Lab case 441 interpretation


PH = 7.15, that is severe acidaemia

HCO3 = 6.5 mmol/L, so we have metabolic acidosis.

Since we have metabolic acidosis, then we need to calculate compensation and anion gap.

For expected respiratory compensation for metabolic acidosis we use Winter’s Formula. That is: Expected pCO2 = 1.5 x HCO3 + 8 (+/-2).

Accordingly, expected  pCO2 for this patient should be: 1.5 x 6.5 + 8 = 17.75 mmHg, With accepted range between 15.75 – 19.75. This patient’s pCO2 is within the accepted range (19). So there is no additional respiratory process going.

Anion Gap is calculated as: AG = Na – (Cl + HCO3) = 20.5, So this patient has HAGMA.

Since, we have HAGMA then we need to calculate the delta ratio. Delta ratio is calculated as: (AG – 12) / (24 – HCO3) = 0.485. (Ratio between 0.4 – 0.8 means we have mixed HAGMA and NAGMA).

So, this patient has combined HAGMA and NAGMA.

Other abnormal findings:

K = 4.4 mmol/L, that is normal. However, K level can be falsely elevated in the presence of acidosis. On Average, K level increases by 0.6 for ever 0.1 PH less than 7.35. Accordingly, corrected K level is 4.4 – 2 x 0.6 = 3.2 mmol/L. that is mild hypokalaemia.

Cl = 112 mmol/L, that is hyperchloraemia and that most probably is the cause for NAGMA.

So, final conclusion: We have combined HAGMA and NAGMA with severe ketosis and mild hyperchloraemia.

Now we will look through our differential diagnosis list

For HAGMA we use the mnemonic CAT MUDPILES

  • C = cyanide, carbon monoxide
  • A = alcoholic ketoacidosis and starvation Ketoacidosis.
  • T = toluene
  • M = methanol, metformin
  • U = uraemia
  • D = diabetic ketoacidosis
  • P = phenformin, pyroglutamic acid, paraldehyde, propylene glycol, paracetamol
  • I = iron, isoniazid
  • L = lactate
  • E = ethanol, ethylene glycol
  • S = salicylates

Non of the above potential causes explained the patient’s acidosis.

However, GHB is chemically similar to β-hydroxybutyrate. (GHB =gamma hydroxybutyrate).

There are 3 types of ketones in the body,  acetoacetate, β-hydroxybutyrate, and acetone. 

Blood ketones finger prick test is designed to check for Beta-hydroxybutyrate and the lab ketones test is designed to check for acetoacetate.


Near-fatal persistent anion- and osmolal-gap acidosis due to massive gamma-butyrolactone/ethanol intoxication ( 

Hyperchloreamia, is the result of loss of HCO3. In Ketosis/ ketoacidosis, the loss of ketoacid anions (beta-hydroxybutyrate and acetoacetate) into the urine with sodium or potassium. Such urinary loss of sodium or potassium keto-anion salts represents the loss of “potential bicarbonate” and will lower the plasma anion gap toward normal but not raise the serum bicarbonate. By contrast, the loss of ketoacid anions with either hydrogen or ammonium will lower the anion gap and raise the serum bicarbonate concentration toward normal. *** (2)




*** CJEM. 2018 Oct;20(S2):S2-S5.  doi: 10.1017/cem.2017.10. Epub 2017 May 2.

Gamma-hydroxybutyrate (GHB), an unusual cause of high anion gap metabolic acidosis