PROLONGED PARALYSIS AFTER NEUROMUSCULAR BLOCKADE

Non-depolarizing neuromuscular blocking agents have been used with inc reasing frequency in critically ill patients. Recently, numerous repor ts have described patients with prolonged muscle weakness after use of these agents for more than two days. Brief weakness lasting several h ours to several days is likely the result of prolonged neuromuscular b lockade, while more prolonged weakness lasting several weeks to months is likely caused by a myopathy. Specific features of this myopathic d isorder are reviewed. Clinically, patients have flaccid paralysis with intact sensation and cognition. Electrodiagnostic findings include de creased M-wave amplitudes, mild positive waves and fibrillations and s mall, polyphasic motor unit potentials. Muscle biopsy findings include atrophy of type I and type II fibers, myofiber necrosis and selective loss of thick myofilaments. This myopathic disorder is felt to be rel ated to the prolonged use of non-depolarizing neuromuscular blocking a gents either alone or in combination with other medications or disorde rs. Many authors feel that the disorder is caused specifically by a co mbination of prolonged neuromuscular blockade and corticosteroids. Sel ective loss of thick myofilaments on muscle biopsy has been produced e xperimentally in rats by combining denervation with high doses of cort icosteroids. As this disorder likely lends to additional respiratory c ompromise, difficulty weaning from the ventilator, and prolonged hospi talization, prevention is warranted. Methods of prevention include min imizing the dosage of nondepolarizing neuromuscular blocking agents an d of other drugs with an effect on the neuromuscular junction, twitch monitoring with a peripheral nerve stimulator and allowing patients to come to an unparalyzed state for brief periods.