A 65-year-old woman from Mumbai is brought to the hospital 6 hours after sudden onset left-sided weakness and facial droop. Neurological examination confirms right-sided hemiparesis (3/5) with right facial weakness. Non-contrast CT head shows no hemorrhage. MRI brain with DWI shows acute ischemia in the distribution of the left middle cerebral artery affecting the internal capsule. What is the most appropriate immediate next step in management?