaesthesia by Cullen and Gross in 1951. Has a potency roughly equivalent to ethylene. Is non-flammable. Causes no respiratory depression and no cardiac arrythmias.
Sounds ideal! Pity it’s so rare and expensive, or we would all be using it.
The amount of xenon in the arterial blood is directly proportional to the partial pressure of the gas in the inspired atmosphere.
Well, that was pretty obvious, wasn’t it? I wondered why they bothered to say it. Now we were back to the sentence about argon and sulphur hexafluoride. So that’s the chapter dealt with. Interesting stuff, but I did not expect they will ask about any of those things in the exam.
A.D. 1962
Here I was swotting at the books once again. I looked through the last few years journals just as I had done when I had been studying for the DA, though somehow it all seemed more important this time. I flicked the pages of the BJA; now what’s this?
A Trial of Xenon as a Non-Explosive Anaesthetic.
Xenon? Yes, I remembered reading about xenon a couple of years ago in Synopsis of Anaesthesia. It had always seemed strange to me that xenon, an inert elemental gas, should have anaesthetic properties. Let’s see what it says:
The solubility of xenon in water and the oil/water partition coefficient indicate that the gas might have anaesthetic properties according to the Meyer-Overton hypothesis.
What on earth is the Meyer-Overton hypothesis?, I wondered.
In addition it has been shown that, in the lower members of the inert gas series, narcotic potency at elevated pressure increases with increasing atomic weight.
Sometimes these articles were difficult to follow!
Xenon would therefore be expected to be the most potent apart from radon. This has been confirmed in observations on mice.
On mice, eh? Amazing. Who would have thought it? I did what I usually did and I jumped ahead to the end of the article to read the final paragraph:
Xenon appears to have anaesthetic properties slightly more potent than nitrous oxide. It is of theoretical interest that a chemically inert gas can produce a pharmacological effect. The anaesthetic properties of xenon, however, are not sufficiently greater than nitrous oxide to warrant its clinical use, the price being many times that of nitrous oxide
A real pity. It would have been fascinating to try it out. Still it all sounded a bit unlikely, didn’t it?
A.D. 1971
Southmead Hospital, Bristol
It was a good thing that I had given up smoking two weeks earlier, for this particular day when I turned on the cylinder of hydrogen the diaphragm in the reducing valve blew and hydrogen hissed fiercely out into the lab in a thoroughly alarming manner. I nearly dropped the cylinder key in my haste to turn the cylinder off.
Of course, it should never have been in the lab in the first place, but we had wanted to use the gas chromatograph and we had not yet had the small storage hut built outside. By some good chance I did not blow the place apart, but it made me realise just how stupid I had been to have the cylinder inside the building; no more stupid, I suppose, than the House Committee that only the week before had given me the task of acting as Safety Officer for the building.
A.D. 1973
I have always loved browsing in the stack room of the Medical School library. One day when I was searching for a particular paper in the 1966 Journal of Applied Physiology I came across a splendid article called Demonstration without instruments of ‘first gas into the lung is last gas out’. How intriguing! And the authors names were intriguing too: Stanley C. Glauser and Elinor M. Glauser. Man and wife? Or perhaps brother and sister? Who could tell?
I looked at the summary at the start of the paper:
It has been shown that the principle of the first gas to enter the lung is the last gas to leave can be demonstrated without the use of instrumentation. This is done by using the fact that the frequency spectrum of the voice is determined by the density of the gas in the trachea.
So far so good. I knew that breathing helium made your voice go squeaky rather like Donald Duck, but I could not remember exactly where and when I had tried it myself. I read on:
A subject first inhales sulphur hexafluoride ......
Sulphur hexafluoride? That sounded rather strange and unlikely, and yet I had read about it somewhere.
..., a gas of high density, followed by completing the breath with helium, a gas of low density. The subject then talks and the frequency spectrum of the voice which at first has high frequency overtones ...
I assumed they meant was squeaky!
... loses these high frequency overtones to become ‘low pitched’. This demonstrates that the first gas to enter the lung is the last gas to leave.
Reading the short paper that followed the summary I found that it contained dire warnings about the dangers of hypoxia when breathing the gases pure. Of course, it was all right to add some oxygen to the two gases but this did slightly spoil the experiment because it made the contrast between the two gases less marked.
