EC_(50) of continuous epidural sufentanil infusion analgesia after gynecological surgery

OBJECTIVE To determine the median effective concentration(EC50) of continuous epidural sufentainil infusion analgesia after gynecological surgery.METHODS Forty ASA Ⅰ or Ⅱ patients aged 20-50 yr with body weight index30 kg·m-2 undergoing elective lower abdominal gynecological operation under epidural anesthesia received continuous epidural sufentanil infusion(CEI) for 48h.epidural catheter was placed at L1-2.CEI device was set up to deliver sufentanil solution at 2 mL·h-1 after a loading dose of 5 mL.The EC50 of sufentanil was determined by up and down sequential test.The concentration of sufentanil was increased or decreased with ratio of 1.2.If effective,the next patient received sufentanil at a lower concentration,if ineffective a higher concentration.VAS(0-10,0=no pain,10=worst pain)was used to assess the analgesia.If the VAS score was ≦3 within 8h after sufentanil administration,analgesia was defined as effective.The up and down sequences were analyzed by using Dixon method to determine the EC50 and 95% confidence interval(CI).The side effects were also recorded.RESULTS The EC50 of sufentanil CEI was 0.87 mg L-1.95% confidence interval was between 0.79 mg·L-1 and 0.96 mg·L-1.The incidence of pruritus was 3.8%.There were 3 patients who had nausea and vomiting.No patients had respiratory depression.CONCLUSION The EC50 of continuous epidural sufentanil infusion analgesia after gynecological surgery was 0.87 mg·L-1.