Effect of spinal anesthesia for elective cesarean section on cerebral blood oxygenation changes: comparison of hyperbaric and isobaric bupivacaine.

We used near-infrared spectroscopy (NIRS) to evaluate cerebral blood oxygenation changes in subjects undergoing cesarean section under spinal anesthesia (SP) with hyperbaric bupivacaine (group H, 27 subjects) or isobaric bupivacaine (group I, 15 subjects). In group H, total-Hb, oxy-Hb, and mean blood pressure (MBP) within 20 min after SP were significantly lower than the baseline values. In contrast, there was no significant change from baseline in total-Hb, oxy-Hb, or MBP in group I after SP. Total-Hb and MBP in group H were significantly lower than those in group I within 10 min after SP. There was no significant change of deoxy-Hb, tissue oxygen index, or heart rate from baseline in either of the groups. These results suggest that isobaric bupivacaine may be superior to hyperbaric bupivacaine for preventing a decrease of maternal cerebral blood flow after SP for cesarean section.