title: Closed-loop feedback computer-controlled infusion of phenylephrine for maintaining blood pressure during spinal anaesthesia for caesarean section: a preliminary descriptive study.
abstract: We describe the novel use of a closed-loop feedback computer-controlled infusion of phenylephrine for maintaining blood pressure in 53 patients having spinal anaesthesia for elective caesarean section. A simple on-off algorithm was used that activated an intravenous phenylephrine infusion at 100 microg.min(-1) when systolic blood pressure was less than or equal to baseline and stopped the infusion when systolic blood pressure exceeded baseline. Up to uterine incision, 94.6% of all systolic blood pressure measurements were within the range (baseline +/- 20%). Seven patients (13.2%) had one or more episodes of hypotension (systolic blood pressure < 80% of baseline) and 23 patients (37.7%) had one or more episodes of hypertension (systolic blood pressure > 120% of baseline). No patient had nausea or vomiting and in no case was umbilical arterial blood pH < 7.2. Calculated system performance parameters were comparable with those of previously published closed-loop systems and provide a reference for the potential development and comparison of more advanced algorithms.
authors.affiliation: Department of Anaesthesia and Intensive Care, The Chinese Unviersity of Hong Kong, Prince of Wales Hospital, HShatin, Hong Kong, China. warwick@cuhk.edu.hk
authors.forename: W D
authors.initials: WD
authors.lastname: Ngan Kee
authors.forename: Y H
authors.initials: YH
authors.lastname: Tam
authors.forename: K S
authors.initials: KS
authors.lastname: Khaw
authors.forename: F F
authors.initials: FF
authors.lastname: Ng
authors.forename: L A
authors.initials: LA
authors.lastname: Critchley
authors.forename: M K
authors.initials: MK
authors.lastname: Karmakar
mesh_terms: D000328:Adult; D000465:Algorithms; D000773:Anesthesia, Obstetrical / Q000009:adverse effects*; D000775:Anesthesia, Spinal / Q000009:adverse effects*; D001794:Blood Pressure / Q000187:drug effects; D002585:Cesarean Section; D004334:Drug Administration Schedule; D016503:Drug Delivery Systems / Q000379:methods; D004360:Drug Therapy, Computer-Assisted / Q000379:methods; D005240:Feasibility Studies; D005246:Feedback; D005260:Female; D006801:Humans; D007022:Hypotension / Q000209:etiology / Q000517:prevention & control*; D007431:Intraoperative Complications / Q000517:prevention & control; D010656:Phenylephrine / Q000008:administration & dosage* / Q000627:therapeutic use; D011247:Pregnancy; D014662:Vasoconstrictor Agents / Q000008:administration & dosage* / Q000627:therapeutic use
chemical_list: D014662:Vasoconstrictor Agents; D010656:Phenylephrine