Here is the design of a clinical trial:

Official Title: Effect of Dexmedetomidine on Postoperative Delirium in Patients Undergoing Brain Tumor Resections: a Randomized Controlled Study

Included conditions:
- Dexmedetomidine
- Postoperative Delirium

Study Armgroups:
- {'label': 'DEX group', 'type': 'ACTIVE_COMPARATOR', 'description': 'The DEX group will receives dexmedetomidine intraoperative.', 'interventionNames': ['Drug: Dexmedetomidine']}
- {'label': 'Placebo group', 'type': 'PLACEBO_COMPARATOR', 'description': 'The placebo group will receives 0.9% saline intraoperative.', 'interventionNames': ['Drug: 0.9% saline']}

Interventions:
- {'type': 'DRUG', 'name': 'Dexmedetomidine', 'description': 'Ten minutes after anesthesia induction and endotracheal intubation, patients assigned to dexmedetomidine group were given a loading dose of dexmedetomidine 0.6 μg/kg over 10 minutes, followed by continuous infusion at a rate of 0.4 μg/kg/h until the start of dural closure.', 'armGroupLabels': ['DEX group']}
- {'type': 'DRUG', 'name': '0.9% saline', 'description': '0.9% saline is administered with the same volume at the same speed as the other group.', 'armGroupLabels': ['Placebo group']}

Primary Outcomes:
- {'measure': 'The incidence of postoperative delirium', 'description': 'Postoperative delirium is assessed by the combination of the Richmond Anxiety Scale (RASS) and the Confusion assessment method for intensive care unit (CAM-ICU) or the 3-minute diagnostic interview for CAM (3D-CAM) as applicable.\n\nDelirium consists of four main characteristics: acute onset of a change in mental status or a fluctuating level of consciousness, inattention, disorganized thinking and an altered level of consciousness. The patient was diagnosed as delirious if both the first and second features were present, and either the third or fourth was present.\n\nIn the ICU, the delirium assessment was performed in two steps. The arousal level was first assessed by RASS. If the patient was not responsive to verbal stimuli (i.e. RASS score ≤-4), the remaining delirium assessment was aborted, and the patient was recorded as comatose. When the RASS score was greater than or equal to 3, delirium was evaluated using the CAM-ICU. Patients in general ward were evaluated by 3D-CAM.', 'timeFrame': 'postoperative 5 day'}

Please estimate the sample size based on the assumption: 
Significance level is set at 0.05 (two-sided) and power at 80%. A 5% loss in follow-up is considered.
Sample size estimation and statistical analysis
        According to previous studies, the incidence of delirium after surgery is about 20%.36 In our institution, POD incidence was 31.2% among 154 patients with temporal tumours in a prospective cohort study.10 A meta-analysis reported that dexmedetomidine relatively reduced the incidence of delirium by approximately 54%.21 We hypothesise that the incidence of POD is 30% and would be reduced by 50% after administration of dexmedetomidine comparing with the placebo. With a significance and power set at 0.05 (two sided) and 80%, respectively, the sample size required to detect the difference is 242 patients. Considering about 5% of the loss in follow-up, 260 (130 in each group) patients need to be enrolled.
        The analysis will be done by using SPSS software (V.23.0). The continuous variables will be described with mean and SD or median and IQR. Categorical data will be presented with counts (percentage). The difference in cumulative incidence of POD between the dexmedetomidine and control groups will be analysed by the Ï2 test. The primary outcome will also be analysed in the subgroups, including age (more than 65 years or not), gender, American Society of Anesthesiologists physical status and WHO classification of tumours in the central nervous system.37 The changes in NRS scores and the cumulative consumption of opioids will be compared by using repeated measurement. Other secondary outcomes such as MMSE score, quality of sleep, postoperative quality of recovery and intraoperative data (BIS and haemodynamic parameters) will be analysed by t test or Mann-Whitney U test. We will apply the intention-to-treat analysis on the primary outcome according to group allocation. In addition, missing data will be imputed by using the worst-case imputation scenarios.