Efficacy and Safety of Transcutaneous Electrical Nerve Stimulation in Patients Undergoing Inguinal Hernia Repair: A Systematic Review and Meta-analysis

Background: Postoperative pain is a major cause of delayed recovery following inguinal hernia repair. Transcutaneous electrical nerve stimulation (TENS) is a simple, low-cost method of noninvasive analgesia. This study aimed to assess the efficacy and safety of TENS for pain management following inguinal hernia repair.Methods: We searched nine electronic databases and trial registries to identify randomized controlled trials (RCTs). The primary outcomes were postoperative pain and the use of rescue analgesics. The Risk of Bias 2 tool was used to evaluate the risk of bias in the included trials. The certainty of the evidence was assessed using Grading of Recommendations, Assessment, Development, and Evaluations (GRADE). Subgroup analyses were conducted based on the anesthesia type or TENS dose and frequency. This study is registered with PROSPERO (CRD42022353932).Results: Eleven RCTs, with a total of 559 patients, were included. The overall risk of bias was concerning due to the lack of information about concealment or published protocols. TENS may reduce pain on postoperative day (POD) 0 (standardized mean difference [SMD], -2.14; 95% confidence interval [CI], -3.54 to -0.73; moderate certainty of the evidence), POD 1 (SMD, -1.22; 95% CI, -1.92 to -0.52; moderate certainty of the evidence), and POD 2 (SMD, -0.97; 95% CI, -2.04 to 0.10; low certainty of the evidence). According to the subgroup analyses, postoperative pain was reduced, particularly with local anesthesia or repetitive and frequent TENS (P < 0.05). TENS may result in little-to-no difference in rescue analgesic use (risk ratio, 0.75; 95% CI, 0.47-1.18; low certainty of the evidence). No serious adverse events occurred (moderate certainty of the evidence).Conclusions: TENS may reduce pain in patients who have undergone inguinal hernia repair. Further trials are warranted to confirm our findings.