Sleep disturbances are common early after major surgery, and are associated with delayed recovery. A previous study showed that dexmedetomidine-esketamine combination as a supplement to patient-controlled intravenous analgesia improved postoperative analgesia and subjective sleep quality in patients after scoliosis correction surgery. The purpose of this trial is to test the hypothesis that dexmedetomidine-esketamine combination used as a supplement during general anesthesia and postoperative intravenous analgesia may reduce sleep disturbances in adult after major noncardiac surgery.

Sleep disturbances after surgery is usually manifested as sleep deprivation, altered circadian rhythm, and disturbed sleep structure. The reported incidence of sleep disturbances was 31.4% after gynecologic surgery, 31.9% after urologic surgery, and 35.9% after spine surgery. The occurrence of sleep disturbances is associated with worse perioperative outcomes, including aggravated pain intensity, increased delirium, higher risk of cardiovascular events, and delayed hospital discharge.

Dexmedetomidine is a high-specific alpha 2-adrenergic agonist with anxiolytic, sedative, and analgesic effects. When used during general anesthesia and for postoperative analgesia, dexmedetomidine is associated with improved analgesia and sleep quality. The effect of dexmedetomidine is dose-dependent. However, even commonly used dosage increases bradycardia and hypotension.

Ketamine is a non-competitive N-methyl-D-aspartate (NMDA) receptor antagonist. Esketamine is the S-enantiomer of racemic ketamine with a higher affinity for NMDA receptors and is approximately twice as potent as racemic ketamine in analgesia. When used during general anesthesia and for postoperative analgesia, esketamine improves analgesia and reduces opioid consumption, but psychiatric symptoms may occur.

The sedative effect of dexmedetomidine is helpful to relieve psychiatric side effects of ketamine/esketamine. A previous study showed that dexmedetomidine-esketamine combination as a supplement to patient-controlled intravenous analgesia improved postoperative analgesia and subjective sleep quality in patients after scoliosis correction surgery.

This trial is designed to test the hypothesis that dexmedetomidine-esketamine combination used as a supplement during general anesthesia and postoperative intravenous analgesia may reduce sleep disturbances in adult after major noncardiac surgery.

Inclusion Criteria:

1. Aged ≥18 years.
2. Scheduled for major noncardiac surgery (≥60 minutes) under general anesthesia with an expected end of surgery no later than 18:00 pm.
3. Required patient-controlled intravenous analgesia after surgery.

Exclusion Criteria:

1. Emergency surgery, transurethral surgery, organ transplantation.
2. Pregnant or lactating women.
3. Patients who need hypnotics for sleep disturbance or antidepressants for depression prior to surgery.
4. History of schizophrenia, epilepsy, Parkinson's disease, or myasthenia gravis.
5. Inability to communicate due to coma, severe dementia, or speech disorders, endured hypoxic encephalopathy or traumatic brain injury, or after neurosurgery.
6. Comorbid with hyperthyroidism and pheochromocytoma.
7. Preoperative left ventricular ejection fraction <30%, sick sinus syndrome, severe sinus bradycardia (heart rate <50 beats/min), atrioventricular block of degree II or higher without pacemaker implantation, or systolic blood pressure below 90 mmHg despite use of vasopressors.
8. Diagnosed as sleep apnea, or judged to be at high risk of moderate-to-severe sleep apnea as assessed by STOP-Bang.
9. Severe hepatic dysfunction (Child-Pugh class C), severe renal dysfunction (on dialysis), or ASA classification ≥IV.
10. Hypersensitive to dexmedetomidine and/or esketamine.
11. Other conditions that are deemed unsuitable for study participation.