Postoperative delirium is common after major surgery, and is associated with adverse outcomes. Systematic reviews and meta-analyses of randomized controlled trials have shown that perioperative administration of dexmedetomidine may decrease the incidence of postoperative delirium in patients after either cardiac or non-cardiac surgery. However, neurosurgical patients are often excluded in clinical trials of postoperative delirium.

In this prospective, multicenter, randomized, double-blinded, and placebo-controlled trial with two parallel arms, ICU admitted adult patients after intracranial operation for brain tumor will be enrolled. Low-dose dexmedetomidine will be applied during the early postoperative phase. The investigators aim to evaluate the efficacy and safety of low-dose dexmedetomidine for prevention of postoperative delirium in this patient population. The primary hypothesis is that, compared to the placebo group, the prophylactic use of low-dose dexmedetomidine can decrease the incidence of postoperative delirium without significant adverse events in patients after intracranial operation for brain tumor.

Postoperative delirium is common after major surgery, and is associated with adverse outcomes. However, patients with neurological illness are usually excluded from previous researches. Recently, limited studies have shown that the incidence of postoperative delirium in neurosurgical patients is approximately 20%, which is comparable to the results in other major surgery. Potential associations between postoperative delirium and adverse outcomes have also been found in neurosurgical patients. These results indicate that early prevention of postoperative delirium should be employed in this population.

As a highly selective α2-adrenergic receptor agonist, dexmedetomidine has been investigated as a preventive agent for postoperative delirium. Systematic reviews and meta-analyses of randomized controlled trials have shown that perioperative administration of dexmedetomidine may decrease the incidence of postoperative delirium in patients after either cardiac or non-cardiac surgery. However, neurosurgical patients are often excluded in clinical trials of postoperative delirium.

In this prospective, multicenter, randomized, double-blinded, and placebo-controlled trial with two parallel arms, ICU admitted adult patients after intracranial operation for brain tumor will be enrolled. Low-dose dexmedetomidine will be applied during the early postoperative phase. The investigators aim to evaluate the efficacy and safety of low-dose dexmedetomidine for prevention of postoperative delirium in this patient population. The primary hypothesis is that, compared to the placebo group, the prophylactic use of low-dose dexmedetomidine can decrease the incidence of postoperative delirium without significant adverse events in patients after intracranial operation for brain tumor.

The inclusion criteria are adult patients after elective intracranial operation for brain tumor under general anesthesia and who are admitted to the ICU directly from the operating room or postoperative care unit.

The exclusion criteria include:

1. Admitted to the ICU after 22:00 PM;
2. Medical records documented preoperative history of mental or cognitive disorders including schizophrenia, epilepsy, Parkinsonism, or dementia;
3. Medical records documented inability to communicate in the preoperative period due to coma or language barrier;
4. History of drug abuse of psychoactive and anesthetic drugs;
5. Known preoperative severe sinus bradycardia (lower than 50 beats/min), sick sinus syndrome, second- or third-degree atrioventricular block, or left ventricular ejection fraction lower than 30%;
6. Serious hepatic dysfunction (Child-Pugh class C);
7. Severe renal dysfunction requiring renal replacement therapy before the surgery;
8. Allergies to ingredients or components of 5-[(1S)-1-(2,3-dimethylphenyl)ethyl]-1H-imidazole (dexmedetomidine hydrochloride);
9. American Society of Anesthesiologists (ASA) classification of IV to VI;
10. Moribund condition with low likelihood of survival for more than 24 hours;
11. Pregnancy or lactation women;
12. Current enrolment in another clinical trial;
13. Refuse to participate.