This is a 3-year follow-up of patients enrolled in a previous randomized controlled trial which showed that intraoperative dexmedetomidine reduced delirium in elderly patients after major non-cardiac surgery. The purpose of this study is to clarify the effects of intraoperative dexmedetomidine on long-term outcomes of these patients.

Dexmedetomidine is a highly selective α-2-receptor agonist with sedative, analgesic and anxiolytic effects. When used as an supplement during general anaesthesia, it reduces the consumption of the anaesthetics and relieves surgery-related stress response and inflammation. In a recent randomized ontrolled trial of the applicants, 620 elderly patients who underwent major non-cardiac surgery were randomized to receive dexmedetomidine or normal saline during general anesthesia. The results showed that use of dexmedetomidine reduced delirium (5.5% [17/309] with dexmedetomidine vs. 10.2% [32/310] with placebo, P=0.026) and 30-day non-delirium complications (9.4% [60/309] with dexmedetomidine vs. 26.1% [81/310] with placebo, P=0.047) after surgery.

The effects of intraoperative dexmedetomidine on long-term outcomes after surgery remains unclear. In another study of the applicants, use of low-dose dexemeditomidine in ICU patients after surgery increased survival up to 2 years and improve quality of life in 3-year survivors. On the contrary, it was reported in a retrospective study that intraoperative use of dexmedetomidine was associated with shortened overall survival in patients after lung cancer surgery. Therefore, it is urgent to clarify the impact of intraoperative dexemeditomidine on long-term outcomes of patients undergoing major surgery, especially those undergoing cancer surgery.

This study is a 3-year follow-up of patients who were enrolled in a randomzied controlled trial of the applicants in order to clarify the effects of intraoperative dexmedetomidine on long-term outcomes after surgery.

Inclusion Criteria:

• Elderly patients (age ≥60 years);
• Scheduled to undergo elective major non-cardiac surgery with expected duration ≥2 hours under general anaesthesia.

Exclusion Criteria:

• Do not provide written informed consent;
• Previous history of schizophrenia, epilepsy or Parkinson's disease;
• Visual, hearing, language or other barriers which impede communication and preoperative delirium assessment;
• History of traumatic brain injury;
• Severe bradycardia (heart rate <40 beats per minutes), sick sinus syndrome, or atrioventricular block of degree 2 or above without pacemaker;
• Severe hepatic dysfunction (Child-Pugh grade C);
• Renal failure (requirement of renal replacement therapy);
• Neurosurgery.