Ethical approval and patient consent are not required because this is a systematic review and meta-analysis of previously published studies. The systematic review and meta-analysis are conducted and reported in adherence to PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) [14, 15].
Search strategy and study selection
Two investigators have independently searched the following databases (inception to April 2021): PubMed, EMbase, Web of science, EBSCO, and Cochrane library databases. The electronic search strategy is conducted using the following keywords: dexamethasone, and interscalene block, and arthroscopy, and shoulder. We also check the reference lists of the screened full-text studies to identify other potentially eligible trials.
The inclusive selection criteria are as follows: (i) patients undergo shoulder arthroscopy; (ii) intervention treatments are perineural versus intravenous dexamethasone supplemented to interscalene block; (iii) study design is RCT.
Data extraction and outcome measures
We have extracted the following information: author, number of patients, age, female, body weight, American Society of Anesthesiologists (ASA) physical status and detail methods in each group etc. Data have been extracted independently by two investigators, and discrepancies are resolved by consensus. We also contact the corresponding author to obtain the data when necessary. The primary outcome is block duration. Secondary outcomes include pain scores at 12 h, pain scores at 24 h, opioid consumption, nausea/vomiting.
Quality assessment in individual studies
Methodological quality of the included studies is independently evaluated using the modified Jadad scale . There are 3 items for Jadad scale: randomization (0-2 points), blinding (0-2 points), dropouts and withdrawals (0-1 points). The score of Jadad Scale varies from 0 to 5 points. An article with Jadad score ≤ 2 is considered to be of low quality. If the Jadad score ≥ 3, the study is thought to be of high quality .
We estimate the standard mean difference (SMD) with 95% confidence interval (CI) for continuous outcomes (block duration, pain scores at 12 h, pain scores at 24 h and opioid consumption) and odd ratios (ORs) with 95% CIs for dichotomous outcomes (nausea/vomiting). The random-effects model is used regardless of heterogeneity. Heterogeneity is reported using the I2 statistic, and I2 > 50% indicates significant heterogeneity [15, 18]. Whenever significant heterogeneity is present, we search for potential sources of heterogeneity via omitting one study in turn for the meta-analysis or performing subgroup analysis. All statistical analyses are performed using Review Manager Version 5.3 (The Cochrane Collaboration, Software Update, Oxford, UK).