A prospective observational study of the change in regional cerebral oxygen saturation during cesarean delivery in women receiving phenylephrine prophylaxis for spinal hypotension

Background: Spinal hypotension causes decreased regional cerebral oxygen saturation (ScO ₂ ) in women undergoing cesarean delivery. In this study we aimed to measure the change in ScO ₂ using near infrared spectroscopy in women receiving a prophylactic phenylephrine infusion during cesarean delivery under spinal anesthesia. Methods: This was a prospective, observational cohort study. Fifty-three women had ScO ₂ measurements at the following time points: preoperatively, in the supine position with 30° of left lateral tilt; one and five minutes after spinal anesthesia; at the time of skin incision; immediately after delivery; one minute after commencing the oxytocin infusion; at completion of surgery, and one hour after surgery. Spinal anesthesia and a prophylactic phenylephrine infusion were administered according to a standard treatment protocol. Statistical analysis used the Wilcoxon Signed Rank test with Bonferroni's correction for multiple comparisons. Results: Blood pressure was maintained within 20% of baseline throughout surgery. The baseline mean (range) ScO ₂ was 61.5% (54.0–66.3%). It decreased significantly at all subsequent measurement points. The maximum decrease was five minutes after spinal anesthesia. Thirty-four (64.2%) of the parturients exhibited ScO ₂ values <20% of baseline, or a decrease to below an absolute value of 50%. There was no significant correlation between systolic blood pressure and mean ScO ₂ . Conclusion: Spinal anesthesia with phenylephrine infusion during cesarean delivery is associated with a significant decrease in ScO ₂ levels, maximal five minutes later. Further studies are required to establish the clinical significance of this finding.