Abstract
BackgroundCompared with singleton pregnancy, twin gestation is featured by a greater increase in cardiac output. Therefore, norepinephrine might be more suitable than phenylephrine for maintaining blood pressure during cesarean section for twins, as phenylephrine causes reflex bradycardia and a resultant decrease in cardiac output. This study was to determine whether norepinephrine was superior to phenylephrine in maintaining maternal hemodynamics during cesarean section for twins.MethodsInformed consent was obtained from all the patients before enrollment. In this double-blinded, randomized clinical trial, 100 parturients with twin gestation undergoing cesarean section with spinal anesthesia were randomized to receive prophylactic norepinephrine (3.2 μg/min) or phenylephrine infusion (40 μg/min). The primary outcome was the change of heart rate and blood pressure during the study period. The secondary outcomes were to compare maternal complications, neonatal outcomes, Apgar scores and umbilical blood acid-base status between the two vasopressors.ResultsThere was no significant difference observed for the change of heart rate between two vasopressors. The mean standardized area under the curve of heart rate was 78 ± 12 with norepinephrine vs. 74 ± 11 beats/min with phenylephrine (mean difference 4.4, 95%CI − 0.1 to 9.0; P = .0567). The mean standardized area under the curve of systolic blood pressure (SBP) was significantly lower in parturients with norepinephrine, as the mean of differences in standardized AUC of SBP was 6 mmHg, with a 95% CI from 2 to 9 mmHg (P = .0013). However, requirements of physician interventions for correcting maternal hemodynamical abnormalities (temporary cessation of vasopressor infusion for reactive hypertension, rescuing vasopressor bolus for hypotension and atropine for heart rate less < 50 beats/min) and neonatal outcomes were also not significantly different between two vasopressors.ConclusionInfusion of norepinephrine was not associated with less overall decrease in heart rate during cesarean section for twins, compared with phenylephrine.Trial registrationChinese Clinical Trial Registry (ChiCTR1900021281).
Highlights
Compared with singleton pregnancy, twin gestation is featured by a greater increase in cardiac output
The primary objective of this randomized, doubleblinded study was to compare the changes in heart rate and blood pressure following prophylactic intravenous infusions of norepinephrine or phenylephrine in women with twin pregnancies undergoing cesarean section under spinal anesthesia
The primary outcome was the change in heart rate and blood pressure during the study period, from intrathecal injection to delivery of the second twin, which was calculated as the standard area under the curve of heart rate and systolic blood pressure
Summary
This study was reviewed and approved by ethics committee Hypotension, defined as a systolic blood pressure (SBP) < 90 mmHg or 80% of the baseline SBP, was rescued by 1-ml bolus of the study drug, i.e. NE 8 μg for parturients with NE infusion and PE 100 μg for parturients with PE. These boluses were prepared beforehand in 10-ml syringes labelled as “rescuing drug”. The primary outcome was the change in heart rate and blood pressure during the study period, from intrathecal injection to delivery of the second twin, which was calculated as the standard area under the curve of heart rate and systolic blood pressure (please find below, in the section of statistical analysis). Considering the potential withdraw of consent or loss of follow-up, a final sample size of 50 per group was determined
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