Optimum ratio of medicine dosage for dexmedetomidine mixed with oxycodone used for PCIA after gastrointestinal surgery

Objective To investigate the optimum ratio of medicine dosage for dexmedetomidine mixed with oxycodone used for patient-controlled intravenous analgesia (PCIA) after gastrointestinal surgery. Methods Eighty patients of both sexes, aged 35–64 yr, weighing 55–75 kg, of American Society of Anesthesiologists physical status Ⅰor Ⅱ, undergoing elective gastrointestinal surgery, were randomly divided into 4 groups (n=20 each) using a random number table: oxycodone group (group O), and different ratios of medicine dosage when dexmedetomidine was added to sufentanil groups (OD1-3 groups). At 15 min before the end of surgery, oxycodone 0.1 mg/kg was injected intravenously, and PCIA pump was connected simultaneously.In group O, the PCIA solution contained oxycodone 1.00 mg/kg in 100 ml of normal saline.In group OD1, the PCIA solution contained oxycodone 1.00 mg/kg and dexmedetomidine 2.5 μg/kg in 100 ml of normal saline.In group OD2, the PCIA solution contained oxycodone 0.75 mg/kg and dexmedetomidine 2.5 μg/kg in 100 ml of normal saline.In group OD3, the PCIA solution contained oxycodone 0.50 mg/kg and dexmedetomidine 2.5 μg/kg in 100 ml of normal saline.The PCIA pump was set up to deliver a 0.5 ml bolus dose with a 15-min lockout interval and background infusion at 2 ml/h.Oxycodone 0.05 mg/kg was injected intravenously as a rescue analgesic, and visual analogue scale score was maintained≤4.The requirement for rescue analgesics was recorded.The requirement for the rescue analgesic was recorded within 48 h after surgery.The number of successfully delivered doses, and occurrence of adverse reactions such as bradycardia, hypotension, nausea, vomiting, over-sedation, somnolence, pruritus, and respiratory depression were recorded.Patient's satisfaction with analgesia was recorded at 72 h after surgery. Results No patients required the rescue analgesic or developed over-sedation, vomiting, respiratory depression and hypotension in the four groups.Compared with group O, the incidence of somnolence was significantly increased in group OD1, the incidence of nausea, somnolence, bradycardia and pruritus was decreased in OD2 and OD3 groups, and the degree of patient's satisfaction with analgesia was increased in OD1-3 groups (P 0.05). Compared with group OD2, no significant was found in the incidence of adverse reactions (P>0.05), and the degree of patient's satisfaction with analgesia was significantly decreased in group OD3 (P<0.05). The number of successfully delivered doses was significantly larger in group OD3 than in O, OD1 and OD2 groups (P<0.05). Conclusion Dexmedetomidine 2.5 μg/kg added to oxycodone 0.75 mg/kg is the optimum ratio of medicine dosage when used for PCIA after gastrointestinal surgery. Key words: Oxycodone; Dexmedetomidine; Analgesia, patient-controlled