A 78 year old with fever and diarrhoeaPH is low (7.29) => acidaemia.

HCO3 is low (13) => metabolic acidosis.

Check for compensation using Winter’s formula: Expected PCO2 = 1.5 X (HCO3) + 8 (+/- 2), ie.1.5 X 13 + 8 = 27.5, close to 29, we can say that there is no respiratory component or there is full respiratory compensation.

Calculate the Anion gap: Na – (Cl+HCO3),126 – (92+13) = 21 => High anion gap metabolic acidosis.

Then calculate the delta gap/ratio (as the anion gap is elevated): AG-12/24-HCO3:

21-12/24-13 = 0.8 => Patient has HAGMA and NAGMA

Calculated Osmolarity = Na x 2 +BSL + urea = 129X2 + 14 + 5 = 277 is normal

Mild hyponatraemia, hypokalaemia, hypochloraemia

Acute renal failure – likely pre-renal (dehydration)

Cause: Lactic acidosis due to infection and dehydration associated with excessive loss of HCO3 through diarrhoea.

Consider infectious or surgical causes for presentation