'Brain-tissue acidosis inferred by cerebrospinal fluid (CSF) lactic acidosis is considered to play an impoant role in the clinical course of severe head injury. Patients with a poor outcome had significantly higher ventricular CSF lactate levels than did those with moderate disabilities or a good outcome. Patients showing orable outcome had a significant decrease in ventricular CSF lactate levels 48 hours after injury. This decrease was not observed in patients with a poor outcome. Increased ventricular CSF lactate concentration was also reliably associated with increased intracranial pressure (ICP). Ventricular CSF lactate levels did not correlate with the magnitude of intraventricular bleeding. Aerial and jugular venous blood lactate levels, although high after head injury, were usually lower than the levels in the ventricular CSF and reached a normal range by the 3rd day following head trauma. Ventricular CSF pH did not generally correlate with the ventricular CSF lactate concentration in patients under controlled ventilation. '- Prognostic signcance of ventricular CSF lactic acidosis in severe head injury. J. Neurosurg (">