Oops

I drew up some saline from the drawer in the birth suite to flush the cannula before putting in an epidural.

When I checked again I found that the drawer was filled with a mixture of saline and lignocaine.

 

 

 

 

 

 

BT_RA1.3  Discuss the pharmacology of local anaesthetic agents including:
· Mechanisms of action
· Comparative pharmacology of different agents
· Toxicity
· Use of adjuvant agents to enhance the quality or extend duration of block
· Pharmacokinetics of drugs administered in the epidural and subarachnoid space

 

 

 

 

 

If I had given the 20mls as an intravenous bolus:

T/F The best volume of distribution to estimate the peak plasma concentration would be V area.

T/F The most likely arrhythmia to occur would be Ventricular Fibrillation

T/F Seizures occur at a plasma concentration of 5µg/ml

T/F Cardiac arrhythmias occur at a plasma concentration of around 2 times that which cause seizures

T/F Lignocaine causes dose dependent negative inotropy

Bonus questions:

Why is bupivacaine more cardiotoxic than lignocaine?

Is ropivacaine less toxic than bupivacaine?

Why should you treat the seizures?

Pharmacoeconomics of volatile anaesthesia

BT_GS 1.23 Describe the physical properties of inhalational agents, including the principles of vaporisation

Following on from yesterday’s post is another about volatile agents.

While pharmacoeconomics is not part of the primary exam it does have an LO in the curriculum (AR_MG 3.2) but the answers to most of the following questions require primary exam knowledge.

1. Demonstrate that liquid volatile usage in ml per hr, for agents used in 2017, is approximately 3 x fresh gas flow (l/min) x inspired concentration (%)
2. Estimate the amount of sevoflurane used the next time it is part of your anaesthetic.
3. Some anaesthetic machines will provide you with an exact usage.  See how close you can get with your calculations.
4. How much did the sevoflurane cost?

Schrödinger’s Registrar – Part 2

BT_GS 1.23 Describe the physical properties of inhalational agents, including the principles of vaporisation

Yesterday the following was asserted:

“You will be anaesthetised if you smash a bottle of sevoflurane in an anaesthetic room (assume the air-conditioning is broken and the doors are sealed)”

If you had some trouble coming to a conclusion then here are a few hints:

Assume the sevoflurane completely vaporises.

Assume the room is a certain size – e.g. 5m x 4m x 3m

How much gaseous sevoflurane is produced from the liquid sevoflurane?

Avogadro is important here (PV = nRT)

What concentration of sevoflurane will cause anaesthesia?

Tomorrow, we will be looking at the reverse situation – i.e. how much liquid sevoflurane is consumed from a certain amount of gaseous sevoflurane.

 

 

 

 

Schrödinger’s Registrar – Part 1

BT_GS 1.23 Describe the physical properties of inhalational agents, including the principles of vaporisation

This LO has been the subject of previous posts, but volatiles and vaporisation are core knowledge and a detailed understanding is important.

Today there is only one question.  You can treat it as a True/False statement or consider a longer answer by treating it as a discussion point.  You decide which will lead you to greater understanding.

This question will require you to make a few assumptions in addition to the two provided. See if you can varying those assumptions to change your conclusion.

“You will be anaesthetised if you smash a bottle of sevoflurane in an anaesthetic room (assume the air-conditioning is broken and the doors are sealed)”

If you are having trouble with this question, stay tuned for hints tomorrow.

 

Evolution of a viva- Part 1

Before you get your hopes up I will not be revealing the intimate details of a viva but I will attempt to convey some of the thought processes that are employed in the creation of a viva. I can only speak for myself here but I suspect my colleague examiners do similar things.

It begins with an idea (as do most things) which is often formed during the actual viva exams. I think to myself, “Gee the candidates don’t know much about basic propofol pharmacokinetics.” Often this thought is engendered as I watch a colleague examine on a particular topic. I like to examine on topics that satisfy a few criteria:

• I think anaesthetists should know this stuff
• The topic is clinically relevant (hopefully these two aren’t mutually exclusive)
• I have seen a knowledge deficit about the topic in my trainees (if they already know it then someone else can ask them that!)
• The ‘answers’ or responses I want need to be in the set texts (this can be quite difficult and has scuppered a few viva ideas along the way)
• Another person with a FANZCA would at least understand most of what the viva was getting at
• The nature of the topic lends itself to being asked in a viva format

Once I have the idea I write down what the main points I want candidates to demonstrate an understanding of are. (I also need to make sure there is a learning objective pertaining to the viva!!) Each viva topic is only five minutes long so the path to pass responses needs to be direct and hopefully short. Next I hit the books and confirm that the topic is adequately covered. Occasionally I discover that my understanding of the topic is at odds with what the books say! Not uncommonly I may have to look at six different books and it is frustrating for all of us if they say six slightly different things. Next I need to formulate the questions to get the information I want. Each viva should ideally start with a simple and brief question to allow the candidate to answer the opening question correctly and begin in a good frame of mind. So, for a propofol PK viva I might ask “What is the induction dose of propofol for a healthy unpremedicated 20 year old?” Subsequent questions need to flow on naturally from the opening question. I like a diagram or two in a viva but it needs to be simple and easily drawn. Sometimes it may be better to provide a diagram. It may be deliberately incomplete. Lastly I run through the viva myself a few times to check the timing and make sure the flow of the viva is alright. Then the real hard work starts. Part 2 will elaborate.

