Phenylephrine vs. Norepinephrine Infusion After Spinal Anesthesia for Cesarean Delivery
Condition: Effects of; Anesthesia, in Labor and Delivery
MeSH terms: Hypotension
Study type: Interventional
Phase: Phase 4

Summary: 
      The purpose of the study is to determine if a medication called phenylephrine, which helps to
      control blood pressure, is more effective as a continuous intravenous (IV) infusion compared
      to continuous IV norepinephrine in maintaining blood pressure during a spinal anesthetic for
      a cesarean delivery. Good blood pressure control has been shown to decrease nausea and
      vomiting during and after cesarean delivery under spinal anesthesia. For elective cesarean
      delivery, all participants will receive spinal anesthesia with a local anesthetic and
      morphine (provides long term pain control after cesarean delivery). This study plans to
      enroll 80 pregnant research subjects 18 years and above. Patients will be randomly assigned
      according to a computer generated system to be in one of two groups.
    

Detailed description: 
      This study will be a prospective, experimental, observational, randomized open label, active
      treatment controlled trial.

      After written and informed consent are obtained, the study participants are randomly assigned
      using a computer generated table to 1 of 2 treatment groups prior to cesarean delivery.

      Group A will consist of: A continuous phenylephrine infusion 0.1 mcg/kg/min to maintain
      systolic blood pressure (SBP) within 100-120% of baseline before the spinal.

      Group B will consist of: A continuous norepinephrine infusion 0.05 mcg/kg/min to maintain
      systolic blood pressure (SBP) within 100-120% of baseline before the spinal.

      Patients will be admitted to holding area. Baseline arterial blood pressure and heart rate
      will be measured in supine position, with left uterine displacement. Baseline blood pressure
      will be calculated by taking the mean of three consecutive SBP measurements taken 5 minutes
      apart. IV will be placed. Intravenous ondansetron 4 mg and up to 500 mL of Lactated Ringers
      solution administered prior to induction of spinal anesthesia.

      The primary endpoint is the number of provider interventions needed to maintain the SBP
      within 100-120% of baseline for both groups. The secondary endpoint is nausea measured with
      each provider intervention after induction of spinal anesthesia, and immediately following
      delivery with 11 point verbal rating scale (0 = no nausea, 10 = worst possible nausea).
      Patients will also be instructed to report episodes of nausea at any other time during the
      study. Emesis will be recorded whenever present during the surgical procedure.

      Hypertensive episodes (SBP greater than 120% of baseline) will be treated with cessation of
      infusion. Infusion will be restarted when SBP has decreased to below the upper limit of the
      target range (120% of baseline SBP). If the infusion must be stopped on three occasions, it
      will be discontinued permanently and the blood pressure maintained with phenylephrine boluses
      only.

      Bradycardia (HR less than 50 BPM) will be treated with glycopyrrolate 0.4mg IV or ephedrine 5
      mg - 10 mg IV bolus.

      Study participants will receive a standard spinal anesthetic consisting of 0.75% hyperbaric
      bupivacaine (1.6 mL) plus preservative free morphine (0.2 mg) and fentanyl (20 mcg) at L3-4
      or L4-5 interspace (the standard of care for spinal anesthesia at Ruby Memorial Hospital).
      Prior to surgical incision, the spinal sensory level will be tested to the bilateral T4
      dermatomal level which is necessary for cesarean section under spinal anesthesia. The
      patients will be positioned supine with a wedge placed under the right hip to avoid
      aortocaval compression. Both the patient and the clinical research assistant (who will
      collect data) will not be blinded as to the administered phenylephrine infusion or
      norepinephrine infusion. The study will end when care is transferred to the labor and
      delivery room nurse.

      Measured variables will include blood pressure (BP), the number and type of provider
      interventions for control of blood pressure (BP), heart rate (HR), cardiac output (CO) as
      measured by a noninvasive CO monitor, APGAR scores at 1 and 5 minutes, nausea and vomiting,
      and fetal cord blood analysis at delivery.
    

Intervention name(s): Phenylephrine; Norepinephrine
Intervention type(s): Drug; Drug
Other intervention name(s): Levophed
Intervention MeSH terms: Phenylephrine; Oxymetazoline; Norepinephrine
Allocation: Randomized
Intervention model: Parallel Assignment
Masking: None (Open Label)
Primary purpose: Prevention
Keywords: Hypotension; Cesarean Delivery; Phenylephrine; Spinal Anesthesia; Norepinephrine