title: Cardiovascular effects of vasopressors in halothane-anesthetized dogs before and after hemorrhage.
abstract: Exogenously administered vasopressors (sympathomimetics) were evaluated in halothane-anesthetized dogs to determine the effects of these drugs on cardiovascular function before and after hemorrhage. Six dogs were anesthetized with thiamylal sodium (20 mg/kg of body weight) and halothane (1.25 minimal alveolar concentration) in 100% oxygen. After instrumentation, cardiac output, systemic arterial blood pressure (SAP), heart rate (HR), left ventricular pressure, pulmonary arterial pressure, and an index of cardiac contractility (dP/dT) were measured. Stroke volume, cardiac index (CI), stroke index (SI), rate-pressure product, and systemic vascular resistance (SVR) were calculated. Epinephrine (0.1, 0.3, and 0.5 micrograms/kg/min [low, medium, and high doses, respectively]) and dobutamine (1, 5, and 10 micrograms/kg/min [low, medium, and high doses, respectively]) were infused. Methoxamine was given in a bolus of 0.22 mg/kg, IV. All measurements were taken at 2.5 minutes after infusion, and were repeated after removal of 40% of the estimated blood volume. Dobutamine administered at the low dose before hemorrhage increased SAP and dP/dT. At the high and medium dose, dobutamine significantly increased CI, dP/dT, and SAP, with no significant change in HR or SVR. The medium dose of epinephrine was the most effective dose of epinephrine at increasing key variables (CI, SI, dP/dT). The response of CI and SI to this dose was not significantly different from the changes seen with high-dose administration of dobutamine. The dP/dT was significantly lower with epinephrine than with dobutamine, and SVR and HR were unchanged with epinephrine, except at the low dose, which decreased SVR.
authors.affiliation: Department of Surgical Sciences, School of Veterinary Medicine, University of Wisconsin, Madison 53706.
authors.forename: M B
authors.initials: MB
authors.lastname: Curtis
authors.forename: R M
authors.initials: RM
authors.lastname: Bednarski
authors.forename: L
authors.initials: L
authors.lastname: Majors
mesh_terms: D000769:Anesthesia, Inhalation / Q000662:veterinary; D000818:Animals; D001794:Blood Pressure / Q000187:drug effects; D002302:Cardiac Output / Q000187:drug effects; D004280:Dobutamine / Q000494:pharmacology; D004283:Dog Diseases / Q000503:physiopathology; D004285:Dogs / Q000502:physiology*; D004837:Epinephrine / Q000494:pharmacology; D005260:Female; D006221:Halothane; D006339:Heart Rate / Q000187:drug effects; D006439:Hemodynamics / Q000187:drug effects*; D006470:Hemorrhage / Q000503:physiopathology / Q000662:veterinary*; D008297:Male; D008729:Methoxamine / Q000494:pharmacology; D009200:Myocardial Contraction / Q000187:drug effects; D013318:Stroke Volume / Q000187:drug effects; D013566:Sympathomimetics / Q000494:pharmacology*; D014655:Vascular Resistance / Q000187:drug effects
chemical_list: D013566:Sympathomimetics; D004280:Dobutamine; D008729:Methoxamine; D006221:Halothane; D004837:Epinephrine