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Comparison of Continuous Intravenous Phenylephrine vs. Norepinephrine Infusions in Prevention of Spinal Hypotension during Cesarean Delivery: Assessment of Hemodynamic Parameters and Outcomes
Abstract Number: GM-06
Abstract Type: Original Research
Introduction: Phenylephrine is currently the drug of choice in the treatment of maternal hypotension because it causes less neonatal acidosis and does not interfere with uteroplacental blood flow while maintaining blood pressure. However, phenylephrine does have dose dependent side effects such as a baroreceptor-mediated decrease in heart rate leading to a subsequent drop in cardiac output. We assessed the hemodynamic parameters throughout CD and aimed to determine which continuous infusion, phenylephrine or norepinephrine is more efficacious in the prevention of spinal hypotension.
Methods: After IRB approval, we conducted a prospective randomized clinical trial on 39 ASA I/II parturients scheduled for CD under spinal anesthesia. Subjects were randomized to Group A (continuous phenylephrine infusion 0.1 mcg/kg/min, n=16) or Group B (continuous norepinephrine infusion 0.05 mcg/kg/min, n=23) to maintain systolic blood pressure (SBP) within 100-120% of baseline under standardized spinal anesthesia [0.75% hyperbaric bupivacaine (1.6 mL) with preservative free morphine (0.2 mg) and fentanyl (20 mcg)]. Measured variables included Blood Pressure (BP), number and type of provider interventions to control blood pressure, Heart Rate (HR), Cardiac Output (CO), Cardiac Index (CI), Stroke Volume (SV), Systemic Vascular Resistance (SVR) as measured by Nexfin® (a noninvasive hemodynamic monitor), newborn APGAR scores at 1 and 5 minutes, and intraoperative maternal nausea and emesis. Results were analyzed using t-test, Mann-Whitney, or Chi-square. P values < 0.05 were considered significant.
Results: No differences were noted between study groups in demographic data (age, height, weight, gravidity, parity, and gestation). There was no difference in hemodynamic parameters (Fig), continuous infusion duration, number and total dose of vasopressor boluses between groups, APGAR scores and incidence of maternal nausea episodes. Maternal emesis was less in the norepinephrine infusion group (0.83% vs. 3.98%, P = 0.03).
Conclusion: A continuous intravenous phenylephrine or norepinephrine infusion produces comparable hemodynamic effects, and are both effective choices for prevention of spinal hypotension during CD. In the prevention of emesis, norepinephrine appears to offer an added benefit.
Refs: CNS Neurosci & Therap 2012;18:591-7; A&A 2002;94:920-6; A&A 2010;111:1230-7.