Lab case 392 interpretation

Posted on by

Answers:

PH = 7.10, that is severe acidaemia.

HCO3 = 11 mmol/L, this means we have metabolic acidosis.

Next, we need to calculate the anion gap and the compensation.

Anion gap is calculated as: Na – (Cl+HCO3) = 18, So we have HAGMA.

To calculate the compensation, we use Winter’s formula. That is:

Expected pCO2 = 1.5 x HCO3 + 8 (+/-2). Accordingly, expected pCO2 for this patient is: 1.5 x 11 + 8 (+/-2) = 24.5 (accepted range of 22.5 to 26.5). This patient’s pCO3 is 36, it means this patient has additional respiratory acidosis.

Since we have HAGMA, then we need to calculate the delta ratio to exclude the presence of additional metabolic process. Delta ratio is calculated as:

Delta ratio = (AG – 12) / (24 – HCO3) = 0.46.

Ratio between 0.4 and 0.8 means that we have combined HAGMA and NAGMA.

This patient has triple acidotic condition. He is suffering from HAGMA, NAGMA and respiratory acidosis.

Other abnormal findings:

The most significant abnormal finding is the severe hyperlactataemia (Lactate level = 8 mmol/L).

Cl = 110 mmol/L. That is hyperchloremia.

Next, we need to look at the causes of these abnormalities.

For the differential diagnosis of HAGMA we use the mnemonic CAT MUDPILES, that is:

  • 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

For this list we can tell that hyperlactataemia is the most probable cause. (Lactate level more than 5 mmol/L is almost always associated with HAGMA).

For the differential diagnosis of NAGMA, we use the mnemonic USED CARP, that is:

  • U = Ureteroenterostomy
  • S = Small bowel fistula
  • E = Extra chloride
  • D = Diarrhea
  • C = Carbonic anhydrase inhibitors
  • A = Adrenal insufficiency/ Addison’s disease
  • R = Renal tubular acidosis
  • P = Pancreatic fistula.

From that list, high chloride was the cause

That patient had cold sepsis secondary to gram -ve pneumonia, which also explains the respiratory acidosis on these blood gases.