title: The effects of prophylactic bolus phenylephrine on hypotension during low-dose spinal anesthesia for cesarean section.
abstract: BACKGROUND
  Continuously infused phenylephrine is frequently used to reduce the incidence of hypotension in women undergoing cesarean section under spinal anesthesia, but less is known about the prophylactic bolus method. We evaluated three prophylactic bolus doses of phenylephrine during low-dose spinal anesthesia for cesarean section.
  
  
  METHODS
  One-hundred-and-eighty-four patients were randomized to receive 0.9% saline 2mL (Control Group) or phenylephrine 1.0μg/kg (PHE1 Group), 1.5μg/kg (PHE1.5 Group), or 2.0μg/kg (PHE2 Group) immediately after induction of combined spinal-epidural anesthesia. Maternal blood pressure and heart rate were recorded at 1-min intervals until delivery. Hypotension, defined as systolic blood pressure <80% of baseline, was treated with rescue doses of phenylephrine 100μg at 1-min intervals until hypotension resolved. The incidence of nausea, vomiting, bradycardia, and hypertension, as well as Apgar scores and umbilical blood gases, were recorded.
  
  
  RESULTS
  The incidence of hypotension was 71.7% (33/46) in the Control Group, 68.9% (31/45) in the PHE1 Group, 37.0% (17/46) in the PHE1.5 Group and 45.7% (21/46) in the PHE2 Group (P=0.001). The total rescue dose of phenylephrine was greater in the Control Group than those in the PHE1.5 Group (P<0.05) and PHE2 Group (P<0.05). The incidence of hypertension increased as the dose of prophylactic phenylephrine increased (P<0.001) and was highest in the PHE2 group (37%). Other variables did not differ among the four groups.
  
  
  CONCLUSIONS
  Under the conditions of this study, prophylactic bolus injection of phenylephrine 1.5μg/kg was a suitable alternative method for reducing the incidence of hypotension during low-dose spinal anesthesia for cesarean section.
authors.affiliation: Department of Anesthesiology and Pain Medicine, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Republic of Korea; Department of Anesthesiology and Pain Medicine, Gangneung Asan Hospital, University of Ulsan College of Medicine, Gangneung, Republic of Korea.
authors.forename: H-M
authors.initials: HM
authors.lastname: Lee
authors.affiliation: Department of Anesthesiology and Pain Medicine, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Republic of Korea.
authors.forename: S-H
authors.initials: SH
authors.lastname: Kim
authors.affiliation: Department of Anesthesiology and Pain Medicine, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Republic of Korea.
authors.forename: B-Y
authors.initials: BY
authors.lastname: Hwang
authors.affiliation: Department of Anesthesiology and Pain Medicine, Gangneung Asan Hospital, University of Ulsan College of Medicine, Gangneung, Republic of Korea.
authors.forename: B-W
authors.initials: BW
authors.lastname: Yoo
authors.affiliation: Department of Anesthesiology and Pain Medicine, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Republic of Korea.
authors.forename: W-U
authors.initials: WU
authors.lastname: Koh
authors.affiliation: Department of Anesthesiology and Pain Medicine, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Republic of Korea.
authors.forename: D-M
authors.initials: DM
authors.lastname: Jang
authors.affiliation: Department of Anesthesiology and Pain Medicine, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Republic of Korea. Electronic address: woojongchoi@amc.seoul.kr.
authors.forename: W-J
authors.initials: WJ
authors.lastname: Choi
mesh_terms: D000328:Adult; D000773:Anesthesia, Obstetrical / Q000009:adverse effects*; D000775:Anesthesia, Spinal / Q000009:adverse effects*; D002585:Cesarean Section; D005260:Female; D006801:Humans; D007022:Hypotension / Q000453:epidemiology / Q000517:prevention & control*; D015994:Incidence; D010656:Phenylephrine / Q000008:administration & dosage / Q000009:adverse effects / Q000627:therapeutic use*; D011247:Pregnancy; D011446:Prospective Studies
chemical_list: D010656:Phenylephrine
keywords: Cesarean section; Phenylephrine; Spinal hypotension