title: Positional effects on maternal cardiac output during labor with epidural analgesia.
abstract: OBJECTIVE
  Our purpose was to test the hypothesis that the supine versus the lateral position is associated with a greater decrement in cardiac output after epidural analgesia in labor.
  
  
  METHODS
  Twenty-one normal term subjects were randomized to the left lateral or supine position in early labor. Cardiac output measured by the acetylene rebreathing method, stroke volume, heart rate, mean arterial pressure, and systemic vascular resistance were obtained at 5-minute intervals, beginning before a 500 ml intravenous fluid bolus (baseline) and ending 45 minutes after epidural injection.
  
  
  RESULTS
  Mean baseline supine versus lateral group differences were significant for 21% lower cardiac output, 21% lower stroke volume, 19% higher mean arterial pressure, 50% higher systemic vascular resistance, and equivalent heart rate. In the supine group fluid bolus resulted in significantly increased cardiac output and stroke volume, decreased mean arterial pressure and systemic vascular resistance, and unchanged heart rate. In the supine group cardiac output and stroke volume decreased significantly after epidural injection. The lateral position group exhibited no hemodynamic alterations after fluid bolus or epidural.
  
  
  CONCLUSIONS
  In contrast to the lateral position, the supine position is associated with a significant postepidural decrement in cardiac output, not identified by a change in heart rate. This likely reflects an inability to maintain stable preload volume in the supine position.
authors.affiliation: Department of Obstetrics and Gynecology, Brown University, Women and Infants Hospital, USA.
authors.forename: D R
authors.initials: DR
authors.lastname: Danilenko-Dixon
authors.forename: L
authors.initials: L
authors.lastname: Tefft
authors.forename: R A
authors.initials: RA
authors.lastname: Cohen
authors.forename: B
authors.initials: B
authors.lastname: Haydon
authors.forename: M W
authors.initials: MW
authors.lastname: Carpenter
mesh_terms: D000328:Adult; D015360:Analgesia, Epidural; D001794:Blood Pressure; D002302:Cardiac Output; D005260:Female; D006339:Heart Rate; D006801:Humans; D007743:Labor, Obstetric; D011247:Pregnancy; D013318:Stroke Volume; D016683:Supine Position; D014655:Vascular Resistance