Key Points • Neuromuscular blocking agents are used to improve conditions for tracheal intubation, to provide immobility during surgery, and to facilitate mechanical ventilation. • The main site of action of neuromuscular blocking agents (muscle relaxants) is on the nicotinic cholinergic receptor at the endplate of muscle. They also have effects at presynaptic receptors located on the nerve terminal. • Succinylcholine is a blocking agent that produces depolarization at the endplate and binds to

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... extrajunctional receptors. In spite of many side effects, such as hyperkalemia, its rapid offset makes it the drug of choice for rapid sequence induction. • All other drugs available are nondepolarizing. They compete with acetylcholine for the same binding sites. • Fade in response to high-frequency stimulation (e.g. train-of-four, 2 Hz for 2 seconds) is a characteristic of nondepolarizing blockade. Train-of-four fade is difficult to evaluate manually or visually during recovery when ratio is >0.4. • The upper airway is particularly sensitive to the effects of nondepolarizing blockade. Complete recovery does not occur until train-of-four ratio at the adductor pollicis is >0.9. • Residual paralysis is more frequent with long-duration than intermediate-duration agents.