Humidification

BT_SQ 1.5 Describe basic physics applicable to anaesthesia, in particular:
…. principles of humidification and use of humidifiers ….

 

T / F   during quiet breathing, air reaching the carina is close to 37 degrees C and 100% relative humidity

T / F   at 37 degrees C, air can hold a maximum of 44 mg/L of water vapour

T / F   during expiration, water vapour condenses onto the airway mucosa

T / F   absolute humidity depends upon both the temperature and the atmospheric pressure

T / F   a HME can warm inspired gases to about 30 degrees C, but this takes about 20 minutes

Study tip : Capitalise on your freshness

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Last week I hosted a webinar, through ANZCA, entitled “Tips for the Primary Exam”. For those of you who are registered with ANZCA, you can watch it via the College networks (it is a bit of a time investment, but the fast forward button is always available).

One of the other contributors to this blog, asked me whether there were any noteworthy points that could be highlighted here. A lot of what I discussed has already been touched in the previous study tips on this blog.

With the upcoming exam, there has been single, but significant change – the increase in reading time to 15 mins and the allowance for you to write on the question paper during that time. I discussed how to use this change to your best advantage in the webinar and that is the point I will focus on today.

The written portion of the exam is a real feat of endurance – 2.5hrs of MCQs in the morning, backed up with 2.5 hrs of writing the SAQs in the afternoon. Exhausting! None of us write for that long continuously these days. By the end of the afternoon, you will be very tired.

A the start of the SAQ paper however you will still be reasonably fresh – capitalise on your freshness in the 15 mins reading time:

1. Read the questions carefully – those that look like repeated questions may have had important changes made. The answer you have practised for the old question may not be able to be successfully transplanted into the new question

2. Highlight important words – this may include those important word changes, things you wish to define, anything that helps you ANSWER THE QUESTION

3. Jot down a couple of notes to help you structure your answer – your brain will be thinking quite well at this stage. If something great enters it, take 30 sec to write it down. This may be especially helpful for questions you plan to answer towards the end of the 2.5 hrs. To be able to refer back to your little notes, when your brain is fatigued, may provide that little spark that helps you through.

I suggest that you include “Reading Time” in any set of SAQs you practice (1 min per question). The more times you use that extra minute per question in practice, the more useful it is likely to be for you in the exam.

SS_PA 1.52 Pharmacokinetic differences in  neonates and children compared with adults and the implications for anaesthesia

A little person I know had an anaesthetic last week having swallowed a curtain hook, probably a couple of months ago. He had not been very keen to eat solid food!!


SS_PA 1.52 Describe how the pharmacokinetics of drugs commonly used in anaesthesia in neonates and children differ from adults and the implications for anaesthesia

Water soluble drugs have a larger volume of distribution in neonates TRUE/FALSE

Drugs that depend on redistribution into fat compartments for their termination of action have longer durations of action in neonates    TRUE/FALSE

The absorption of oral drugs is more rapid in neonates compared with adults   TRUE/FALSE

The relationship between weight and drug elimination is linear in children  TRUE/FALSE

Remifentanil’s half life is unchanged in neonates    TRUE/FALSE

BT_GS 1.12 Context sensitive half time

A topical area for us as we often run intra-operative infusions of drugs, sometimes for quite long periods of time!

The topic is not brilliantly covered in that many books. Pharmacology and Physiology for Anaesthesia Ch 2 by Hemmings and Egan, is a great chapter full stop and does discuss the topic. This article in BJA Education also gives a good little summary.

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Another photo from beautiful Tasmania today, Wineglass Bay

The context sensitive half time of a drug will never be longer than its elimination half life   TRUE/FALSE

The “context” is the duration of the infusion   TRUE/FALSE

Following cessation an infusion, the fall in plasma concentration is proportional to elimination of drug from the body  TRUE/FALSE

Prolongation of the half time, as the duration of the infusion increases, is directly proportional to the lipid solubility of the drug  TRUE/FALSE

Context sensitive half time is a term that only applies to multi compartmental models   TRUE/FALSE

BT_GS 1.21 Isomers

I think isomerism is a very cool little trick of nature! How amazing to think that one chemical structure can have such different properties due to the orientation of the same atoms on a single carbon, and also that our bodies are able to recognise these differentially.

