Increased levels of nitrite/nitrate in the cerebrospinal fluid of patientswith subarachnoid hemorrhage

The role of nitric oxide (NO) in the mechanism of delayed cerebral vasospas m (VS) after subarachnoid hemorrhage (SAH) was investigated by analyzing th e stable metabolites of NO, nitrite and nitrate, by the Griess method in th e cerebrospinal fluid (CSF) and venous blood of 29 patients with SAH, the C SF of 22 control patients, and venous blood from eight normal subjects. VS was defined as diffuse and severe angiographical vasospasm detected by angi ography performed around days 7-9 after the onset. Six of the 29 patients h ad VS. The nitrite/nitrate levels in the blood of patients with SAH were al most within the range of those in normal subjects, but the levels in the CS F of patients with SAH were significantly higher than those of the control group. Patients with VS after SAH had significantly lower levels in the CSF than patients without VS on days 7-9, when VS is most likely to occur. The se observations suggest that NO production in the CSF environment occurs fo llowing SAH, but possibly may not provoke VS.