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New Site....

Image by Indian Boy via FlickrWell, the new site is coming along nicely, and hopefully we'll have some interesting content to go with the blog as well!

Do come back to see when it's up, which should be very shortly!

Potential questions?

One of the hot topics at the moment in hospitals is something called the "Saving Lives Campaign", basically all about reducing HAI (hospital acquired infections). If you don't know anything about it, don't worry too much, BUT you should be aware that there are several potential questions for the SAQ and the viva brewing as a result of it.

One of the two main drives is about cannulation and insertion of intravenous lines, and how to reduce infection as a result of careful use of skin cleansing for both peripheral AND central lines (Not sure there's a huge amount of evidence for that as far as peripheral lines are concerned - Ed.) Also, insertion of urinary catheters has been targeted, use of enteral feeding systems, and how to do it properly, and the prevention of spread of infection by hand washing, safe sharps disposal, good aseptic technique and use of PPE (Personal Protective Equipment). (See this page at www.clean-safe-care.nhs.uk (!! When will the Vieux Boulogne come to an end? - Ed.))

I would just like to bring to your attention this quote from the RCOA Commentary on the April SAQ

The SAQ paper was set on February 28th 2008. At this meeting the members of the SAQ group noted
that some of the repeat questions continued to be poorly answered, and that questions relating to
issues of public interest and patient safety were poorly done. Although matters relating to patient
safety are not textbook knowledge, they will continue to be part of the syllabus and candidates can
expect that the examiners will emphasise this important aspect of the College’s work.

What this means is that you definitely need to be aware of stuff coming out of the NPSA and NICE as related to anaesthesia and medicine in general, and we will bring you some more information on those kinds of things when the new website goes live at the beginning of next week! More on that in another post...

MCQ Answers

1. The following are associated with a decrease in muscle strength/power:
A. Eaton-Lambert syndrome - TRUE
Myasthaenic syndrome is associated with a decreased release of Acetylcholine from the nerve terminal, and therefore patients will have decreased strength.

B. Fallot’s Tetralogy - FALSE
Sorry, we just made that up. You can find out all about the Tetralogy of Fallot by looking at this link (http://www.emedicine.com/med/topic3579.htm)

C. Treacher-Collins syndrome - FALSE
This one too. Treacher-Collins is a syndrome known by several other names. As a hater of eponyms (and I would hate to inflict my name on future students of medicine for some little known group of signs or symptoms), I would rather people just called it mandibulofacial dysostosis. Read about, and see photos of patients with it, here (http://www.treachercollins.net/syndrome.html). Once you have seen the gallery of photos, you will not forget it. It is important to anaesthetists because of the associated airway problems that may arise.

D. Guillain-Barrè syndrome - TRUE
Need we say more?

E. Kawasaki disease - FALSE
Nope. This is an acute febrile vasculitic syndrome of early childhood. There is increasing evidence for an infective cause. The vasculitis is most can occur in veins, capillaries, small arterioles, and arteries. characterized by fever, rash, conjunctival injection, cervical lymphadenitis, inflammation of the lips and oral cavity, and erythema and edema of the hands and feet.

2. Tetanus
A. is caused by the Gram-positive bacillus Tetanus botulinum - FALSE
Um, no. It’s a Gram-positive rod-shaped anaerobic bacterium called Clostridium tetani.

B. has an incubation period from 1 to 36 days - FALSE
The incubation period is 3-21 days.

C. is fatal >50% of the time - FALSE
Mortality in untreated patients is apparently up to 45% (66% in neonates), with treatment <10%, the rate in those who have received 1-2 doses of vaccine previously being approximately half that of the unvaccinated. (http://www.patient.co.uk/showdoc/40000432/)

D. is associated with myocardial infarction - FALSE
Nope.

E. can be prevented by vaccination with inactivated tetanus toxoid which should be boosted every 3 years. - FALSE
Vaccination is a core tenet of the childhood vaccination program. Its normally given as part of “triple vaccine”, followed by boosters at school entry and leaving. It is thought that 5 doses likely to confer lifelong immunity. Additional boosters may be given to travellers to areas where medical attention may be unavailable,(and likely to sustain at-risk injury) if last dose >10yrs ago, even if completed 5 dose schedule.

EXCITING NEWS....(and a less exciting few MCQ)

As a part of a drive to bring you better intelligence we are developing a new website. This will be up and running very very shortly. We're just learning how to operate the more sophisticated parts of our webhost, which is a stunning machine based in the US, with ridiculous amounts of bandwidth, power and storage, so keep checking back.

