title: Cardiovascular effects of dopexamine HCl in conscious and halothane-anaesthetised horses.
abstract: The cardiovascular effects of serial increasing infusions of dopexamine HCl were investigated in six conscious (1, 2, 4, 6, 10 micrograms/kg bodyweight [bwt]/min) and eight (0.5, 1, 5, 10, 20 micrograms/kg bwt/min) halothane-anaesthetised horses. Dopexamine produced dose-dependent increases in heart rate, +dP/dtmax' -dP/dtmax and cardiac output, and a decrease in systemic vascular resistance in conscious and halothane-anaesthetised horses. Mean arterial blood pressure did not change in conscious horses but increased to a maximum value at 10 micrograms/kg bwt/min in halothane-anaesthetised horses. Thereafter, median artery blood flow decreased. Ventricular arrhythmias occurred in two conscious horses during the infusion of 10 micrograms/kg bwt/min dopexamine HCl. No cardiac arrhythmias other than sinus tachycardia were observed in halothane-anaesthetised horses. The administration of propanolol eliminated the haemodynamic response to the infusion of 5 and 10 micrograms/kg bwt/min dopexamine HCl in halothane-anaesthetised horses. The haemodynamic effects of dopexamine HCl offer specific advantages over dopamine and dobutamine for the treatment of low cardiac output states in horses.
authors.affiliation: Department of Veterinary Clinical Sciences, Ohio State University, Columbus 43210, USA.
authors.forename: W W
authors.initials: WW
authors.lastname: Muir
mesh_terms: D000318:Adrenergic beta-Agonists / Q000008:administration & dosage / Q000494:pharmacology* / Q000627:therapeutic use; D000758:Anesthesia / Q000009:adverse effects / Q000662:veterinary; D000818:Animals; D001794:Blood Pressure / Q000187:drug effects; D002302:Cardiac Output / Q000187:drug effects; D004298:Dopamine / Q000008:administration & dosage / Q000031:analogs & derivatives* / Q000494:pharmacology / Q000627:therapeutic use; D004305:Dose-Response Relationship, Drug; D005260:Female; D006221:Halothane / Q000008:administration & dosage; D006339:Heart Rate / Q000187:drug effects; D006736:Horses / Q000502:physiology*; D007261:Infusions, Intra-Arterial / Q000662:veterinary; D008297:Male; D008638:Mesenteric Arteries / Q000187:drug effects; D012039:Regional Blood Flow / Q000187:drug effects; D014655:Vascular Resistance / Q000187:drug effects; D014665:Vasodilator Agents / Q000008:administration & dosage / Q000494:pharmacology* / Q000627:therapeutic use
chemical_list: D000318:Adrenergic beta-Agonists; D014665:Vasodilator Agents; C046318:dopexamine; D006221:Halothane; D004298:Dopamine