Train-of-four (TOF) monitoring uses four supramaximal stimuli at 2 Hz. A TOF ratio of 0.7 indicates:

• A Adequate reversal — safe to extubate
• B Phase II block from succinylcholine — administer anticholinesterase
• C Complete neuromuscular blockade — no twitches detectable
• D Significant residual neuromuscular blockade — extubation not safe; administer reversal agent ✓

Explanation

TOF ratio (T4/T1) must reach ≥0.9 (ideally ≥0.95 as measured by quantitative acceleromyography) before extubation is safe. At TOF 0.7, significant residual neuromuscular blockade (RNMB) is present — pharyngeal muscle weakness impairs swallowing and airway protection, risk of regurgitation and aspiration is elevated, and hypoxic ventilatory response is blunted. Clinical signs (head lift for 5 seconds, hand grip strength) are unreliable at TOF <0.9. Reversal with sugammadex (for rocuronium/vecuronium) or neostigmine + glycopyrrolate (for benzylisoquinoliniums) should be administered. Clinical assessment alone cannot reliably detect RNMB at TOF 0.7.

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

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.