Serum nitrate levels in patients with severe sepsis and renal failure

Abstract

Objective: To determine serum concentrations and 24-hour urinary excretion of nitrate (NO3-), the stable bioreaction product of nitric oxide, in patients with severe septic shock and renal failure, in patients with chronic renal failure and in healthy controls. Design: Prospective study. Setting: Intensive care units at Ullevål University Hospital and Akershus Central Hospital, Oslo, Norway. Patients: Seven patients admitted with severe septic shock and renal failure, six patients undergoing chronic ambulatory haemodialysis (CAHD) for end-stage kidney disease and six healthy volunteers for serum NO 3 determination. Twenty-four-hour urinary NO3- excretion on a low nitrate diet was also studied in six healthy volunteers. Interventions: Daily serum sampling was performed without any study interventions. Volunteers were given a low nitrate diet (NO3- intake <6 mg/24 hr) during urine sampling to determine the basal 24-hour urine excretion of NO3-. Measurements and main results: NO3- was determined by ion chromatography. On admission, serum NO3- levels in septic patients were 80±26 μM, compared to 37±5 μM in healthy controls. Due to the large variability in the septic group this difference did not reach a level of statistical significance (p=0.16). Preterminal serum NO3- levels in septic patients were significantly higher than in healthy controls (76±12 μM, p<0.01). Levels of NO3- in predialysis sera from CAHD patients were 85±8 μM, also significantly higher than in healthy controls (p<0.01). No statistical difference was found between serum NO3- levels in preterminal patients with irreversible septic shock and CAHD patients (p=0.55). The 24-hour urine excretion of NO3- was not elevated above control levels in patients with severe septic shock. Conclusion: Admission levels of serum NO3- show great variability and are of negligible value in diagnosing and estimating prognosis in septic shock. Serum NO3- does not seem to be a useful variable to evaluate the role of nitric oxide in septic shock. Patients with lethal septic shock have significantly elevated preterminal serum levels of NO3- compared to healthy controls. However, NO3- levels are not consistently elevated in patients with irreversible septic shock compared to CAHD patients with the same degree of renal failure.