Lab case 421 interpretation

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Question 1:

PH = 7.599 That is moderate alkalaemia (very close to the severe range – Moderate alkalaemia is PH between 7.5 – 7.6. Severe alkalaemia is PH > 7.6).

PCO2 = 22 mmHg, that is low. So we have respiratory alkalosis.

Next step is compensation.

For acute respiratory alkalosis, we expect HCO3 to drop by 2 for every 10 PCO2 below 40. Accordingly, expected HCO3 is ( 24 – 18 x 0.2) = 20.4,, this is close to 22. However, when we have properly compensated respiratory alkalosis we should expect PH to be close to normal range. In this case PH is close to severe alkalaemic range. According to that, this condition is unlikely to be well compensated acute respiratory alkalosis.

The other possibility is chronic respiratory alkalosis.

For chronic respiratory alkalosis, we expect HCO3 to drop by 5 for every 10 CO2 below 40. Accordingly, HCO3 should be (24 – 18x 0.5) = 13. that is less than 22. because the difference is toward the alkalotic range we have additional metabolic alkalosis.

It is always a good practice to calculate the anion gap, That is Na – (Cl +HCO3), that will be 134 – (89 + 22) = 23. So we have additional HAGMA.

Na = 134 (low normal), however this patient had glucose level of 22 mmol/L. Hyperglycemia will cause false Na level (low Na level).

Correct Na level = measured Na + (glucose – 5)/3. According to that the corrected Na level for this patient will be 140 mmol/L.

Other abnormal finding is severe hyperlactataemia. 6.5 ( lactate level of 5 or more is associated with HAGMA).

Final conclusion: This patient had Chronic respiratory Alkalosis with HAGMA and metabolic alkalosis.

Patient had large ascites, that put pressure on the diaphragm leading to reduced tidal volume and the patient was hyperventilating as a compensatory mechanism.

Was vomiting (due to the withdrawal) which led to metabolic alkalosis.

High lactate caused metabolic acidosis:

A) Type A (due to reduced O2 delivery):

  • Shock
  • Severe hypoxia
  • Severe anaemia
  • CO poisoning

B) Type B (BLACK MIST mnemonic)

  • Beta-2 agomist
  • Liver failure
  • Alcohols (ethanol, methanol, ethylene glycol) and anticonvulsant (Valproate).
  • Cyanide poisoning
  • Ketoacidosis
  • Inborn error of metabolism, INH and Iron
  • Salicylate and Sepsis
  • Thiamine deficiency.

This patient had Liver failure and Thiamine deficiency that could explain the high lactate level.

 Question 2:

Types of alcohol withdrawal:

  1. Minor withdrawal, 6 – 24 hours after last alcoholic drink. Usually presents with tremer, anxiety, nausea and vomiting and insomnia.
  2. Major withdrawal, 10 – 72 hours after last alcoholic drink. Usually presents sweating, tachycardia, increase blood pressure and hallucinations (visual or auditory)/
  3. Seizures, 2 days after last alcoholic drink
  4. Delirium tremen. 2,3 – 10 days after last alcoholic drink. It present with confused, disoriented state and fever.