A 56 year old, homeless man was admitted to the emergency department with clinical features suggestive of a bowel obstruction.   As he is confused, it is not possible to elicit a clear history.

The first set of blood tests show-

Sodium     137 mmol/L (137-145)

Potassium  4.0 mmol/L (3.1-4.2)

Chloride    98 mmol/L (101-109)

Bicarbonate  15mmol/L (22-32)

Glucose    48mmol/L (3.0-6.0)

Urea        18.0 mmol/L (3.0-8.0)

Creatinine   0.2 mmol/L (0.05-0.12)

What are the possible causes of his metabolic acidosis?

The rest of the viva focussed on the management of hyperglycaemic emergencies

Disclaimer: the viva stem above is the original CICM stem, acquired from their publicly available past papers. However, because the college do not make the rest of the viva text or marking criteria available, the rest has been confabulated. It sounds like a plausible viva and it can be used for the purpose of practice, but all should be aware that it does not represent the "true" canonical CICM viva station.