Phenylephrine Versus Norepinephrine for Maintenance of Hemodynamic During Cesarean Section Under Spinal Anesthesia

Randomized, Double-blind, Controlled Clinical Trial for Comparison of Continuous Phenylephrine Versus Norepinephrine Infusion for Maintenance of Hemodynamic Stability During Cesarean Section Under Spinal Anesthesia

Comparison between prophylactic continuous variable infusion of phenylephrine (starting dose 0,5mcg/kg/min) and norepinephrine tartrate (starting dose 0,1mcg/kg/min) to prevent hypotension and maintain cardiac output under spinal anesthesia during cesarean delivery.

Maternal hypotension is a frequent complication after spinal anesthesia for cesarean delivery. Many vasopressors have been studied and used, but the perfect vasopressor is yet to be found. Phenylephrine is the most common used in obstetric anesthesia but its cardiac depressant activity, being an only alpha-adrenergic agonistic, is linked to frequent side effects such as bradycardia and decreased cardiac output.

Norepinephrine is a vasopressor characterized by both alpha and minor beta-adrenergic agonistic activity, it has then a minimal cardiac depressant activity. Hence it would provide a better stability of hemodynamic and cardiac output, and appears as a better alternative to phenylephrine.

In this study, the investigators will compare prophylactic continuous variable infusion of both vasopressors. Phenylephrine started at the dose of 0,5mcg/kg/min and Norepinephrine tartrate started at the dose of 0,1mcg/kg/min. The doses will be adjusted according to maternal systolic blood pressure in order to prevent hypotension (defined by a systolic blood pressure under 80% of baseline).

Inclusion Criteria:

• Pregnancy higher than 36 weeks of amenorrhea
• Scheduled or semi-urgent (interval between decision and delivery by cesarean section higher than 12hours) cesarean section under spinal anesthesia

Exclusion Criteria:

• Extreme height (less than 140cm; higher than 180cm)
• Weight less than 50kg
• Weight higher than 120kg
• Cardiovascular disease with use of cardiac medication (including antihypertensive drug)
• Active neurological disease
• Anti-hypertension treatment.
• High blood pressure or severe pre-eclampsia
• American Society of Anesthesiologists physical status class higher than 3
• Placenta accrete/percreta
• Cesarean section scheduled under general anesthesia
• Contraindications to spinal anesthesia
• Minor (age less than 18 years old)
• Guardianship/ curatorship
• Anemia less than or equal to 8 g/dl
• Allergy to any study medication
• Simultaneous participation in another study