Depolarising Block No Fade — FRCA Primary MCQ

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ModeratePharmacology - NeuromuscularDepolarising Block No FadeFRCA Primary

Depolarising neuromuscular block is characterised by which pattern on nerve stimulator?

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Correct answer: A — Equal reduction in all four twitches of the TOF (no fade)

A depolarising (Phase I) block produces equal reduction in all four twitches of the TOF (no fade / TOF ratio remains approximately 1.0). Non-depolarising block produces fade (progressive reduction in twitch height). Phase II block (prolonged suxamethonium exposure) develops characteristics of non-depolarising block including fade and post-tetanic potentiation.

Reference: Peck Hill Williams 2014 Pharmacology for Anaesthesia and Intensive Care