Mannitol 20% has long been used to treat elevated intracranial hypertension in trauma and intensive care settings. More recent data indicate that hypertonic saline may be as effective or more effective than mannitol for this purpose, with possible fewer side effects.

This study compares both agents in favoring cerebral relaxation during elective supratentorial procedures for tumor resection.

Study hypothesis: 3% hypertonic saline will provide better cerebral relaxation with fewer side effects than 20% mannitol.

Inclusion Criteria:

• Patients scheduled for elective supratentorial craniotomy for tumor resection
• Presumed preoperative diagnosis of : astrocytoma (any grade), meningioma (any sub-type) or cerebral metastasis (any primary neoplasm)

Exclusion Criteria:

• Age < 18 years
• Reintervention
• Glasgow coma scale < 13
• Emergency surgery or American Association of Anesthesiologists physical status class 4 or 5
• Prone or lateral positioning
• Hypo or hypernatremia (serum sodium below 135 or above 150 meq/L)
• Osmotherapy (either mannitol or hypertonic saline) given in the last 24 hours
• Congestive heart failure (LVEF < 40% or restrictive diastolic dysfunction on echocardiography)
• Chronic renal failure (creatinine clearance < 30 ml/min)
• Pregnancy
• Obesity (BMI > 40)