Comparison of Surgical Rectus Sheath Block and Intrathecal Morphine

The incidence of Caesarean section is increasing worldwide. Adequate post-operative analgesia is becoming an essential expectation of patients after Caesarean section. The process of recovery will be hindered by suboptimal pain control and eventually it will leads to immobilization and prolonged hospital stay.

Spinal anesthesia is usually the mode of anesthesia in pregnancy in view of increase general anesthetic risks. Intrathecal morphine can provide good pain control. However, pruritus can occur in up to 51% of patient, nausea and vomiting in up to 21%. Despite its significant side effects, there is an overall better patient satisfactory over use of intrathecal morphine. Due to its concern on respiratory depression, intrathecal morphine is not recommended in patients with severe respiratory disease, obstructive sleep apnoea or those receiving central nervous system depressants. As a result, there were numerous studies on alleviating the adverse effect and to search for other alternatives.

Rectus sheath block aims at blocking the terminal branches of 9th -12th intercostals nerve within the rectus sheath. They form rectus sheath plexus after piercing the posterior aspect of the rectus sheath and then branch into muscular and cutaneous branches. It can be given by anesthetist with or without ultrasound guidance. However, it involved additional time for administration of rectus sheath block and possibility of incorrect placement of catheter leading to ineffective analgesia.

On the contrary, surgical rectus sheath block was administrated by surgeon before closure of rectus sheath. It involves injection of local anesthetic in the rectus sheath space before closure of the wound under direct visual control. Surgical rectus sheath block was shown to be effective in postoperative pain control after transverse laparotomy in paediatrics patients. It was shown to be effective in postoperative pain control in Caesarean section without intrathecal morphine.

Surgical rectus sheath block may be a simple and safe alternative for intrathecal morphine. However, the evidence on its use in Obstetrics and Gynaecology was sparse and there is no study directly comparing the two different mode of analgesia. The aim of the study is to evaluate the use of surgical rectus sheath and intrathecal morphine for postoperative pain in Caesarean section; and its side effects profile.

Inclusion criteria

• Planned for elective lower segment Caesarean section, using suprapubic transverse incision
• Willing and able to participate after the study has been explained
• Those understand either Cantonese, Putonghua or English

Exclusion criteria

• Patient with treatment for chronic pain
• History of narcotic abuse/ recreational drug use
• Allergy to opioids/ local anesthesia/ paracetamol/ tramadol/ non-steroidal anti-inflammatory drugs
• Patient with pre-eclampsia