title: Analgesia with sevoflurane during labour: i. Determination of the optimum concentration.
abstract: BACKGROUND
  Sevoflurane has favourable physical qualities for inhaled analgesia during labour pain. The aim of this preliminary study was to identify its optimum concentration.
  
  
  METHODS
  In this open-labelled escalating-dose study, 22 parturients in labour self-administered sevoflurane at 10 contractions using an Oxford Miniature Vaporiser. The inspired concentration was increased by 0.2% after each contraction from 0% to 1.4% or decreased if sedation occurred. Visual analogue scores (0-100 mm) for pain intensity, pain relief, sedation, mood and coping were measured after each contraction.
  
  
  RESULTS
  The median (IQR [range]) pain relief and sedation scores increased from 44 (43-56 [4-93]) mm and 55 (43-56 [0-98]) mm at 0.2% sevoflurane, to 74 (72-78 [50-80]) mm and 71 (71-73 [33-97]) mm at 1.2% sevoflurane, respectively. Pain relief scores did not show any significant increase above 0.8% whilst sedation continued to increase, with excessive sedation occurring at 1.2% sevoflurane. No significant changes in other scores were measured.
  
  
  CONCLUSIONS
  We concluded that the optimal sevoflurane concentration in labour was 0.8%. This concentration allows a safety margin and balances the risk of sedation with the benefit of pain relief in labour.
authors.affiliation: Magill Department of Anaesthesia, Imperial College London, Chelsea and Westminster Hospital, 369 Fulham Road, London W12 0HS, UK. sengyeo@hotmail.com
authors.forename: S T
authors.initials: ST
authors.lastname: Yeo
authors.forename: A
authors.initials: A
authors.lastname: Holdcroft
authors.forename: S M
authors.initials: SM
authors.lastname: Yentis
authors.forename: A
authors.initials: A
authors.lastname: Stewart
mesh_terms: D000223:Adaptation, Psychological / Q000187:drug effects; D000328:Adult; D016362:Analgesia, Obstetrical / Q000379:methods*; D016058:Analgesia, Patient-Controlled / Q000379:methods; D018685:Anesthetics, Inhalation / Q000008:administration & dosage*; D004305:Dose-Response Relationship, Drug; D004334:Drug Administration Schedule; D005260:Female; D006801:Humans; D008738:Methyl Ethers / Q000008:administration & dosage*; D010147:Pain Measurement / Q000379:methods; D010865:Pilot Projects; D011247:Pregnancy; D000077149:Sevoflurane
chemical_list: D018685:Anesthetics, Inhalation; D008738:Methyl Ethers; D000077149:Sevoflurane