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NMB Monitoring Site Accuracy — FRCA Final MCQ

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HardGeneral AnaesthesiaNMB Monitoring Site AccuracyFRCA Final

A 45-year-old woman (ASA II, 68 kg) is undergoing a laparoscopic appendicectomy. She receives rocuronium 50 mg (0.7 mg/kg) at induction. The TOF monitor at the orbicularis oculi shows a TOF ratio of 0.92 at the end of surgery. Can she be safely extubated?

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Correct answer: E — Yes – TOF ratio >0.9 confirms adequate recovery

While a TOF ratio >0.9 at the adductor pollicis (AP) is the accepted threshold for safe extubation, monitoring at the orbicularis oculi can be misleading. The orbicularis oculi recovers BEFORE the adductor pollicis – a TOF ratio of 0.9 at the orbicularis oculi does NOT guarantee a TOF ratio of 0.9 at the adductor pollicis. The AP is the gold-standard monitoring site for neuromuscular block assessment because it best reflects the degree of block at the diaphragm and upper airway muscles. Extubation based on orbicularis oculi monitoring alone risks residual neuromuscular block.

Reference: RCOA – 2023 – Neuromuscular monitoring: monitoring site selection; Naguib M – 2018 – Neuromuscular pharmacology