Increased levels of nitrite/nitrate in the cerebrospinal fluid of patients with subarachnoid hemorrhage.

The role of nitric oxide (NO) in the mechanism of delayed cerebral vasospasm (VS) after subarachnoid hemorrhage (SAH) was investigated by analyzing the stable metabolites of NO, nitrite and nitrate, by the Griess method in the cerebrospinal fluid (CSF) and venous blood of 29 patients with SAH, the CSF of 22 control patients, and venous blood from eight normal subjects. VS was defined as diffuse and severe angiographical vasospasm detected by angiography performed around days 7-9 after the onset. Six of the 29 patients had VS. The nitrite/nitrate levels in the blood of patients with SAH were almost within the range of those in normal subjects, but the levels in the CSF 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. These observations suggest that NO production in the CSF environment occurs following SAH, but possibly may not provoke VS.