ED₅₀ And ED₉₅ Of Isobaric Bupivacaine Combined With Intrathecal Small-dose Fentanyl(10μg) For Cesarean Section

Objective:The study was aimed to determine the ED50 and ED95 of isobaric bupivacaine combined with a small dose fentanyl,if injected intrathecally in patients undergoing cesarean section.Methods:Forty parturients with singleton term pregnancies undergoing cesarean section with combined spinal-epidural anesthesia were enrolled this study.The median effective dose (ED50)was determined by up-down sequential allocation.The patiants were randomly divided into two groups and received intrathecally injection of isobaric 0.5% bupivacaine single or combined with a small dose fentanyl respectively. Success was defined as a bilateral T6 sensory level to pinprick within 10 min of the intrathecal drug administration, with no additional epidural anesthetic required during surgery.A failure was recorded when a T6 sensory level was not obtained within 10 min after intrathecal drug administration.If a failure was recorded ,an epidural supplementation was administered to attain a T6 level. In cases of failures , supplemental epidural anesthesia consisted of 2% lidocaine administered as 5-ml bolus injections,repeated as required.To observe the differentation in SBP/DBP,MAP,HR,sensory block,motor block and adverse reactions to drugs.Records of patients with hypotension , bradycardia,respiatory depression,chills,nausea and vomiting and the occurrence of the number of cases.Records of newborns 1 min,5 min of the Apgar score.Results:The ED50 and ED95 of bupivacaine were 7.29mg and 8.02mg;the ED50 and ED95 of bupivacaine with 10 ug fentanyl were 4.08mg and4.75mg.