title: ED50 and ED95 of intrathecal hyperbaric bupivacaine coadministered with opioids for cesarean delivery.
abstract: BACKGROUND
  Successful cesarean delivery anesthesia has been reported with use of small doses (5-9 mg) of intrathecal bupivacaine coadministered with opioids. This double-blind, randomized, dose-ranging study determined the ED50 and ED95 of intrathecal bupivacaine (with adjuvant opioids) for cesarean delivery anesthesia.
  
  
  METHODS
  Forty-two parturients undergoing elective cesarean delivery with use of combined spinal-epidural anesthesia received intrathecal hyperbaric bupivacaine in doses of 6, 7, 8, 9, 10, 11, or 12 mg in equal volumes with an added 10 microg intrathecal fentanyl and 200 microg intrathecal morphine. Sensory levels (pinprick) were evaluated every 2 min until a T6 level was achieved. The dose was a success(induction) if a bilateral T6 block occurred in 10 min; otherwise, it was a failure(induction). In addition to being a success(induction), the dose was a success(operation) if no intraoperative epidural supplement was required; otherwise, it was a failure(operation). ED50 and ED95 for both success(induction) and success(operation) were determined with use of a logistic regression model.
  
  
  RESULTS
  ED50 for success(induction) and success(operation) were 6.7 and 7.6 mg, respectively, whereas the ED95 for success(induction) and success(operation) were 11.0 and 11.2 mg. Speed of onset correlated inversely with dose. Although no clear advantage for low doses could be demonstrated (hypotension, nausea, vomiting, pruritus, or maternal satisfaction), this study was underpowered to detect significance in these variables.
  
  
  CONCLUSIONS
  The ED95 of intrathecal bupivacaine under the conditions of this study is considerably in excess of the low doses proposed for cesarean delivery in some recent publications. When doses of intrathecal bupivacaine less than the ED95, particularly near the ED50, are used, the doses should be administered as part of a catheter-based technique.
authors.affiliation: Department of Anesthesia, Stanford University, California, USA. ginosar@md.huji.ac.il
authors.forename: Yehuda
authors.initials: Y
authors.lastname: Ginosar
authors.forename: Edward
authors.initials: E
authors.lastname: Mirikatani
authors.forename: David R
authors.initials: DR
authors.lastname: Drover
authors.forename: Sheila E
authors.initials: SE
authors.lastname: Cohen
authors.forename: Edward T
authors.initials: ET
authors.lastname: Riley
mesh_terms: D000328:Adult; D016362:Analgesia, Obstetrical; D000701:Analgesics, Opioid / Q000009:adverse effects; D000779:Anesthetics, Local / Q000008:administration & dosage* / Q000009:adverse effects; D002045:Bupivacaine / Q000008:administration & dosage* / Q000009:adverse effects; D002585:Cesarean Section; D004305:Dose-Response Relationship, Drug; D004311:Double-Blind Method; D005260:Female; D006801:Humans; D007278:Injections, Spinal; D016015:Logistic Models; D010147:Pain Measurement; D011247:Pregnancy; D011446:Prospective Studies
chemical_list: D000701:Analgesics, Opioid; D000779:Anesthetics, Local; D002045:Bupivacaine