[Modern muscle relaxants and their clinical application]

Various new muscle relaxants are available: atracurium, rocuronium and vecuronium all have an intermediate duration of action, whereas doxacurium and pipecuronium are long-acting and mivacurium is a short-acting nondepolarizing muscle relaxant. The duration of action of atracurium and mivacurium is determined by their degradation, which makes them unique among the nondepolarizing muscle relaxants in this respect. The time of onset is shortest with rocuronium, while vecuronium is probably the muscle relaxant with the fewest undesirable side-effects. In clinical practice, muscle relaxants of short and intermediate duration of action should be preferred, since such agents carry the least risk of residual neuromuscular block postoperatively. Because recovery from them is slow, long-acting agents should preferentially be used only when postoperative mechanical ventilation is intended. The use of a peripheral nerve stimulator is the only reliable guide to appropriate administration of muscle relaxants.