Adding dexmedetomidine to morphine-based analgesia reduces early postoperative nausea in patients undergoing gynecological laparoscopic surgery: a randomized controlled trial

BACKGROUND: Few studies have investigated the effect of dexmedetomidine on postoperative nausea and vomiting (PONV) in patients underwent gynecological laparoscopic surgery. We investigated if adding dexmedetomidine to a morphine-based patient-controlled analgesia (PCA) could decrease the incidence of PONV in this high-risk patient population. METHODS: In this prospective, randomized, double-blind and placebo-controlled study, 122 patients underwent gynecological laparoscopic surgery were assigned into two groups. Patients in the dexmedetomidine group (Group Dex) received a loading dose of dexmedetomidine 0.4 μg/kg before the end of surgery, followed by morphine 0.5 mg/ml plus dexmedetomidine 1 μg/ml for postoperative i.v. PCA. Patients in the control group (Group Ctrl) received normal saline before the end of surgery, followed by morphine 0.5 mg/ml alone for postoperative i.v. PCA. PCA pump was programmed as followed: bolus dose 2 ml, lockout interval 8 min and background infusion at a rate of 1 ml/h. The primary outcome was the incidence of nausea and vomiting within the first postoperative 24 h. RESULTS: Although there were no significant differences in regard to the total incidence of PONV (41.0% vs 52.5%, P = 0.204), PONV score, time to first onset of PONV, or the need for rescue antiemetics within the first postoperative 24 h between the two groups, the incidence of nausea and total PONV during the first 2 h period was significantly lower in the Group Dex than in the Group Ctrl (9.8% vs 24.6%, P = 0.031 and 0.031, respectively). More patients in Group Dex were over sedated or had bradycardia during the PACU compared with Group Ctrl (P = 0.040 and 0.036, respectively). CONCLUSION: Our protocol in which dexmedetomidine was administered postoperatively – after a loading dose – to intravenous PCA morphine in patients undergoing gynecological laparoscopic surgery, had only early antiemetic effects, while no clinically meaningful antiemetic effect could be evidenced within the first 24 h after surgery. TRIAL REGISTRATION: Current control trial registered at Chictr.org.cn: ChiCTR1800017172. Date registered: 07/16/2018.