Ischemic stroke, which is due to the occlusion of a cerebral blood vessel, comprises nearly 80-90% of all strokes. Currently, reperfusion of the salvageable tissue via thrombolytic drug or endovascular treatment is the most effective strategy to reduce brain damage. However, after recanalizing the occluded vessels, subsequent reperfusion injury is inevitable. It may not only weaken the therapeutic effects of timely reperfusion but also impede patients' recovery. Moreover, thousands of neuroprotective drugs effective in experimental models have been proved to be unsuccessful in clinical trials. Therefore, effective strategies are urgently needed to prevent and treat cerebral reperfusion injury and further improve the prognosis of acute ischemic stroke.

Researchers applied remote ischemic conditioning to mouse model of focal cerebral reperfusion injury and found that it could reduce cerebral infarct size. And clinical researches demonstrated that remote ischemic conditioning was an effective strategy to improve cerebral perfusion and prevent recurrent stroke in patients with ischemic stroke. However, whether remote ischemic conditioning is safe and effective in protecting patients with large-vessel ischemic stroke and undergoing endovascular treatment is still unclear. The investigators' hypothesis is that RIC is a safe and effective strategy to reduce brain injuries in stroke patients undergoing endovascular treatment.

Inclusion Criteria:

1. Acute ischemic stroke where patient is ineligible for intravenous thrombolytic treatment or the treatment is contraindicated, or where patient has received intravenous thrombolytic therapy without recanalization;
2. Suspected proximal anterior circulation occlusion;
3. No remarkable pre-stroke functional disability (mRS ≤ 1);
4. Baseline NIHSS score obtained prior to randomization must be ≥6;
5. Age ≥18 and ≤ 80;
6. Patient treatable within 24 hours of symptom onset;
7. Informed consent obtained from patient or acceptable patient's surrogate

Exclusion Criteria:

1. Identified hemorrhagic diathesis, coagulation factor deficiency, or oral anticoagulant therapy with INR > 3.0;
2. Baseline platelet count < 30*109/L;
3. Baseline blood glucose of < 2.7mmol/L or >22.2mmol/L;
4. Renal insufficiency with creatinine ≥ 265 umol/L;
5. Severe, sustained hypertension (SBP > 185 mmHg or DBP > 110 mmHg);
6. Rapidly improving symptoms at the discretion of the investigator;
7. Seizures at stroke onset which would preclude obtaining a baseline NIHSS;
8. Serious, advanced, or terminal illness with anticipated life expectancy of less than one year;
9. History of life threatening allergy to contrast medium, Nickel, Titanium metals or their alloys;
10. Woman of childbearing potential who is known to be pregnant or lactating or who has a positive pregnancy test on admission;
11. Subject participating in a study involving other drug or device trial study;
12. Patients with a pre-existing neurological or psychiatric disease that would confound the neurological or functional evaluations;
13. Unlikely to be available for 90-day follow-up;
14. Contraindication for remote ischemic conditioning: severe soft tissue injury, fracture, or peripheral vascular disease in the upper limbs;
15. Hypodensity on CT or restricted diffusion amounting to an ASPECTS score of <7 on noncontrast CT or <6 on DWI MRI;
16. CT or MRI evidence of hemorrhage;
17. Significant mass effect with midline shift on CT or MRI scans;
18. Angiogram shows arterial tortuosity, pre-existing stent, and/or other arterial disease, which would prevent the device from reaching the target vessel and/or preclude safe recovery of the device;
19. Subjects with artery occlusions in multiple vascular territories;
20. Evidence of intracranial tumor.