Effects of Head-of-Bed on Intracranial Pressure

Inclusion Criteria: * Patients with subarachnoid hemorrhage confirmed by CT scan, MRI, or cerebral angiogram * Age ≥ 18 years old * Patients with intracranial pressure monitoring device * Patients with continuous arterial blood pressure monitoring * The subject or legally authorized representative must be available and able to consent Exclusion Criteria: * Intubated patients who are prone * Patients with left ventricular ejection fraction \<20% as evidenced by echocardiogram previously documented at any time in the electronic medical record * Patients with a diagnosis of pulmonary hypertension * Patients with a diagnosis of cirrhosis and/or evidence of liver failure. Evidence of liver failure will be assessed by the presence of ascites, edema, abnormal lab values including low albumin, elevated PTT, elevated PT, elevated INR, or elevated bilirubin without another etiology, or MELD score \>8. * Patients who are clinically unstable defined as those who are unable to lie flat for 30 minutes for any reason, patients on more than one continuous IV medications to increase blood pressure, or patients who are actively undergoing resuscitation.