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