Is the dose-related reduction in succinylcholine-induced myalgia due to cointervention?

To the Editor:—Schreiber et al. noted an association between larger doses of succinylcholine and a reduced incidence of fasciculation and myalgia. However, pretreatment with a nondepolarizing neuromuscular blocker is also associated with a reduced risk of fasciculation and myalgia. It is a common practice for clinicians to use a larger dose of succinylcholine when they have provided pretreatment with a nondepolarizing neuromuscular blocker, making pretreatment a potential cointervention. Consequently, pretreatment with a nondepolarizing neuromuscular blocker could be a confounder in the association between higher doses of succinylcholine and a reduced risk of fasciculation and myalgia: Pretreatment is a determinant of the outcome under investigation, it is not germane to the association under investigation, and it may not be equally distributed among study groups. Does the available data permit adjusting for this potential confounder, or is it better to consider the associations between the dose of succinylcholine and the risks of fasciculation and myalgia as hypotheses for future investigation?