POSITIONAL EFFECTS ON MATERNAL CARDIAC-OUTPUT DURING LABOR WITH EPIDURAL ANALGESIA

OBJECTIVE: Our purpose was to test the hypothesis that the supine vers us the lateral position is associated with a greater decrement in card iac output after epidural analgesia in labor. STUDY DESIGN: Twenty-one normal term subjects were randomized to the left lateral or supine po sition in early labor. Cardiac output measured by the acetylene rebrea thing method, stroke volume, heart rate, mean arterial pressure, and s ystemic vascular resistance were obtained at 5-minute intervals, begin ning 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 outp ut, 21% lower stroke volume, 19% higher mean arterial pressure, 50% hi gher systemic vascular resistance, and equivalent heart rate. In the s upine group fluid bolus resulted in significantly increased cardiac ou tput and stroke volume, decreased mean arterial pressure and systemic vascular resistance, and unchanged heart rate. In the supine group car diac output and stroke volume decreased significantly after epidural i njection. The lateral position group exhibited no hemodynamic alterati ons after fluid bolus or epidural. CONCLUSIONS: In contrast to the lat eral position, the supine position is associated with a significant po stepidural decrement in cardiac output, not identified by a change in heart rate. This likely reflects an inability to maintain stable prelo ad volume in the supine position.