RESUMEN
Objective To determine the optimal dose of oxycodone for patient-controlled intravenous analgesia (PCIA) after gastrointestinal surgery when combined with dexmedetomidine in elderly patients.Methods Sixty patients of both sexes,aged 65-80 yr,weighing 50-75 kg,of American Society of Anesthesiologists physical status Ⅱ or Ⅲ,undergoing elective open gastrointestinal surgery,were divided into 3 different doses of oxycodone groups (group O1,group O2 and group O3,n=20 each) using a random number table.At 15 min before the end of surgery,oxycodone 0.1 mg/kg was intravenously injected,and PCIA pump was connected simultaneously.In O1,O2 and O3 groups,the PCIA solution contained dexmedetomidine 2.0 μg/kg and oxycodone 0.3,0.5 and 0.7 mg/kg in 100 ml of 0.9％ normal saline,respectively.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 intravenously injected as a rescue analgesic after surgery,postoperative pain was assessed using a verbal rating scale,and the verbal rating scale score was maintained ≤4.The number of successfully delivered doses and requirement for rescue analgesics were recorded within 48 h after surgery,and the rate of rescue analgesia was calculated.The occurrence of adverse reactions such as nausea,vomiting,dizziness,respiratory depression,somnolence,bradycardia,hypotension and over-sedation was recorded.Patients' satisfaction with analgesia at postoperative 72 h and the length of postoperative hospital stay were also recorded.Results Compared with group O1,the rate of rescue analgesia after surgery and the number of successfully delivered doses were significantly decreased,and the degree of patients' satisfaction with analgesia was increased in O2 and O3 groups,and the incidence of nausea and somnolence was significantly increased in group O3 (P＜0.05).Compared with group O2,no significant change was found in the rate of rescue analgesia after surgery or the number of successfully delivered doses (P＞0.05),and the incidence of nausea and somnolence was increased in group O3 (P＜0.05).Conclusion When combined with dexmedetomidine 2.0 μg/kg,the optimal dose of oxycodone for PCIA is 0.5 mg/kg after gastrointestinal surgery in elderly patients.