Delirium is a common consequence of cardiac surgery and associates with poor outcomes. Multiple causes can trigger delirium occurence, and it has been hypothesised that sleep disturbances can be one of them. Dexmedetomidine may be effective in reducing delirium. The aim of this study was to demonstrate preoperative dexmedetomidine nasal spray in cardiac surgery patients can reduce postoperative delirium by improving preoperative sleep.

Due to special reasons such as surgical trauma, irritability, extracorporeal circulation, the incidence of postoperative delirium (POD) after cardiovascular surgery ranges from 26% to 52%. POD is an acute organic brain syndrome characterised by cognitive impairment and alteration of consciousness. The implications of this acute form of brain injury are profound. Patients who experience delirium are more likely to experience increased short- and long-term mortality, decrease in long-term cognitive function, increase in hospital length of stay and increased complications of hospital care. Given the numerous adverse effects of POD, it is crucial to explore the mechanisms for the prevention and management of POD.

Dexmedetomidine (Dex) is a highly selective α 2-adrenergic receptor agonist that produces sedative and hypnotic effects by activating the α 2-adrenergic receptor in the brainstem locus coeruleus, and has a certain neuroprotective effect. In recent years, the prevention of postoperative delirium by Dex has been a hot topic in the field of anesthesia. However, recent studies have found contradictory conclusions on aforementioned topic.

The heterogeneity of the subject population may be the reason for the current contradictory conclusions. Tang et al. conducted a meta-analysis of all RCTs regarding perioperative sleep interventions and postoperative delirium, and found that in the subgroup where interventions effectively improved patients' sleep quality, the effect of reducing the incidence of postoperative delirium was more significant. At the same time, the incidence of delirium did not decrease in the subgroup where sleep quality was not improved. Sleep disorders play a crucial role in the pathogenesis of POD.

In this DREAMS study, we plan to conduct a single center double-blind randomized controlled trial involving patients undergoing extracorporeal circulation cardiac surgery to explore whether administering Dex nasal spray the night before surgery and 30 minutes before anesthesia induction can improve preoperative sleep quality and reduce the incidence of postoperative delirium.

Inclusion Criteria:

1. Aged 18 years or older.
2. Cardiac surgery with cardiopulmonary bypass.
3. Ability to provide consent.

Exclusion Criteria:

1. Preoperative schizophrenia, epilepsy, Parkinson's disease, myasthenia gravis, history of neurosurgery, or Mini-mental State Examination(MMSE) score: illiteracy<17, primary school level<20, high school level <24.
2. Patients with sick sinus syndrome, severe sinus bradycardia (heart rate<50 beats/minute), grade II or above atrioventricular block, and no pacemaker implanted.
3. Unable to communicate due to coma, severe dementia, or language barriers prior to surgery.
4. Patients with severe liver dysfunction (Child Pugh C grade), renal dysfunction (preoperative dialysis), ASA grade V or expected survival ≤ 24 hours.
5. Heart transplant surgery
6. Surgery for congenital heart disease.
7. Deep hypothermic circulatory arrest surgery.
8. Already enrolled in other study patients.
9. Refuse to participate.

Individual participant data that underline the results reported in this article, after deidentification.

beginning 12 months