We had some helium back in the lab. Even before I had put the book back on the shelf I had decided to try the experiment out, at least with the helium. I would not bother with the sulphur hexafluoride, as I had no idea how difficult it would be to get hold of some. I knew that the difference in density between helium and air would be enough to produce a contrast in note, even if it was not so striking as the Glausers had described.
When I got back to the lab I put a small quantity of helium in an anaesthetic rebreathing bag. Then I breathed out as far as I could, put the bag to my lips and breathed in till the bag was empty. At this point I took the bag away from my lips, opened my mouth and breathed in air until my lungs were as full as I could get them. Here goes then; I breathed out slowly and steadily singing a long constant ‘aaaaaaaaaaaaaaah’ as I did so. I was almost out of breath when, at last, the low pitched ‘aaah’ suddenly shot up the scale to become a high-pitched ‘eeeh’. The helium that I had breathed in first really had been the gas I had breathed out last! Of course, when you came to think about it, it was only what you would have guessed and expected, but it had been fun all the same.
I wondered briefly if you could use this as a test of lung function; if someone had diseased lungs with abnormal air distribution and unequal alveolar filling, perhaps the point of change of the note would not be so precise. Still it was unlikely to be useful in clinical practice any more than the paper I had once read that proved that people with bad lungs had a partial pressure of nitrogen in their urine which was different from healthy people.
I had a nasty headache for the rest of the day. It might have had nothing to do with the helium, but all the same I decided never to breathe it again.
A.D. 1974
It was on impulse that I phoned the Department of Molecular Enzymology. I had discovered only the week before that one of the authors of a much quoted paper about anaesthesia at the molecular level was working in the university. He and some others had demonstrated that a molecule of xenon would fit inside a cleft in a molecule of myoglobin[1], which is a large protein found inside muscle cells. Now xenon was already known to be capable of producing anaesthesia, which seems quite remarkable for something so chemically inert; now we knew it would actually fit inside a large protein molecule. If it could do that anything was possible; perhaps its presence altered the shape of the larger molecule or changed its electrical charge somehow, and this might be the sort of thing that produced anaesthesia. When I got through to his secretary she said it would be all right to call in any time I wanted. So I said I would be there sometime during the afternoon.
When I arrived I was shown into a huge L-shaped room which was filled with vast machines that I guessed were for determining the resonance of crystals. These machines were surrounded by earnest intelligent-looking young men who were standing around clearly waiting for Nobel prizes to fall from the sky. I was quite overwhelmed by it all. I was reminded of the first ward round I had attended in a Swedish hospital; I had stood around, just like I was now, pretending that I understood what was being said but in reality not having a clue.
Herman Watson came across to me and waved his arm expansively.
‘Here,’ he said, ‘is a model of ATPase.’
He gestured towards an enormous molecular model looking like a myriad of Lowry clockwork men. ‘We only need to sort out this tiny bit here to have the secret of life in our hands.’
One of the young men came up to him excitedly with some information on a computer printout. They looked at it together for a few moments.
‘It will be midnight before it’s finished,’ the young man said.
‘Or later. It could be the small hours. Who is going to be here?’
‘I am,’ came the reply.
I tried to explain why I had come. I don’t think he was really listening to me, he was so engrossed in what he and his colleagues were doing. It was probably just as well because I had not thought through what I was expecting from him, and he was far more interested in telling me about his own research than in listening to my unformed ideas.
‘Let me know if I can help you at any time,’ he said firmly, his attention already back in his own world.
‘Yes, I will.’
I walked away totally overwhelmed. Of course, I had known all along that I was only a scientific babe-in-arms; now it had had been fully confirmed.
‘What did he say?’ Sheila asked me when I got back to Southmead.
‘I don’t really know,’ I replied. ‘I was out of my depth altogether. But it seemed very exciting whatever it was. I sometimes wonder if I wouldn’t be better working for the NHS instead of the University. Perhaps I’ll move across one day.’
Still it had been fascinating to meet him. When next I came across reference to xenon fitting inside the myoglobin molecule I would have a notion of what that sort of research was really like.
A.D. 1980
‘What do you think is the third most abundant gas in this operating theatre?’ I asked the young student who was working with me, while we were waiting for the next patient to arrive.
‘Oh, carbon dioxide I should think.’
‘No, that’s certainly not right. It might sometimes be the fourth, but never the third. You should really be countering my question by saying it depends on how full the cylinders at the back of the machine are, and how big the theatre is.’
