There is no bibliography that evidenciates a correlation between cerebrovascular reactivity and the stage of hepatic encephalopathy. There are however, papers that reveal generalized systemic vasoconstriction in patients with cirrhosis and others that affirm the presence of vascular disregulation and altered reactivity in the Middle Cerebral Artery in cirrhotic patients. In the other hand, there is published data that correlates the neurological manifestations of diseases characterised by altered blood flow and cerebrovascular reactivity with the degree of the vascular disregulation itself, identified by US Doppler. However, there are no studies correlating transcranial US Doppler findings of cerebrovascular reactivity and hepatic encephalopathy in patients with cirrhosis. Giving its importance to the chance of revealing a new way of pathophysiology and therefore, early therapeutic management.