The effects of medetomidine on cardiac contractility in autonomically blocked dogs.
The effects of medetomidine on load-dependent and relatively load-independent indices of left ventricular contractility and hemodynamics were studied in 8 chloralose-anesthetized, autonomic-blocked dogs. Left ventricular contractility was assessed by the maximum rate of increase in pressure (dP/dtmax), the slope of the end-systolic pressure volume relationship (Ees), preload recruitable stroke work (PRSW), and dP/dtmax-end-diastolic volume relation (SdPV). Dogs received 5 or 10 micrograms/kg of medetomidine IV. The dP/dtmax decreased significantly 30 minutes after both doses of medetomidine. The Ees did not change. Both SdPV and PRSW increased 5 minutes after both doses of medetomidine. Mean arterial pressure, left-ventricular end-diastolic and end-systolic pressures, peripheral vascular resistance and effective arterial elastance increased 5 minutes after both doses of medetomidine. Stroke volume, cardiac output, and stroke work decreased 5 minutes after medetomidine administration. End-diastolic volume did not change. End-systolic volume increased but the difference was not significant. Our study suggests that medetomidine increases inotropy and vascular resistance in autonomic-blocked dogs and that both ventricular and vascular responses to pharmacological manipulation must be considered for a complete assessment of the inotropic effects of a drug.
de Morais
H S
HS
Departamento de Clínicas Veterinárias, Universidade Estadual de Londrina, Paraná, Brazil.
Muir
W W
WW
D000316:Adrenergic alpha-Agonists / Q000494:pharmacology*; D000758:Anesthesia / Q000662:veterinary; D018686:Anesthetics, Intravenous / Q000008:administration & dosage; D000818:Animals; D001285:Atropine; D001340:Autonomic Nerve Block; D001794:Blood Pressure / Q000187:drug effects / Q000502:physiology; D002302:Cardiac Output / Q000187:drug effects / Q000502:physiology; D002698:Chloralose / Q000008:administration & dosage; D004285:Dogs / Q000502:physiology*; D006321:Heart / Q000187:drug effects* / Q000294:innervation; D006352:Heart Ventricles / Q000187:drug effects; D007093:Imidazoles / Q000494:pharmacology*; D008297:Male; D020926:Medetomidine; D009200:Myocardial Contraction / Q000187:drug effects* / Q000502:physiology; D010276:Parasympatholytics; D011897:Random Allocation; D013318:Stroke Volume / Q000187:drug effects / Q000502:physiology; D014655:Vascular Resistance / Q000187:drug effects / Q000502:physiology; D016276:Ventricular Function
D000316:Adrenergic alpha-Agonists; D018686:Anesthetics, Intravenous; D007093:Imidazoles; D010276:Parasympatholytics; D002698:Chloralose; D001285:Atropine; D020926:Medetomidine