Lab case 426 interpretation


PH = 7.415, this is within normal range. slightly more to the alkelaemic side.

pCO2 = 34 mmHg, that is slightly low, this patient is hyperventilating. (Normal pCO2 is 40 mmHg on arterial blood and 48 mmHg on venous blood).

Next we are going to look for the metabolic/kidneys compensation for the reduced level of pCO2.

If the condition is acute, we expect HCO3 level to drop by 2 mmol for every 10 pCO2 less than 40. Accordingly, expected HCO3 should be 24-1.2 = 22.8 mmol. If the case is acute.

If the condition is chronic, we expect HCO3 level to drop by 5 mmol for every 10 pCO2 less than 40. Accordingly, expected HCO3 should be 24 – 3 = 21 mmol/L.

This patient’s HCO3 is 21.6, This value is between acute and chronic expected compensation, closer to the chronic value.

This patient’s PH is within the normal range, most probably there is an additional metabolic acidosis. Then we should calculate the anion gap. However, this patient has extremely high K level (13.1 mmol/L). This value is incompatible with life (Likely to be wrong)…This will limits the assessment of the anion gap. We can’t assess the acidosis further.

The most striking abnormalities in these results are:

  • Extremely high K level of 13.1 mmol/L
  • Extremely high Hb level of 232 g/L

Alkalosis and severe hyperkalaemia don’t happen together. This mean the problem most be in vitro. Usually due to haemolysis.

This patient had polycythemia. Because of high volume of RBC there is not enough energy (ATP) available outside the body to maintain the cells integrity. That results in haemolysis which in turn leads to pseudohyperkalaemia a mild hyponatraemia.


Special thanks to:

  • Dr Elissa Poulter for providing the details of this case
  • Dr Woon Nga Tan for presenting this case