Background and objectives: To determine whether intraoperative systemic dexmedetomidine improves postoperative pain and interacts with epidural neostigmine to produce analgesic effects. Methods: Sixty patients undergoing gynaecological surgery were randomly divided into four groups to receive epidural neostigmine and/or systemic dexmedetomidine: control (Group C), epidural neostigmine (Group N), systemic dexmedetomidine (Group D) and co-administered neostigmine and dexmedetomidine (Group ND). Epidural neostigmine (0.3 mg) was administered with 10 mL of 0.75% ropivacaine before the induction of general anaesthesia. Systemic dexmedetomidine (loading dose of 1 μg kg-1 over 10 min followed by 0.4 μg kg-1 h -1) was infused after the induction of general anaesthesia and continued until the end of surgery. The pain status of patients was assessed using the visual analogue scale at 2, 4, 6, 24 and 72 h postoperatively. Results: Intraoperative systemic dexmedetomidine alone did not reduce postoperative pain scores. However, co-administered neostigmine and dexmedetomidine significantly decreased scores at 24 and 72 h (Group C: 3.0 [1.0-5.8] and 2.0 [0.3-3.0]; Group N: 1.5 [0.3-3.4] and 0 [0-1.3]; Group D: 3.5 [0-5.0] and 0 [0-1.4]; and Group ND: 0 [0-1.0]* and 0 [0-0]+; median [interquartile range] *P = 0.0031, +P = 0.0045 compared with Group C). Conclusions: The intraoperative systemic infusion of dexmedetomidine alone at doses causing sedation does not result in postoperative analgesic effects. However, the co-administration of systemic dexmedetomidine and epidural neostigmine at higher doses may be a useful method to improve postoperative pain although side-effects have to be evaluated.
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