Analgesic Effect of Bilateral Subcostal Quadratus Lumborum Block in Laparoscopic Colorectal Surgery

Bilateral ultrasound-guided subcostal quadratus lumborum block (20 mL, 0.25% bupivacaine, bilaterally) will be performed. All patients will receive multimodal analgesia, including a single dose of IV tenoxicam 20 mg. Additionally, 15 mg/kg IV paracetamol (based on IBW) will be administered at skin closure and continued every 6 hours postoperatively. A standardized IV PCA protocol will be initiated using a PCA device programmed to deliver morphine boluses of 0.01-0.015 mg/kg (IBW), with a 6-minute lockout and a 4-hour maximum of 0.1-0.15 mg/kg (IBW). Upon arrival in the PACU, patients with a resting NRS ≥4 will receive titrated IV morphine boluses of 0.03 mg/kg (IBW; max 10 mg) every 10 minutes until pain is controlled. In the surgical ward, patients with breakthrough pain (NRS ≥4) despite PCA use will receive IV tramadol 1-1.5 mg/kg (IBW) in 50-100 mg slow doses, not exceeding 400 mg/day.All patients will receive 8 mg dexamethasone and 0.15 mg/kg ondansetron (IBW) for PONV prophylaxis.

Patients in this group will not undergo plane blocks. IV morphine PCA multimodal analgesia will be provided: all patients will receive a single dose of IV tenoxicam 20 mg. Additionally, 15 mg/kg IV paracetamol (based on IBW) will be administered at skin closure and continued every 6 hours postoperatively. A standardized IV PCA protocol will be initiated for all patients using a PCA device, programmed to deliver morphine boluses of 0.01-0.015 mg/kg (IBW), with a 6-minute lockout and a 4-hour maximum dose of 0.1-0.15 mg/kg (IBW). Upon arrival in PACU, patients with a resting NRS ≥4 will receive titrated IV morphine boluses of 0.03 mg/kg (IBW; max 10 mg) every 10 minutes until pain is controlled. In the ward, patients with breakthrough pain (NRS ≥4) despite PCA use will receive IV tramadol 1-1.5 mg/kg (IBW), administered slowly in 50-100 mg doses (max 400 mg/day). All patients will receive IV dexamethasone (8 mg) before induction and IV ondansetron (0.15 mg/kg IBW) near surgery end.

A standardized IV PCA protocol will be initiated for all patients using a PCA device (Body Guard 575 pain manager, UK), programmed to deliver morphine boluses of 0.01-0.015 mg/kg (IBW), with a 6-minute lockout and a 4-hour maximum dose of 0.1-0.15 mg/kg (IBW). No basal infusion will be used.