All the patients meeting the study criteria will be randomized into two groups. After
standardized induction to general anesthesia all patients will be given the infusion of
hyperosmotic NaCl 5 ml/kg/BW during 30 min, group A 1.5% NaCl, group B 3% NaCl.
Corticosteroids will be administered as usually. After dura opening the brain relaxation
score will be assessed by surgeon (1 = completely relaxed, 2 = satisfactorily relaxed, 3 =
firm brain, 4 = bulging brain), and the first measurement of the brain microcirculation
provided by use of SDF probe in the area of the healthy brain, and of perifocal oedema. Both
sites of investigation will be marked for the second measurement, which will be done after
the end of tumor resection. Laboratory examinations: natremia preoperatively, natremia and
osmolarity peroperatively 1 hour after NaCl infusion and at the end of surgery. Concentration
of natrium will be examined in CSF after dura opening. Anesthesia management will be
according to the standardised protocol, the patients will be awaken and extubated after the
end of the procedure at the operating theatre.