During train-of-four (TOF) monitoring, a patient shows a TOF ratio of 0.7 after neostigmine reversal. The anaesthetist plans to extubate. Which clinical deficit is MOST likely to be present at this TOF ratio?

• A Inability to sustain tetanic stimulation for 5 seconds
• B Complete loss of tidal volume and apnoea
• C Impaired upper airway dilator muscle function and aspiration risk ✓
• D Absent corneal reflexes and loss of airway protective cough

Explanation

Adequate reversal requires a TOF ratio ≥0.9 measured with acceleromyography. At a TOF ratio of 0.7, gross limb movements and tidal volume may appear adequate, but upper airway dilator muscles (especially genioglossus) and pharyngeal muscles are differentially sensitive to residual paralysis, remaining significantly impaired. This leads to upper airway obstruction, impaired hypoxic ventilatory response, and increased aspiration risk. Complete apnoea occurs at TOF ratios near zero. The threshold for safe extubation is specifically ≥0.9, not 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.