SEACOAST 1 is a prospective, randomized, blinded endpoint trial comparing collateral vigor and clinical outcomes, with different forms of GA in patients with acute ischemic stroke due to anterior circulation large vessel occlusion (LVO) undergoing mechanical thrombectomy. The study compares GA with normocarbia (GAN) versus GA with mild hypercarbia (GAH), with a primary outcome of collateral robustness at measured at catheter angiography and clinical efficacy as secondary outcome. It is anticipated that the SEACOAST 1 will be followed by a larger, pivotal trial, SEACOAST 2, with primary clinical endpoints, in which the best method of GA identified in SEACOAST 1 is compared with the alternative strategy of anesthesia care (MAC) with minimal or no sedation. The current study focuses uppn SEACOAST 1, which is to be conducted in University of California, Los Angeles Ronald Reagan Medical Center and Santa Monica Medical Center. All acute stroke patients who arrive to one of these two stroke centers and are deemed eligible for thrombectomy will be considered for the proposed study. Physician-investigators will determine study eligibility. Informed consent to participate in the study will be obtained from legally authorized representatives or competent patients. For non-competent patients without on-scene legally authorize representatives, the consent process will utilize enrollment in emergency circumstances with exemption of informed consent (EFIC).