Lab case 400 interpretation

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Question 1:

PH = 6.9, that is severe acidaemia

HCO3 = 22 mmol/L. So, we have metabolic acidosis.

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

Anion gap = Na – (Cl + HCO3) = 19, So we have HAGMA.

Compensation in metabolic acidosis is calculated using Winter’s formula, that is: Expected pCO2 = 1.5 x HCO3 + 8 (+/-2) = 41 (The range is 39 to 43). This patient’s pCO2 is 24. So, we have additional respiratory alkalosis.

Because we have HAGMA, then we need to calculate the delta ratio to exclude the presence of additional metabolic process.

Delta ration is calculated as: (AG – 12) / (24 – HCO3) = 7/2 = 3.5. Delta ratio more than 2 means we have additional metabolic alkalosis (This number is too high. We will explain the reason why later on).

So far, we have triple metabolic processes (HAGMA, respiratory alkalosis and metabolic alkalosis).

Other abnormal findings:

The most obvious other abnormal finding is lactate level of 27 mmol/L.

Creatinine of 132 umol/L, that is high. (Unknown if this is acute or chronic).

 

 Question 2:

For the causes of 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

From the list above, high lactate is clearly a cause of HAGMA for this patient. We still need to think about the other causes as we still don’t have enough information about this patient.

For the causes of respiratory alkalosis, we use the mnemonic CHAMPS

  • C = CNS diseases
  • H = Hypoxia
  • A = Anxiety
  • M = Mechanical ventilation/ over ventilation
  • P = Progesterone
  • S = Salicylates / sepsis

This patient was hyperventilating with his agitation.

Next, we will look at the causes of Metabolic alkalosis. For the causes of metabolic alkalosis we use the mnemonic CLEVER PD.

  • C = Contraction alkalosis (dehydration)
  • L = Liquorice (diuretic), laxative abuse
  • E = Endocrine (Conn’s, Cushing’s)
  • V = Vomiting, GI loss (villous adenoma)
  • E = Excess alkali (antacids)
  • R = Renal (Bartter’s), severe K depletion
  • P = Post hypercapnia
  • D = Diuretics

This patient was very agitated due to Meth use. He was resistive 6 men, this excessive muscle work lead to the production of lactate. The high lactate level for this patient was due to overproduction of lactate due to excessive work rather than due to anaerobic metabolic process. Since the mechanism for acidosis is very acute the kidneys didn’t have enough time to compensate. That is why HCO3 level was relatively high and the delta ratio was very high.

Blood gases were tested again in 30 minutes, and they were completely normal.

Question 3:

The easiest way is to apply the AEIOU TIPS mnemonic. Then investigate or exclude these potential causes. Some of the causes are difficult to confirm immediately. In these cases, we might consider treating these possible causes until we confirm/exclude them (For example encephalitis).