Hemodynamic effects of low-dose bupivacaine spinal anesthesia for cesarean section: A randomized controlled trial

Spinal anesthesia is the most common technique for cesarean section. The conventional local anesthetic dose has been decreasing over time to 8-12.5 mg of bupivacaine. Lower doses of bupivacaine may be associated with reduced incidence of hypotension and other complications. This low dose also may be associated with improved maternal cardiac index (CI). We hypothesized that low dose spinal anesthesia using 4.5 mg bupivacaine would result in improved maternal CI when compared with conventional dose (9 mg) intrathecal bupivacaine.

This randomized controlled trial included all healthy parturients presenting for elective cesarean section. In addition to standard monitors, an arterial line was placed for pulse contour cardiac output measurement. Due to limited data on maternal cardiac output during cesarean section, we had to power our study on recovery room length of stay. Secondary outcomes included the change in maternal CI, fluid administration, vasopressor usage, maternal satisfaction, and adequacy of surgical blockade and recovery time from motor and sensory blockade.

The low dose group had significantly faster motor recovery times (132 [122-144] versus. 54 [48-66] min conventional versus. low-dose, respectively, P < 0.01), and a shorter recovery room stay (92 ± 21 vs 70 ± 11 min, conventional vs. low-dose, respectively, P < 0.01, 95% CI -35 to -10 min). There was no difference in CI between the conventional dose and low dose spinal groups. Both groups had a drop in CI with spinal anesthesia. The low-dose group demonstrated equivalent surgical anesthesia and block onset times compared to the conventional group.

Low-dose spinal anesthesia provides adequate surgical anesthesia, improved recovery time, but no difference in maternal cardiac index when compared to conventional dose spinal anesthesia.NCT02046697.