The problem of the development of delirium in the postoperative period is quite a serious problem, because it leads to an increased risk of mortality as a consequence of lengthening the time of treatment. Unfortunately prevention and treatment of cognitive dysfunction today has no clear algorithm of actions. Even despite some successes in conservative treatment of acute cognitive dysfunction and complications, mortality in this disease remains high. The purpose of this study was to identify possible ways of prevention of cognitive disorders in the elderly in the postoperative period. We studied the factors influencing the disorder of cognitive function after surgery in patients of elderly and senile age. As a result of the conducted research we have identified that the development of delirium in elderly patients is significantly associated with three factors noted in the postoperative period: a higher level of peripheral blood leukocytes, a higher concentration of sodium in the plasma and the epidural method of pain relief. Thus, it is shown that timely and proper correction tactics postoperative management of patients, aimed at maintaining normal levels of plasma sodium, allows to achieve a reliable reduction in the incidence of postoperative delirium.