In the meantime, for a little fun, we thought you might like to see some MCQs, which are definitely different from the ones you'll have seen elsewhere:

Some of them will be at the same level, some will be harder, some will be easier, and some of them will be plain ridiculous (and therefore tagged as work distraction).

So:

1. The following are associated with a decrease in muscle strength/power:
A. Eaton-Lambert syndrome
B. Fallot’s Tetralogy
C. Treacher-Collins syndrome
D. Guillain-Barrè syndrome
E. Kawasaki disease

2. Tetanus
A. is caused by the Gram-positive bacillus Tetanus botulinum
B. has an incubation period from 1 to 36 days
C. is fatal >50% of the time
D. is associated with myocardial infarction
E. can be prevented by vaccination with inactivated tetanus toxoid which should be boosted every 3 years.

Critical and Pseudocritical Temperature

Image via Wikipedia Critical Temperature is the temperature above which, no matter how much pressure you apply, you cannot force a gas to become a liquid. Interestingly enough, though, if you apply sufficiently high pressures, you can form a solid. Essentially, distinct liquid and solid phases of a substance no longer exist.

If you measure the vapour pressure of a substance at the critical temperature, that pressure is called the critical pressure. Alternatively it could be defined as the pressure which is required to liquefy a vapour at its critical temperature.

A substance is a vapour when it is in equilibrium with the substance in another phase, and a gas when there is no liquid or solid present. Therefore, by definition, except at the extremely high pressures mentioned above, any substance above its critical temperature, is a gas. A liquid does not have to boil, nor a solid to sublime (change state directly from solid to vapour/gas-Ed.) to form a vapour. You can draw a serious of lines, plotted on a graph where the x-axis shows volume, and the y-axis shows pressure, which correspond to different temperatures and called isotherms, which demonstrate what will happen to a substance as you increase temperature with a given volume (or pressure). The one with most relevance of course is nitrous oxide...(see here).

Pseudo-critical temperature is the critical temperature of a mixture of gases. In anaesthesia it is commonly used to describe the temperature at which a 50:50 mixture of oxygen and nitrous oxide separates (laminates) forming liquid nitrous oxide and gaseous oxygen, which occurs at (depending on the pressure) temperatures in the range -7 to -5.5 degrees Celsius in cylinders, and lower temperatures in a pipeline (due to lower pressures) at around -20 degrees Celsius.

Book Review: Final FRCA Short answer questions by Nikells et al

FINAL FRCA Short answer questions by James Nickells, Maan Hasan, Vino Ramachandra and Neville Robinson (ISBN: 0-7279-1289-5; Publisher: BMJ Books)


Published way back in 1998, this book is looking a bit dated now, and that's not just in terms of it's cover, but also it's typeface (better known as font, nowadays). The layout is in the form of nine exam papers which are the same format as the current paper, and include some old favourites, such as writing notes on statistical tests, describing the anatomy of the trachea, stress ulcers in ICU and anaesthetising in an MRI. From this point of view it gives you the opportunity to set a timer, and sit down and do "a practice paper under exam conditions".

The model answers are simply laid out with bullet points and subheadings given to show a suggested framework, and the explanations are generally short and sweet. The questions chosen for inclusion were quite cleverly chosen for the principles of management and principles of answering, and answers are still applicable today. However, because the book is from 1998 some of the answers can be out of date and/or dated. For example magnets are no longer recommended for routine use (Anaesthesia 2006) with pacemakers. After a prolonged re-read, however, no massive glaring problems were discovered, and any issues there are with answers are fairly obvious, on the whole, and should only cause a minor irritation to the reader.

Less wordy than some other SAQ books in its answers, this proved a useful revision aid for it's simle layout and simple answers. There are no "for extra bonus points" points, instead the authors stuck to the KISS principle. (Keep it simple, silly - Ed.)

Would we recommend it? Difficult one. Questions in this book are covered in other books which also cover more topics. I preferred the style and layout of the answers in this to some of the other books, but not everyone will do. Overall, it wouldn't be top of the list, because other books have slightly more to offer, but it's a useful adjunct to revision.

Another Hot Topic

If like us you are a member of the AAGBI then you will recently have received a copy of their latest glossy on Red Cell Transfusion. Sadly they don't appear to have put it up on their website yer, and we've not had time to review it, but we will try to keep an eye on the website and put up a link as soon as we can.

Keep an eye on the site as we get closer to the closing date for entry and we will put up a list of what we consider are likely to be the hot topics from the previous 12 months. Also, watch James Shorthouse's blog over at Passing the Final, as he keeps a good update going, which often includes the hot topics.

