Complications of muscle relaxants

T HIS ARTICLE reviews the complications of muscle relaxants in clinical practice. Their introduction more than 50 years ago revolutionized the practice of anesthesia but was also associated with a new set of anesthetic-induced complications. Much of the development of new compounds has been with the aim of avoiding or reducing these effects, some of which contributed to postoperative morbidity and mortality. This review emphasizes the complications that have attracted recent attention, and is restricted to those agents in current use and to the recently introduced compounds, doxacurium, mivacurium, pipecuronium, and rocuronium. It should be considered an update of the article published in this journal 10 years ago. ~ Complications of muscle relaxants can be unwanted effects of the normal action of the drugs at the neuromuscular junction, actions at other sites, abnormal or idiosyncratic responses, or result from their use in unusual situations. Some of the complications are common to all relaxants (general complications), eg, slow recovery from block or residual blockade, anaphylaxis, etc, others are restricted to a few or single drugs (specific complications), eg, prolonged block after succinylcholine or mivacurium from a decrease in plasma cholinesterase activity. This review has less emphasis on succinylcholine, in part because most of its specific complications are well recognized but also because it is now used much less frequently than the estimate 10 years ago of its use in 75% of all anesthetics.