Lab case 388 interpretation

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Question 1:

PH = 7.55, that is moderate alkalaemia.

pCO2 = 26 mmHG (<40), so we have respiratory alkalosis.  This can be acute or chronic respiratory alkalosis.

Next we need to consider the compensation. For both acute and chronic respiratory alkalosis we expect HCO3 to drop below 24. However, HCO3 for this patient is 25. It means that this patient has additional metabolic alkalosis.

It is good practice to calculate the anion gap in every blood gas. For this patient, The anion gap is 131 – (100+25) = 6. That means we don’t have additional HAGMA.

Other abnormal findings:

Na = 131 mmol/L, that is mild hyponatraemia.

K = 3.3 mmol/L, that s mild hypokalaemia.

Lactate = 2.1 mmol/L, that is hyperlactataemia (Mild).

Creatinine = 121 umol/L, that will this lady at

Final conclusion, this patient has combined respiratory and metabolic alkalosis with mild hypokalaemia and mild hyponatraemia.

Question 2:

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

From the list above, anxiety was only possible cause.

For the causes of metabolic alkalosis we use the mnemonic CLEVER PD,

  • C – contraction (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)
  •  P – post hypercapnia
  •  D – diuretics

From the list above vomiting and possible contraction are the causes.

This patient had THC hyperemesis that was the cause of these blood results.

Question 3:

For more detailed answers look at lab case 363 interpretation.

The management of cannabinoid hyperemesis consists of the following:

  • IV fluids to correct dehydration and electrolytes imbalance
  • Anti-emetics to suppress the vomiting
  • Consider medication to treat associated anxiety (Benzodiazepines)
  • Pain medication.

We need to consider replacing Mg for these patients for the correction of hypokalaemia.