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

Inclusion Criteria: 1. Age ≥18 years 2. Presenting with symptoms of acute ischemic stroke 3. CTA or MRA confirmed occlusion of the anterior circulation (intracranial carotid artery or M1, M2 segment of the middle cerebral artery) 4. Randomization finished within 24 hours of symptom onset or time last know well 5. Pre-stroke mRS score ≤2 6. NIHSS score ≥6 at the time of randomization 7. ASPECTS value ≥3 8. Informed consent signed Exclusion Criteria: General 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. Planned to receive general anesthesia for EVT 6. Uncontrolled hypertension or hypotension (defined as systolic blood pressure \>185 mmHg or \< 90 mmHg, diastolic blood pressure \>110 mmHg or \< 60 mmHg) 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\\\*109 /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 less than 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 CT or 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)