Nondepolarizing neuromuscular blocking agents (NMBA) are being used wi
th increasing frequency in critically ill patients. Recently, many cen
ters have described patients with prolonged muscle weakness after long
-term use of these agents, either alone or in combination with other a
gents or disorders. Brief weakness lasting several hours to several da
ys is probably the result of prolonged neuromuscular blockade, while m
ore prolonged weakness lasting several weeks to months is, in all like
lihood, caused by a myopathy. Patients with this myopathic disorder ha
ve flaccid paralysis with intact cognition and sensation. Electrodiagn
ostic findings include decreased M-wave amplitudes, positive waves and
fibrillations, and rapid recruitment of small amplitude short duratio
n, polyphasic motor unit potentials. Muscle biopsy findings include at
rophy of type I and type II fibers, myofiber necrosis, and selective l
oss of thick myofilaments. The myopathy is believed to be related to t
he prolonged use of NMBA either alone or in combination with other dis
orders or medications, particularly corticosteroids. The weakness expe
rienced by these patients leads to additional respiratory compromise,
difficulty weaning from the ventilator, and prolonged hospitalization.
(C) 1995 Judith L. Gooch, MD. Published by John Wiley and Sons, Inc.