Hyperdynamic circulation in cirrhosis: a role for nitric oxide? Hypotension, low systemic vascular resistance, and a reduced sensitivity to vasoconstrictors are features of cirrhosis. These cardiovascular changes might be the result of increased synthesis of a vasodilator. Nitric oxide (NO), a potent vasodilator, is synthesised in and released from peripheral blood-vessels in man. Studies in animals indicate that bacterial endotoxin and cytokines induce NO synthase expression in vessel walls, with sustained NO release and consequent hypotension. Endotoxaemia is a common feature of cirrhosis; persistent induction of NO synthase may account for the associated haemodynamic changes. 