2017 Second Sitting SAQs

The provision of nutrition is a core skill in ICU. An understanding of its key elements enables prescription and modification. However, most answers lacked detailed information which is available in the standard texts. Better responses outlined the caloric requirements including each major element (water, carbohydrate, fat and protein) along with the caloric values and potential sources. Essential amino acids, fatty acids, fat and water-soluble vitamins were expected. A list of the requirements for major electrolytes and some of the trace elements were expected. Some candidates seemed to confuse calories, kilocalories and kilojoules. Some answers did not provide the nutritional requirements, as asked, but instead discussed the fate of the nutrients; hence did not score marks. Candidates are reminded to read the question carefully.

A good place to start was with the correct equation for a filtered load and a description of the components. Better answers described the components and how they differ and change over the glomerulus. Many candidates usefully based answers around the Starling forces. A summary of factors including the role of plasma concentration, protein binding, molecular size and charge was required to pass. Many answers gave examples for the effects of size and charge and relate endocrine responses to specific alterations in arteriolar tone and how this affected filtration. A detailed discussion of cardiovascular and endocrine responses to hypovolaemia was not required. Some candidates confused clearance with filtered load. Candidates are reminded to write legibly - especially where subscripts and Greek letters are used. Directional arrows (if used) should correlate with text.

Candidates had a limited understanding of this area of the syllabus. It was expected that answers would describe important concepts including the anatomy of venous structures, valves and lymphatics, permeability and factors which influence permeability. A description of hydrostatic forces, other pressures involved, and the role of osmotic and electric forces were required.

Overall answers lacked sufficient detail on a core area of respiratory physiology. Answers expected included a description of V/Q ratios throughout the lungs and an explanation of how V/Q inequality lowers PaO2

This question was generally well answered A table or diagram lent structure to the answer. More complete answers included details on the function, anatomy, a description of the pre- and post-ganglionic fibres, ganglia, receptors and neurotransmitters involved. Whilst most commented on ‘fight or flight’ for the SNS and ‘rest and digest’ for the PNS, no candidate observed that the SNS is a diffuse physiological accelerator and that the PNS acts as a local brake. No candidate included the fact that the SNS supplies viscera and skin whilst the PNS only supplies the viscera. Many candidates failed to make reference to the fact that the postganglionic SNS receptor is G protein coupled and the PNS postganglionic receptor is Gcoupled on muscarinic receptors but operates an ion channel when nicotinic. Candidates may have scored higher if they had provided a little more detail in their answers.

The classification was done well. Most candidates demonstrated that they had a structure for a “drug” question, but were often challenged to fill in the detail of that structure and failed to deliver enough content to secure a pass. Many candidates wrote a generic answer for calcium channel blockers instead of the specifics of nimodipine. Frequently the pharmacokinetic data recounted was incorrect. Candidates failed to distinguish between absorption and bioavailability. The difference between oral and intravenous dosing was often omitted. Few answered the section on important drug interactions.

The question spelt out very specific areas of CSF physiology to outline and the marks were evenly distributed among these areas. The candidates who did not pass this question usually did not provide enough detailed information. Details of the production and absorption of CSF were commonly lacking. The majority of candidates correctly described the composition of CSF; indicating whether a particular variable was higher or lower than in plasma, scored less marks than more specific information.

Good answers began with a definition of cardiac output. For each method, it was expected that candidates discuss the theoretical basis, equipment, advantages and disadvantages / sources of error and limitations. Additional marks were awarded when an attempt was made to compare and contrast the two methods (often helped by the use of a table).

A good answer included a definition of the resting membrane potential and a clear description of the factors that determine it. Explanation of these factors should have included a detailed description of the selective permeability of the membrane, electrochemical gradients and active transport mechanisms. Answers should demonstrate awareness of the Nernst equation and the Goldman-Hodgkin-Katz equation. These were often confused, sometimes with the GibbsDonnan effect. Descriptions of the Gibbs-Donnan effect generally lacked detail and understanding. The better answers included a definition and discussed in detail the influence of non-diffusible ions (intracellular proteins) on the distribution of diffusible ions.

Many candidates scored very highly on this core topic. It was expected information be included on pharmaceutics, cost, availability and compatibilities. Relevant pharmacokinetics (onset/offset, titratability) and pharmacodynamics (including relevant receptors, nuances of haemodynamic effects e.g. effect on diastolic pressure and regional perfusion) should have been detailed. Adverse effects and safety profile (e.g. use in pregnancy, therapeutic index) should also have been included. Good answers were structured and highlighted differences with specific facts and data

Candidates should have provided a definition of adverse drug reactions and then a classification. There are at least two widely accepted systems for classification, either was acceptable; though candidates often switched between both which led to a less structured answer. The WHO classification is comprehensive and logical, though both Rang and Dale and Goodman and Gilman also have sections on this topic. Common errors were the citing of examples with the incorrect mechanism, describing only drug interactions rather than all adverse reactions and focussing the answer on the 4 hypersensitivity reactions which could only score a low mark. Some candidates confused drug errors with adverse reactions.

Concise definitions were required with a clear explanation of the underlying physical principles. The response time of the system, degree of overshoot, effect on amplitude, noise and ability to faithfully reproduce frequencies relative to the natural resonant frequency were important considerations. Many candidates interpreted the question as relating to arterial lines and a detailed discussion of the components and characteristics of an intra-arterial catheter and transducer system did not attract marks

This core respiratory physiology topic was well answered by most candidates. Candidates generally were able to draw a spirogram. A common omission was inspiratory capacity.

Generally, there was a lack of knowledge about this topic with many candidates confusing vasovagal syncope with a Valsalva or orthostatic hypotension. A “vasovagal” is from excessive autonomic reflex activity in contrast to orthostatic hypotension which is a failure of the autonomic reflex response. A good place to start was with a description of vasovagal syncope, also known as neurocardiogenic syncope. It is benign, self-limiting and caused by an abnormal or exaggerated autonomic response to various stimuli (which should have been listed). The mechanism should have been described including the various receptors involved.

This is a very straightforward question testing breadth of knowledge rather than depth. It was well answered by the majority of candidates.

This topic was well understood and answered by most candidates. Some candidates had a good knowledge base but missed out on potential marks by failing to compare and contrast. A diagram outlining the various phases was a useful way to approach the question.

Many candidates did not specify that bioavailability describes the proportion/fraction of drug reaching the systemic circulation (to differentiate from the portal circulation). Some candidates considered only factors impacting absorption from the GI tract or stated that bioavailability related only to orally administered drugs. Candidates failed to provide an equation, or got equations or graphs wrong. Nearly all candidates failed to provide a comprehensive list of factors affecting bioavailability.

Good answers were structured including origin, termination, tributaries, relationships, surface anatomy and common variations. Factual inaccuracies were common and there was confusion about the relations of the internal jugular vein. Many candidates did not mention the changing relationship between the internal jugular and the carotid artery as they travel through the neck or the changes that result from repositioning for insertion. Many candidates also forgot to mention surface anatomy and a number talked about ultrasound and views used for insertion of central lines. Common omissions included the origin, tributaries, relationship with the correct cranial nerves and the fact that it is usually larger on the right. Almost nobody mentioned the relationship to the pleura

Most candidates could state 2 methods of measuring FRC. Some candidates (especially for nitrogen wash out) failed to provide enough information e.g. statements such as "if the amount of nitrogen is measured then FRC can be derived" were insufficient to score many marks.