We sometimes talk about enantiomers as being non superimposable mirror images of each other, which made me think of mirror twins ( apologies for the high class nature of the “journal” I took this from! However, if you are interested in twins, these episodes of Insight from SBS may interest you)

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No photos of mirrors today, just this (not perfect) reflection of Cradle Mountain in Dove Lake, Tasmania. One of my favourite parts of the world. I have seen the lake surface truly glass like, but do not have an image of it to share with you.

BT_GS 1.21 Describe and give examples of the clinical importance of isomerism

Ketamine, propofol and bupivacaine are all presented as racemic mixtures for use in Australia TRUE/FALSE

The D isomer of amphetamine is more potent as a CNS stimulant than the L isomer TRUE/FALSE

The (+) enantiomer of tramadol is more potent inhibitor of serotonin reuptake than the   (-) enantiomer TRUE/FALSE

D isomers of naturally occurring catecholamimes are 10x more potent than the L isomers TRUE/FALSE

Thiopentone is a drug which has stereoisomers TRUE/FALSE

BT_GS 1.68 Describe the physiological responses to lowered and raised environmental temperature, and the effects of anaesthesia on these responses

I have been fortunate enough to have had a recent holiday on a Japanese ski field, where the temperature was consistently about -30°C with wind chill factor. Whilst we were away, (and unfortunately since my return) the temperature in my hometown of Adelaide was well above 40°C.

Humans have a range of adaptations to enable them to cope with these widely diverse environmental temperatures. Anaesthesia has an important effect on our ability to regulate out own body temperature and the theatre environment is often a cold one (although it is all relative 😉)

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The hills beyond Nozawa Onsen, Japan

BT_GS 1.68  Describe the physiological responses to lowered and raised environmental temperature, and the effects of anaesthesia on these responses

The “thermoneutral zone” is the range of body temperatures at which metabolic rate is minimal  TRUE/FALSE

Cutaneous blood flow can increase 30 fold in heat stress  TRUE/FALSE

Shivering thermogenesis DOES NOT significantly increase adult metabolic rate TRUE/FALSE

In the neonate non-shivering thermogenesis can increase the metabolic rate to twice the resting rate TRUE/FALSE

General anaesthesia doubles the size of the interthreshold range   TRUE/FALSE

Tapentadol

BT_PM 1.22

Tapentadol (Palexia) is relatively new, but has some major advantages over conventional mu agonists. Several surgeons I work with now use it for their routine postop pain control rather than oxycodone.

T/F Tapentadol is a combined µ agonist and SSRI

T/F Tapentadol causes less constipation compared to oxycodone

T/F Tapentadol has a similar rate of abuse and diversion as oxycodone

T/F Tapentadol is ineffective in neuropathic pain

T/F Tapentadol is safe to use in a breast feeding mother

Carbon dioxide carriage in the blood

BT_PO 1.32   Discuss the carriage of carbon dioxide in blood, the carbon dioxide dissociation curve and their clinical significance and implications

Most of the dissolved carbon dioxide in the blood is in the erythrocytes     TRUE/FALSE

Carbonic anhydrase is found in erythrocytes   TRUE/FALSE

Carbonic anhydrase is found in pulmonary capillary endothelium   TRUE/FALSE

As temperature decreases, there is a lower pCO2 for a given mass of CO2 in the blood   TRUE/FALSE

Reduced Hb has a tenfold ability to carry CO2 over oxyhaemoglobin   TRUE/FALSE

Work of Breathing

BT_PO 1.10 Describe the Work of Breathing

1 Joule of work is done when 1 litre of gas moves in response to a pressure gradient of 1 kilopascal     TRUE/FALSE                                    This uses the SI unit of kPa, how many cm of water is that? So how many joules per breath? How many joules per minute? What is the efficiency of breathing? How many joules/calories are you expending on breathing? What % of your daily calorie use is that?

Breathing at rest is responsible for approximately 0.5% of the body’s oxygen consumption     TRUE/FALSE

Work is calculated by integrating a pressure volume curve     TRUE/FALSE

1/2 of the energy created in inspiration is stored as heat to be used for expiration      TRUE/FALSE

Bonus unexaminable question : Earth’s gravity accelerates a falling body at approximately 10 m/s/s and 1 Newton is defined as the force moving 1 kg at 1 m/s/s. Assuming that a 17th century apple had a mass of 100g, with what force would it have hit a man’s head if it fell out of a tree?