Cerebral oxygen extraction during severe viral encephalitis.

Viral encephalitis can cause devastating neurologic injury. Little is known about cerebral hemodynamics and metabolism in this condition. We report two patients with severe encephalitis, one proven and the other suspected to be due to herpes simplex, in whom the global cerebral oxygen extraction ratio (OER) and carbon dioxide (CO2) responsiveness was assessed. OER was low in both patients throughout the acute period. CO2 responsiveness was present initially in both and disappeared later in the more severely affected child. These cases demonstrate that cerebral hyperemia occurs in severe viral encephalitis and that hyperventilation can effectively reduce the intracranial pressure.