The Iceberg Theory — Fact or Fiction? Implication for Monitoring
Paton and Waud (1), demonstrated an apparent excess of receptor sites for antagonist drugs which they proposed constituted a “Margin of Safety” for neuromuscular transmission. They suggested that in view of the reported vast excess of ACh released from the motor terminals up to 80% of the available ACh receptors on the post synaptic membrane had to be ‘occupied’ by non-depolarizing drug before the indirectly elicited twitch response was depressed. Waud and Waud (2) subsequently demonstrated that if a 50Hz tetanic stimulus was used the margin of safety was reduced from 80% to 50–60%. Complete ablation of the twitch response occurred when over 95% of the receptors were ‘occupied’.
KeywordsReceptor Occupancy Neuromuscular Transmission Neuromuscular Blocking Agent Effect Compartment Antagonist Drug
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