BACKGROUND Pectoral nerve blocks (PECS block) might be an interesting new regional anaesthetic technique in patients undergoing breast surgery. OBJECTIVE The aim of this meta-analysis was to investigate postoperative pain outcomes and adverse events of a PECS block compared with no treatment, sham treatment or other regional anaesthetic techniques in women undergoing breast surgery. DESIGN We performed a systematic review of randomised controlled trials (RCT) with meta-analysis and risk of bias assessment. DATA SOURCES The databases MEDLINE, CENTRAL (until December 2019) and clinicaltrials.gov were systematically searched. ELIGIBILITY CRITERIA All RCTs investigating the efficacy and adverse events of PECS compared with sham treatment, no treatment or other regional anaesthetic techniques in women undergoing breast surgery with general anaesthesia were included. RESULTS A total of 24 RCTs (1565 patients) were included. PECS (compared with no treatment) block might reduce pain at rest [mean difference −1.14, 95% confidence interval (CI), −2.1 to −0.18, moderate quality evidence] but we are uncertain regarding the effect on pain during movement at 24 h after surgery (mean difference −1.79, 95% CI, −3.5 to −0.08, very low-quality evidence). We are also uncertain about the effect of PECS block on pain at rest at 24 h compared with sham block (mean difference −0.83, 95% CI, −1.80 to 0.14) or compared with paravertebral block (PVB) (mean difference −0.18, 95% CI, −1.0 to 0.65), both with very low-quality evidence. PECS block may have no effect on pain on movement at 24 h after surgery compared with PVB block (mean difference −0.56, 95% CI, −1.53 to 0.41, low-quality evidence). Block-related complications were generally poorly reported. CONCLUSION There is moderate quality evidence that PECS block compared with no treatment reduces postoperative pain intensity at rest. The observed results were less pronounced if patients received a sham block. Furthermore, PECS blocks might be equally effective as PVBs. Due to mostly low-quality or very low-quality evidence level, further research is warranted. PROTOCOL REGISTRATION CRD42019126733.

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