ED 50 and ED 95 of intrathecal bupivacaine coadministered with sufentanil for cesarean delivery under combined spinal-epidural in severely preeclamptic patients

Abstract

Background: Spinal anesthesia was considered as a reasonable anesthetic option in severe preeclampsia when cesarean delivery is indicated, and there is no indwelling epidural catheter or contraindication to spinal anesthesia. However, the ideal dose of intrathecal bupivacaine has not been quantified for cesarean delivery for severe preeclamptic patients. This study aimed to determine the ED 50 and ED 95 of intrathecal bupivacaine for severely preeclamptic patients undergoing elective cesarean delivery.

Methods: Two hundred severely preeclamptic patients are undergoing elective cesarean delivery under combined spinal-epidural anesthesia enrolled in this randomized, double-blinded, dose-ranging study. Patients received 4 mg, 6 mg, 8 mg, or 10 mg intrathecal hyperbaric bupivacaine with 2.5 μg sufentanil. Successful spinal anesthesia was defined as a T6 sensory level achieved within 10 minutes after intrathecal drug administration and/or no epidural supplement was required during the cesarean section. The ED 50 and ED 95 were calculated with a logistic regression model.

Results: ED 50 and ED 95 of intrathecal bupivacaine for successful spinal anesthesia were 5.67 mg (95% confidence interval [CI]: 5.20-6.10 mg) and 8.82 mg (95% CI: 8.14-9.87 mg) respectively. The incidence of hypotension in Group 8 mg and Group 10 mg was higher than that in Group 4 mg and Group 6 mg (P < 0.05). The sensory block was significantly different among groups 10 minutes after intrathecal injection (P < 0.05). The use of lidocaine in Group 4 mg was higher than that in other groups (P < 0.05). The use of phenylephrine in Group 8 mg and Group 10 mg was higher than that in the other two groups (P < 0.05). The lowest systolic blood pressure before the infant delivery of Group 8 mg and Group 10 mg was lower than the other two groups (P < 0.05). The satisfaction of muscle relaxation in Group 4 mg was lower than other groups (P < 0.05). There was no significant difference in patients' satisfaction and the newborns' Apgar score and the blood gas analysis of umbilical artery serum (P > 0.05).

Conclusion: Our study showed that the ED 50 and ED 95 of intrathecal bupivacaine for severely preeclamptic patients undergoing elective cesarean delivery were 5.67 mg and 8.82 mg, respectively. In addition, decreasing the dose of intrathecal bupivacaine could reduce the incidence of maternal hypotension.

Figure 1

Success of anesthesia at different doses of intrathecal bupivacaine.

Figure 2

Logistic regression plot of the probability of successful spinal anesthesia versus intrathecal bupivacaine dose. Probability of 0.5 and 0.95 was used for deriving the ED₅₀ and ED₉₅ of intrathecal bupivacaine to achieve successful spinal anesthesia for C-section.

Figure 3

The systolic blood pressure (SBP) at baseline and the lowest SBP during the period from intrathecal drug administration to fetal delivery in the four groups.