Progressing stroke is associated poor functional outcome and neurological deficit.

Currently, no treatment for progressing stroke is recommended on the guideline.

Carbogen is a mixture of 5% CO2 with 95% O2. Carbogen is safe and it is used for the treatment of sudden sensory neural hearing loss or ocular ischemia.

CO2 dilate cerebral arteriole and concentration of CO2 is correlated with cerebral blood flow.

Increased cerebral blood flow following dilation of cerebral arteriole by CO2 might halt and revert progressing stroke.

Induced hypertension is alternative treatment of progressing stroke. Increasing blood pressure also induce cerebral blood flow. Phenylephrine is an α1 agonist, phenylephrine act on peripheral artery and little effect on cerebral artery or heart. Several studies reported that the effectiveness of phenylephrine on progressing stroke.

Therefore, this study will compare the effectiveness of carbogen + phenyleprhine versus phenlyephrine in progressing stroke patients.

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.

Three months after discharge, the independence assessment will be perfomred by the researcher who don't know the patietns group.