Effects of low-dose ketamine on succinylcholine-induced postoperative myalgia in outpatient surgeries: a randomized, double-blind study

OBJECTIVE: Despite the many complications of succinylcholine, it is still widely used as a superior muscle relaxant for rapid sequence induction. One of these complications is postoperative myalgia (POM). The aim of this study was to investigate the prophylactic effect of low-dose ketamine on the incidence and severity of POM. MATERIALS AND METHODS: In this double-blind clinical study, a total of 148 patients scheduled for general anesthesia were randomly divided into two equal groups. Initially, in Group K, 0.5 mg/kg of ketamine was injected intravenously, whereas in Group N, the same volume (5 mL) of normal saline was injected. Thereafter, anesthesia was induced in all patients, by injecting 1.5 mg/kg of fentanyl and 2 mg/kg of propofol intravenously. Following the loss of eyelid reflex, 1.5 mg/kg of succinylcholine was injected intravenously as a muscle relaxant and then the patients were intubated. POM was defined as a pain with no surgical interferences, and its intensity was graded based on a four-point scale. The incidence and severity of myalgia were assessed by a blinded observer 24 hours after surgery. RESULTS: In terms of demographic data, the results of this study showed that there is no significant difference between patients in both groups (P>0.05). Overall, the incidence of POM in Group K was significantly less, when compared with Group N (P<0.05), but both groups were comparable based on the grade 2 of POM. After the induction of anesthesia, the systolic and diastolic blood pressure values were found to reduce in both groups (P<0.05). However, the changes were somehow similar, and repeated measures of variance analysis showed no significant difference in the two study groups (P>0.05). CONCLUSION: The addition of 0.5 mg/kg of ketamine to propofol for the induction of anesthesia can be effective in reducing the incidence of low-grade POM.