Perioperative Care — Assessing Postoperative Respiratory Failure
A 90-year-old woman is two days after emergency laparotomy for small bowel obstruction and is receiving morphine for wound pain. She has shallow breathing with reduced bilateral chest movement and reduced air entry at both bases. She is alert, speaks full sentences and is not using accessory muscles. Respiratory rate is 24 breaths/min and oxygen saturation is 89% on 2 L/min nasal oxygen. What is the most appropriate next step?
- A.Endotracheal intubation
- B.Arterial blood gas analysisCorrect
- C.Portable chest radiograph
- D.Start bilevel non-invasive ventilation
Explanation
This elderly woman has hypoxaemia after upper abdominal surgery, with shallow breathing from wound pain and opioid use and bibasal hypoventilation, most likely atelectasis. She is alert and not tiring, so there is time to assess before escalating, and the decision that matters now is what kind of respiratory support she needs. An arterial blood gas answers that directly: it gives the true PaO2, shows whether she is retaining carbon dioxide from opioid-related hypoventilation, and reveals acidosis. Normal carbon dioxide points to titrated oxygen, physiotherapy, incentive spirometry and better analgesia; hypercapnic acidosis points to reviewing opioids and considering non-invasive ventilation. A chest radiograph is also needed to look for collapse, effusion or aspiration, but it identifies the cause rather than the severity of ventilatory failure and should not delay the gas. Intubation is for exhaustion, falling consciousness or failure of other measures, none of which is present. Starting non-invasive ventilation before knowing her carbon dioxide is premature. Pulse oximetry alone can hide significant hypercapnia when supplemental oxygen is running, which is why the gas is decisive.
Why each option
- A.
- Intubation is for exhaustion, depressed consciousness or failed non-invasive measures; this alert, unfatigued patient needs assessment first.
- B.
- Correct. A blood gas shows oxygenation, carbon dioxide retention and pH, which decide whether oxygen alone or ventilatory support is needed.
- C.
- A chest radiograph helps find atelectasis or effusion, but it does not measure ventilatory failure and should follow the gas.
- D.
- Non-invasive ventilation is indicated for hypercapnic acidosis, which has not yet been shown; starting it blind is premature.
Reference: BTS Guideline for oxygen use in healthcare and emergency settings (2017); BTS/ICS Guideline for ventilatory management of acute hypercapnic respiratory failure in adults (2016); UpToDate — Overview of postoperative pulmonary complications
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