Background: There is no agreement about exhaled nitric oxide (FE(NO)) and its change after haemodialysis (HD) in end-stage renal disease (ESRD) patients. To comprehensively assess NO production in the respiratory system, NO metabolites in exhaled breath condensate (EBC) needs to be measured in addition to FE(NO), taking into account the influence on these markers of airway pH, which may be regulated by ammonia (NH3+), present in large amounts in the breath of ESRD patients and removed by HD.
Study design: FE(NO) and NO metabolites (NOx, NO2-,NO3- ), pH and NH3+ in EBC were measured in 12 ESRD patients, before and after HD. Twelve healthy subjects acted as controls.
Results: FE(NO )values of ESRD patients were similar to normals, while EBC-NOx, NO2-, NH3+ and pH were significantly higher in ESRD patients compared to normals (EBC-NOx 12.3, range 11.1-41.9 microm vs. 9.4, range 4.6-10.9 microm, P = 0.007; NO2- 4.70, range 1.17-8.22 microm vs. 0.90, range 0.72-1.17 microm, P = 0.023; NH3+ 2340, range 1325-3922 microm vs. 660, range 406-872 microm, P < 0.001; pH 7.16, range 6.82-7.44 vs. 6.60, range 6.42-6.76, P = 0.004, respectively). HD caused a mild significant decrease of FE(NO), and normalization of NH3+, NOx, NO2- and pH. A significant positive relationship between EBC-pH and EBC-NH3+ before and after HD (r(2) = 0.65, P = 0.000) was observed, explaining higher than normal EBC-pH before HD, while no relationship was found between EBC-pH and FE(NO) or NO metabolites.
Conclusion: Oxidative stress, and not EBC-pH, is the most probable cause of increased NO metabolites in ESRD patients before HD.