title: Cardiovascular effects of dobutamine and phenylephrine infusion in sevoflurane-anesthetized Thoroughbred horses.
abstract: To determine dose-dependent cardiovascular effects of dobutamine and phenylephrine during anesthesia in horses, increasing doses of dobutamine and phenylephrine were infused to 6 healthy Thoroughbred horses. Anesthesia was induced with xylazine, guaifenesin and thiopental and maintained with sevoflurane at 2.8% of end-tidal concentration in all horses. The horses were positioned in right lateral recumbency and infused 3 increasing doses of dobutamine (0.5, 1.0 and 2.0 µg/kg/min) for 15 min each dose. Following to 30 min of reversal period, 3 increasing doses of phenylephrine (0.25, 0.5 and 1.0 µg/kg/min) were infused. Cardiovascular parameters were measured before and at the end of each 15-min infusion period for each drug. Blood samples were collected every 5 min during phenylephrine infusion period. There were no significant changes in heart rate throughout the infusion period. Both dobutamine and phenylephrine reversed sevoflurane-induced hypotension. Dobutamine increased both mean arterial blood pressure (MAP) and cardiac output (CO) as the result of the increase in stroke volume, whereas phenylephrine increased MAP but decreased CO as the result of the increase in systemic vascular resistance. Plasma phenylephrine concentration increased dose-dependently, and these values at 15, 30 and 45 min were 6.2 ± 1.2, 17.0 ± 4.8 and 37.9 ± 7.3 ng/ml, respectively.
authors.affiliation: Racehorse Clinic, Ritto Training Center, Japan Racing Association (JRA), 1028 Misono, Ritto-shi, Shiga 520-3085, Japan.
authors.forename: Minoru
authors.initials: M
authors.lastname: Ohta
authors.forename: Shinjiro
authors.initials: S
authors.lastname: Kurimoto
authors.forename: Yuhiro
authors.initials: Y
authors.lastname: Ishikawa
authors.forename: Hirotaka
authors.initials: H
authors.lastname: Tokushige
authors.forename: Naomi
authors.initials: N
authors.lastname: Mae
authors.forename: Shun-ichi
authors.initials: S
authors.lastname: Nagata
authors.forename: Masayuki
authors.initials: M
authors.lastname: Mamada
mesh_terms: D018685:Anesthetics, Inhalation / Q000008:administration & dosage*; D000818:Animals; D001794:Blood Pressure / Q000502:physiology; D002302:Cardiac Output / Q000502:physiology; D002316:Cardiotonic Agents / Q000008:administration & dosage / Q000494:pharmacology*; D002319:Cardiovascular System / Q000187:drug effects*; D004280:Dobutamine / Q000008:administration & dosage / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D006339:Heart Rate / Q000502:physiology; D006736:Horses / Q000601:surgery*; D008297:Male; D008738:Methyl Ethers / Q000008:administration & dosage*; D010656:Phenylephrine / Q000008:administration & dosage / Q000494:pharmacology*; D000077149:Sevoflurane
chemical_list: D018685:Anesthetics, Inhalation; D002316:Cardiotonic Agents; D008738:Methyl Ethers; D010656:Phenylephrine; D000077149:Sevoflurane; D004280:Dobutamine