Lending support to the hypothesis that acute inflammation leads to brain injury and subsequent development of delirium, a recent study found that delirium in postoperative hipfractured patients was significantly associated with serum levels of C-reactive protein, an acute-phase protein that is a marker of acute inflammation [55] . Importantly, patients in the study were diagnosed with delirium using the Confusion Assessment Method (the ward-based predecessor to the Confusion Assessment Method for the ICU), providing the first DSM-IV based evidence that acute inflammation may be in the causative pathway of delirium. The brain is a target for free radical damage because of its large lipid content, high rate of metabolism, and low antioxidant capacity. Free radical induced oxidative stress may play a role in the delirium seen after cardiopulmonary bypass. Karlidag and colleagues [56] noted that patients with low preoperative levels of catalase, a erythrocyte-based antioxidant enzyme, were more susceptible to delirium postoperatively. They suggested that preoperative catalase levels might some day be used to identify at-risk patients who could then be put on antioxidant treatment preoperatively. Whether this would reduce the incidence of delirium remains speculative.