THE METABOLIC-FATE OF LONG-TERM INHALED NITRIC-OXIDE

Purpose: The fate of inhaled nitric oxide (NO) has not been precisely defined in critically ill patients. This study aimed at defining the e ffects of long-term NO inhalation on circulating NO byproduct levels. Material and Methods: During NO therapy, plasma and urine from 13 crit ically ill patients were sampled daily for determination of the stable byproducts of NO (nitrite [NO2-] and nitrate [NO3-]. Routine monitori ng data included inhaled NO concentration, hemodynamic parameters, art erial blood gases, creatinine clearance, and C-reactive protein. Resul ts: For the first 24 hours of NO inhalation (6.3 +/- 1.1 ppm), NO3- pl asma concentration increased (from 13.3 +/- 5.4 to 52.3 +/- 17.6 mu mo l/L), but NO2- plasma concentration was not affected. The NO3- plasma concentration was correlated with the C-reactive protein level, the in haled NO concentration, Renal excretion of NO metabolites was unaltere d by NO inhalation. The NO3 concentrations returned to baseline when N O therapy was discontinued. Conclusion: Long-term NO inhalation was as sociated with a consistent increase in the NO3- plasma concentration. NO byproducts may be implicated in the systemic effects associated wit h this treatment. Copyright (C) 1998 by W.B. Saunders Company.