Two studies attempted to examine the relationship of ischemic brain injury to delirium. In one study of 84 patients with severe sepsis and multiple organ dysfunction [53] , severe hypotension was the only factor in multivariable analyses that was associated with delirium, suggesting that sepsis-related encephalopathy may be caused by ischemic damage rather than metabolic abnormalities. Another study examined cerebral blood flow and cerebral oxygen metabolic rates in patients with septic encephalopathy and multiple organ dysfunction [54] , and it found that both were significantly lower than those in normal awake individuals. Although these studies support the idea of occult brain injury as a cause of delirium, the authors did not use a standardized Diagnostic and Statistical Manual of Mental Disorders (DSM)-IV based tool to diagnose delirium, such as the Confusion Assessment Method for the ICU [6] .