Auricular stimulation for preoperative anxiety - A systematic review and meta-analysis of randomized controlled clinical trials

Study objective: Previous randomized controlled trials (RCTs) suggest that auricular stimulation (AS) is safe and effective in treatment of preoperative anxiety; however, a systematic evaluation is lacking. The aim was to summarize the evidence on efficacy and safety of AS for preoperative anxiety, as well as for other outcomes.

Design: We conducted a systematic review of RCTs including patients from all available populations. The search was done through MEDLINE (PubMed), EMBASE, Cochrane Central Register of Controlled Trials (CENTRAL), ISI Web of Science and Scopus Database from inception to June 2020. Study selection and data extraction were performed in by 2 independent reviewers with ability to resolve disagreements by a third author. Meta-analyses as well as the risk of bias and evidence quality assessments were performed according to the Cochrane 6.2, 2021 handbook recommendations.

Interventions: We compared AS with pharmacological and non-pharmacological interventions for different outcomes.

Measurements: We assessed the repercussion of the evaluated interventions over anxiety scores and their safety, physiological parameters, perioperative medications requirement and intensity of postoperative pain.

Main results: We have included 15 studies with 1603 patients. AS has presented reduced anxiety scores as compared to the sham control (Standardized Mean Difference (SMD) -0.72, 95% confidence interval (CI) -1.09 to -0.36, p < 0.0001; 8 trials; 701 patients; heterogeneity: I² 80%; GRADE: moderate certainty) and to no intervention (SMD -1.01, 95% CI -1.58 to -0.45, p = 0.0004; 4 trials; 420 patients; heterogeneity: I² 84%; GRADE: very low certainty). There was no difference between AS and benzodiazepines (SMD -0.03; 95% CI: -0.34 to 0.28; p = 0.84; 3 trials; 158 patients; heterogeneity: I² 0%; GRADE: very low certainty). No trials reported serious adverse effects of AS.

Conclusions: AS may be useful in treatment of preoperative anxiety. Due to heterogenous certainty in effect estimates, further research is needed to clarify the actual efficacy of AS for preoperative anxiety.