A comparative study of the effects of adding intrathecal morphine and pethidine to bupivacaine in spinal anesthesia during cesarean section: A randomized clinical trial

Background: Intrathecal opioids are routinely used during spinal anesthesia for post cesarean analgesia. In this research, the analgesic effects of adding pethidine or morphine to intrathecal bupivacaine have been compared. Methods: In a double-blinded, randomized trial, 110 parturients who were scheduled for elective cesarean section were randomized into two groups of 55 patients each. In one group, 12 mg of bupivacaine (0.5%) plus 200 mcg of intrathecal morphine and in the second group 12 mg of bupivacaine (0.5%) plus 20 mg of pethidine in a total volume of 3 cc was injected as an intrathecal injection. Data variables were recorded at 1st, 4th, and 24th hours postoperatively. The primary outcome was the pain intensity numerical rating scale (0-10). The secondary outcomes were nausea, vomiting, itching, sedation (Ramsey Sedation Scale), shivering, and demand for analgesic medication. Results: No statistically significant differences were found between the two groups in terms of shivering, sedation, pain and pain severity, duration of painlessness period, number of demanded analgesics and level of sensory block, at 1st, 4th, and 24th hours post-operatively. At 24 hours after surgery, the rate of nausea and vomiting was significantly lower in the pethidine group (3 vs. 11, p=0.02), but at the same time, itching complaints were higher in the morphine group (10 vs. 0, p=0.001). Conclusion: Adding intrathecal morphine and pethidine to bupivacaine in spinal anesthesia for cesarean section both creates a long-term and acceptable analgesia. However, in controlling itching, nausea and vomiting, pethidine showed to be more effective than morphine. Thus, it is suggested that 12 mg of bupivacaine (0.5%) is applied in combination with 20 mg of pethidine in spinal anesthesia for this surgery.