Carbon monoxide in a cat rescued from a house fire
5-year-old cat rescued by firefighters from a house fire. It arrives disorientated, tachypnoeic and smelling of smoke. On room air, SpO2 is 98% and arterial PaO2 is 95 mmHg.
Which statement about diagnosis and treatment is correct?
chevron_right Show answer and explanation
A. Normal SpO2 and PaO2 rule out significant tissue hypoxia
PaO2 measures dissolved oxygen, which is normal, and a standard pulse oximeter cannot distinguish carboxyhaemoglobin; arterial oxygen content may be severely reduced.
B. Oxygen is only needed if SpO2 falls below 95%
In CO poisoning SpO2 overestimates oxygenation, so it cannot guide the decision. Every symptomatic smoke-exposed patient should receive oxygen.
C. The pulse oximeter overestimates oxygenation; carboxyhaemoglobin should be measured by co-oximetry and the highest possible FiO2 given
Correct. CO binds haemoglobin with far greater affinity than O2 and the pulse oximeter reads it as oxyhaemoglobin. 100% oxygen shortens the half-life of carboxyhaemoglobin from several hours to under an hour.
D. The treatment of choice is bicarbonate for lactic acidosis and furosemide to prevent oedema
Lactic acidosis resolves when oxygen delivery is restored, and smoke-inhalation oedema is not cardiogenic; neither drug is the mainstay of treatment.
lightbulb Key takeaway
After smoke inhalation, monitor for 24–48 h: upper airway oedema from thermal injury, bronchospasm and chemical pneumonitis can appear late. Do not use prophylactic antibiotics or corticosteroids; also consider cyanide poisoning.
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Updated: October 31, 2026 · Educational content for veterinary professionals. It does not replace current clinical guidelines or the judgement of the attending veterinarian.