BT GS 1.36 Describe the PK of neuromuscular blocking agents

Regarding rocuronium:

It is a more potent agent than vecuronium   T/F

If you drank it, it would paralyse you eventually         T/F

Its duration of action is dependent on what time of the day you administer it    T/F

It commonly causes stinging when injected*    T/F

It is presented as a racemic mixture                 T/F

 

*Read this paper for a description of what it feels like to have rocuronium and suxamethonium injected when you are wide awake.  Response of the bispectral index to neuromuscular block in awake volunteers. P Schuller et al. British Journal of Anaesthesia 2015; 115(Supp 1): i95-103.

Reading any clinical paper about rocuronium should allow you to answer the third question. Unfortunately, reading any of the recommended texts for the exam won’t be enlightening about this particular property of rocuronium.

BTGS 1.30 and 1.31 Describe and compare the PK/PD of sedative/ induction agents

Regarding midazolam:

It can sting on administration because it has a high pKa   T/F

It has very poor bioavailability   T/F

It can induce anaesthesia when used as a sole agent    T/F

It tastes nice hence its popularity as a paediatric premed   T/F

It has an active metabolite   T/F

Despite what the practice of many trainees may suggest, the t1/2 keo of midazolam is significantly more than about thirty seconds.

BT GS 1.29 Describe the physical properties of sedative/ hypnotic agents

Regarding a propofol ampoule:

It contains egg products so shouldn’t be given to patients with an egg allergy   T/F

The contents are white because it contains soya bean oil$       T/F

It costs more than an ampoule of thiopentone               T/F

It contains antimicrobial preservative                            T/F

If you drank a 100ml ampoule it would make you quite sleepy*     T/F

$ Ask yourself what colour most oils are and what colour mayonnaise is and why they aren’t the same…

*In the trial of Michael Jackson’s cardiologist come ‘anesthesiologist’, Conrad Murray, an expert witness for the defence suggested that Jackson swigged a whole lot of propofol. This hypothesis was strongly refuted by the expert witness for the prosecution who happened to be none other than Steve Shafer. Who was correct?

Phew – well done!

 

A big congratulations to all of you who sat the exam today – it is quite a feat of physical and mental endurance!

Now time for a bit of a break. Give yourselves a chance to recuperate and participate in normal life – can you remember it😉 –  for the next week or so. Read a novel, take your partner out for dinner or enjoy dinner with friends, permit yourself an extra hour at the gym ( only if that won’t be torture), go to the beach or the bush, binge watch your favourite TV show….

For those of you who like cooking, and who are not too health obsessed, I could recommend making this recipe, pictured above, touted by my favourite podcast.

It is quite normal to feel a bit down in the dumps after a big effort such as today’s. Here is my post from after the written exam in February. We seem to be programmed to remember and dwell on the things we have done wrong, or that upset or scare us, rather than those we have done right. Perhaps this has an evolutionary advantage to stop us getting ourselves into dangerous situations. In the coming days you are likely to mull over those things that you forgot to write down in the exam. It’s Ok. No one can possibly write all there is to know about a topic, under pressure, in 10 minutes…

I like the advice at the end of this article. We can overcome those negative thoughts by creating a bank of good ones. So have a go now, whilst the day is fresh in your mind, and think of 5 or 10 things that went well today ( making it through the exam definitely counts as one). In the coming days, if misery sets in, look back at your list and encourage yourself – well done!

Mineraloglucoaldosticosteroids

BT_PO 1.90

Describe the pharmacology of * insulin preparations *oral hypoglycaemic *corticosteroid drugs.

Intravenous dexamethasone has a slow onset of action. TRUE/FALSE

Prednisone and dexamethasone are synthetic corticosteroids with predominantly mineralocorticoid effects. TRUE/FALSE

The anti-inflammatory response of corticosteroids is a mineralocorticoid effect. TRUE/FALSE

Mineralocorticoid effects of synthetic corticosteroids are less than the natural hormones. TRUE/FALSE

Dexamethasone lacks mineralocorticoid effects. TRUE/FALSE