title: Increased pain relief with remifentanil does not improve the success rate of external cephalic version: a randomized controlled trial.
abstract: BACKGROUND
  Our objective was to compare the effect of two pain relief methods (remifentanil vs. nitrous oxide) on the success rate of external cephalic version.
  
  
  METHODS
  We conducted a randomized open label parallel-group controlled single-center clinical trial with sequential design, at Cruces University Hospital, Spain. Singleton pregnancies in noncephalic presentation at term that were referred for external cephalic version were assigned according to a balanced (1:1) restricted randomization scheme to analgesic treatment with remifentanil or nitrous oxide during the procedure. The primary endpoint was external cephalic version success rate. Secondary endpoints were adverse event rate, degree of pain, cesarean rate and perinatal outcomes.
  
  
  RESULTS
  The trial was stopped early after the second interim analysis due to a very low likelihood of finding substantial differences in efficacy (futility). The external cephalic version success rate was the same in the two arms (31/60, 51.7%) with 120 women recruited, 60 in each arm. The mean pain score was significantly lower in the remifentanil group (3.2 ± 2.4 vs. 6.0 ± 2.3; p < 0.01). No differences were found in external cephalic version-related complications. There was a trend toward a higher frequency of adverse effects in the remifentanil group (18.3% vs. 6.7%, p = 0.10), with a significantly higher incidence rate (21.7 events/100 women vs. 6.7 events/100 women with nitrous oxide, p = 0.03). All reported adverse events were mild and reversible.
  
  
  CONCLUSIONS
  Remifentanil for analgesia decreased external cephalic version-related pain but did not increase the success rate of external cephalic version at term and appeared to be associated with an increased frequency of mild adverse effects.
authors.affiliation: Obstetrics and Gynecology Service, BioCruces Health Research Institute, Cruces University Hospital (UPV/EHU), Barakaldo, Spain.
authors.forename: Jorge
authors.identifier: http://orcid.org/0000-0002-9923-9403
authors.initials: J
authors.lastname: Burgos
authors.affiliation: Clinical Epidemiology Unit, BioCruces Health Research Institute, Cruces University Hospital (UPV/EHU), Barakaldo, Spain.|Spanish Clinical Research Network (SCReN), Madrid, Spain.|CIBER de Epidemiología y Salud Pública (CIBERESP), Madrid, Spain.
authors.forename: José I
authors.identifier: http://orcid.org/0000-0002-5974-5280
authors.initials: JI
authors.lastname: Pijoan
authors.affiliation: Obstetrics and Gynecology Service, BioCruces Health Research Institute, Cruces University Hospital (UPV/EHU), Barakaldo, Spain.
authors.forename: Carmen
authors.identifier: http://orcid.org/0000-0003-2093-8349
authors.initials: C
authors.lastname: Osuna
authors.affiliation: Obstetrics and Gynecology Service, BioCruces Health Research Institute, Cruces University Hospital (UPV/EHU), Barakaldo, Spain.
authors.forename: Patricia
authors.identifier: http://orcid.org/0000-0003-1368-9452
authors.initials: P
authors.lastname: Cobos
authors.affiliation: Obstetrics and Gynecology Service, BioCruces Health Research Institute, Cruces University Hospital (UPV/EHU), Barakaldo, Spain.
authors.forename: Leire
authors.identifier: http://orcid.org/0000-0003-4853-6376
authors.initials: L
authors.lastname: Rodriguez
authors.affiliation: Obstetrics and Gynecology Service, BioCruces Health Research Institute, Cruces University Hospital (UPV/EHU), Barakaldo, Spain.
authors.forename: María del Mar
authors.identifier: http://orcid.org/0000-0003-1724-4442
authors.initials: Mdel M
authors.lastname: Centeno
authors.affiliation: Anesthesia Service, BioCruces Health Research Institute, Cruces University Hospital (UPV/EHU), Barakaldo, Spain.
authors.forename: Rosa
authors.identifier: http://orcid.org/0000-0002-2610-0427
authors.initials: R
authors.lastname: Serna
authors.affiliation: Anesthesia Service, BioCruces Health Research Institute, Cruces University Hospital (UPV/EHU), Barakaldo, Spain.
authors.forename: Antonia
authors.identifier: http://orcid.org/0000-0002-1802-951X
authors.initials: A
authors.lastname: Jimenez
authors.affiliation: Anesthesia Service, BioCruces Health Research Institute, Cruces University Hospital (UPV/EHU), Barakaldo, Spain.
authors.forename: Eugenia
authors.identifier: http://orcid.org/0000-0001-6431-3397
authors.initials: E
authors.lastname: Garcia
authors.affiliation: Obstetrics and Gynecology Service, BioCruces Health Research Institute, Cruces University Hospital (UPV/EHU), Barakaldo, Spain.
authors.forename: Luis
authors.identifier: http://orcid.org/0000-0002-1089-2810
authors.initials: L
authors.lastname: Fernandez-Llebrez
authors.affiliation: Obstetrics and Gynecology Service, BioCruces Health Research Institute, Cruces University Hospital (UPV/EHU), Barakaldo, Spain.
authors.forename: Juan C
authors.identifier: http://orcid.org/0000-0001-5805-419X
authors.initials: JC
authors.lastname: Melchor
mesh_terms: D000328:Adult; D000700:Analgesics / Q000008:administration & dosage / Q000009:adverse effects; D001946:Breech Presentation / Q000175:diagnosis / Q000503:physiopathology; D002585:Cesarean Section / Q000706:statistics & numerical data; D057239:Early Termination of Clinical Trials; D005260:Female; D006801:Humans; D048949:Labor Pain / Q000175:diagnosis / Q000188:drug therapy / Q000209:etiology / Q000503:physiopathology; D007743:Labor, Obstetric / Q000187:drug effects*; D009609:Nitrous Oxide / Q000008:administration & dosage / Q000009:adverse effects; D059408:Pain Management / Q000379:methods; D010147:Pain Measurement / Q000379:methods; D010880:Piperidines / Q000008:administration & dosage / Q000009:adverse effects; D011247:Pregnancy; D011256:Pregnancy Outcome; D000077208:Remifentanil; D016896:Treatment Outcome
chemical_list: D000700:Analgesics; D010880:Piperidines; D009609:Nitrous Oxide; D000077208:Remifentanil
keywords: Analgesia; breech presentation; fetal; nitrous oxide; remifentanil; version