Therapeutic hypothermia (TH) in stroke has demonstrated robust neuroprotection in animals especially after ischemia-reperfusion injury, but its safety and efficacy remain controversial. The investigators propose this trial to study the clinical and radiological effects of therapeutic hypothermia in acute ischemic stroke patients treated with intravascular thrombectomy (IVT).

The study intervention is therapeutic hypothermia. After intubation, patients assigned to therapeutic hypothermia will receive central venous catheterization through right jugular vein or femoral vein depending on the cooling application and the unique needs, a flexible catheter will be inserted and iced saline will be circulated through the multiple balloons of the catheter in a closed-loop design to induce therapeutic hypothermia. This system also has a hydrophilic coating with heparin and a triple-lumen central venous catheter to satisfy the need of fluid or drug infusion, blood draw and central venous pressure monitoring. After central venous catheterization, patients assigned to TH will receive intravascular temperature management to achieve the target temperature of 34-35 °C, which is superior to surface methods in cooling performance in terms of faster rate of cooling, shorter induced cooling time, precise control during maintenance. Thereafter, hypothermia will be maintained for 24 hrs from the start of hypothermia. The patients will be rewarmed slowly at a rate of no greater than 0.5 °C every 4 h. What's more, patients in TH group will execute anti-shivering protocol during awaking and extubation.

Inclusion Criteria:

1. Aged 18-85 years(inclusive);
2. Patients have clinical signs consistent with acute ischemic stroke,
3. Patients with acute large vessel occlusion including internal carotid artery and middle cerebral artery M1 and M2 demonstrated by CTA，MRA or DSA
4. The possibility to receive arterial thrombus removal treatment （within6 or24 hr of large vessel occlusion ）;
5. Provide the informed consent form of the patient or the patient's agent.

Exclusion Criteria:

1. Coma or altered vigilance defined as a score ≥2 on the level of consciousness 1A subscale of the NIHSS.
2. Associated cerebral hemorrhage.
3. There is dysfunction before the onset, mRS score >= 2 points;
4. Accompanied by severe comorbidities (such as severe cardiopulmonary insufficiency, the expected survival period of advanced malignant tumors is less than 90 days);
5. Multi-mode CT/MRI examination of the corresponding contrast agent use contraindications (such as contrast agent allergy, etc.);
6. Women during pregnancy or lactation;
7. Patients currently participating in other clinical research trials;
8. Other conditions judged by the investigator as not suitable for inclusion in the clinical study.

This trial is open labeled, the treatment allocation is known to the treating physicians and the patients