Metabolic Acidosis and Metabolic Alkalosis

Occurs in:

  • The combination of a raised anion gap metabolic acidosis (e.g. uraemia, ketoacidosis, lactic acidosis) and vomiting (loss of H+)
  • The combination of a raised anion gap metabolic acidosis and diuretic therapy (with low K+)
  • Lactic or ketoacidosis and bicarbonate therapy

For example in a patient with diabetic ketoacidosis secondary to infection and vomiting:

  • pH   7.37
  • pCO2   3.4 kPa
  • pO2   10.2 kPa
  • bicarbonate   6.5 mmol/L

 

A patient with ongoing ketoacidosis who has compensated to the extent that the bicarbonate is only 6.5 is unlikely to have fully restored their pH to normal levels. This is a falsely reassuring picture and the clinical condition should be considered, or the patient could be undertreated. Therefore if the patient is also vomiting, consider direct loss of [H+].