35 year old man – heavy alcohol intake, abdominal pain and vomiting with signs of compensated shock.

1. Describe the abnormalities

severe metabolic acidosis  (HCO3 low, BE -ve)

High anion gap  (21.5)

Delta ratio 0.52

therefore mixed high and normal anion gap acidosis

additional respiratory acidosis (or partial compensation) – expected = 16, actual = 26

with K and Cl at upper limits of normal and mild hyponatraemia

Normal glucose and lactate – lactic acidosis and DKA unlikely causes of high anion gap acidosis

Total body depletion of Potassium due to severe acidosis (likely around 3), requiring monitoring and replacement

A-a gradient = 38 – high

Triple acid base disorder – mixed high anion gap and normal anion gap metabolic acidosis with additional respiratory acidosis and elevated Aa gradient.

2. Differentail Diagnosis

High anion gap – renal failure (require UEC), toxins (toxic alcohols, paracetamol, etc)

Normal anion gap acidosis – normal saline rehydration, RTA (type IV)

Respiratory acidosis – altered mental state with hypoventilation, underlying disease, toxins

Aa gradient – VQ mismatch, shunt – ?? aspiration, infection, other – PE

Consider other causes of abdominal pain –  surgical – pancreatitis, perforated ulcer, upper GI haemorrhage, bowel obstruction, perforation

Sepsis must also be considered