Changes of regional cerebral oxygen saturation during spinal anesthesia.

Background: During spinal anesthesia, hemodynamic status is routinely monitored, but this may not give an accurate assessment of cerebral oxygenation. Cerebral oximetry, facilitated by using a near-infrared spectroscope, is a way of estimating regional cerebral oxygen saturation (SrO2). We designed this prospective clinical study to determine whether the changes in mean arterial pressure (MAP) and heart rate (HR) could predict changes in SrO2 during spinal anesthesia.
Methods: The study sample available for analysis included 45 patients, ASA class I to II, who were scheduled for elective ureteroscopic surgery requiring spinal anesthesia. Spinal anesthesia was performed with 12 mg 0.5% hyperbaric bupivacaine injected intrathecally via L3-4 or L4-5 interspace. MAP, HR, oxygen saturation by pulse oximeter, and SrO2 by near-infrared spectroscope were recorded every 2 min throughout the procedure.
Results: SrO2 was tested by the Shapiro-Wilk test and the results departed from the multivariate normal distribution. The method of generalized estimating equations (GEE) was then used to estimate the model. The output of the GEE analysis for the time-lag model showed that there were relationships between SrO2 and two predictors (MAP and HR) with the correction of the baseline values. All the parameters were significant at a level of 5%. The effects of the decreases of MAP and HR on SrO2 lasted continuously for at least 6 min.
Conclusions: Based on the time-lag pattern between two predictors (MAP and HR) and SrO2 during spinal anesthesia, we ventured to conclude that a change in MAP or HR caused a significant decrease in SrO2. Since no patient developed any neurologic complication perioperatively, further study must be performed to elucidate the clinical importance of our findings.