Metabolic acidosis
Metabolic acidosis is commonly classified according to the anion gap. This can be calculated by: (Na+ + K+) - (Cl- + HCO-3). If a question supplies the chloride level then this is often a clue that the anion gap should be calculated. The normal range = 10-18 mmol/L
Normal anion gap ( = hyperchloraemic metabolic acidosis)
Raised anion gap
Normal anion gap ( = hyperchloraemic metabolic acidosis)
- gastrointestinal bicarbonate loss: diarrhoea, ureterosigmoidostomy, fistula
- renal tubular acidosis
- drugs: e.g. acetazolamide
- ammonium chloride injection
- Addison's disease
Raised anion gap
- lactate: shock, hypoxia
- ketones: diabetic ketoacidosis, alcohol
- urate: renal failure
- acid poisoning: salicylates, methanol