Renal blood flow and function during recovery from experimental septic acute kidney injury

Objective: To measure renal blood flow ( RBF) and renal function during recovery from experimental septic acute kidney injury ( AKI). Design: Controlled experimental study. Subjects: Nine merino ewes. Setting: University physiology laboratory. Intervention: We recorded systemic and renal hemodynamics during a 96- h observation period ( control) via implanted transit- time flow probes. We then compared this period with 96 h of septic AKI ( 48 h of Escherichia coli infusion) and subsequent recovery ( 48 h of observation after stopping E. coli). Measurements and results: Compared with the control period, E. coli infusion induced hyperdynamic sepsis ( increased cardiac output and decreased blood pressure) and septic AKI ( serum creatinine 65.4 +/- 8.7 vs. 139.9 +/- 33.0 mu mol/l; creatinine clearance 73.8 +/- 12.2 vs. 40.2 +/- 17.2 ml/ min; p < 0.05) with a mortality of 22%. RBF increased ( 278.8 +/- 33.9 vs. 547.9 +/- 124.8 ml/ min; p < 0.05) as did renal vascular conductance ( RVC). During recovery, we observed a decrease in RVC and RBF with all values returning to control levels. Indices of tubular function [ fractional excretion of sodium ( FENa) and urea ( FEUn) and urinary sodium concentration ( UNa)], which had been affected by sepsis, returned to control values after 18 h of recovery, as did serum creatinine. Conclusions: Infusion of E. coli induced a hyperdynamic circulatory state with hyperemic AKI. Recovery was associated with relative renal vasoconstriction and reduction in RBF and RVC back to control levels. Indices of tubular function normalized more rapidly than changes in RBF.