Haemodynamic Effects of Labetalol-Induced Hypotension in the Anaesthetized Dog

Abstract

Central haemodynamic changes and regional blood flow were studied using the microsphere technique, during labetalol-induced hypotension in dogs anaesthetized with pentobarbitone and fentanyl. Labetalol 15 mg kg-1 decreased mean arterial pressure from an average of 88 mm Hg to 47 mm Hg. Mean pulmonary arterial pressure was unchanged. Cardiac output was reduced by decrease in stroke volume, while heart rate remained unchanged. Myocardial blood flow decreased approximately in parallel with left ventricular work. Perfusion of the brain and kidneys was unchanged.

Retrospective evaluation of labetalol as antihypertensive agent in dogs

“…Heart rate was only slightly and not significantly ( p = 0.2454) increased during labetalol therapy, as expected from its reversible antagonism activity at both α- and β-adrenoceptor [ 30 ]. This is in agreement with studies in humans and experimental dogs [ 3 , 9 , 20 ], and it is a considerable advantage, as compensatory tachycardia can delay the antihypertensive effect and increase myocardial oxygen consumption [ 31 ].…”

“…To date, all published literature describing use of labetalol in dogs is limited to experimental models. Studies in anaesthetized dogs demonstrated the hypotensive effect of labetalol at the dose of 0.1 to 15 mg/kg intravenously [ 6 , 20 ], and that a bolus of 100 mg followed by a constant rate infusion (CRI) of 30 mg/min produces a significative reduction in mean arterial pressure (MAP) without affecting intracranial pressure in experimental dogs weighing 27–33 kg [ 21 ]. Intravenous administration at doses of 0.1 to 3 mg/kg in anaesthetized dogs produced a dose-dependent reduction in blood pressure and myocardial contractility [ 2 ].…”