Comparison of Perioperative Conscious Sedation During Endovascular Thrombectomy in Acute Ischemic Stroke

1. Age ≥ 18 years; 2. Presenting with symptoms of acute ischemic stroke within 24 hours of last known well; 3. Computed tomography angiography or magnetic resonance angiography confirmed occlusion of the intracranial segment of the internal carotid artery, M1 or M2 segment of the middle cerebral artery; 4. Pre-stroke modified Rankin scale (mRS) score ≤ 2; 5. National Institutes of Health Stroke Scale (NIHSS) score ≥ 6 before randomization; 6. Alberta Stroke Program Early CT Score (ASPECTS) ≥ 3 prior to randomization; 7. The patient or their legal representative provides written informed consent. Exclusion criteria 1. Pregnant or lactating women; 2. Known allergy to contrast agents or nitinol devices; 3. Known allergy to midazolam or other benzodiazepines; 4. Known allergy to dexmedetomidine or its components; 5. Long-term use of sedative medications, α2-adrenergic receptor agonists (such as clonidine), or potent CYP450 inhibitors or inducers before randomization; 6. Uncontrolled hypertension or hypotension (defined as systolic blood pressure \> 185 mmHg or \< 90 mmHg, diastolic blood pressure \> 110 mmHg or \< 60 mmHg) measured prior to randomization; 7. Second-degree or third-degree heart blockage or bradyarrhythmia with a baseline heart rate lower than 50 beats / min; 8. Any major surgery or serious trauma within 14 days; 9. Known genetic or acquired bleeding diathesis (platelet count \< 100\*10\^9/L, activated partial thromboplastin time \> 50 s or international normalized ratio \> 1.7); 10. Blood glucose \< 2.8 or \> 22.2 mmol/L; 11. Severe renal insufficiency (defined as glomerular filtration rate \< 30 ml/min or serum creatinine \> 220 mmol/L \[2.5mg/dl\]); 12. Receiving hemodialysis or peritoneal dialysis; 13. Life expectancy ≤ 1 year; 14. Severe agitation or seizures; 15. Clinical manifestations of central nervous system vasculitis; 16. Premorbid neurological disease or mental disorders confounding evaluation; 17. Unwilling to be followed up within 90 days; 18. Participation in other interventional randomized clinical trials. Imaging exclusion criteria 1. Evidence of intracranial hemorrhage on computed tomography (CT) or magnetic resonance imaging (MRI); 2. Cerebellar infarction with obvious space-occupying effects and fourth ventricle compression on CT or MRI; 3. Any untreated or incompletely treated intracranial aneurysm or any intracranial vascular malformation; 4. Bilateral occlusion or multiple intracranial vessels occlusions; 5. Intracranial tumors (with mass effect).