title: A study to determine the optimum dose of metaraminol required to increase blood pressure by 25% during subarachnoid anaesthesia.
abstract: We studied dosage optimization for metaraminol when managing hypotension during subarachnoid anaesthesia. Twenty patients aged 53 to 84 years, were recruited. Non-invasive blood pressure (BP) and heart rate were recorded one-minutely. A series of four i.v. metaraminol boluses (0.25 to 1.0 mg per 50 kg adult) were administered. From individual patient time plots of BP predicted dosages for a 25% elevation in BP were estimated. Dose-related elevations in systolic BP [mean (SD)] occurred following dosages of 0.5 mg [25 (11)%] and 1.0 mg [50 (23)%]. Similar elevations occurred in mean and diastolic BP. Overall estimated dosage (median) to produce a 25% elevation in systolic BP was 0.5 mg (per 50 kg adult). However, individual patient responses varied (10-90th centiles = 0.23 to 0.80 mg). Thus, we now recommend a starting dose of 0.25 mg, increasing to 0.5 mg if necessary, to treat hypotension (25% decrease in systolic BP) during subarachnoid anaesthesia.
authors.affiliation: Dept of Anaesthesia and Intensive Care, Chinese University of Hong Kong, Prince of Wales Hospital, Shatin, Hong Kong.
authors.forename: L A
authors.initials: LA
authors.lastname: Critchley
authors.forename: M K
authors.initials: MK
authors.lastname: Karmakar
authors.forename: J H
authors.initials: JH
authors.lastname: Cheng
authors.forename: J A
authors.initials: JA
authors.lastname: Critchley
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000765:Anesthesia, Conduction; D001794:Blood Pressure / Q000187:drug effects*; D004305:Dose-Response Relationship, Drug; D004562:Electrocardiography; D005260:Female; D006339:Heart Rate / Q000187:drug effects; D006801:Humans; D007022:Hypotension / Q000188:drug therapy; D007262:Infusions, Intravenous; D008297:Male; D008680:Metaraminol / Q000008:administration & dosage*; D008875:Middle Aged; D016343:Monitoring, Intraoperative; D013346:Subarachnoid Space; D014662:Vasoconstrictor Agents / Q000008:administration & dosage*
chemical_list: D014662:Vasoconstrictor Agents; D008680:Metaraminol