‘Oh, you mean including the gases in the cylinders? I hadn’t thought of them. How full are they?’
‘For the moment let’s assume they are all full.’
‘And how big is the theatre?’
‘We’ll have to count the squares on the floor. You do the width and I’ll do the length.’
The floor was twelve squares wide and eighteen squares long. I knelt down and measured one of the squares; it was exactly two spans of my outstretched fingers which I knew meant it was eighteen inches across. So the floor was 12ft by 18ft, or six yards by nine.
‘We’ll need it in metres if we are going to make any sense of it. How many square metres are 54 square yards?’
‘My watch will tell us; it’s got a calculator built into it. Now let’s see: 54 times 36, times 36, divide by 39, divide by 39, equals 46. So the floor area is 46 sq metres.’
‘What about the height? I’ll stand against the wall; I’m 6ft 1inch. How much is there above my head?’
‘I’ll use the drip stand to measure it... Here, that’s the distance from the ceiling to the top of your head.’
I measured it with my hand span again. The height above my head was six spans.
‘6ft and one inch is 73 inches, plus 54... is 127, divide by 39... is 3.26 metres. So the theatre is 46 x 3.26 = 149.96 cubic metres, which is 150 in nice round numbers, isn’t it? Now how much nitrous oxide is there in a full cylinder?’
‘I don’t know.’
‘It tells you on the label. Have a look.’
‘It says 1800 litres.’
‘And the carbon dioxide?’
He looked at the grey cylinder.
‘450 litres.’
‘So which is the third most abundant gas in the room?’
‘It must be nitrous oxide.’
‘Yes, if the cylinder is full. And the fourth?’
‘That will be carbon dioxide, then.’
‘No, you have forgotten about argon; everyone forgets about argon even though we breathe nearly 1% all our lives. Now if this room is 150 cubic metres then 1% is 1.5 cubic metres, which is how many litres?’
‘Let me see. A litre is a cubic decimetre so there are a thousand litres in one cubic metre, and 1500 litres in 1.5 cubic metres.’
‘So there will always be more argon than carbon dioxide, though there will be more nitrous oxide than either of these if the nitrous oxide cylinder is more than 5/6ths full. Now we can’t tell how much nitrous oxide there is in a cylinder by looking at the gauge, because it liquifies under pressure, and, so long as the temperature is constant, the pressure above the liquid stays the same whether it is full or almost empty. We could weigh the cylinder, of course, or we could tap it and tell from the note, though I can’t tell middle C from top A myself. Anyway it means that if the all the cylinders are full the third most abundant gas in the room is nitrous oxide, the fourth is argon and the fifth is carbon dioxide; if the nitrous oxide cylinder is less than a quarter full while the carbon dioxide is full then the third gas would be argon, the fourth carbon dioxide and nitrous oxide would be fifth.’
‘But what if all the cylinders were empty and the surgeon had had beans for supper?’
We both laughed. He had a good point there!
‘Talking of argon, how anaesthetised are you at this moment?’
‘Anaesthetised? What do you mean? Is argon an anaesthetic?’
‘Yes, it is - at a pressure of about 15 atmospheres. Nitrogen is, too, at about 20 atmospheres; you will have heard of ‘nitrogen narcosis’ in divers; that’s just a form of anaesthesia. Oxygen is probably anaesthetic at about 15 atmospheres.’
‘But I thought that oxygen at high pressure made you convulse.’
‘So it does, but 15 atmospheres is the concentration predicted to be anaesthetic from its solubility in oil, and there is some work... Anyway we can say that as far as nitrogen is concerned we are breathing 4/5ths of 1/20th of an anaesthetic dose. For oxygen it is 1/5th of 1/15th, which is a 1/75th, and for argon 1/100th of 1/15th, which is a 1/1500th. If we add 1/25 and 1/75 and 1/1500 it comes to 1/19 or thereabouts. So we can say that we all spend our lives one nineteenth part anaesthetised.’
‘No wonder I sometimes feel sleepy during lectures!’
A.D. 1990
‘Isabel, I’ve told Chris that we will have another journal club at our house one evening in November. Is that ok?’
‘Yes, certainly. I was thinking only the other day that it was time we had one of those. I’ve got a huge lasagne in the freezer, which has been there for over a year, and it needs eating up. I was going to have it sometime over Xmas week last year but never got around to it. We’ll have it with some salad and some garlic bread.’
‘Sounds delicious! Can we have some now?’
Isabel laughed.
