Effectiveness of Rectus Sheath Block as an Adjunct to General Anesthesia for Postoperative Pain and Inflammation in Patients Undergoing Midline Incision Laparotomy at RSUP Sanglah

This is a double-blind randomized controlled trial conducted in adult patients (18-64 years) undergoing midline incision laparotomy under general anesthesia at Sanglah Hospital. Eligible participants are enrolled consecutively and randomized using permuted block randomization with sealed envelopes into two parallel groups:

Group A (Control): General anesthesia without rectus sheath block.

Group B (Intervention): General anesthesia plus bilateral ultrasound-guided posterior rectus sheath block (RSB) using bupivacaine 0.25%.

Anesthetic management is standardized. Patients receive IV midazolam 0.02 mg/kg as premedication. Induction is performed with propofol 1-2 mg/kg and fentanyl 2 mcg/kg, followed by atracurium 0.5 mg/kg for intubation. Maintenance includes pressure-controlled ventilation (FiO₂ 40%, flow 2 L/min) and propofol infusion 50-150 mcg/kg/min. Intraoperative analgesia is supplemented with fentanyl 0.5 mcg/kg every 45 minutes. Hemodynamics are maintained within 20% of baseline.

RSB technique (Group B): After intubation, the abdominal skin is disinfected. A linear ultrasound probe is placed lateral to the umbilicus to identify the rectus abdominis muscle and posterior rectus sheath. Using an in-plane approach, a 50 mm needle is advanced from lateral to medial until the needle tip lies between the rectus abdominis muscle and posterior rectus sheath. After negative aspiration, 20 mL of bupivacaine 0.25% is injected as a single-shot on one side with aspiration every 3 mL, visualizing separation of the rectus muscle from the posterior sheath. The procedure is then repeated on the contralateral side (bilateral block).