Two hours after total knee replacement, a patient receiving intravenous morphine has a respiratory rate of 7/min, minimal response to voice, and SpO2 of 90% on 2 L/min nasal oxygen. The MOST appropriate immediate management is:
- A Naloxone 0.4 mg intravenous bolus
- B Flumazenil 0.2 mg intravenously
- C Titrate naloxone in 40 to 100 microgram increments until respiration improves ✓
- D Immediate tracheal intubation
Correct answer: C. Titrate naloxone in 40 to 100 microgram increments until respiration improves
Explanation
Opioid-induced respiratory depression is treated with naloxone diluted and titrated in small increments of 40 to 100 micrograms, repeating every two minutes until respiratory rate recovers, so that analgesia is preserved and acute withdrawal with hypertension, tachycardia and pulmonary oedema is avoided. A full 400 microgram bolus reverses both depression and analgesia abruptly. Flumazenil addresses benzodiazepine overdose, and intubation is rarely needed when titrated reversal succeeds.
Reference: Miller's Anesthesia, 9th ed.
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