Optimal dose of dexmedetomidine to prevent nausea and vomiting when used for postoperative analgesia after gynecological laparoscopic surgery

Objective To determine the optimal dose of dexmedetomidine required to prevent nausea and vomiting when used for postoperative analgesia after gynecological laparoscopic surgery. Methods A total of 135 patients, aged 18-60 yr, weighing 52-80 kg, of American Society of Anesthesiologists physical status Ⅰ or Ⅱ, scheduled for elective gynecological laparoscopic surgery, were divided into 3 groups (n=45 each) using a random number table method: control group (group C), dexmedetomidine 1 μg/kg group (group D1) and dexmedetomidine 2 μg/kg group (group D2). Immediately after anesthesia induction, dexmedetomidine 0.4 μg·kg-1·h-1 was injected intravenously until 30 min before the end of surgery in all the patients.When the patient was fully awake at the end of surgery, the tracheal tube was removed, and patients were sent to postanesthesia care unit and received patient-controlled intravenous analgesia (PCIA). The PCIA solution contained sufentanil 1.2 μg/kg and dezocine 20 mg in 100 ml of 0.9% normal saline.The PCIA pump was set up with a 0.5 ml bolus dose, a 15 min lockout interval and background infusion at a rate of 2 ml/h.Dexmedetomidine 1 and 2 μg/kg were added to PCIA solution in group D1 and group D2, respectively.The occurrence of nausea and vomiting was recorded in postanesthesia care unit stay period (P1) and in 0-12 h (P2), 12-24 h (P3), 24-36 h (P4) and 36-48 h (P5) periods after patients returned to the ward.Ramsay sedation score was recorded at 12, 24, 36 and 48 h after patients returned to the ward.When visual analogue scale score >3, patients were told to press PCIA.Patients were followed up for 48 h after surgery, and patients′ satisfaction, pressing times of PCIA and occurrence of pruritus, respiratory depression, bradycardia and dizziness were recorded. Results Compared with group C, the incidence of nausea was significantly decreased in P2 period, and the pressing times of PCIA were reduced in P2, 3 period in D1 and D2 groups (P 0.05). No patients developed pruritus, respiratory depression or dizziness in the three groups. Conclusion The optimal dose of dexmedetomidine required to prevent nausea and vomiting is 1 μg/kg when used for postoperative analgesia after gynecological laparoscopic surgery. Key words: Dexmedetomidine; Postoperative nausea and vomiting; Dose-response relationship, drug; Analgesia, patient-controlled; Pain, postoperative