Objectives are to assess safety and tolerability of VAS203, to evaluate concentrations of metabolites of VAS203 in plasma and microdialysate and to assess pharmacodynamic effects of VAS203 on surrogate parameters. Safety parameter will include vital signs (blood pressure heart rate, respiration rate, oxygen saturation and blood gases), fluid balance, ECG, laboratory examinations (clinical chemistry, liver function, haematology/coagulation, urinalysis, renal parameters) and adverse events. Concentration of VAS203 will be determined in plasma and microdialysate. Pharmacodynamic parameters will include intracranial pressure (ICP), biochemical parameters in microdialysate (nitrite/nitrate, arginine, citrulline, pyruvate, lactate, glucose), Partial Oxygen Pressure in brain parenchyma and Therapy Intensity Level (TIL).