CARDIOVASCULAR EFFECTS OF PROPOFOL IN THE ANAESTHETIZED DOG

This study was designed to investigate if propofol producedcardiovascular effects by indirect actions or by indirect actionssecondary to depression of the central nervous system. Experimentswere performed on chloralose anaesthetized dogs in which allneurogenic cardiovascular reflexes were abolished by bilateralvagotomy and common carotid ligatures, in combination with i.v. bretylium and propranolol. Bolus doses of propofol followedby infusions at rates up to 160 mg kg^–1 h^–1 producedblood concentrations of propofol from 1.99 to 112 µg ml–1.Infusions of hydroxyethyl starch given to maintain central venouspressures and pulmonary artery occlusion pressures at controlvalues were used as an index of changes in capacitance. Bloodconcentrations of propofol less than 10 µg ml^–1caused an increase in mean capacitance of 8.0 (SEM 1) ml kg^–1with no significant changes in systemic vascular resistance,pulmonary vascular resistance or intropic state of the heart.We conclude that anaesthesia with propofol may be accompainedby decreased cardiac output secondary to reduction in preloadby a direct venodilator effect. Our experiments indicate thatcardiac output and arterial pressure are preserved well at normalanaesthetic blood concentrations of propofol if the preloadis maintained.