The purpose of this study is explore how cerebrospinal fluid (CSF) drainage impacts outcomes for patients diagnosed with subarachnoid hemorrhage (SAH). This is a non-randomized observational study of two physician-prescribed approaches to managing intracranial pressure monitoring and CSF drainage for SAH patients. The study will enroll only those patients who have intracranial pressure (ICP) monitoring in situ. Because this is an observational study, there are no physical risks to the patient, the only risk is loss of confidentiality.