The purpose of this study was to investigate whether the balanced fluids therapy change plasma osmolality in neurosurgical procedures due to brain tumors, meningeomas and arterio-venous malformation.

Normal saline or 0.9% sodium chloride solution is the most commonly used intravenous fluid worldwide and its composition are 154 mmol Na+ and 154 mmol Cl- per litter with osmolality of 308 mOsmol/L. That composition is not "normal" because plasma contains potassium in range between 137-146 mmol/L, and chloride in range between 98-106 mmol/L, with plasma osmolality of 280-295 mOsmol/kg. Recently published data suggested detrimental effects of chloride rich fluids on renal blood flow and glomerular filtration rate, urine output and acute kidney injury. One alternative to saline solution is a buffered, balanced, crystalloid solution with an electrolyte composition similar to plasma and osmolality between 286-295 mOsmol/L. Someone could indicate that such balanced solutions are not suitable for neurosurgical patients because of a possible impact on the brain edema development.

Inclusion Criteria:

• Patients with brain tumor, meningeomas and vascular malformation.

Exclusion Criteria:

• Patients with signs of elevated intracranial pressure; History of kidney disease, History of heart disease

Patients who underwent neurosurgical procedure because of brain tumor, meningeoma and vascular malformation. And without signs of elevated intracranial pressure and any history of kidney or heart disease.