title: Cardiovascular effects of 1.0, 1.5, and 2.0 minimum alveolar concentrations of isoflurane in experimentally induced hypothyroidism in dogs.
abstract: This study was performed to determine the cardiovascular responses to isoflurane in euthyroid and hypothyroid dogs. Four healthy mixed-breed dogs were studied prior to thyroidectomy (PRE), 6 months after thyroidectomy (HYP), and after 2 months of oral supplementation with 1-thyroxine (SUP). Heart rate (HR), cardiac output (Q), stroke volume (SV), systolic, diastolic, mean arterial blood pressure (SAP, DAP, MAP), and total peripheral resistance (TPR) were determined in awake dogs and in the same dogs when end-tidal isoflurane concentration were 1.28%, 1.92%, and 2.56%. Ventilation was controlled in anesthetized dogs and PACO2 maintained between 38 to 42 mm Hg. Isoflurane caused significant (P < .05) dose-dependent reduction in Q, SV, SAP, DAP, and MAP in the PRE, HYP, and SUP dogs. Cardiac output was lower in the HYP dogs than in the PRE or SUP dogs during awake measurement. TPR was increased in the awake HYP dogs compared with the PRE or SUP dogs. During anesthesia, HYP dogs tended to have lower Q, SV, SAP, and MAP PRE or SUP groups, but the only significant reduction was SAP during 1.5 MAC. The cardiovascular responses to isoflurane in hypothyroid dogs are similar to euthyroid animals with a dose-dependent depression in Q, SV, and arterial pressure.
authors.affiliation: Department of Clinical Science, Kansas State University, College of Veterinary Medicine, Manhattan, USA.
authors.forename: R M
authors.initials: RM
authors.lastname: McMurphy
authors.forename: D S
authors.initials: DS
authors.lastname: Hodgson
authors.forename: D S
authors.initials: DS
authors.lastname: Bruyette
authors.forename: R B
authors.initials: RB
authors.lastname: Fingland
mesh_terms: D018685:Anesthetics, Inhalation / Q000008:administration & dosage / Q000494:pharmacology*; D000818:Animals; D004283:Dog Diseases / Q000503:physiopathology* / Q000601:surgery; D004285:Dogs; D006439:Hemodynamics / Q000187:drug effects*; D007037:Hypothyroidism / Q000503:physiopathology / Q000601:surgery / Q000662:veterinary*; D007530:Isoflurane / Q000008:administration & dosage / Q000494:pharmacology*; D013965:Thyroidectomy / Q000662:veterinary; D013974:Thyroxine / Q000008:administration & dosage
chemical_list: D018685:Anesthetics, Inhalation; D007530:Isoflurane; D013974:Thyroxine