During train-of-four stimulation in a patient receiving a non-depolarizing muscle relaxant, fade is observed. This phenomenon is due to:

• A Depletion of plasma cholinesterase with repeated nerve stimulation
• B Desensitization of postsynaptic nicotinic receptors to acetylcholine
• C Metabolic acidosis impairing acetylcholine synthesis
• D Presynaptic inhibition of acetylcholine mobilization and release with repeated stimulation ✓

Explanation

Fade with TOF stimulation in non-depolarizing block is primarily due to presynaptic inhibition. With high-frequency stimulation, acetylcholine mobilization from presynaptic stores is impaired, reducing quantal release. This is a hallmark of non-depolarizing block. Phase I block with succinylcholine shows no fade (all four responses are equally depressed). Receptor desensitization is a separate phenomenon.

Reference: Miller's Anesthesia, 9th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.