Post-craniotomy pain is common and often undertreated. Inadequate analgesia can lead to patient discomfort and higher opioid consumption, which may result in respiratory depression, sedation risks and impaired neurological assessment in the early postoperative period. The incidence of post-operative delirium after intracranial surgery was 19%, ranging from 12 to 26% caused by variation in clinical features and delirium assessment methods1. It is associated with increased morbidity, longer length of hospital stay, and harm to self or staffs.

Dexmedetomidine (Precedex) is a highly selective α2-adrenergic agonist with the properties of analgesia, sedative, anxiolytic and neuroprotection without significant respiratory depression. Most of the trials administered a loading dose of 0.5-1.0 μg/kg intravenous dexmedetomidine over 10 minutes followed by infusion dose 0.2-0.7 μg/kg/hour. The use of intraoperative dexmedetomidine is believed to reduce the usage of postoperative opioids where frequent neurological assessment is often required in neurosurgical patients. Beyond the benefit of analgesia, perioperative dexmedetomidine has been studied for prevention of postoperative delirium. Randomized trials in mixed noncardiac surgical populations reported that low-dose perioperative dexmedetomidine may reduce the incidence of delirium. Dexmedetomidine produces dose-dependent bradycardia and hypotension, which should be carefully monitored to maintain the cerebral perfusion pressure in brain surgery. However, most trials and meta-analyses have focused on general surgical or cardiac cohorts; the evidence remains limited in neurosurgical (craniotomy) patients.

Although it showed promising benefits of analgesia and neuroprotection in non-neurosurgical patients, recent meta-analyses of intraoperative dexmedetomidine reported high degree of heterogeneity due to the inclusion of varied procedures (elective vs emergent craniotomy), dosing regimes (loading dose only versus loading dose + infusion versus infusion only) and varied primary endpoints (postoperative pain scores, cumulative opioid consumption or incidence of delirium). Therefore, this randomized, double-blind, placebo-controlled trial is designed to examine the use of intravenous dexmedetomidine in the reduction of postoperative pain score and delirium in neurosurgical patients. We hypothesised that intravenous dexmedetomidine reduces postoperative pain score and delirium with lower need of rescue analgesia and amount of morphine consumption in patients undergoing craniotomy.

There are several similar studies been conducted in the literature search. However, the majority of the studies focus on the intensive care unit patient or non-neurosurgery patients. It is believed that intravenous dexmedetomidine can reduce the postoperative pain score with lesser need for rescue analgesia and morphine consumption to facilitate postoperative neurological assessment.

Inclusion Criteria:

• All adult (American Society of Anaesthesiologists (ASA 1-2) who >18 years old and <65 years old undergoing elective craniotomy

Exclusion Criteria:

• Patients who are ASA 3-5 or BMI <18/ >40 or allergic to dexmedetomidine will be excluded. Patients with high-grade heart block or uncontrolled bradyarrhythmia will also be excluded.