Relationship between changes in regional cerebral blood volume and oxygenation and changes in cardiac output and systemic vascular resistance during spinal anesthesia in women undergoing cesarean section.

Purpose: The decrease in maternal regional cerebral blood volume (rCBV) and oxygenation (rCBO) during spinal anesthesia for cesarean section depends on the severity of hypotension. We examined the relationships between changes in the systemic circulatory parameters, cardiac output (CO) and systemic vascular resistance (SVR), and rCBV and rCBO after induction of spinal anesthesia, evaluated by near-infrared spectroscopy (NIRS) and an arterial pressure-based cardiac output monitoring system (APCOs).

Methods: Seventeen patients undergoing elective cesarean section under spinal anesthesia were monitored every 1 min for mean arterial pressure (MAP), heart rate (HR), end-tidal carbon dioxide (EtCO) and oxygen saturation (SpO), and at 20 s intervals for CO, SVR, concentrations of oxy-hemoglobin (Hb), deoxy-Hb, total-Hb, and tissue oxygenation index (TOI), until 15 min after the intrathecal injection of bupivacaine. We investigated changes in the parameters from baseline and evaluated correlations between the changes in total-Hb and TOI and changes in CO and SVR, respectively, at the same timepoints.

Results: Oxy-Hb, total-Hb, TOI, and SVR significantly decreased and HR significantly increased with a decrease in MAP (P < 0.01). Deoxy-Hb, CO, SpO and EtCO levels did not change from baseline. There were statistically significant, although weak, positive correlations between both total-Hb and TOI with SVR (total-Hb; r = 0.18, P < 0.01, TOI; r = 0.38, P < 0.01).

Conclusion: The decreases in both rCBV and rCBO after induction of spinal anesthesia for cesarean section are probably dependent on the decrease in SVR due to spinal anesthesia.