That sweet acid OSCE by Michael

You have 3 minutes reading time. This OSCE will run for a maximum of 7 minutes.


A junior doctor comes to you having assessed a 16-year-old girl with vomiting, lethargy, polyuria and polydipsia. Her BSL is 30 mmol/L. She has never been diagnosed with diabetes mellitus prior.The doctor has just performed an ABG and seeks out your assistance.

View attached:  Attachment 1

Instructions for the candidate

You are to analyse and interpret the ABG, explaining findings to the junior doctor. You are then to explain to and advise the junior doctor on appropriate management for the patient.

Domains being examined

  • Medical Expertise
  • Communication
  • Scholarship and Teaching
  • Professionalism
The candidate has 3 minutes reading time. This OSCE is expected to run for a maximum of 7 minutes.

For the actor

The scenario commences as soon as the candidate enters the room when the bell rings. Start with: “Hello. You must be the consultant. Can you please take me through the patient’s ABGs?”
You are a competent, reasonably knowledgeable intern, but lacking in the experience needed interpret ABGs confidently. Questions you should ask if the relevant issues are not already covered:
“Is there respiratory compensation?”
“What is the anion gap?”
“Why is the Na low, and the K high?”
“Remind me about the Aa gradient please?”
“So, how do we treat this guy?”
Ideally, the scenario should take all of the allotted 7 minutes. Please ensure you engage the candidate in a full discussion, to address all relevant issues to this case. Imagine what your character will need to know about this case.

For the examiner

Introduce yourself, and ask the candidate if s/he understands the scenario briefing. After that, introduce him/her to the junior doctor, and allow the scenario to commence. Do NOT be involved in the scenario beyond this, unless there is a critical issue that the role-player cannot address. The candidate may finish the scenario early, if all tasks are completed and the role-player has no further issues to discuss.

Domains Assessment Objectives

Medical Expertise
Interpret the ABG: Acidaemia. HAGMA cw ketoacidosis. Anion gap of 26. Adequate resp response. Minor (prob insignificant) rise in Aa gradient. Na dropped by hyperglycaemia, and K raised by acidaemia.
Corrected Na is 138, predicted K is 3.5.
Delta ratio is 1.4, suggesting a pure HAGMA.
Needs NSaline resus, insulin infusion, close K and glucose monitoring. Concurrent glucose infusion if BSL 15 mmol/L or lower. Watch fluid status carefully. Seek and treat possible trigger, such as infection.
Education of patient and family re illness and implications.

Verbal clarity, conciseness, specificity

Scholarship and Teaching
Permits doctor to ask questions
Teaching method that is structured and tailored to doctor's understanding

Shows respect
Professional appearance, demeanour and conduct

Other Assessment Notes

This OSCE based on one from TEEMwork course 2015.1:

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