‘You and your stomach, John! We have only just finished supper.’
‘I thought that I would get one SHO, one registrar, one senior registrar and one consultant, which will be me, of course, to review things of interest to anaesthetists that appeared in non-anaesthetic journals, say the BMJ, the Lancet, JAMA, and the New England Journal of Medicine.’
So I farmed out three of the journals to Karen, Janaan and Ian. I chose the Lancet for myself as I always enjoyed reading it when I made the time, which was always the problem.
So I went off to the library and settled down to the last four months Lancets. In the July 7th issue there was an interesting comment by Diana Brahams in the Medicine and the Law column concerning Age and the medical experts, which dealt, amongst other things, with a dispute between a retired professor of anaesthesia and one still actively in post. I would certainly mention this. It was great stuff:
Ideally, a medical expert should be at the peak of his powers and independent and willing to appear for plaintiff or defendant as the occasion arises. In practice, experts would sometimes have retired.
Clumsy sentence that! How did she get a subjunctive in there?
... the doctor who has retired from full-time practice will have more time and probably fewer inhibitions about criticising his colleagues skills.
She went on to report a case where a judge had been critical of a long retired neurosurgeon whom, in effect, he blamed for the pursuit of a case.
In dismissing the plaintiff’s claim, the judge suggested the Legal Aid Board should see what could be done... ‘to prevent complex claims from being supported in future at public expense on the uncorroborated evidence of a consultant who has retired from practice so long ago’.
And then there was the bit about the two anaesthetic professors:
Only two months before this court decision Anaesthesia News had published an article... that was highly critical of the part played by some consultants in encouraging litigation by plaintiffs. In March 1990 Anaesthesia News had to publish an apology... had complained that the article had been understood to refer to him... Anaesthesia News had paid ... damages and costs.
Well, I wondered what had been the real meat of that story. I was particularly interested as I had known one of the two professors involved when I had been a medical student at Guy’s and I had met the other many years ago at a meeting of the Anaesthetic Research Society and had heard him describe himself as ‘an iconoclast’. I had always wondered exactly what he meant.
I moved on to the next issue. Now what was this?
Uncertain future of the NHS. The parliamentary battle is over. The National Health Service and Community Care Bill has become an Act.
Yes, and what a shambles it has been! How any one could have introduced change of this magnitude without proper pilot studies I will never understand.
The politics begins almost immediately with the delivery of a 27-page booklet to all 20 million homes in the country extolling the virtues of the Government’s changes. This is costing £2.75 million, which the Opposition parties, with justification, have suggested should be billed to the Conservative Party rather than the Department of Health.
Hear, hear! I glanced further down the page. Oh, yes. I like this:
Like Humpty Dumpty, Kenneth Clarke has his own definition of the meaning of words: Consultation, n, a period of time in which the central government finalises its instructions for institutions at the periphery.
Brilliant! I’ll certainly quote that remark. I turned the page.
Round the World.
USA: Danger from electromagnetic fields
It seemed that the American Environmental Protection Agency had just published a paper discussing whether electromagnetic fields could cause cancers. The original version of the paper had been shown to White House staff and other health agencies and some of the more startling recommendations had been deleted, though the final document still said that studies of electromagnetic fields and cancer among children and electrical workers ‘show a consistent pattern of response that suggests, but does not prove, a causal link’, and recently a paper in the American Journal of Epidemiology has recommended that women who were pregnant should not use electric blankets. A bit scary, really!
A few pages on my eye was caught by a headline over a letter:
Xenon in Anaesthesia
The letter was from the Clinical Research Centre at Harrow: it referred back to an article that had appeared in the Lancet in June extolling the virtues of xenon as an anaesthetic. It pointed out that xenon was 2000 times as expensive as nitrous oxide and it would cost £8000 to fill an cylinder with xenon, and that even if the price was reduced there would be a lot of research needed to put it on a proper scientific footing.
I would have to read the original article, but as that would mean getting up from my comfortable chair I decided to skip through the rest of the journals I already had by my side.
Can life-style changes reverse coronary heart disease?
Yes, apparently they could.
Health hazards of volcanic gases
Apparently a sudden release of gas from a crater lake in Cameroon in 1986 had killed 1700 people. Now there were worries about a volcano in Northern Italy which was getting hotter and giving off more gas, including CO2, SO2, H2S, HCl, HF and radon. Sounded nasty!
