Left Lateral Table Tilt for Elective Cesarean Delivery under Spinal Anesthesia Has No Effect on Neonatal Acid-Base Status: A Randomized Controlled Trial.

Background: Current recommendations for women undergoing cesarean delivery include 15° left tilt for uterine displacement to prevent aortocaval compression, although this degree of tilt is practically never achieved. We hypothesized that under contemporary clinical practice, including a crystalloid coload and phenylephrine infusion targeted at maintaining baseline systolic blood pressure, there would be no effect of maternal position on neonatal acid base status in women undergoing elective cesarean delivery with spinal anesthesia.

Methods: Healthy women undergoing elective cesarean delivery were randomized (nonblinded) to supine horizontal (supine, n = 50) or 15° left tilt of the surgical table (tilt, n = 50) after spinal anesthesia (hyperbaric bupivacaine 12 mg, fentanyl 15 μg, preservative-free morphine 150 μg). Lactated Ringer's 10 ml/kg and a phenylephrine infusion titrated to 100% baseline systolic blood pressure were initiated with intrathecal injection. The primary outcome was umbilical artery base excess.

Results: There were no differences in umbilical artery base excess or pH between groups. The mean umbilical artery base excess (± SD) was -0.5 mM (± 1.6) in the supine group (n = 50) versus -0.6 mM (± 1.5) in the tilt group (n = 47) (P = 0.64). During 15 min after spinal anesthesia, mean phenylephrine requirement was greater (P = 0.002), and mean cardiac output was lower (P = 0.014) in the supine group.

Conclusions: Maternal supine position during elective cesarean delivery with spinal anesthesia in healthy term women does not impair neonatal acid-base status compared to 15° left tilt, when maternal systolic blood pressure is maintained with a coload and phenylephrine infusion. These findings may not be generalized to emergency situations or nonreassuring fetal status.