This study aims to conduct a multicenter, prospective, randomized clinical trial to scientifically evaluate the safety and efficacy of different perioperative sedation methods during endovascular thrombectomy in acute ischemic stroke patients with large vessel occlusion in the anterior circulation.

In the perioperative period of endovascular thrombectomy, the main sedation options are midazolam (MDZ) and dexmedetomidine (DEX). Research has shown that both sedation methods have their advantages and disadvantages, and there is no consensus on how to choose between them. Therefore, this study aims to conduct a multicenter, prospective, randomized clinical trial to scientifically evaluate the safety and efficacy of different perioperative sedation methods during endovascular thrombectomy (EVT) in AIS patients with large vessel occlusion in the anterior circulation and hopes to contribute to the advancement of EVT in clinical practice.

In this trial, acute ischemic stroke patients with large vessel occlusion in the anterior circulation within 24 hours of symptom onset or last known well will be included. In the screening stage, participants who meet the inclusion criteria of the trial, upon completion of screening/baseline assessment and after signing the informed consent, will be randomly assigned in a 1:1 ratio to one of the following two treatment groups: the dexmedetomidine and midazolam conscious sedation groups. The primary end point is the proportion of modified Ranking score of 0-2 at 90 days.

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)