Impact of adding opioids to paravertebral blocks in breast cancer surgery patients: A systematic review and meta-analysis

BACKGROUND: Several breast cancer studies have reported the use of adjuvant opioids with the paravertebral block (PVB) to improve outcomes. However, there is no level-1 evidence justifying its use. AIM: To elucidate if the addition of opioids to PVB improves pain control in breast cancer surgery patients. METHODS: We conducted an electronic literature search across PubMed, Embase, Scopus, and Google Scholar databases up to October 20, 2020. Only randomized controlled trials (RCTs) comparing the addition of opioids to PVB with placebo for breast cancer surgery patients were included. RESULTS: Six RCTs were included. Our meta-analysis indicated significantly reduced 24-h total analgesic consumption with the addition of opioids to PVB as compared to placebo [standardized mean difference (SMD) -1.57, 95% confidence interval (CI): -2.93, -0.21, I(2) = 94%]. However, on subgroup analysis, the results were non-significant for studies using single PVB (SMD: -1.76, 95%CI: -3.65, 0.13 I(2) = 95.09%) and studies using PVB infusion (SMD: -1.30, 95%CI: -4.26, 1.65, I(2) = 95.49%). Analysis of single PVB studies indicated no significant difference in the time to first analgesic request between opioid and placebo groups (mean difference -11.28, 95%CI: -42.00, 19.43, I(2 )= 99.39%). Pain scores at 24 h were marginally lower in the opioid group (mean difference -1.10, 95%CI: -2.20, 0.00, I(2 )= 0%). There was no difference in the incidence of postoperative nausea and vomiting between the two groups. CONCLUSION: Current evidence suggests a limited role of adjuvant opioids with PVB for breast cancer surgery patients. Further homogenous RCTs with a large sample size are needed to clarify the beneficial role of opioids with PVB.