A postoperative patient in recovery complains of inability to take a deep breath and has shallow breathing with a weak cough. Acceleromyography shows a train-of-four ratio of 0.5 at the adductor pollicis. This finding indicates:
- A Complete recovery from neuromuscular blockade, symptoms unrelated to the relaxant
- B Deep block requiring immediate re-intubation
- C Residual neuromuscular block, since clinically important weakness persists until the TOF ratio exceeds 0.8 to 0.9 ✓
- D Phase II depolarising block from suxamethonium metabolism
Correct answer: C. Residual neuromuscular block, since clinically important weakness persists until the TOF ratio exceeds 0.8 to 0.9
Explanation
Clinical signs of residual curarisation, including impaired breathing, weak cough, diplopia and difficulty swallowing or lifting the head, persist until the train-of-four ratio exceeds 0.8 to 0.9. A ratio of 0.5 therefore confirms clinically significant residual block, which should be reversed with neostigmine or sugammadex depending on the agent used. A deep block would show no twitches, and phase II block follows large or repeated suxamethonium doses, not routine recovery.
Reference: Miller's Anesthesia, 9th ed.
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Written and medically reviewed by the StethoPrep medical team.