[Clinical study of postoperative delirium in the elderly]

It is said that the surgery is often followed by a delirious state (postoperative delirium) in the elderly, but there are few reports on detailed studies of this condition. To determine the frequency with which postoperative delirium occurs in the elderly, its main causes and clinical characteristics, etc., the author made a clinical study of 127 patients, aged 60 years and over, who were about to undergo operations. In this study, polygraphy was used in a postoperative electrophysiological study. Of the 127 patients, delirium was noted in 20 (15.7%), there being little difference according to age or sex in the rate of occurrence, but in patients with malignancy, the rate was appreciably higher. Delirium became apparent between one day and two days after the operation and lasted for up to 6 days. We classified the types of delirium into the following three on the basis of clinical symptoms: hallucination type (5 cases), confusion type (8 cases) and hallucination-confusion type (7 cases). The possible causes of postoperative delirium include the patient's condition as shown in the pre and postoperative polygrams, the invasive effects of anesthesia and surgery (surgical procedures, length of time under anesthetic, time required for the operation, amount of blood lost and amount of blood received by transfusion, etc., the serum albumin before surgery, WBC after surgery, %delta PaO2, and whether ICU was used or not, and so on. Quite often in patients with postoperative delirium, the pre and postoperative polygrams show slow abnormality in the EEGs before surgery, and the eye movements of R(++)/RS pattern in the EOGs before and after surgery. Slow abnormality in the EEGs was much more frequently seen in the confusion type and hallucination-confusion type patients than in the hallucination type. In view of these results, we feel that any consideration of the occurrence of delirium must include the following factors. In cases where the effects of surgical invasion and metabolic disorder are greater, quite often consciousness is clouded following surgery. If the eye movements of R(++)/RS pattern is shown in the EOGs before surgery, as the clouding of consciousness is alleviated after the operation, considerable activity takes place in some of the brain's functions (those related to anxiety and tension, etc.) and a state of dissociation occurs in brain functions which would normally undergo integrated changes. It was thought that this dissociated state is manifested as the delirium.