Correlation of breath ammonia with blood urea nitrogen and creatinine during hemodialysis

We have spectroscopically determined breath ammonia levels in seven patient s with end-stage renal disease while they were undergoing hemodialysis at t he University of California, Los Angeles, dialysis center. We correlated th ese measurements against simultaneously taken blood samples that were analy zed for blood urea nitrogen (BUN) and creatinine, which are the accepted st andards indicating the level of nitrogenous waste loading in a patient's bl oodstream. Initial levels of breath ammonia, i.e., at the beginning of dial ysis, are between 1,500 ppb and 2,000 ppb (parts per billion). These levels drop very sharply in the first 15-30 min as the dialysis proceeds. We foun d the reduction in breath ammonia concentration to be relatively slow from this point on to the end of dialysis treatment, at which point the levels t apered off at 150 to 200 ppb. For each breath ammonia measurement, taken at 15-30 min intervals during the dialysis, we also sampled the patient's blo od for BUN and creatinine. The breath ammonia data were available in real t ime, whereas the BUN and creatinine data were available generally 24 h rate r from the laboratory. We found a good correlation between breath ammonia c oncentration and BUN and creatinine. For one of the patients, the correlati on gave an R-2 Of 0.95 for breath ammonia and BUN correlation and an R-2 Of 0.83 for breath ammonia and creatinine correlation. These preliminary data indicate the possibility of using the real-time breath ammonia measurement s for determining efficacy and endpoint of hemodialysis.