Random Factoid: Perlite

Image via WikipediaEver wondered what Perlite is?

It's the stuff that goes in between the two layers of steel in a Vacuum Insulated Evaporator (VIE) which is used for storing about 10 days worth of oxygen on hospital grounds.

It's a form of volcanic glass, which when heated expands from being a glass to being about 10-15 times the original volume. This means that it becomes very low density, and also acts as a good insulator.

It is also used in plaster (as in for walls) and in hydroponics because it's very good at holding water.

Needle-stick injuries; and consent

We're back!

EI has been on holiday in sunny sunny Spain (y Viva España...), although we didn't take a plane to the Costa Brava or anything like that. In fact, we were in one of the highest villages on the Iberian Peninsula, so look out for an altitude physiology article to follow.

In the meantime, a question regarding needlestick injuries has come in, i.e. are there any definitive guidelines. The answer is that there are several documents which have various aspects about what to do when suffering a needlestick injury. We have tried to bring you the ones we consider the most important and most relevant. Also, every trust will have its own set of guidelines, and these should be available from your Microbiology department, A&E (or Emergency Medicine) department or on your hospital intranet.

Take a look at the following links:

DoH Guidance for Clinical Health Care Workers: Protection Against Infection with Blood-borne Viruses (see section 5.12 onwards) (which could be considered definitive)
DoH guidance on Post-Exposure Prophylaxis for HIV
Patient Plus report on Needlestick Injury

Consent

Whilst were on this, and as a result of the fact that there were references to consent for testing for blood-borne viruses, the GMC has published new guidance: Consent: patients and doctors making decisions together.

Bearing in mind that the new Mental Capacity Act 2005 (MCA2005) has now come into force, I would keep a look out for Consent as a hot topic. The AAGBI published guidelines in 2006: Consent for Anaesthesia. Also, the BMA has published guidance on the Mental Capacity Act here.

Consent for anaesthesia has always been a debated topic. Should we take written consent? What risks should we explain? Should we explain nothing at all if the patient tells us just to do what we think is best?

Intensive Care is the area which brings up more issues on consent and capacity, however, as the new Act directly impacts on what will happen. In one trust we are aware that the Consultant in ICU have requested an Independent Mental Capacity Advocate (IMCA) be present at all Multi-disciplinary rounds in order to ensure that they are complying with the Act...

If you want to find out more about the MCA2005, take a look at this link, which explains it all in very simple terms. For something more substantial, try the links on this page.

Adiabatic change

EI has been asked about this concept, and spent some time trying to explain it. However, although EI understood the concept, it actually became quite difficult to explain. So we’ve thought about it some more, and here is our attempt at trying to explain it.

Firstly, an adiabatic change is one in which NO HEAT is TRANSFERRED TO or FROM a fluid (gas/liquid) doing work, or having work done on it. Normally this occurs when there is a change in pressure in a gas.

In other words, as a gas is compressed, it’s temperature will increase. Have you ever pumped up your bicycle tyre, and the nozzle or barrel of the pump has got really hot, almost too hot to touch by the time you’ve finished pumping the last bit of air in? That’s because of adiabatic HEATING. Diesel engines work on the same process of compression generating enough heat to cause ignition. There is no external source of heat, but the temperature has still increased. This must all have come from the act of pumping, i.e. pressurising, the air. The energy of the pumping has been converted to heat energy (internal energy) of the compressed gas.

Conversely, if a gas is suddenly allowed to expand, it will cool. A CO2 fire extinguisher (They used to be solid black, didn’t they? Now we’ve just got those EU compliant red things with different labels on. How the hell are you supposed to recognise the difference in a hurry now?? – Ed.)…when it is used, or any gas cylinder opened and allowed to vent suddenly will rapidly cool. In fact, if you are using a CO2 extinguisher, don’t put your hand on the funnel, because it might freeze to it. Why does this happen? As the gas expands, it does work on the surrounding air, pushing it out of the way. Since energy cannot be created or destroyed, merely converted from one form to another, the energy has to come from somewhere, and it comes from the internal energy of the gas doing the expanding, which we conveniently refer to as temperature.

So, as a gas is compressed or expands rapidly, it’s temperature changes, but no HEAT energy has been transferred into or out of the system. If heat is added to or lost from the surroundings, this is NOT a-diabatic. So for example a gas expanding as a result of being heated is not adiabatic, and a gas contracting as a result of being cooled is not adiabatic either. These processes involve a transfer of heat energy.

