Inclusion Criteria:  Male or female 18 to 80 years old Diagnosis of ruptured saccular aneurysm confirmed by cerebral angiography or computed tomography angiography (CTA) Aneurysm securement via open neurosurgical clipping or endovascular coiling Modified fisher grade 3 or 4 on admission cranial computed tomography scan External ventricular drain placed as part of routine care Mechanical ventilation requiring sedation Ability to enroll within 72h following bleed Informed consent  Exclusion Criteria:  Subarachnoid hemorrhage due to causes other than a saccular aneurysm (e.g. non-aneurysmal, traumatic, rupture of a fusiform or mycotic aneurysm) Pregnancy or currently breast-feeding an infant Forensic patient Known significant baseline neurologic deficit Glasgow coma scale 3 with fixed and dilated pupils or other signs of imminent death Increased intracranial pressure >30mmHg in sedated patients lasting >4 hours anytime since the initial bleed Presence of systemic or CNS infection Cardiopulmonary resuscitation after the initial bleed Angiographic vasospasm prior to aneurysm repair, as documented by cerebral angiography or CTA Surgical complication including but not limited to massive intraoperative hemorrhage, vascular occlusion, or inability to secure the ruptured aneurysm Severe coronary artery disease (e.g. obstructive disease with stenosis >50% of any vessel on coronary angiography), angina, symptoms or evidence of myocardial ischemia, myocardial infarction within 3 months of study enrollment Heart failure or cardiomyopathy with ejection fracture <35%, symptoms or evidence of decompensated heart failure on admission or within preceding 6 months Tachyarrhythmia (e.g. history or evidence of any symptomatic ventricular tachycardia, ventricular fibrillation, atrial fibrillation or flutter with rapid ventricular rate, or any supraventricular tachycardia) Active psychotic symptoms, history of primary psychotic disorder (e.g. schizophrenia or schizoaffective disorder), or mania History of ketamine dependence or abuse Hypersensitivity to ketamine or any component of the formulation Increased intraocular pressure or history of glaucoma Known or suspected cirrhosis or evidence of moderate-severe liver dysfunction on laboratory evaluation (e.g. ALT and AST>3x upper limit of normal, alkaline phosphatase and gamma-glutamyl transferase>2.5x upper limit of normal, and/or bilirubin>1.5x upper limit of normal) Severe kidney disease (e.g. plasma creatinine ≥2.5 mg/dL)