Role of prophylactic mirtazapine and different doses of intrathecal morphine in preventing nausea and vomiting after cesarean section: s randomized controlled trial

Abstract

Background Postoperative nausea and vomiting (PONV) are common side effects of intrathecal morphine (ITM). This study aimed to evaluate the role of prophylactic mirtazapine and different doses of ITM in preventing PONV induced by ITM. Patients and methods This randomized, controlled, double-blinded trial involved 120 women aged 18–40 years undergoing cesarean section. Patients were divided into four equal groups. One hour before surgery, patients received 30 mg of oral mirtazapine in groups I and II or placebo in groups III and IV. Patients received spinal anesthesia using 10 mg bupivacaine 0.5% with preservative-free morphine diluted in 0.5 ml saline 0.9%, either 0.2 mg in groups I and III or 0.1 mg in groups II and IV (total volume 2.5 ml). Results There was a significant decrease in the incidence of PONV in group I compared to group III, and in group II than group III at 6 and 18 h ( P <0.05) and in mirtazapine groups than placebo groups at 12 h ( P <0.05). Mirtazapine groups had a significantly longer time to first rescue than placebo groups ( P <0.05). In the first 24 h after surgery, mirtazapine groups consumed significantly less pethidine than placebo groups ( P <0.05). At 6 h, mirtazapine groups had a significantly lower numeric rating scale compared to placebo groups, while group III had a lower score than group IV ( P <0.05). Conclusions Preventative use of mirtazapine decreases the occurrence of PONV and enhances analgesia. The analgesic effects of higher doses of ITM are better, but the risks of side effects are higher as well.