title: The median effective seated time for hypotension induced by spinal anesthesia at Cesarean delivery with two doses of hyperbaric bupivacaine: a randomized up-down sequential allocation study.
abstract: BACKGROUND
  Extending the time a parturient is left sitting after induction of spinal anesthesia (i.e., the seated time) has had varying success in decreasing hypotension at Cesarean delivery. This may be due to the current lack of information concerning the dose-response relationship of seated time and rates of hypotension.
  
  
  METHODS
  Term parturients scheduled for Cesarean delivery were randomized to receive 11.25 or 15.0 mg of 0.75% intrathecal hyperbaric bupivacaine, and they remained seated after injection for a length of time determined by an up-down sequential method. They were then placed in a wedged position and their blood pressure was measured every minute. Pre-delivery hypotension was considered present if there was a > 20% from baseline drop in systolic blood pressure. The seated time at which 50% of parturients avoided pre-delivery hypotension (median effective seated time) was determined with isotonic regression.
  
  
  RESULTS
  Fifty patients were studied. For the 11.25-mg and 15.0-mg groups, the median effective seated time (95% confidence interval [CI]) was 130 sec (95% CI 117 to 150) and 385 sec (95% CI 381 to 396), respectively.
  
  
  CONCLUSIONS
  There exists a seated time after intrathecal injection of hyperbaric bupivacaine where 50% of parturients do not experience hypotension. This seated time increases with an increased dose of bupivacaine. Further work is required to determine the full relationship between seated time and hypotension for other doses of anesthetic and to investigate the clinical utility of this technique for prevention of hypotension. This trial was registered at www.clinicaltrials.gov (NCT01561274).
authors: Department of Anaesthesia, Royal Victoria Hospital, McGill University Health Centre, 687 Avenue des Pins Ouest, Montreal, QC, Canada, moore_albert@hotmail.com.
authors: Albert
authors: A
authors: Moore
authors: Samuel
authors: S
authors: Bourrassa-Blanchette
authors: Eva
authors: E
authors: El Mouallem
authors: Ian
authors: I
authors: Kaufman
authors: Aly
authors: A
authors: El-Bahrawy
authors: William
authors: W
authors: Li-Pi-Shan
authors: Roupen
authors: R
authors: Hatzakorzian
mesh_terms: D000328:Adult; D000773:Anesthesia, Obstetrical / Q000009:adverse effects / Q000379:methods; D000775:Anesthesia, Spinal / Q000009:adverse effects / Q000379:methods*; D000779:Anesthetics, Local / Q000008:administration & dosage / Q000009:adverse effects; D001794:Blood Pressure; D002045:Bupivacaine / Q000008:administration & dosage* / Q000009:adverse effects; D002585:Cesarean Section / Q000379:methods*; D004305:Dose-Response Relationship, Drug; D005260:Female; D006801:Humans; D007022:Hypotension / Q000139:chemically induced / Q000517:prevention & control*; D007278:Injections, Spinal; D011247:Pregnancy; D013997:Time Factors
chemical_list: D000779:Anesthetics, Local; D002045:Bupivacaine