title: Analgesia with sevoflurane during labour: ii. Sevoflurane compared with Entonox for labour analgesia.
abstract: BACKGROUND
  We determined the optimal inspired sevoflurane concentration for use during labour as 0.8% in our previous study. This study compared sevoflurane at a concentration of 0.8% and Entonox((R)) (nitrous oxide 50%: oxygen 50%) for analgesia during labour in 32 healthy parturients.
  
  
  METHODS
  Each mother underwent two open-label, three-part sequences in random order, Entonox-sevoflurane-Entonox or sevoflurane-Entonox-sevoflurane. In each part the agent was self-administered during 10 contractions. A 100 mm visual analogue scores for pain relief and sedation was completed immediately after each contraction.
  
  
  RESULTS
  Two patients withdrew during administration of sevoflurane (because of its odour) and five during Entonox (requesting epidural analgesia). Of the remaining women, data were available for analysis from 29 participants: median (IQR [range]) pain relief scores were significantly higher for sevoflurane 67 (55-74 [33-100]) mm than for Entonox 51 (40-69.5 [13-100]) mm (P<0.037). Nausea and vomiting were more common in the Entonox group [relative risk 2.7 (95% CI 1.3-5.7); P=0.004]. No other adverse effects were observed in the mothers or babies. There was significantly more sedation with sevoflurane than with Entonox {74 (66.5-81 [32.5-100]) and 51 (41-69.5 [13-100]) mm, respectively; P<0.001}. Twenty-nine patients preferred sevoflurane to Entonox and found its sedative effects helpful.
  
  
  CONCLUSIONS
  We conclude that self-administered sevoflurane at subanaesthetic concentration (0.8%) can provide useful pain relief during the first stage of labour, and to a greater extent than Entonox. Although greater sedative effects were experienced with sevoflurane, it was preferred to Entonox.
authors.affiliation: Magill Department of Anaesthesia, Imperial College London, Chelsea and Westminster Hospital, 369 Fulham Road, London SW10 9NH, 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
authors.forename: P
authors.initials: P
authors.lastname: Bassett
mesh_terms: D000328:Adult; D016362:Analgesia, Obstetrical / Q000009:adverse effects / Q000379:methods*; D016058:Analgesia, Patient-Controlled / Q000379:methods; D018685:Anesthetics, Inhalation / Q000008:administration & dosage* / Q000009:adverse effects; D016292:Procedural Sedation; D018592:Cross-Over Studies; D004338:Drug Combinations; D005260:Female; D006801:Humans; D008738:Methyl Ethers / Q000008:administration & dosage* / Q000009:adverse effects; D009325:Nausea / Q000139:chemically induced; D009609:Nitrous Oxide / Q000008:administration & dosage* / Q000009:adverse effects; D010100:Oxygen / Q000008:administration & dosage* / Q000009:adverse effects; D010147:Pain Measurement / Q000379:methods; D017060:Patient Satisfaction; D011247:Pregnancy; D000077149:Sevoflurane; D014839:Vomiting / Q000139:chemically induced
chemical_list: D018685:Anesthetics, Inhalation; D004338:Drug Combinations; D008738:Methyl Ethers; D000077149:Sevoflurane; C001147:Entonox; D009609:Nitrous Oxide; D010100:Oxygen