NDT Advance Access originally published online on September 23, 2006
Nephrology Dialysis Transplantation 2006 21(12):3389-3397; doi:10.1093/ndt/gfl541
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Urinary biochemistry in experimental septic acute renal failure
1Department of Intensive Care and Department of Medicine, Austin Hospital and University of Melbourne, Heidelberg, Melbourne and 2Howard Florey Institute, University of Melbourne, Parkville, Melbourne, Australia
Correspondence and offprint requests to: Prof. Rinaldo Bellomo, Department of Intensive Care, Austin and Repatriation Medical Centre, Heidelberg, Victoria 3084, Australia. Email: rinaldo.bellomo{at}austin.org.au
Background. Several biochemical urine tests and derived indices are reported as useful in the diagnosis of acute renal failure (ARF) and its classification in prerenal (hypoperfusion) or intrarenal (acute tubular) necrosis. However, they have not been adequately studied in sepsis, the most frequent cause of ARF in ICU.
Methods. In 10 female Merino ewes, we implanted flow probes around the pulmonary and renal arteries to measure cardiac output and renal blood flow (RBF) continuously. Cardiovascular variables were monitored and urine samples collected during a 48 h control period and one week later during a 48 h period of hyperdynamic sepsis induced by an infusion of live Escherichia coli.
Results. Infusion of live E. coli induced systemic hyperdynamic sepsis with renal vasodilatation and increased RBF. Serum creatinine increased from 73.3 ± 15.1 to 276.9 ± 156.3 µmol/l (P < 0.05) and creatinine clearance decreased from 84.6 ± 21.4 to 27.5 ± 21.4 ml/min (P < 0.05). Urine sodium concentration (UNa) decreased significantly from 164.5 ± 50.4 to 14.6 ± 14.3 mmol/l, fractional excretion of sodium (FeNa) from 1.5 ± 0.17 to 0.12 ± 0.11%, fractional excretion of urea nitrogen (FeUn) from 62.7 ± 9.5 to 11.5 ± 15.4%, and urine osmolality from 724.8 ± 277.1 mosmol/l to 329.0 ± 52.1 mosmol/l. The u/p creatinine ratio did not change.
Conclusion. Sustained Gram-negative sepsis induced a hyperdynamic state and hyperaemic ARF. Despite increased renal perfusion, UNa, FeNa and FeUn decreased significantly. Our findings suggest that, in sepsis, these urinary biochemical changes are not reliable markers of renal hypoperfusion.
Keywords: acute renal failure; fractional excretion of sodium; fractional excretion of urea nitrogen; renal blood flow; sepsis; urinary marker
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  S. M. Bagshaw, S. Uchino, R. Bellomo, H. Morimatsu, S. Morgera, M. Schetz, I. Tan, C. Bouman, E. Macedo, N. Gibney, et al. Septic Acute Kidney Injury in Critically Ill Patients: Clinical Characteristics and Outcomes Clin. J. Am. Soc. Nephrol., May 1, 2007; 2(3): 431 - 439. [Abstract] [Full Text] [PDF]
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