Hemodynamic effects of hyperbaric bupivacaine versus isobaric bupivacaine for spinal anesthesia during cesarean delivery

Abstract

Introduction: Hyperbaric bupivacaine is widely used for spinal anesthesia during cesarean section. Hypotension is one of the most common complications after spinal block

thus, a continuous infusion of phenylephrine is frequently used to prevent maternal hypotension. Isobaric bupivacaine is reported to maintain stable hemodynamics more than hyperbaric bupivacaine during spinal anesthesia. Therefore, the purpose of this study is to demonstrate that isobaric bupivacaine could maintain hemodynamics without intravenous phenylephrine infusion.

Methods: This study is a prospective, double-blind and single-center trial. Sixty-six patients undergoing elective cesarean section under spinal anesthesia were randomized into one of four groups receiving 10 mg of hyperbaric bupivacaine or isobaric bupivacaine with or without a phenylephrine infusion (0.4 µg/kg/min). Before the induction of anesthesia, baseline systolic blood pressure (SBP) was calculated from three consecutive measurements. After the intrathecal injection, SBP was measured every 1 min until placenta was expelled and every 2.5 min till end of surgery. Hypotension was defined as a decrease in SBP by more than 20% of the baseline value and treated by administering a 100 µg bolus of phenylephrine. We recorded SBP 10, 20, and 30 min after intrathecal injection and the incidence of hypotension for 30 min after spinal anesthesia.

Results: SBP at 30 min in the hyperbaric bupivacaine group without phenylephrine (HS) was lower than that in the isobaric bupivacaine group with (IP) or without phenylephrine (IS) (102.43 ± 4.14 vs 119 ± 4.20 and 119 ± 4.09, p = 0.005 and 0.005, respectively). Patients in the HS group experienced hypotension more often than those in IP group for 10 min after spinal anesthesia had been induced (88.2% vs 43.8%, p=0.007). There was no difference in the incidence of hypotension between HP group and IS group (50.0% vs 47.1%). No differences in quality of anesthesia, side effects of spinal anesthesia, or neonatal outcomes were observed among the four groups.

Conclusion: Intrathecal isobaric bupivacaine maintained stable hemodynamics when compared to intrathecal hyperbaric bupivacaine without infusing phenylephrine.