Objective: To measure serum nitrite and nitrate levels in critically ill children as indicators of endogenous nitric oxide (NO) production.
Hypothesis: Endogenous NO production is increased in children with conditions characterised by immune stimulation.
Design: Prospective descriptive study in a multidisciplinary paediatric intensive care unit.
Patients: 137 consecutive critically ill children with a variety of clinical conditions.
Interventions: Using a rapid microtitre plate technique, daily serum nitrite and nitrate levels were measured from serum samples that remained in the clinical laboratory after daily routine phlebotomy. Clinical and laboratory information was also gathered daily for each patient.
Results: The maximum serum nitrite plus nitrate levels (microM) reached by children with infection (41.8 (SD 18.1)), sepsis syndrome (85.1 (39.9)), shock without sepsis (36.4 (19.1)), transplantation alone (61.0 (43.4)), transplantation with sepsis (200.7 (150.5)), or rejection (161.7 (70.4)), were higher than in controls (18.1 (9.3)). In the absence of exogenous NO donors, levels greater than 80 microM were reached only in children with the sepsis syndrome, organ transplantation, or acute rejection.
Conclusions: Increased endogenous NO production occurs in children with clinical conditions associated with immune stimulation. Further investigation is warranted to determine the value of this simple and rapid test as a clinically useful diagnostic tool and therapeutic monitor in the evaluation of children at risk for the sepsis syndrome or acute allograft rejection.