I had a discussion the other day with one of the attendings at work on whether pretreatment of rocuronium prevents myalgia. We all know that the most common practice is to administer a small dose (10–30%) of the ED95 of a nondepolarizing neuromuscular blocker such as rocuronium a few minutes prior to administration succinylcholine, with the hope of abolishing the fasciculations and the postoperative myalgia. Although many studies have been done on this topic, it appears that there are conflicting results on whether pretreatment of non depolarizing agent can prevents myalgia. In addition, there are debates on the agent of choice for pretreatment, the optimal dose and timing of nondepolarizing muscle relaxants on prevention of fasciculation and myalgia. Some studies have shown the small dose of Rocuronium attenuates myalgia to some extent, however, the risk of potentially serious adverse effects such as muscle weakness before loss of consciousness and not optimal intubation condition are not negligible.
Although pretreatment decreases the degree of fasciculations significantly, it is interesting that the severity of fasciculations has no direct correlation with the frequency of postoperative myalgia. The presumed mechanism of decreasing nondepolarising neuromuscular blockers block prejunctional nicotinic receptors and thus prevent fasciculations, producing a decrease in postoperative myalgia. Interestingly, the increase of creatine kinase is not attenuated by any non-depolarizing muscle relaxant. There are two studies, however, that didn’t show any benefits of using pretreatment of non-depolarizing agent prior to administration of succinylcholine.
So what is the conclusion? You may ask. I personally feel that if patient has a difficult airway, I would not want to take a chance of not having the optimal intubation condition by giving pretreatment of rocuronium. Lidocaine (1.5mg/kg) on the other hand, has been effectively shown to reduce succinylcholine induced myalgia and provide better relief at 48 hours post surgery compared to pretreatment of rocuronium. If I can’t use lidocaine, I would consider the pretreatment of rocuronium if patient is high risk for myalgia such as female with past history of myalgia. I wouldn’t use it on a regular basis as there is not one single study that has fully demonstrated its efficacy in attenuating myalgia with pretreatment of rocuronium.
Spencer D. et al. A comparison of rocuronium and lidocaine for the prevention of postoperative myalgia after succinylcholine administration.AANA J. 2002 Oct;70(5):367-72.
Amornyotin S, et al. Can lidocaine reduce succinylcholine induced postoperative myalgia? J Med Assoc Thai. 2002 Sep;85 Suppl 3:S969-74.
Josh GP, et al. Effects of pretreatment with cisatracurium, rocuronium, and d-tubocurarine on succinylcholine-induced fasciculations and myalgia: a comparison with placebo. J Clin Anesth. 1999 Dec;11(8):641-5.
Mencken et al. Pretreatment before succinylcholine for outpatient anesthesia? Anesth Analg. 2002 Mar;94(3):573-6