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

<bold>Background: </bold>Spinal hypotension causes decreased regional cerebral oxygen saturation (ScO2) in women undergoing cesarean delivery. In this study we aimed to measure the change in ScO2 using near infrared spectroscopy in women receiving a prophylactic phenylephrine infusion during cesarean delivery under spinal anesthesia.<bold>Methods: </bold>This was a prospective, observational cohort study. Fifty-three women had ScO2 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.<bold>Results: </bold>Blood pressure was maintained within 20% of baseline throughout surgery. The baseline mean (range) ScO2 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 ScO2 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 ScO2.<bold>Conclusion: </bold>Spinal anesthesia with phenylephrine infusion during cesarean delivery is associated with a significant decrease in ScO2 levels, maximal five minutes later. Further studies are required to establish the clinical significance of this finding. [ABSTRACT FROM AUTHOR]