Quadro-Iliac Plane Block for Postoperative Analgesia in Laparoscopic Inguinal Hernia Repair

Laparoscopic inguinal hernia repair (TAPP or TEP) causes less pain than open repair, but many patients still report moderate to severe pain in the early postoperative period, with both somatic and visceral components. The quadro-iliac plane block is a recently described fascial plane block in which local anesthetic is injected between the inner surface of the iliac crest and the posterior surface of the quadratus lumborum muscle. Cadaveric data show spread to the ilioinguinal, iliohypogastric, subcostal and genitofemoral nerves and the lumbar plexus, and case series suggest effective analgesia after inguinal hernia surgery.

This single-center, prospective, randomized, controlled, outcome-assessor-blinded trial will be conducted at Marmara University Pendik Training and Research Hospital. Sixty-four patients will be randomized 1:1 by computer-generated random numbers to Group QIPB or Group C (control). The anesthesia team will know the group allocation; the investigator assessing outcomes will be blinded.

All patients will receive standard monitoring (ECG, non-invasive blood pressure, SpO2, EtCO2, bispectral index) and IV midazolam 0.02 mg/kg premedication. Anesthesia will be induced with remifentanil 2 µg/kg, propofol 2-2.5 mg/kg and rocuronium 0.6 mg/kg, and maintained with desflurane and remifentanil infusion, targeting BIS 40-60. In Group QIPB, after induction and in the lateral position, a unilateral QIPB will be performed on the surgical side with a low-frequency convex probe placed parasagittally at the attachment of the quadratus lumborum to the iliac crest. Using an in-plane approach with a 100-mm block needle, needle position will be confirmed with 5 mL saline, followed by 40 mL of 0.25% bupivacaine with intermittent aspiration. Group C will receive no block.

Fifteen minutes before the end of surgery, all patients will receive IV paracetamol 1 g, tramadol 1.5 mg/kg and ondansetron 8 mg. After surgery, all patients will receive IV tramadol PCA (10 mg/mL; 1 mL bolus; 10-minute lockout). Patients with NRS > 4 will receive rescue IV morphine 4 mg. Pain scores at rest and on coughing and cumulative tramadol consumption will be recorded at 0, 6, 12 and 24 hours. The QoR-15 questionnaire will be administered preoperatively (baseline) and at 24 hours.

The sample size was calculated using G*Power 3.1. Assuming a mean 24-hour tramadol consumption of 85 mg in the control group, a minimum clinically relevant reduction of 25 mg (approx. 30%) and an SD of 30 mg (Cohen's d = 0.83), with α = 0.05 and power = 0.80, 24 patients per group are required. To allow for dropouts and protocol violations, 32 patients per group (64 in total) will be enrolled. Data will be analyzed using the independent-samples t-test or Mann-Whitney U test, repeated-measures ANOVA or linear mixed-effects models for pain scores over time, Kaplan-Meier analysis with the log-rank test for time to first PCA demand, chi-square or Fisher's exact test for categorical outcomes, and ANCOVA adjusted for baseline QoR-15. A two-sided p < 0.05 will be considered statistically significant.