[Postoperative delirium after regional anesthesia]

Abstract

Postoperative delirium or acute confusional state is common after major surgery. The objective of this article is to provide an overview of the current knowledge of the risk factors and the importance of anesthetic technique in postoperative delirium. The risk factors for postoperative delirium include patient characteristics such as advanced age, poor preoperative functional state, depression, and abnormal serum levels of sodium, potassium, glucose and albumin. The type of surgery is also important, so delirium is common after high operative stress procedures. Perioperative risk factors also include blood loss, postoperative hematocrit, hypotension and hypoxemia, pain and polypharmacy. Anesthetic technique is a potentially modifiable risk factor. Although administration of many drugs can be avoided or limited with regional anesthetic techniques and reduction in the prevalence of postoperative delirium has been analyzed in many studies, the results are inconsistent. Literature data were analyzed to determine whether type of anesthesia determines the incidence of postoperative delirium. According to PubMed, there are several studies comparing postoperative delirium after regional or general anesthesia. Many of these studies showed a trend toward increased postoperative delirium with general anesthesia, but the difference was not significant. On interpreting these results, it should be taken in consideration that many of these studies were retrospective and nonrandomized with a small number of participants, so further large, multicenter, randomized trials are needed to make any firm conclusion on the influence of anesthetic technique on postoperative delirium. Although the pathophysiology of delirium is not fully understood, it appears that multiple metabolic and neurochemical insults disrupt neuronal functioning in susceptible patients. Prevention and optimal treatment consist of minimizing or correcting these metabolic and other insults. Early detection of coexisting postoperative medical problems, pain, infections, or other complications is crucial. Regional anesthetic techniques have many potential advantages such as reduced stress response and good postoperative analgesia, but further investigations are needed to confirm these observations.