Parabanic acid for monitoring of oxygen radical activity in the injured human brain.

The authors used intracerebral microdialysis to harvest allantoin and parabanic acid, potential markers of in vivo oxygen radical activity, from the frontal lobe cortex of three patients in the neurointensive care unit after serious aneurysmal subarachnoid haemorrhage. Clinical events involving severe secondary ischaemia, ultimately leading to structural damage, were associated with a dramatic elevation of the microdialysate level of parabanic acid, whereas allantoin showed less robust changes. In one patient with an uneventful clinical course and without signs of secondary ischaemia parabanic acid levels remained low. The results support the involvement of highly reactive oxygen radical species in human cerebral ischaemia. Parabanic acid appears to be an important marker of free radical reactions in vivo and may be used to monitor free radical activity and to evaluate pharmacological therapy with radical scavengers.