The first aim of this study is to investigate the frequency and severity of a specific pathological metabolic pattern, mitochondrial dysfunction, of the brain in comatose patients under neurocritical care. This pattern is recognized as a complication after compromised blood flow to the brain and may be amenable to treatment. The other main aim of this study is to correlate patterns of metabolites between brain and jugular venous blood. It is probable but not proven that jugular venous microdialysis can mirror the global metabolic state of the brain.