Variable Rate Phenylephrine Infusion for Prevention of Spinal-induced Hypotension for Cesarean Delivery
Condition: Anesthetic Complication Spinal
MeSH terms: Hypotension
Intervention: Phenylephrine; saline
Intervention description: Prophylactic variable rate of phenylephrine infusion started at 0.75 µg/kg/min vs saline; Prophylactic variable rate of saline infusion where we adjusted the pump at a starting rate of 0.75 µg/kg/min, equivalent to 0.0075 mL/kg/min of saline
Intervention MeSH terms: Phenylephrine; Oxymetazoline
Phase: Phase 4
Study type: Interventional
Primary purpose: Prevention
Allocation: Randomized
Intervention model: Parallel Assignment
Masking: Double (Participant, Investigator)
Enrollment: 80.0
Sex: Female
Minimum age: 18 Years
Maximum age: 50 Years
Healthy volunteers: Accepts Healthy Volunteers
Keywords: spinal; cesarean delivery; phenylephrine; hypotension

Summary:

      Rapid administration of crystalloid immediately after induction of spinal anesthesia (coload)
      to be more effective in terms of managing hypotension as compared to administering
      crystalloid before spinal anesthesia (preload).

      Phenylehrine infusion is a safe and effective way to reduce incidence and frequency of
      hypotension during SA for cesarean delivery. Hypotension was virtually eliminated by use of
      high-dose prophylactic phenylephrine infusion at a rate of 100 µg/min and rapid crystalloid
      coload up to two liters (administration at the time of SA). However, incidence of reactive
      hypertension was frequent up to 47% with decrease in maternal heart rate (HR). This may raise
      concern in patients in whom increase of blood pressure may be detrimental, like chronic
      hypertension and in the presence of a compromised uteroplacental blood flow. A recent study
      found that infusing phenylephrine at a fixed rate of 75 and 100 ug/min is associated with
      more episodes of hypertension than placebo or the lower infusion rates of 25 and 50 ug/min
      respectively. However, there was no reduction in the number of physician interventions
      (phenylephrine boluses and stopping the infusion) needed to maintain maternal systolic blood
      pressure within 20% of baseline among all groups. Prophylactic fixed rate infusions may have
      limited application in clinical practice, and a variable rate (i.e. modifying the rate
      according to hemodynamics) has been advocated. The bolus administration of phenylephrine to
      treat hypotension is still commonly used, but requests multiple interventions from the
      anesthesiologists and is time consuming.

      Eighty patients scheduled for cesarean delivery under spinal anesthesia will be assigned to
      one of two groups. Immediately after spinal injection, rapid crystalloid colaod of lactated
      Ringer of 15 mL/kg over a period of 10-15 min will be initiated. Patients in Group I will
      receive infusion of normal saline (placebo) and patients in group II variable infusion rate
      of phenylephrine started at 0.75 ug/kg (close to the dose of 50 ug/min recommended for fixed
      infusion rate). The number of interventions needed to maintain maternal systolic blood
      pressure within 20% of baseline, hemodynamic performance, intraoperative nausea and vomiting,
      and umbilical cord blood gases will be compared between the two groups.

      We will define a reliable and safe method to ensure maternal hemodynamic stability during
      spinal anesthesia for cesarean delivery with the least physician interference.
    

Eligibility criteria:

        Inclusion Criteria:

          -  Parturients beyond 37 weeks gestation

          -  ASA І or ІІ

        Exclusion Criteria:

          -  pregnancy-induced hypertension

          -  chronic hypertension

          -  multiple pregnancy

          -  fetal compromise

          -  diabetes mellitus

          -  polyhydramnios

          -  body weight >100 kg

          -  major systemic disease

          -  anemia (hemoglobin concentration<10 g/dl)

          -  clotting diathesis