Rectus Sheath Block as an Adjunct to General Anesthesia for Midline Laparotomy Pain

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).

Postoperative management and assessments: Pain is evaluated by an independent observer using the Numeric Rating Scale (NRS 0-10) at T1 (15 minutes in the recovery room), T2 (1 hour), T3 (3 hours), T4 (6 hours), T5 (12 hours), and T6 (24 hours) postoperatively. Postoperative analgesia includes patient-controlled analgesia (PCA) morphine demand-only (1 mg per demand dose) for patients with GCS 15, plus oral paracetamol 500 mg every 6 hours. The time to first opioid request is recorded (minutes), and total morphine consumption during the first 24 hours is collected.

Inflammation assessment: Neutrophil-to-lymphocyte ratio (NLR) is measured from complete blood count (CBC) preoperatively (one day before surgery) and postoperatively (in the recovery room).

Key outcomes include postoperative NRS scores (T1-T6), time to first opioid request, total opioid requirement in the first 24 hours, and perioperative changes in NLR.

Inclusion criteria

• Adults aged 18-64 years.
• Patients undergoing midline laparotomy incision (incision extending above to below the umbilicus) for digestive, obstetric, or oncology cases (corresponding to T7-T12 dermatomes) under general anesthesia.
• ASA physical status I-III.
• Body mass index (BMI) 18.5-30 kg/m².
• Willing and able to provide written informed consent.

Exclusion criteria

• Refusal to participate.
• Infection or wound at the planned block site.
• Decreased level of consciousness.
• Known allergy to local anesthetics or opioids.
• Coagulation disorder.
• History of chronic pain.
• Hyperalgesia.