Improved Perioperative Analgesia with Ultrasound- Guided Ilioinguinal/iliohypogastric Nerve or Transversus Abdominis Plane Block for Open Inguinal Surgery: A Systematic Review and Meta-Analysis of Randomized Controlled Trials

Ilioinguinal/iliohypogastric (II/IH) nerve and transversus abdominis plane (TAP) blocks are both effective perioperative analgesic techniques for open inguinal surgery. Ultrasound-guided II/IH nerve and TAP blocks have been increasingly utilized in patients for perioperative analgesia. Yet the use of ultrasound has not been fully evaluated. We conducted this meta-analysis to evaluate the clinical efficacy of ultrasound-guided II/IH nerve or TAP blocks for perioperative analgesia in patients undergoing open inguinal surgery. A systematic search of seven databases was conducted from database inception to March 5, 2015. Randomized controlled trials (RCTs) comparing the clinical efficacy of either ultrasound-guided or landmark-based techniques to perform II/IH nerve and TAP blocks for perioperative analgesia in patients with open inguinal surgery were included. Two reviewers independently (and in duplicate) screened abstracts and full texts. We constructed random effects models to pool standardized mean difference (SMD) for continuous outcomes and odds ratio (OR) for dichotomized outcomes. Heterogeneity between studies was estimated by I2statistic. One hundred thirty-nine articles were identified and among them 4 articles were eligible for the final analysis. Ultrasound-guided II/IH nerve or TAP blocks were associated with reduced use of intraoperative additional analgesia with OR=0.21 (95% CI: 0.09 to 0.49; p<0.001; I2= 0.00%) and significant reduction of pain scores during day-stay with SMD=-0.96 (95% CI: -1.68 to -0.24; p<0.001; I2=88.3%). The use of rescue drug was also significantly lower in the ultrasound-guided group (OR=0.16; 95% CI: 0.06, 0.40; p<0.001, I2=10.2%). In conclusion, the use of ultrasound-guidance to perform an II/IH nerve or a TAP block was associated with improved perioperative analgesia in patients following open inguinal surgery compared to landmark-based methods.