Anesth Pain Med.  2020 Jan;15(1):53-60. 10.17085/apm.2020.15.1.53.

Systemic hemodynamic effects of norepinephrine versus phenylephrine in intermittent bolus doses during spinal anesthesia for cesarean delivery

• Cho WJ
• Cho SY
• Lee AR

• KMID: 2500455
• DOI: http://doi.org/10.17085/apm.2020.15.1.53

Abstract

Background
Norepinephrine, a potent α-adrenergic agonist with β-adrenergic effects, has recently emerged as a potential alternative to phenylephrine that does not lower cardiac output (CO) and heart rate (HR) during cesarean deliveries. We examined the systemic hemodynamic effects of both agents in this setting, using intermittent bolus doses to treat spinal anesthesia-induced hypotension.
Methods
A total of 56 parturients consenting to spinal anesthesia for elective cesarean delivery were randomly assigned to phenylephrine (100 μg/ml) or norepinephrine (5 μg/ ml) intermittent bolus dosing. The primary study outcome was maternal normalized CO, examining and other hemodynamic variables, maternal side effects, and fetal outcomes secondarily.
Results
In terms of systolic blood pressure and HR, there were significant within-group differences over time (P < 0.001 and P < 0.001, respectively). Normalized CO and stroke volume (SV) also showed significant differences between groups (P < 0.001 and P = 0.002, respectively). In the phenylephrine group, normalized CO and SV declined (relative to baseline values) by as much as 13% and 9%, respectively; whereas in the norepinephrine group, normalized CO did not differ significantly from baseline, and SV increased up to 5% (relative to baseline). Normalized total peripheral resistance likewise displayed significant within-group differences over time (P < 0.001).
Conclusions
During elective cesarean delivery, intermittent bolus doses of norepinephrine proved effective for treating spinal anesthesia-induced hypotension, while maintaining CO and SV. No maternal complications or fetal effects were evident.

Keyword

Cesarean section; Norepinephrine; Phenylephrine

Figure

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  Fig. 1 CONSORT diagram showing patient recruitment and flow.

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  Fig. 2 Serial changes in systolic blood pressure at four time periods. There is no difference between the two groups (P = 0.175); whereas there is within-group difference (P < 0.001). Values are presented as mean and standard deviation. T0: baseline, T1: 5 min after intrathecal injection, T2: start surgery, T3: delivery. *P < 0.05 vs. T0 in norepinephrine group. †P < 0.05 vs. T0 in phenylephrine group.

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  Fig. 3 Serial changes in heart rate at four time periods. There is no difference between the two groups (P = 0.622); whereas there is withingroup difference (P < 0.001). In post-hoc analysis, as heart rate had not shown normal distribution, Mann–Whitney U test for intergroup comparisons and the paired-sample Wilcoxon test for within-group comparisons were invoked, with Bonferroni correction. Values are presented as median and interquartile range. T0: baseline, T1: 5 min after intrathecal injection, T2: start surgery, T3: delivery. *P < 0.05 vs. T0 in norepinephrine group. †P < 0.05 vs. T0 in phenylephrine group.

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  Fig. 4 (A) Normalized CO. There is significant difference between groups (P < 0.001; overall). In the phenylephrine group, mean of normalized CO at T1, T2, and T3 declined relative to CO at T0 (94%, 89%, and 87%, respectively) and differed significantly at T2 and T3 relative to T0 (P < 0.001 and P < 0.001, respectively); whereas in the norepinephrine group, mean of normalized CO at T1, T2, and T3 maintained the CO at T0 (104%, 99%, and 100%, respectively). (B) Normalized SV. There is significant difference between groups (P = 0.002, overall), whereas there is no difference within group (P = 0.238, overall). (C) Normalized TPR. There is no difference between groups (P = 0.726, overall). In the phenylephrine group, normalized CO are differed at T1 and T3 relative to T0 (P < 0.001, overall). Values are presented as mean and standard deviation. Normalized value = measured value / baseline value × 100 (%). CO: cardiac output, SV: stroke volume, TPR: total peripheral resistance, T0: baseline, T1: 5 min after intrathecal injection, T2: start surgery, T3: delivery. *P < 0.05 vs. T0 in norepinephrine group. †P < 0.05 vs. T0 in phenylephrine group. ‡P < 0.05 between groups.

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