Lab case 444 interpretation

Ph = 7.25, that is moderate acidaemia.

pCO2 = 58 mmHg, so we have respiratory acidosis.

Next we need to look at the compensation, from the history the condition is most likely acute. For the renal compensation of acute respiratory acidosis, we expect HCO3 to increase by 1 for every 10 pCO2 above 40 mmHg.

Accordingly, expected HCO3 should be: 24 + 18 x 0.1 = 25.8 mmol/L. This patient’s HCO3 is 24 mmol/L, that is slightly lass than the expected. (Could be either normal or abnormal).

Next we will calculate the anion gap for this patient. We calculate the anion gap as:  AG= Na – (Cl + HCO3) = 13, that is slightly higher than normal (Normal AG is 12).

So, we are going to consider this patient as having additional HAGMA until prove otherwise.

Other abnormal findings:

Cl = 106 mmol/L – that is very slightly elevated.

Glucose = 3.3 mmol/L, that is mild hypoglycaemia (In non-diabetic person).

Final conclusion, that lady had combined acute respiratory acidosis and HAGMA with associated mild hypoglycaemia and hyperchloraemia.

Respiratory acidosis was due to the respiratory centre suppression cause by the unknown medication that she had taken.

Looking at the causes of HAGMA using 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