Rectus Sheath Block Versus Thoracic Epidural Effect on Diaphragmatic Function After Elective Midline Abdominal Surgery

A major proportion of pain experienced by patients undergoing abdominal surgeries is due to somatic pain signals derived from the abdominal wall. The central portion of anterior abdominal wall components (skin, muscles and parietal peritoneum) is innervated by sensory neurons branching from the anterior rami of spinal nerves T7 to T1. These neurons lie between the rectus abdominis muscle and posterior rectus sheath, and pierce the rectus muscle close to the midline. The tendinous intersections of the rectus muscle do not fuse with the posterior rectus sheath, thereby allowing the injectate to spread cephalo‐caudally within this potential space. Rectus sheath (RS) block has been described for any midline abdominal incisions (epigastric and umbilical hernia repairs). As visceral pain becomes attenuated by the 2nd postoperative day, rectus sheath block can also be administered for midline laparotomy. As a single bolus of the local anesthetic has a maximum duration of 12 hours. it is necessary to insert a catheter into this space to allow either a continuous infusion of local anesthetic, or repeated boluses of local anesthetic every 8 to 12 hours for 48 to 72 hours post‐operatively. However, the effects of rectus sheath block catheter analgesia on the respiratory function after abdominal surgery with midline incisions are still under investigation.