[A study of post-operative delirium in elderly patients]

We investigated the post-operative delirium in elderly patients of over 65 years of age. This investigation consisted of two studies, a prospective study and a retrospective study. In the prospective study, we evaluated the incidence of post-operative delirium and the incidence of post-operative delirium was estimated pre-operatively using State-Trait Anxiety Inventory (STAI) and Mini Mental State Examination (MMSE) in 24 patients scheduled for elective surgery under general anesthesia in the period from Nov. 1995 to Oct. 1996. In the retrospective study, we selected patients with post-operative delirium from 1600 patients who had undergone scheduled and emergency operation under general anesthesia in the same period as in the prospective study and analyzed the incidence of post-operative delirium and background of these patients. Twenty four patients in the prospective study were excluded from the retrospective study. In the prospective study, although post-operative delirium was observed in 2 cases (8.3%), no specific changes were observed in anxiety state and the ability of recognition. In the retrospective study, post-operative delirium was observed in 22 cases (1.37%). In these patients, several factors such as blood transfusion, emergency operation, dehydration, thrombosis of the superior mesenteric artery, history of ischemic heart disease, brain infarction and atrial fibrillation were thought to be major risk factors triggering post-operative delirium. In this study we could not conclude that STAI or MMSE are useful to estimate the incidence of post-operative delirium preoperatively. However, our result suggests that we should be careful about the incidence of post-operative delirium in elderly patients with pre-operative risk factors as mentioned above.