Comparison of Two Different Medications Used to Treat Elevated Intracranial Pressure

Inclusion Criteria: * Documented SAH (by computed tomography or lumbar puncture), ICH, TBI or brain tumor * Patient greater than or equal to 18 years of age * ICP monitor in place * ICP greater than 20mmHg, not related to a transient noxious stimulus and not responding to standard measures for controlling ICP (ventricular drainage, elevation of head of the bed and optimizing PaCO2) * Patient or patient's legally authorized representative has provided written informed consent Exclusion Criteria: * Patient less than 18 years of age * Lack of ICP monitoring * Patient received Mannitol prior to placement of ICP monitor * Baseline serum osmolarity of greater than 310 mOsm/L * Patient is currently enrolled in another investigational drug or device study * Congestive heart failure at time of enrollment * Chronic renal failure on hemodialysis * Pregnancy