Blood Gas OSCE by Naanu Neenu

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


47 year old Michael was brought in with acute confusion.He has history of chronic alcoholic liver disease. vital signs: HR100 BP120/65 RR 38 Temp 35.7 GCS 12 .VBG: pH 7.21 PCO2 14 (35-45 mmHg) HCO3 9 (22-28) BE -13 ( -2 to +2) Lactate 11 (<2) Glucose 2.0 (5-8) Na 100( 134-146) K 4.7( 3.5 - 4.5) Cl 73(98-106) Your junior registrar wants help in interpreting the VBG .

Instructions for the candidate

you will be assessed on your ability to interpret the VBG appropriately,given the clinical context and assist the registrar in reaching appropriate conclusion.
You will also be assessed on your ability as an educator ,your professionalism,and communication.

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

You are a junior reg in the department.You have just started seeing the 47 year old Michael with acute confusion, and chronic alcoholic liver disease.

you have asked the consultant for assistance interpreting the VBG you have just done.Introduce yourself.You will hand the VBG result to the candidate and ask them to help you interpret it.

Questions to ask if not addressed by the candidate:
1. what is the anion gap?
2. What is the cause of high lactate?
3.How do i work out the respiratory compensation?
4.What treatment should i start?

For the examiner

Domains Assessment Objectives

Medical Expertise
Interpret VBG:
Resp compensation
very high lactate- Hypoxia,hepatic failure,sepsis,seizure,toxic alcohol,poisoning
Hyponatremia- severe, Liver failure,renal failure, SIADH
Hypoglycemia- Liver failure,seizure,ETOH

Delta Gap

Fluid resuscitation,
Hypertonic saline : slow correction of sodium

Severe illness

Verbal clarity,Concise,Specific

Scholarship and Teaching
Permits registrar to ask questions
Structured and tailored teaching


Other Assessment Notes

scenario taken from the practice in our department.not written by me.

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