Low-dose Dexmedetomidine and Postoperative Delirium After Cardiac Surgery

Delirium is an acutely occurred and fluctuating cerebral dysfunction characterized with inattention, altered consciousness, cognitive decline and/or abnormal perception. It is common in the elderly after cardiac surgery and is associated with worse outcomes. The development of delirium is a consequence of multiple factors. For patients undergoing cardiac surgery, surgical stress and/or cardiopulmonary bypass can produce hyper-inflammatory and stress response, both of which are important factors leading to delirium. Meanwhile, patients in ICU after major surgery often develop sleep disturbances, which are also associated with increased risk of delirium. Dexmedetomidine is a highly selective α2-adrenoceptor agonist with sedative, analgesic and anxiolytic properties. In previous studies of elderly patients admitted to ICU after non-cardiac surgery, continuous infusion of low-dose dexmedetomidine during nighttime improves sleep quality, reduces delirium, and improves 2-year survival. The investigators hypothesize that, for patients admitted to ICU after cardiac surgery, nighttime infusion of low-dose dexmedetomidine can decrease the incidence of delirium and improve long-term survival. The purpose of this study is to investigate the effect of nighttime infusion of low-dose dexmedetomidine on postoperative sleep quality, delirium, and 2-year survival in elderly patients admitted to ICU after cardiac surgery.