Eventually, after the sudden compression or expansion, there will be a transfer of heat energy, but at the time of the expansion or compression, there is not.

And that, in a nutshell, is adiabatic changes.

(It also happens with magnets, apparently, and they’re not fluids…- Ed.) Okay, yes it does happen with magnets, but don’t try and complicate the issue. (If you want to know more, see Adiabatic Demagnetisation on Wikipedia, but make sure you have your maths head on. You have been warned!)

Usually drink, usually dance, usually bubble

EI has relations with a Street Style blog over at Stitsh.com, and recently a little vid caught our attention over there. Click here and scroll down to 28.06.08.

It reminded us of a little law that the examiners sometimes like to question, that is Henry's Law:

At a constant temperature, the amount of a given gas dissolved in a given type and volume of liquid is directly proportional to the partial pressure of that gas in equilibrium with that liquid.

Okay, so what does that mean.

Most of the time we refer to Henry's law by the formula p=kc (that's one way of looking at it - Ed).

Another way is to say:

where:

is approximately 2.718, the base of the natural logarithm

is the partial pressure of the solute (the gas being dissolved) above the liquid in which is being dissolved.

is the concentration of the solute in the solution

is the Henry's Law constant, which has units such as L·atm/mol, atm/(mol fraction) or Pa·m³/mol (this is so that the dimensions all work out correctly - the funny thing about constants is that they usually can be expressed in many different units, depending on what units the rest of the equation is being calculated in....more on that another time).

(In other words, most of the time, we take the natural logarithms of both sides).

The pressure above a solution dictates how many collisions occur between the gas and the liquid. So if you increase the pressure above the solution, the partial pressure of the gas increases, the number of collisions increases, and more gas is dissolved. What will then happen is that an equillibrium will be achieved, where the number of molecules of gas crashing into the surface of the liquid will be the same as the number of molecules leaving the surface of the liquid.

The more observant amongst you will have realised that temperature hasn't been mentioned yet except in the definition....

So what effect does temperature have?

Well, think of a can of "fizzy pop" (you're showing your age there - Ed). When it comes out of the fridge, it's not that fizzy, is it? However, the longer you leave it standing around, the closer it's temperature comes to room temperature, and then when you go back to the can, first it will seem quite gassy, and then eventually it will go flat. This is because the gas in the drink is coming out of solution. The gas solubility relationship with temperature is very similar to the reason that vapor pressure increases with temperature. (This is Gay-Lussac's Law: The pressure of a given number of moles (given amount) of gas, is directly proportional to its temperature in Kelvin (absolute temperature scale), when the volume is kept constant. Better known as P/T=k).

Increased temperature causes an increase in kinetic energy, which in a gas causes either expansion or an increase in pressure, or in this instance, more movement of the molecules, which break free of the surface of the solution! (The surface could be the gas side of a small bubble of gas trapped within the solution, which is one reason we get bubbles!)

If you want to see another demonstration of Henry's law in action, look at a pan of water. As you warm the pan, small bubbles start to form, well before the pan reaches 100°C (373K). Those bubbles are air coming out of solution.

So why do the examiners like this concept: the Bends.

Decompression Sickness occurs when gas (specifically nitrogen) is breathed at higher than atmospheric pressure, and the diver then returns to atmospheric pressure without allowing the gas to come out of solution slowly, resulting in gas bubble formation, and hence, "the bends" (gas in the joints) and "the staggers" (gas bubbles in the brain causing confusion and ataxia) and "the chokes" (probably PE).

It is also a concept that comes into play when talking about Ostwald and Bunsen coefficients....(more on that another time).



(Equations courtesy of Wikipedia)

Lurking in the background? Lurk no more....

To all those readers out there who are lurking....we know you're there....see that little counter at the bottom?

Please help EI improve. Leave a comment, an email, a request. If you have a problem, if no one else can help, maybe we can.

And you can bet that there are others out there struggling as we did...

We've become skilled at seeking out the information and presenting it to each other in a simple understandable manner, and have accumulated notes over some considerable period of time to draw on. So if you're struggling with something, let us know! We'll learn something too!

Don't know much about history....

Did you know that cyclopropane was discovered in 1881 by August Freund?

It's chemical structure can be represented in standard molecular shorthand by a simple equilateral triangle, because each Carbon has 2 bonds to other carbons, and is bound to 2 hydrogen atoms as well.

It's mixture with oxygen is highly explosive, because it breaks down to form linear propane, which is itself a potentially explosive reaction, and there is a reaction with the oxygen as well!

And we used to use this as an anaesthetic gas....