The effects of human burn injury on urinary nitrate excretion

Different studies have demonstrated both an increase and a decrease in the biosynthesis of nitric oxide (NO) during the first 2 days following experim ental and human burn trauma. This study investigated changes in urinary nit rate excretion in humans following thermal injury in order to determine the temporal relationship between NO release and the initial injury. Urinary n itrate was measured in daily 24-h urine collections taken on days 1-7 follo wing burn injury from 15 patients. The control group consisted of 11 health y, age- and sex-matched patients who kept a nitrate-restricted diet for fiv e days prior to collection of a single 24-h urine sample. The burns group h ad a mean age of 41.9 +/- 19.4 (mean +/- S.D.) years and a mean total burn surface area (TBSA) of 30.2 +/- 24.9% (mean +/- S.D.). In the burn injured patients, urinary nitrate levels peaked at day 4 and a 2-fold increase rela tive to day 1 was observed. Urinary nitrate levels were significantly highe r in the burns group than the control group on days 4 and 5 only (p < 0.05 for both days). There was no correlation between TBSA and the measured urin ary nitrate levels. This study confirms that the biosynthesis of NO is incr eased during the first week following burn trauma and establishes that the renal elimination of the by-products of NO metabolism is not increased duri ng the first three days after injury. Notwithstanding the potential effects of burns on nitrate distribution, our findings may reflect a delay in the release of NO following the initial insult. (C) 1999 Elsevier Science Ltd a nd ISBI. All rights reserved.