Effect of butorphanol on etomidate-induced myoclonus: a systematic review and meta-analysis

Objective: To evaluate the effect of butorphanol on the prevention of myoclonus induced by etomidate. Materials and methods: We searched the PubMed, Embase, Cochrane Library, and China National Knowledge Infrastructure databases to collect relevant randomized controlled trials (RCTs) evaluating the effect of butorphanol on etomidate-induced myoclonus in January 2019 without any language restrictions. The primary outcome was the incidence of etomidate-induced myoclonus. Secondary outcomes included the incidence of myoclonus at various degrees and the incidence of adverse effects. Risk ratios (RRs) were calculated for binary outcomes. All statistical analysis were performed by using RevMan 5.3 software. Results: We identified 6 RCTs involving a total of 608 patients who reported the incidence of etomidate-induced myoclonus. In pooled analyses, the incidence of etomidate-induced myoclonus in the butorphanol group was significantly lower than that in the control group (RR =0.15, 95% CI [0.10, 0.22], P<0.00001). Subgroup analyses showed that butorphanol significantly decreased the numbers of patients with mild myoclonus (RR =0.41, 95% CI [0.25, 0.68], P=0.0005), moderate myoclonus (RR =0.18, 95% CI [0.09, 0.34], P<0.00001), and severe myoclonus (RR =0.04, 95% CI [0.01, 0.10], P<0.00001). Additionally, butorphanol did not increase the incidence of postoperative nausea/vomiting (RR =3.0, 95% CI [0.32, 28.42], P=0.34) or dizziness (RR =6.79, 95% CI [0.84, 54.84], P=0.07) associated with etomidate. Conclusion: Our findings suggest that butorphanol can effectively prevent the incidence of etomidate-induced myoclonus and alleviate the intensity of etomidate-induced myoclonus, without inducing postoperative nausea/vomiting and dizziness.