Train-of-four (TOF) monitoring is used to assess neuromuscular block. A TOF ratio of 0.6 corresponds to which clinical finding?

• A Patient can sustain head lift for 5 seconds — adequate reversal
• B No twitch visible but patient can open eyes
• C Total paralysis with no visible or palpable twitch response
• D Inability to sustain head lift for 5 seconds; pharyngeal muscle dysfunction and aspiration risk ✓

Explanation

A TOF ratio below 0.9 indicates residual neuromuscular blockade. At a TOF ratio of 0.6, patients demonstrate pharyngeal and upper oesophageal muscle dysfunction that impairs swallowing, increases aspiration risk, and reduces hypoxic ventilatory response. They may move limbs and appear awake but cannot sustain head lift for 5 seconds (which requires TOF ≥0.7–0.8). The safe extubation threshold is TOF ratio ≥0.9 (preferably ≥0.95) by acceleromyography. Subjective tactile assessment of TOF is unreliable below a ratio of 0.4.

Reference: Morgan & Mikhail's Clinical Anesthesiology, 6th ed.

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