SEACOAST 1- SEdAtion With COllAteral Support in Endovascular Therapy for Acute Ischemic Stroke

Inclusion Criteria: 1. Age ≥18 2. NIHSS ≥ 6 within 0-16h or NIHSS ≥ 10 within 16-24h 3. Anterior circulation large vessel occlusion (ICA, M1, M2) 4. ASPECTS score ≥ 6 within the first 6h, or DEFUSE trial imaging criteria within 6-16h; or DAWN trial clinical/imaging mismatch criteria within 16-24h 5. Premorbid modified Rankin Scale (mRS) 0-2 6. Patient deemed candidate for mechanical thrombectomy with anticipated groin puncture within 24 hours of last known well and within 90 min of ED arrival Clinical Exclusion Criteria: 1. Intubation in ED prior to anesthesiologist evaluation, or intubation for any other medical reason other than planned thrombectomy 2. Rapid neurological improvement, suggestive of revascularization 3. Known serious sensitivity to radiographic contrast agents. 4. Current participation in another investigational drug or device treatment study. 5. Renal Failure as defined by a serum creatinine \> 2.0 mg/dl (or 176.8 μmol/l) or Glomerular Filtration Rate \[GFR\] \< 30. 6. Subject who requires hemodialysis or peritoneal dialysis, or who have a contraindication to an angiogram for whatever reason. 7. Life expectancy of less than 90 days. 8. Clinical presentation suggests a subarachnoid hemorrhage, even if initial CT or MRI scan is normal 9. Subject with a co-morbid disease or condition that would confound the neurological and functional evaluations or compromise survival or ability to complete follow up assessments. 10. Subject currently uses or has a recent history of illicit drug(s) or abuses alcohol (defined as regular or daily consumption of more than 4 alcoholic drinks per day. 11. Septic or cardiogenic shock with severe life-threatening hypotension Imaging Exclusion Criteria: 1. Computed tomography (CT) or Magnetic Resonance Imaging (MRI) evidence of acute intracranial hemorrhage on presentation. 2. CT or MRI evidence of mass effect or intracranial tumor (except small meningioma). 3. CT showing hypodensity or MRI showing hyperintensity involving greater than 1/3 of the middle cerebral artery (MCA) territory (or in other territories, \>100 cc of tissue) on presentation. 4. Baseline non contrast CT or DWI MRI evidence of a moderate/large core defined as extensive early ischemic changes of Alberta Stroke Program Early CT score (ASPECTS) \< 6 5. CT or MRI evidence that ischemia is not in anterior circulation distribution. 6. Imaging evidence that suggests, in the opinion of the investigator, the subject is not appropriate for mechanical thrombectomy intervention (e.g., inability to navigate to target lesion, moderate/large infarct with poor collateral circulation, etc.). Anesthesia exclusion criteria (relative): 1. History of Malignant Hyperthermia 2. History of allergic reaction/anaphylaxis to anesthetic drugs 3. Inability to tolerate supine position (severe CHF) 4. Chronic O2 dependence or any other known pulmonary condition that might lead to difficult extubation and prolonged mechanical ventilation including known pulmonary hypertension