Norepinephrine versus phenylephrine not tied to decrease in heart rate during C-section for twin pregnancy: Study
China: Infusion of norepinephrine versus phenylephrine failed to provide a less overall decrease in heart rate (HR) during the cesarean section for twins, concludes a recent study. However, there was a significant decrease in the incidence of bradycardia with norepinephrine use. The study was published in the journal BMC Anesthesiology on 08 January 2022.
It is known that a twin gestation compared with a singleton pregnancy is featured by a greater increase in cardiac output. Norepinephrine therefore might be more suitable than phenylephrine for blood pressure maintenance during the cesarean section for twins. This is because phenylephrine causes reflex bradycardia and a resultant reduction in cardiac output.
Considering the above, Han Huang, Translational Neuroscience Centre, West China Hospital, Sichuan University, Chengdu, China, and colleagues aimed to determine whether norepinephrine is superior to phenylephrine in maintaining maternal hemodynamics during the cesarean section for twins in a double-blinded, randomized clinical trial.
For this purpose, the researchers obtained informed consent from all the patients before enrollment. The trial included 100 parturients with twin gestation undergoing cesarean section with spinal anesthesia. They were randomized to receive prophylactic norepinephrine (3.2 μg/min) or phenylephrine infusion (40 μg/min). The change of heart rate and blood pressure during the study period was the primary outcome.
Based on the study, the researchers found the following:
· There 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).
· 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.
· 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.
To conclude, the infusion of NE at the rate of 3.2 mcg/min versus PE infused at 40 mcg/min in parturients with twin pregnancy undergoing cesarean delivery under spinal anesthesia was not associated with a less overall decrease in heart rate. Although there was a significant decrease in the incidence of bradycardia
"Also, the requirements of physician intervention to correct maternal hemodynamic abnormalities and the fetal outcomes were similar with these two vasopressors infusion regimens," the authors wrote.
Reference:
Chen, Z., Zhou, J., Wan, L. et al. Norepinephrine versus phenylephrine infusion for preventing postspinal hypotension during cesarean section for twin pregnancy: a double-blinded randomized controlled clinical trial. BMC Anesthesiol 22, 17 (2022). https://doi.org/10.1186/s12871-022-01562-3
