title: An open-label randomized controlled clinical trial for comparison of continuous phenylephrine versus norepinephrine infusion in prevention of spinal hypotension during cesarean delivery.
abstract: BACKGROUND
  During spinal anesthesia for cesarean delivery phenylephrine is the vasopressor of choice but can cause bradycardia. Norepinephrine has both β- and α-adrenergic activity suitable for maintaining blood pressure with less bradycardia. We hypothesized that norepinephrine would be superior to phenylephrine, requiring fewer rescue bolus interventions to maintain blood pressure.
  
  
  METHODS
  Eighty-five parturients having spinal anesthesia for elective cesarean delivery were randomized to Group P (phenylephrine 0.1μg/kg/min) or Group N (norepinephrine 0.05μg/kg/min) fixed-rate infusions. Rescue bolus interventions of phenylephrine 100μg for hypotension, or ephedrine 5mg for bradycardia with hypotension, were given as required to maintain systolic blood pressure. Maternal hemodynamic variables were measured non-invasively.
  
  
  RESULTS
  There was no difference between groups in the proportion of patients who required rescue vasopressor boluses (Group P: 65.8% [n=25] vs. Group N: 48.8% [n=21], P=0.12). The proportion of patients who received ⩾1 bolus of phenylephrine was similar between groups (Group P: 52.6% [n=20] vs. Group N: 46.5% [n=20], P=0.58). However, more patients received ⩾1 bolus of ephedrine in the phenylephrine group (Group P: 23.7% [n=9] vs. Group N: 2.3% [n=1], P<0.01). The incidence of emesis was greater in the phenylephrine group (Group P: 26.3% vs. Group P: 16.3%, P<0.001). Hemodynamic parameters including heart rate, the incidence of bradycardia, blood pressure, cardiac output, cardiac index, stroke volume, and systemic vascular resistance and neonatal outcome were similar between groups (all P<0.05).
  
  
  CONCLUSIONS
  Norepinephrine fixed-rate infusion has efficacy for preventing hypotension and can be considered as an alternative to phenylephrine.
authors.affiliation: West Virginia University School of Medicine, Morgantown, WV, USA. Electronic address: vallejom@wvumedicine.org.
authors.forename: M C
authors.initials: MC
authors.lastname: Vallejo
authors.affiliation: West Virginia University School of Medicine, Morgantown, WV, USA.
authors.forename: A F
authors.initials: AF
authors.lastname: Attaallah
authors.affiliation: West Virginia University School of Medicine, Morgantown, WV, USA.
authors.forename: O M
authors.initials: OM
authors.lastname: Elzamzamy
authors.affiliation: West Virginia University School of Medicine, Morgantown, WV, USA.
authors.forename: D T
authors.initials: DT
authors.lastname: Cifarelli
authors.affiliation: Duquesne University School of Business, Pittsburgh, PA, USA.
authors.forename: A L
authors.initials: AL
authors.lastname: Phelps
authors.affiliation: West Virginia University School of Medicine, Morgantown, WV, USA.
authors.forename: G R
authors.initials: GR
authors.lastname: Hobbs
authors.affiliation: West Virginia University School of Medicine, Morgantown, WV, USA.
authors.forename: R E
authors.initials: RE
authors.lastname: Shapiro
authors.affiliation: West Virginia University School of Medicine, Morgantown, WV, USA.
authors.forename: P
authors.initials: P
authors.lastname: Ranganathan
mesh_terms: D000328:Adult; D000773:Anesthesia, Obstetrical / Q000009:adverse effects*; D000775:Anesthesia, Spinal / Q000009:adverse effects*; D002585:Cesarean Section / Q000009:adverse effects*; D005260:Female; D006801:Humans; D007022:Hypotension / Q000517:prevention & control*; D007262:Infusions, Intravenous; D009638:Norepinephrine / Q000627:therapeutic use*; D010656:Phenylephrine / Q000627:therapeutic use*; D011247:Pregnancy; D016896:Treatment Outcome; D014662:Vasoconstrictor Agents / Q000627:therapeutic use
chemical_list: D014662:Vasoconstrictor Agents; D010656:Phenylephrine; D009638:Norepinephrine
keywords: Cesarean delivery; Norepinephrine; Phenylephrine; Spinal anesthesia