Colloid coload versus crystalloid coload to prevent maternal hypotension in women receiving prophylactic phenylephrine infusion during caesarean delivery: a randomised controlled trial

Effect of crystalloid solution co-loading infusion rate on the dose requirements of prophylactic phenylephrine for preventing hypotension following combined spinal-epidural anesthesia for cesarean delivery

BACKGROUND

Intravenous fluid administration and prophylactic vasopressor infusion are the primary methods for preventing spinal anesthesia-induced hypotension during cesarean delivery. However, evidence regarding the impact of different volumes of crystalloid solution on the phenylephrine infusion dosage for preventing this hypotension remains inconclusive. This study aimed to determine the effect of two IV fluid infusion rates (10 or 20 mL/kg/h) on phenylephrine requirement for preventing spinal anesthesia-induced hypotension.

METHODS

Eighty healthy parturients undergoing elective cesarean delivery under combined spinal-epidural anesthesia were enrolled. Participants were randomly assigned to receive either 10 mL/kg/h (group 10) or 20 mL/kg/h (group 20) of lactated Ringer's solution. The first patient in each group received 0.5 µg/kg/min of phenylephrine infusion immediately after intrathecal injection. The phenylephrine dose in subsequent patients was adjusted by increments or decrements of 0.05 µg/kg/min based on the previous patient's response. The ED50 of phenylephrine infusion for preventing spinal-induced hypotension for cesarean delivery was estimated using a modified up-down sequential analysis, with probit analysis applied as a backup sensitivity analysis.

RESULTS

The ED50 values for preventing spinal anesthesia-induced hypotension were 0.30 µg/kg/min (95% CI, 0.29-0.32 µg/kg/min) for group 10, and 0.19 µg/kg/min (95% CI, 0.16-0.22 µg/kg/min) for group 20, respectively. The estimated relative potency for phenylephrine in group 10 compared to group 20 was 1.52 (95%CI, 1.24-1.97), showing a significant difference in the ED50 values between the two groups.

CONCLUSION

This study found that a higher crystalloid co-loading rate significantly reduces prophylactic phenylephrine requirement for preventing spinal anesthesia induced hypotension.

TRIALS REGISTRATION

https://www.chictr.org.cn/showproj.html?proj=125918 (Trial number: ChiCTR2100048002).

Comparative Dose–Response Study on the Infusion of Norepinephrine Combined with Crystalloid Coload versus Colloid Coload for Preventing Hypotension During Spinal Anesthesia for Cesarean Delivery

Background

Although the optimal infusion dose of norepinephrine combined with crystalloid coload for preventing spinal anesthesia-induced hypotension (SAIH) for cesarean delivery has been established, the infusion regimen of norepinephrine combined with colloid coload has not been fully quantified. The objective of this study was to compare and determine the median effective dose (ED₅₀) and 90% effective dose (ED₉₀) of norepinephrine infusion combined with crystalloid coload versus colloid coload for preventing SAIH during cesarean delivery.

Methods

Two hundred parturients were randomly assigned to receive norepinephrine infusion at 0.02, 0.04, 0.06, 0.08, or 0.10 µg/kg/min in combination with 10 mL/kg crystalloid coload or colloid coload to prevent SAIH. The study period was defined as the interval from the commencement of intrathecal injection to delivery of the neonate. The primary outcome was non-occurrence of hypotension, defined as systolic blood pressure (SBP) less than 80% of the baseline before delivery. The ED₅₀ and ED₉₀ of norepinephrine infusion dose were determined using probit regression analysis. By calculating the 95% confidence intervals (CIs) of relative median potency to determine whether the prophylactic infusion of norepinephrine requirement was different between the two groups.

Results

The derived ED₅₀ and ED₉₀ of norepinephrine infusion combined with crystalloid coload were 0.030 (95% CIs 0.020 to 0.038) and 0.097 (95% CIs 0.072 to 0.157) µg/kg/min, respectively. The ED₅₀ and ED₉₀ of norepinephrine infusion combined with colloid coload were 0.021 (95% CIs 0.013 to 0.029) and 0.070 (95% CIs 0.053 to 0.107) µg/kg/min, respectively. The estimate of relative median potency for norepinephrine between the two groups was 1.37 (95% CIs 0.94 to 2.23).

Conclusion

Under the conditions of this study, 10 mL/kg colloid coload reduced the dose of prophylactic norepinephrine infusion by approximately 30% in parturients during spinal anesthesia for cesarean delivery compared with the crystalloid coload.