Scientists can limit exposure to volcano gases by working in fine weather with frequent rests for fresh air, by standing on the windward side of vents..
Sounds like anaesthetists before they introduced theatre scavenging systems!
... and by wearing full-face respirators with cartridges... Daily CO2 emissions amount to 180 tonnes from the crater and 30 tonnes from the surrounding soils. Ground emanations on parts of the island can be high enough to asphyxiate burrowing animals, feeding birds, and even goats.
Sounded like something from Burl Ives! Still it was certainly interesting.
About eight years ago two children were asphyxiated whilst attempting to retrieve a football from a well... The risk of lung cancer from radon gas is now well recognised... another hazard is the contamination of ground water by H2S and minerals, most of the island’s well water being undrinkable.
I decided we would not go visiting any volcanoes next summer! I moved on to another of the journals. Here was another Medicine and the Law.
Ownership of a spleen: earlier this month, a high court in California ruled that a patient did not hold the rights to body tissue removed in an operation and later used to develop new treatments.
Apparently a man with hairy cell leukaemia had had his spleen removed and his doctor had found the cells to be unique and had taken out a patent on them, and then had sold the cell line to a biotechnology company for $3 million. Now the patient wanted a share of the spoils. Personally, I could not blame him.
Here was another letter about xenon. Someone complaining about the earlier letter:
Since Lachmann et al have demonstrated that a xenon and oxygen mixture can induce a state of anaesthesia and is superior to nitrous oxide, where are the grounds for demanding further controlled studies?
I had wondered myself if the first letter had not been just slightly... what’s the right word to mean something like ‘unnecessarily dismissive’, though its message had been correct enough. I really would have to get the original article. Particularly as I now saw it was published on June the 16th, my birthday.
Finally I did get up and collect the June issues. Here it was:
Safety and efficacy of xenon in routine use as an inhalational anaesthetic. Prof Lachmann and his colleagues had compared, in 40 patients, xenon and nitrous oxide as anaesthetics and their effects on the cardiovascular and respiratory systems.
I read it carefully. It really did seem to be a satisfactory agent. How remarkable that it had surfaced again after being buried for so many years.
It is non-explosive; probably does not undergo biotransformation; is non-toxic; and offers rapid induction and recovery from anaesthesia... more expensive... limited experience... 40 patients... either xenon/oxygen (70/30) or nitrous oxide/oxygen (70/30)... closed circuit... double-blind... fentanyl added if blood pressure rise more than 20% above baseline... groups comparable... changes in BP significantly less in xenon group... five times more fentanyl needed in nitrous oxide group... recovery time from anaesthesia similar in both groups similar... patients treated with xenon reported ‘nice feelings and pleasant dreams’... absence of cardiovascular side-effects... xenon does not present the problems and hazards to patients, medical and nursing staff, and the environment that nitrous oxide and volatile anaesthetics do... average per procedure only 10 litres... closed circuit... cost reduced... not differ substantially from those of other anaesthetic procedures.
So that was it. As we had always known, it depended on cost, and if that was soluble, which I doubted, on whether there were important disadvantages that were not yet known. Of course, the Harrow folk had been right; there would have to be careful studies, but then if the cost problem was solved there was no reason to think that the appropriate studies would not be undertaken in the correct manner. I guessed that nothing would come of it, but wouldn’t it be interesting if it did turn out to be feasible after all to use an inert element as a anaesthetic.
The journal club meeting was a great success. Gina and Janan presented some interesting articles and Ian followed them with some amusing comments.
Isabel called us to supper before I got around to mentioning xenon. The lasagne was delicious.
NOTES
[1] Miller et al. (1973) The pressure reversal of anaesthesia and the critical volume hypothesis. Mol. Pharmacol.. 9:131- 143.
[2] Halsey MJ et al. High -Pressure Studies of Anaesthesia, in Molecular mechanisms in Anaesthesia, edited by Fink BR, Progress in Anesthesiology, Vol. 1. Raven Press. NY 1975.
[1] However Macintosh and Pratt recommend that ‘a boxwood mouth opener is only used by the patient, so ensuring that sufficient force will not be used to break his teeth’ - p242 in Essentials of General Anaesthesia. Blackwell Scientific Publications, Oxford, 1940.
[1] Schoenberg BJ, Watson HC and Kendrew JC (1965) Binding of xenon to sperm whale myoglobin. Nature. 207:28.
email johnpowell@uk2.net
