A study on the influence of ketamine on systemic and regional haemodynamics in conscious rabbits

Effects of ketamine hydrochloride (2, 6 and 18 mg X kg-1, i.v.) were investigated on systemic and regional haemodynamics using a radioactive microsphere method in conscious rabbits. Ketamine decreased respiratory frequency in a dose-dependent manner for up to 5 min. A significant fall in the mean arterial blood pressure (with the two highest doses), together with a short lasting tachycardia, was observed with ketamine. The cardiac output and blood flow to many tissues were not changed by this anaesthetic agent. However, increased blood flow was noticed in discrete regions of the brain (cerebral hemispheres) and heart (left ventricular endocardium). Vasodilation in the cerebral hemispheres with this agent producing dissociative anaesthesia is in contrast to the generally observed decrease in cerebral blood flow with other anaesthetic agents.