MCQ of the Day: ABG

MBBS
,
1

A patient presents with pH 7.52, PaCO₂ = 30 mmHg, and HCO₃⁻ = 24 mEq/L. What is the most likely acid-base disorder?

  1. Metabolic Acidosis
  2. Respiratory Acidosis
  3. Respiratory Alkalosis
  4. Metabolic Alkalosis
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Respiratory alkalosis.

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This is respiratory alkalosis.

  • pH ↑ (alkalemia)
  • PaCO₂ ↓ (hypocapnia — main cause of alkalosis)
  • HCO₃⁻ normal (no compensation yet or acute)
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The combination of increased pH and decreased PaCO2 is indicative of respiratory alkalosis.

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Respiratory Alkalosis

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Informative

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Informative

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So, it can’t be acidosis as ph is slightly alkaline and also another reason is low level of paco2.

Likewise, it can’t be metabolic as hco3 is normal, indicating normal functioning of kidneys.

So it is.. Respiratory Alkalosis.

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  1. Respiratory Alkalosis
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I guess it should be respiratory alkalosis.

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Respiratory Alkalosis
causes Hyperventilation (due to anxiety, pain, fever, high altitude, pulmonary embolism)

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Depending on the changes it is respiratory alkalosis

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On the eve of internal medicine final MBBS exam, an anxious student presents to the ER. This would be the blood gas result!

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Ans
3. Respiratory Alkalosis

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Respiratory Alkalosis

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Respiratory Alkalosis

pH > 7.45 → Alkalosis

PaCO₂ < 35 mmHg → Low CO₂ (causes alkalosis)

HCO₃⁻ is normal → No metabolic compensation

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A rise in the blood pH occurring due to lowered Pco2 consequent to hyperventilation of the lungs (excess removal of CO2) is called respiratory alkalosis. Here pH= 7.52 which is higher than the normsl blood pH (7.35-7.45) hence,it is alkalosis. The Bicarbonate level is normal but there is a decrease in the CO2 level, indicating respiratory cause for imbalace. Thus, this is Respiratory Alkalosis

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Kudos to everyone! :clap: