Intravenous dexmedetomidine versus tramadol for treatment of shivering after spinal anesthesia: a meta-analysis of randomized controlled trials

Background Shivering is a frequent complication after spinal anesthesia. Increasing studies have compared the effect of intravenous dexmedetomidine and intravenous tramadol on shivering after spinal anesthesia, hence we performed a meta-analysis of randomized controlled trials to compare dexmedetomidine with tramadol on the treatment of post-spinal anesthesia shivering. Methods PubMed, Embase, Cochrane library, Web of Science and Google Scholar were searched to find the eligible studies comparing the effect of dexmedetomidine and tramadol on the treatment of shivering after spinal anesthesia. Mean difference (MD) or risk ratio (RR) along with 95% confidence interval (CI) was used to analyze the outcomes. I-2 test was conducted to assess the heterogeneity of the included trials. We utilized Review Manager 5.3 to perform statistical analyses. Results Thirteen randomized controlled trials including 864 subjects were included. Dexmedetomidine had higher effective rate of shivering control (RR =1.03; 95%CI [1.01, 1.06], P = 0.01, I-2 = 14%), shorter time to cease shivering (MD = -2.14; 95%CI [- 2.79, - 1.49], P < 0.00001, I-2 = 98%), lower recurrent rate of shivering (RR = 0.45; 95%CI [0.27, 0.73], P = 0.001, I-2 = 0%), lower incidences of nausea (RR = 0.10; 95%CI [0.05, 0.19], P < 0.00001, I-2 = 48%), and vomiting (RR = 0.13; 95%CI [0.06, 0.30], P < 0.00001, I-2 = 0%), higher incidence of sedation (RR = 2.48; 95%CI [1.32, 4.65], P = 0.005, I-2 = 82%), hypotension (RR = 2.50; 95%CI [1.24, 5.03], P = 0.01, I-2 = 0%) and bradycardia (RR = 4.78; 95%CI [1.76, 13.00], P = 0.002, I-2 = 0%), compared with tramadol. Conclusions Dexmedetomidine is superior to tramadol for shivering treatment, due to higher effective rate of shivering control, earlier onset of action and lesser recurrence of shivering with higher incidence of sedation and lower incidences of nausea and vomiting. However, dexmedetomidine is also associated with higher incidences of hypotension and bradycardia than tramadol.