This multicenter, observational, study will enroll severe neurologically injured patients both prospectively and retrospectively. The aims are to identify the percent of neurocritical care patients with sodium levels ≤ 135 mEq/L, describe treatment strategies employed, determine the correlation of clinical factors (i.e. GCS, ICP) with serum sodium concentrations in patients prior to sodium altering therapy, and evaluate outcomes through evaluation of length of stay, discharge disposition, and modified Rankin score (mRS).

Inclusion Criteria:

• age ≥ 18 years of age
• admitted to an intensive care unit for more than 48 hours
• ICD-9 codes for aneurysmal SAH, TBI, IPH, or intracranial tumor.

Exclusion Criteria:

Patients identified for enrollment will be age ≥ 18 years of age, admitted to an intensive care unit for more than 48 hours with ICD-9 codes for aneurysmal SAH, TBI, IPH, or intracranial tumor.