Acid‐base Pattern of Cerebrospinal Fluid and Arterial Blood in Bacterial Meningitis and in Encephalitis

The acid‐base status of cerebrospinal fluid (CSF) and arterial blood has been investigated in sequential samples from 25 patients with bacterial meningitis and 8 with acute encephalitis. Patients with bacterial meningitis hyperventilated spontaneously throughout the first week to median values for arterial carbon dixoide tension of about 30 mmHg. The pH in CSF was less than 7.30 in 17 cases, within the normal range in 5 and above 7.34 in 7. On admission the following CSF median values were observed: clactate=9 mmol/1, chydrogen carbonate=14 mmol/1 and pH=7.23. The concentration of lactate and pH in CSF approached normal values within a week. Patients with acute encephalitis also hyperventilated, but pH values in CSF were close to normal. Only severe cases of encephalitis had elevated lactate concentrations in the CSF. Even in the presence of spontaneous hypocapnia artificial hyperventilation may be beneficial in cases where arterial carbon dioxide tension rises without a simultaneous clinical improvement.