Clonidine versus other adjuncts added to local anesthetics for pediatric neuraxial blocks: a systematic review and meta-analysis

Background: Clonidine is a common adjunct to local anesthetics for pediatric neuraxial block; however, the pros and cons between clonidine and other adjuncts remain unclear. Thus, we performed this meta-analysis of randomized controlled trials to assess the efficacy and adverse effects between clonidine and other adjuncts added to local anesthetics.

Materials and methods: The systematic search, data extraction, critical appraisal, and pooled analysis were performed according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement. Randomized controlled studies were searched in Cochrane (to present), Medline (1946 to present), Embase (1974 to present), and Biosis (1995 to present). Relative risks (RRs), standard mean difference (SMD), and associated CIs were calculated using RevMan statistical software to assess continuous and dichotomous data. Heterogeneity in studies was measured by forest plots and I² values. Subgroup analysis was performed for continuous and dichotomous variables, while meta-regression was applied for continuous data with high I² values.

Results: A total of 15 randomized controlled studies met the inclusion criteria. There was a longer duration of postoperative analgesia in the clonidine group than for other adjuncts (SMD=1.54, p=0.005, I²=96%). The number of patients requiring rescue analgesia was lower in the clonidine group without the addition of epinephrine (RR=0.55, p=0.0002, I²=0), while the RR for the comparison with epinephrine was significant (p=0.62, I²=95%). The duration of motor block was longer in the clonidine group (mean difference [MD]=1.06, p<0.00001, I²=0). The clonidine group also had a lower incidence of postoperative nausea and vomiting (PONV; RR=0.49, p<0.00001, I²=0). Postoperative bradycardia, hypotension, and urinary retention were not significantly different between clonidine and other adjuncts (p>0.05).

Conclusion: Clonidine, compared with other adjuncts, added to local anesthetics for neuraxial block, provides a longer duration of postoperative analgesia with lower incidence of PONV. However, the duration of motor block may also be prolonged by clonidine.