The investigators have previous shown that regional hypothermia by the intra-arterial infusion of cold saline combined with mechanical thrombectomy in acute ischemic stroke is feasible and safe. The safety of selective brain cooling in patients undergoing mechanical thrombectomy, however, is not established in a randomized trial. The investigators therefore conducted this RCT study to further explore the safety of regional hypothermia in patients with acute ischemic stroke who underwent mechanical thrombectomy.

Inclusion Criteria:

• Age ≥18 and ≤80
• Clinical signs consistent with the diagnosis of an acute ischemic stroke
• Baseline NIHSS score obtained prior to randomization ≥8
• Intracranial arterial occlusion of the distal intracranial carotid artery or
• Middle (M1/M2), demonstrated with CTA, MRA, DSA
• The possibility to start treatment (artery puncture) within 6 hours from onset
• Regional hypothermia is expected to start within 15 minutes after recanalization
• Informed consent given

Exclusion Criteria:

• mTICI<2b after endovascular treatment
• No significant pre-stroke disability (mRS ≤1)
• Previous NYHA grade > 1
• Known hemorrhagic diathesis, coagulation factor deficiency, or oral anticoagulant therapy with INR > 3.0
• Baseline platelet count < 50000/µL
• Baseline blood glucose of < 50mg/dL or >400mg/dl
• Severe, sustained hypertension (SBP > 220 mm Hg or DBP > 110 mm Hg). NOTE: If the blood pressure can be successfully reduced and maintained at the acceptable level using local treatment guidelines recommended medication (including iv antihypertensive drips), the patient can be enrolled.
• Seizures at stroke onset which would preclude obtaining a baseline NIHSS
• Subjects who have received iv t-PA treatment beyond 4,5 hours from the beginning of the symptoms
• Renal insufficiency with creatinine ≥ 3 mg/dl
• Woman of childbearing potential who is known to be pregnant or lactating
• Subject participating in a study involving an investigational drug or device that would impact this study
• Cerebral vasculitis
• Patients with a pre-existing neurological or psychiatric disease that would confound the neurological or functional evaluations
• Unlikely to be available for 3 months follow-up (e.g. no fixed home address, visitor from overseas).
• CT or MR evidence of hemorrhage (the presence of microbleeds on MRI is allowed)
• ASPECT<6
• Subjects with occlusions in multiple vascular territories (anterior circulation and posterior circulation)
• Evidence of intracranial tumor (except small meningioma)