Objectives: The furosemide stress test measures the volume of urine produced after a furosemide challenge. Furosemide stress test has previously demonstrated sensitive and specific prediction of progression to Kidney Disease: Improving Global Outcomes guideline defined acute kidney injury stage III in the ICU. Furosemide is actively excreted into the nephron lumen where it inhibits the sodium-potassium-chloride cotransporter, causing diuresis. We hypothesize that furosemide excretion is a more direct measure of tubule health than diuresis.
Design: We developed a furosemide excretion stress test to evaluate this hypothesis in a murine model of septic-acute kidney injury.
Setting: Basic science laboratory.
Subjects: Male and female 8-week old CD-1 mice.
Interventions: Sepsis was induced by cecal ligation and puncture in male and female mice. Furosemide stress test/furosemide excretion stress test started 42 hours post-cecal ligation and puncture with a 1 mg/kg furosemide bolus and urine was collected for 12 hours. The mice were then euthanized or monitored until 7 days post-cecal ligation and puncture. In another cohort, mice were treated with vasopressin, which decreases urine volume. Furosemide concentration was determined by high performance liquid chromatography.
Measurements and main results: Urine production during the 12-hour collection varied from 0.08 to 2.62 mL. Both urine production (furosemide stress test) and furosemide excretion (furosemide excretion stress test) predicted mortality (area under the receiver operating characteristic curve = 0.925 and 0.916) and time of death (R 2 = 0.26 and 0.74). Male and female mice demonstrated consistent results. Following vasopressin treatment, furosemide stress test specificity fell to 33% (p = 0.016) but furosemide excretion stress test specificity was maintained.
Conclusions: The furosemide stress test and furosemide excretion stress test performed similarly in predicting mortality; however, furosemide excretion stress test was superior in predicting time to death and maintained performance when challenged with vasopressin treatment in a mouse sepsis model.
Keywords: acute kidney injury; distal tubule; furosemide; proximal tubule; sepsis.