MASSETER MUSCLE RIGIDITY AND NONDEPOLARIZING NEUROMUSCULAR BLOCKING-AGENTS

Masseter muscle rigidify has been identified as a possible risk factor for malignant hyperthermia (MH) and is usually noted in children rece iving intravenously administered succinylcholine chloride after mask i nduction with halothane, Nondepolarizing muscle relaxants are consider ed safe for persons susceptible to MH. In this article, we present a c ase of clinically recognized jaw rigidity in the absence of succinylch oline after administration of a nondepolarizing muscle relaxant that w as reported to the Malignant Hyperthermia Association of the United St ates hot line, The patient had recurrent jaw rigidity during subsequen t anesthesia when a different nondepolarizing muscle relaxant was give n, The North American MH Registry was then reviewed for similar cases, Three cases of masseter muscle rigidity in the presence of nondepolar izing muscle relaxants were discovered, Two of the patients were not f ound to be susceptible to MH; however, the third patient had positive findings on muscle biopsy, These cases do not provide enough informati on to confirm the ability of nondepolarizing muscle relaxants to cause jaw rigidity in the absence of MH.