Serum and urine nitrate and nitrite are not reliable indicators of intrathecal nitric oxide production in acute brain injury

This study examined the correlation between nitric oxide (NO) metabolites in the three major body fluid cornpartments and assessed performance of newly described vanadium-based assay for simultaneous detection of nitrite and nitrate (NOx) in human samples. Vanadium reduces nitrate to nitrite, which can be measured after a colorimetric reaction with Griess reagents. Cisternal cerebro spinal fluid (CSF), serum and urine samples from 10 patients with acute brain injury (ABI) were compared to control subjects. Significantly higher CSF NOx levels were found in brain injury patients compared to control patients (19.7 +/- 13.7 vs. 6.5 +/- 2.3 muM; p = 0.01), which persisted for 10-day period of observation. The serum and urine levels of NO, on admission were not statistically different (42.8 +/- 28.2 muM; 584.1 +/- 337.8 mumol/g Cr, respectively) from controls (36.8 +/- 14.8 muM; 819.7 +/- 356.0 mumol/g Cr), but tended to decrease during the disease course reaching the lowest level on day 6 (serum: 19.3 +/- 8.4 muM, urine: 300.4 +/- 111.9 mumol/g Cr). CSF levels of NOx correlated moderately with those in serum (p = 0.001, R-0.5). Serum NOx concentrations correlated weakly with urine levels (p = 0.04, R = 0.3). There was no significant correlation between CSF NOx and urine NOx levels. In conclusion, patients Suffering brain injury had increased NOx concentrations in CSF, which remained independent from other body fluid compartments. Serum and urinary NO(x)levels cannot be used as a reliable index to assess intrathecal NO production. (C) 2002 Flsevier Science B.V. All rights reserved.