Influence of Digoxin Followed by Dopamine on the Cardiovascular Depression During a Standard Halothane Anaesthesia in Dorsally Recumbent, Ventilated Ponies

Abstract

The influence of digoxin (0.01 mg/kg) given as an intravenous bolus followed by dopamine at different infusion rates (1.25, 2.5 and 5.0 micrograms/kg/min) on the cardiovascular depression during a standard halothane anaesthesia was studied in dorsally recumbent ventilated ponies. Preanaesthetic digitalization induced no clear positive cardiovascular effects over 30 minutes, except for non-significant increases in mean pulmonary artery pressure and total pulmonary resistance. These changes were probably time-related. No specific side-effects related to the fast intravenous digitalization were noticed. Dopamine at lower infusion rates (1.25 and 2.5 micrograms/kg/min) given minimally 30 minutes after the digitalization did not induce further changes (only minor non-significant increases in cardiac output and systemic blood pressure). Dopamine infusions at a higher infusion rate (5.0 micrograms/kg/min) improved the cardiovascular depression (significant increases in cardiac output and systemic blood pressure while total peripheral resistance tended to decrease). Heart rate, blood gases and total pulmonary resistance remained constant. The combination of a fast acting inotropic agent, dopamine, and a slow acting inotropic drug, digoxin, induced positive effects in reversing the cardiovascular depression and might therefore be useful during clinical anaesthesia in the horse.