Rectus Sheath Block
Introduction
The rectus sheath block (RSB) is a regional anesthetic technique used for somatic analgesia of the anterior abdominal wall. It provides effective pain relief for midline incisions, umbilical hernia repairs, and laparoscopic procedures.
1. Anatomy of the Rectus Sheath
• The rectus abdominis muscle is enclosed within the rectus sheath, formed by the aponeuroses of the external oblique, internal oblique, and transversus abdominis muscles.
• The posterior rectus sheath contains the inferior epigastric vessels and the ventral rami of the lower thoracic nerves (T6–T12).
- The target for injection is the potential space between the posterior rectus sheath and the rectus abdominis muscle, where the thoracoabdominal nerves (T6-T12) travel.
2. Indications of Rectus Sheath Block
✅ Surgical Applications:
• Midline abdominal incisions (e.g., laparotomy).
• Umbilical and epigastric hernia repair.
• Laparoscopic surgery (as an adjunct).
• Pediatric surgeries (e.g., pyloromyotomy, umbilical hernia).
✅ Non-Surgical Applications:
• Postoperative analgesia for midline incisions.
• Acute and chronic abdominal wall pain.
3. Contraindications
❌ Absolute:
• Local infection at the injection site.
• Allergy to local anesthetics.
❌ Relative:
• Coagulopathy.
• Peritoneal injury (risk of bowel puncture).
4. Techniques of Rectus Sheath Block
A. Landmark-Based Technique
1. Position: Supine.
2. Landmarks:
• Midline of the abdomen.
• Lateral border of the rectus abdominis muscle.
3. Needle Insertion:
• Perpendicular to the skin, advanced until a “pop” sensation is felt as it passes through the anterior rectus sheath.
• Aspirate to avoid vascular injection.
• Inject local anesthetic (e.g., 20–30 mL of 0.25% bupivacaine or ropivacaine).
B. Ultrasound-Guided Technique (Preferred)
1. Position: Supine.
2. Ultrasound Probe Placement:
• Transverse probe above the umbilicus.
• Identify rectus abdominis muscle and posterior rectus sheath.
3. Needle Insertion:
• In-plane technique, targeting the potential space between posterior rectus sheath and rectus muscle.
• Confirm negative aspiration and inject local anesthetic.
🔹 Advantages of Ultrasound Guidance:
• Increased precision.
• Reduced risk of peritoneal or vascular puncture.
5. Drugs and Dosage
Local Anesthetic | Concentration | Volume per side | Duration of Action |
Bupivacaine | 0.25% | 20–30 mL | 6–8 hours |
Ropivacaine | 0.2–0.375% | 20–30 mL | 4–6 hours |
Lidocaine | 1% | 20–30 mL | 2–3 hours |
💡 Additives:
• Epinephrine (1:200,000) prolongs duration and reduces systemic absorption.
• Dexamethasone extends block duration.
6. Complications and Risks
⚠️ Common Risks:
• Peritoneal puncture → Risk of bowel perforation.
• Vascular puncture → Hematoma formation.
• Local anesthetic systemic toxicity (LAST) → If injected into the inferior epigastric vessels.
• Inadequate block → If local anesthetic is not placed correctly in the rectus sheath.
7. MCQs on Rectus Sheath Block
1. Which nerve fibers are blocked in a rectus sheath block?
A) Ilioinguinal and iliohypogastric nerves
B) Lateral cutaneous nerve of the thigh
C) Ventral rami of thoracoabdominal nerves (T6-T12)
D) Femoral nerve
✅ Answer: C (RSB blocks the ventral rami of T6-T12).
2. What is the preferred imaging modality for performing a rectus sheath block?
A) Fluoroscopy
B) Blind landmark technique
C) Ultrasound
D) MRI
✅ Answer: C (Ultrasound improves accuracy and safety).
3. Which of the following is NOT an indication for a rectus sheath block?
A) Laparotomy
B) Midline incisions
C) Hip replacement surgery
D) Umbilical hernia repair
✅ Answer: C (Hip replacement requires a different block, such as femoral or lumbar plexus block).
4. What is the primary mechanism of action of the rectus sheath block?
A) Blockade of visceral pain pathways
B) Blockade of the thoracoabdominal nerves in the posterior rectus sheath
C) Blockade of the lumbar plexus
D) Blockade of the sciatic nerve
✅ Answer: B (RSB blocks somatic pain from T6-T12).