Q1. A 49-year-old female, with a history of pulmonary vasculitis is found collapsed in the ward with shallow breathing and a GCS of 6.
An initial arterial blood gas on room air (FiO2 0.21) reveals:
- What is the cause of the hypoxia? Give the reason for your answer
Q2. A 64-year-old man with a background of heavy alcohol consumption has been admitted to your ICU for several days with a sensitive staphylococcus aureus (MSSA) epidural abscess which has been surgically drained.
The following results were obtained:
On 30% oxygen arterial blood gas analysis as follows:
- What is the likely cause of the acid base disturbance?
- How would you investigate and manage it?
Q3. The following is a CSF sample from a 56-year-old woman with severe rheumatoid arthritis who has presented with fever, malaise and altered mental state.
Describe 4 further tests you would perform upon the CSF to establish an infective cause.
Answer and interpretation
Q1. What is the cause of the hypoxia? Give the reason for your answer
- No reason to believe there is parenchymal disease / vasculitis as the A-a gradient is 13 mmHg.
- This fits with the clinical picture of coma, shallow breathing and hypercapnia
Q2. What is the likely cause of the acid base disturbance? How would you investigate and manage it?
- High anion gap metabolic acidosis secondary to pyroglutamic acidaemia.
- Can be detected by requesting an organic acid screen, or by plasma or urine pyroglutamate levels.
- Management – cessation of precipitating drugs likely paracetamol and flucloxacillin in this case.
- N-Acetyl cysteine infusion has been advocated.
Q3. Describe 4 further tests you would perform upon the CSF to establish an infective cause.
- Herpes Simplex PCR
- Mycobacterium Tuberculosis PCR
- Mycobacterial Stain and Cultures
- India Ink Stain
- Cryptococcal Ag
- Fungal cultures
- Bacterial PCR
- Pass rate: 60%
- Highest mark: 9.3
Chris is an Intensivist and ECMO specialist at the Alfred ICU in Melbourne. He is also a Clinical Adjunct Associate Professor at Monash University. He is a co-founder of the Australia and New Zealand Clinician Educator Network (ANZCEN) and is the Lead for the ANZCEN Clinician Educator Incubator programme. He is on the Board of Directors for the Intensive Care Foundation and is a First Part Examiner for the College of Intensive Care Medicine. He is an internationally recognised Clinician Educator with a passion for helping clinicians learn and for improving the clinical performance of individuals and collectives.
After finishing his medical degree at the University of Auckland, he continued post-graduate training in New Zealand as well as Australia’s Northern Territory, Perth and Melbourne. He has completed fellowship training in both intensive care medicine and emergency medicine, as well as post-graduate training in biochemistry, clinical toxicology, clinical epidemiology, and health professional education.
He is actively involved in in using translational simulation to improve patient care and the design of processes and systems at Alfred Health. He coordinates the Alfred ICU’s education and simulation programmes and runs the unit’s education website, INTENSIVE. He created the ‘Critically Ill Airway’ course and teaches on numerous courses around the world. He is one of the founders of the FOAM movement (Free Open-Access Medical education) and is co-creator of litfl.com, the RAGE podcast, the Resuscitology course, and the SMACC conference.
His one great achievement is being the father of three amazing children.
On Twitter, he is @precordialthump.