Which train-of-four (TOF) ratio value is considered the clinical threshold for adequate neuromuscular recovery, above which residual block-related adverse respiratory events are unlikely?
- A TOF ratio > 0.5
- B TOF ratio > 0.7
- C TOF ratio > 0.9 ✓
- D Any visible twitch response (T1 present)
Correct answer: C. TOF ratio > 0.9
Explanation
A TOF ratio >0.9 (T4:T1 acceleration ratio by quantitative neuromuscular monitoring) is the accepted threshold for adequate reversal, at which pharyngeal muscle function and airway protection are restored. A TOF ratio of 0.7 was historically used but clinical studies demonstrated impaired hypoxic ventilatory response, swallowing, and upper airway muscle tone at ratios 0.7–0.9. Qualitative (visual/tactile) TOF monitoring is unreliable below 0.4 and cannot exclude significant residual block at the 0.9 threshold.
Reference: Morgan & Mikhail's Clinical Anesthesiology, 6th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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