Kijima E, Kayama T, Saito M, et al. - The present study was undertaken to investigate the various risk factors that may contribute to delirium in unilateral and bilateral total knee arthroplasties in the elderly population. Researchers retrospectively examined a total of 170 patients who had undergone unilateral or bilateral total knee arthroplasties for delirium. They evaluated and examined age, gender, comorbidities, use of sedative-hypnotics, peri-operative blood loss, pre- and post-operative laboratory blood test results. The results reveal that individuals with a pre-operative Hb level of < 11.1 g/dL or those applying sedative-hypnotics are correlated with post-operative delirium. Thus, peri-operative management and preventative measures are required to decrease the risks of post-operative delirium in such patients.