CompARing Between CO2 Phenylephrine and Phenylephrine Only Treatment in Patients With proGrEssing Cerebral infarctioN

Inclusion Criteria: * Age ≥20 years * Anterior circulation progressing stroke * Neurological worsening either 1 point in NIHSS score or MRC grade Exclusion Criteria: * Age under 20 years. * Patients with cerebral infarction who are at risk of cerebral edema as determined by the investigator. * Patients with Moyamoya disease. * Patients with severe cerebrovascular reactivity (CVR) impairment due to cerebral vascular stenosis, making study participation challenging as determined by the investigator. * Patients unable to undergo CO2 treatment (e.g., panic disorder, anxiety disorders, or other psychiatric conditions). * Patients with hypersensitivity to phenylephrine. * Patients with persistent bradycardia (heart rate \< 50 bpm). * Patients with a history of hemorrhagic stroke or at risk of cerebral hemorrhage. * Patients with a pre-stroke modified Rankin Scale (mRS) score ≥ 2, indicating impaired functional independence. * Patients ineligible for phenylephrine treatment due to any of the following: Myocardial infarction or unstable angina within the past 3 months. Cardiac ejection fraction \< 25%. Ventricular arrhythmia. Systolic blood pressure \> 200 mmHg. Serum creatinine \> 2 mg/dL. Pregnancy. * Use of monoamine oxidase (MAO) inhibitors. * Patients who do not consent to participate in the study.