A patient develops arterial desaturation on the second postoperative day after open cholecystectomy. The PRINCIPAL mechanism of early postoperative hypoxaemia after upper abdominal surgery is:
- A Reduction in functional residual capacity with basal atelectasis ✓
- B Hypoventilation secondary to opioid analgesia
- C Aspiration pneumonitis
- D Increased dead space ventilation
Correct answer: A. Reduction in functional residual capacity with basal atelectasis
Explanation
Upper abdominal and thoracic surgery reduce functional residual capacity by up to 30 percent, lowest on the first to second postoperative day, producing basal atelectasis with low ventilation-perfusion units and shunt. This explains why hypoxaemia may persist despite supplemental oxygen. Opioid hypoventilation matters mainly in the first hours in the recovery room, and increased dead space is a feature of embolism, not routine postoperative atelectasis.
Reference: Morgan and Mikhail's Clinical Anesthesiology, 7th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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