Ketamine and Postoperative Cognitive Dysfunction

Over 30 million patients require a major surgery annually in the US alone and more than half of them are performed in patients over 60 years of age. Post-operative cognitive dysfunction (POCD) is a keystone complication of these surgeries and affects up to 40% of surgical patients aged over 60 years on discharge from the hospital. Despite controlled longitudinal studies have shown that POCD is transient, it is associated with delirium, higher mortality, earlier retirement, and greater utilization of social financial assistance The pathophysiology of persistent postoperative cognitive dysfunction and causal relationship between POCD and delirium remain incompletely understood. Identified clinical risk factors for both include advanced age, type of surgery, preexisting cognitive impairment, and drug addiction. We and others have provided evidence that the inflammatory response triggered by surgical trauma and pain may contribute to the development of delirium and cognitive impairment after surgery. Ketamine, a N-methyl-D-aspartic acid receptor antagonist, is commonly used in anaesthesia and postoperative analgesia. By reducing both pain and glutamate excitotoxic effects on neuronal and microglial brain cells, it contributes to tone down the neuroinflammatory process associated with surgery. A recent body of evidence has shown that ketamine reduces the depressive-like behavior induced by inflammatory or stress-induced stimuli in mice. Ketamine was also found to reduce levels of inflammatory biomarkers in cardiac surgical patients. Orthopaedic surgery is a high-risk situation for developing postoperative cognitive dysfunction. In patients undergoing non-cardiac surgery, the prevalence of POCD is 26% one week after surgery and decreased to 10% at 3 months postoperatively, and a similar prevalence is found 12 months after the operation. Postoperative delirium is associated with an increased risk of POCD. Hundred thousands of patients \> 60 years undergo elective orthopa