Prevention of Hypotension During Cesarean Section
Condition: Hypotension Symptomatic; Obstetric Anesthesia Problems; Cesarean Section Complications; Vasoconstriction
MeSH terms: Hypotension
Study type: Interventional

Summary: 
      The aim of this double-blind randomized study will be to compare a fixed-rate prophylactic
      noradrenaline infusion to a fixed-rate prophylactic phenylephrine infusion during elective
      cesarean section under combined spinal-epidural anesthesia
    

Detailed description: 
      -  Spinal anesthesia is the anesthetic technique of choice for elective cesarean section.

        -  Spinal anesthesia can be complicated by hypotension, with incidence exceeding 80%
           occasionally. Hypotension can lead to nausea, emesis and a subjective feeling of
           discomfort due to cerebral hypoperfusion. If left untreated, severe or sustained
           hypotension can lead to decreased uteroplacental flow and fetal distress of premature or
           compromised fetuses while severe complications to the parturient might ensue, such as
           loss of consciousness, aspiration, apnea or cardiac arrest

        -  One of the standard techniques to avoid maternal hypotension is the administration of a
           continuous phenylephrine infusion while studies have demonstrated its superiority as
           compared to rescue bolus phenylephrine administration. Additionally, as compared to
           ephedrine, phenylephrine is associated with less neonatal acidosis and better
           maintenance of uteroplacental blood flow. However, phenylephrine can lead to
           baroreceptor-mediated reflex bradycardia, with untoward consequences for maternal
           cardiac output.

        -  Recently, noradrenaline has been shown to be effective in maintaining blood pressure in
           obstetric patients. Noradrenaline is a strong-alpha agonist with weak beta-action, too.
           Therefore, it might prove superior in maintaining cardiac output as compared to
           phenylephrine. There have been a few studies examining the use of noradrenaline as a
           continuous infusion in this context but the optimal dose and safety and efficacy profile
           of noradrenaline continuous infusion in obstetrics is yet to be determined

        -  In all parturients, standard hemodynamic monitoring will be applied. Baseline systolic
           arterial pressure will be considered the average of three consecutive measurements that
           will not differ more than 10% among them. All parturients will have a peripheral
           intravenous catheter placed in the upper extremity after baseline hemodynamic
           measurements are recorded and will be infused 5 mL/kg of hydroxyethylstarch
           (pre-loading) before the regional procedure.

        -  Study group allocation will taker place according to a computer-generated sequence of
           random numbers. A standard spinal anesthetic consisting of ropivacaine 0.75% 1.8 mL plus
           fentanyl 10 μg will be administered in the left lateraL position at the L3-4 or L4-5
           vertebral interspace. The study infusion medication (either phenylephrine or
           norepinephrine, depending on group allocation) will be started at the same time
           cerebrospinal fluid is obtained, immediately before injection of spinal medications.
           After the intrathecal injection, patients will placed in the supine position with a left
           lateral tilt of the table to provide left uterine displacement and to prevent aortocaval
           compression. The spinal sensory level will be tested bilaterally by pinprick to ensure a
           T4 dermatomal level before surgical incision.

        -  Hemodynamic parameters (systolic arterial blood pressure, diastolic arterial blood
           pressure, mean arterial blood pressure and heart rate) will be measured and recorded at
           discrete timepoints throughout the operation (baseline, start of vasoactive agent
           administration, parturient at supine position, sympathetic block at T4, knife-to-skin,
           neonatal delivery, start of oxytocin administration, start of skin closure, end of
           operation.

        -  During the operation, a rescue dose of phenylephrine 50 μg will be administered when
           systolic arterial pressure drops below 80% of baseline in combination with heart rate>80
           bpm. Ephedrine 5 mg will be administered when there is hypotension (systolic arterial
           pressure <80% of baseline) in combination with heart rate less than 80 bpm. Hypertensive
           episodes (systolic blood pressure >120% of baseline) will be treated with halving the
           infusion while when systolic arterial pressure increases above 130% of baseline the
           infusion will be discontinued and will be restarted when systolic blood pressure
           decreases below the upper limit of the target range (120% of baseline value).
    

Intervention name(s): phenylephrine infusion; norepinephrine infusion
Intervention type(s): Procedure; Procedure
Intervention description(s): In parturients allocated to the phenylephrine group, a phenylephrine infusion will be initiated as soon as spinal anesthesia is established; In parturients allocated to the norepinephrine group group, a phenylephrine infusion will be initiated as soon as spinal anesthesia is established
Intervention MeSH terms: Phenylephrine; Oxymetazoline; Norepinephrine
Allocation: Randomized
Intervention model: Parallel Assignment
Masking: Quadruple (Participant, Care Provider, Investigator, Outcomes Assessor)
Primary purpose: Prevention
Keywords: hypotension; phenylephrine; noradrenaline; cardiac output; fetal; maternal hemodynamics; cesarean section