KETA trial is a nonprofit, double-blind, randomized, controlled pilot trial with aiming to determine if co-administration of ketamine with recombinant of tissue type plasminogen activator (tPA) for thrombolysis in acute ischemic stroke compared with tPA co-administered with placebo, decreases cerebral infarction growth in diffusion weighted imaging between admission and day 1. Eligibility applies to patients with symptomatic ischemic stroke seen within 4.5 h of onset with middle cerebral artery or distal internal carotid artery occlusion, no contraindication to intravenous tPA-mediated thrombolysis and eligible to endovascular treatment of stroke (i.e. thrombectomy). The study has been designed to have 80% power to detect a 80% decrease of infarct volume growth in the tPA-ketamine group at a two-sided type I error rate of 5%. For this purpose, at least 25 patients per arm should be enrolled.