Nalbuphine Versus Midazolam as an Adjuvant to Intrathecal Bupivacaine for Postoperative Analgesia in Patients Undergoing Cesarean Section

Analgesia is the main point for each patient postoperatively. It is important to provide good analgesia with less hazardous (1). Cesarean section is a painful operation in need for adequate postoperative analgesia (1). Adequate pain management is important to facilitate the functional recovery and enable the patients for rapid rehabilitation of their normal activity (2).

Cesarean section was done under general anesthesia (GA) or regional anesthesia. The subarachnoid blockade is the preferred procedure (3). It avoids the depressant effect of GA on neonate and also the risk of aspiration, with better postoperative pain relief. However the most commonly local anesthetic used, hyperbaric bupivacaine has limited effect lasts for 1.5 - 2 hours (4). Its onset was slow with short duration of postoperative analgesia (3).

Adjuvant drugs added to bupivacaine intrathecally improve the duration and quality of the blockade and prolong the postoperative analgesia (5). Various adjuvants were being used such as alpha2 agonists, neostigmine, opiates, and ketamine etc, yet no drug was identified to specifically inhibit nociception without side effects (6).

Nalbuphine is a synthetic opioid with mixed agonist antagonist effect. It provides a significantly rapid onset of pain relief probably because of its lipophilic properties. It binds to both mu-and kappa receptors, binding of nalbuphine to mu receptors competitively displace other mu-agonists from these receptors without any agonist activity. Therefore decrease the side effects of mu agonist (nausea, vomiting, respiratory depression , urinary retention, pruritis and prolonged sedation) (7). While when binds to kappa receptors nalbuphine has agonist effect (analgesic effect) through the kappa receptors distributed in the brain and spinal cord(1). There were no documented studies of nalbuphine neurotoxicity (5, 8).

Benzodiazepines are used mainly for sedation, anoxiolysis and amnesia. Discovery of their receptors in spinal cord allow the use of midazolam intrathecally for analgesia. Several studies show that the addition of intrathecal midazolam potentiates the analgesic effect of intrathecal bupivacain without significant side effects, or neurotoxicity (9, 10).