title: Supplementary oxygen for elective Caesarean section under spinal anaesthesia: useful in prolonged uterine incision-to-delivery interval?
abstract: BACKGROUND
  The benefit of administering supplementary oxygen during elective Caesarean section under regional anaesthesia is controversial. It has been hypothesized that its use would improve fetal oxygenation in the event of a prolonged uterine incision-to-delivery (U-D) interval. Our aim was to test this hypothesis in a prospective, randomized, double-blinded, controlled study.
  
  
  METHODS
  We allocated randomly 204 women having elective Caesarean section under spinal anaesthesia to breathe 21, 40 or 60% oxygen. We recorded the U-D interval, umbilical arterial (UA) and venous (UV) blood gases and oxygen content and Apgar scores. Subgroup analysis was performed according to whether the U-D interval was prolonged (>180 s) or not.
  
  
  RESULTS
  The U-D interval was <180 s in 159 patients and >180 s in 45 patients. There were no differences in UV or UA blood gases, oxygen content or Apgar scores between cases with and without a prolonged U-D interval. In cases without a prolonged U-D interval, administering 60% oxygen increased UV PO(2) (mean 4.3 (SD 1.1) vs 3.7 (1.0) kPa, P=0.003) and oxygen content (14.4 (3.3) vs 12.9 (2.7) ml dl(-1), P=0.007) compared with air. In cases with a prolonged U-D interval, administering 60% oxygen increased UV PO(2) (4.6 (0.6) vs 3.9 (0.8) kPa, P=0.019) compared with air but there was no difference in UV oxygen content. There was no increase in the UV PO(2) or oxygen content when 40% oxygen was administered compared with air.
  
  
  CONCLUSIONS
  Supplementary oxygen did not increase fetal oxygenation in cases where the U-D interval was prolonged. Our data do not support the routine administration of supplementary oxygen during elective Caesarean section for this purpose.
authors.affiliation: Department of Anaesthesia and Intensive Care, The Chinese University of Hong Kong, Prince of Wales Hospital, Shatin, New Territories, Hong Kong, China. KimKhaw@cuhk.edu.hk
authors.forename: K S
authors.initials: KS
authors.lastname: Khaw
authors.forename: W D
authors.initials: WD
authors.lastname: Ngan Kee
authors.forename: A
authors.initials: A
authors.lastname: Lee
authors.forename: C C
authors.initials: CC
authors.lastname: Wang
authors.forename: A S Y
authors.initials: AS
authors.lastname: Wong
authors.forename: F
authors.initials: F
authors.lastname: Ng
authors.forename: M S
authors.initials: MS
authors.lastname: Rogers
mesh_terms: D000138:Acidosis / Q000503:physiopathology; D000328:Adult; D000773:Anesthesia, Obstetrical; D000775:Anesthesia, Spinal; D002585:Cesarean Section; D004311:Double-Blind Method; D005260:Female; D005333:Fetus / Q000502:physiology; D006801:Humans; D008431:Maternal-Fetal Exchange / Q000502:physiology; D010100:Oxygen / Q000008:administration & dosage* / Q000032:analysis; D010108:Oxyhemoglobins / Q000032:analysis; D011247:Pregnancy; D011446:Prospective Studies; D013997:Time Factors; D014469:Umbilical Arteries; D014471:Umbilical Veins
chemical_list: D010108:Oxyhemoglobins; D010100:Oxygen