Oliguria, volume overload, and loop diuretics

Acute kidney injury (AKI) is commonly and increasingly encountered in patients with critical illness. In the past, epidemiologic studies have consistently found that oliguria further increases the risk of death from AKI. Compared with patients outside the intensive care unit (ICU), critically ill patients are more likely to have volume overload as a result of impaired solute and water excretion. Recently, broad changes have occurred in ICU practice, such as early goal-directed therapy in sepsis, which may further compound volume overload in the ICU patient with oliguric AKI. Evidence has also emerged to suggest that a positive fluid accumulation in ICU patients can unfavorably affect outcome. Thus, the ICU patient with oliguric AKI presents a dilemma with limited therapeutic options. These would include optimization of systemic hemodynamics, added fluid therapy, administration of loop diuretics, or finally, the initiation of renal replacement therapy. Interestingly, recent survey data and observational studies indicate that a majority of intensivists use loop diuretics, specifically furosemide, at some point during the course of illness in patients with AKI. Paradoxically, loop diuretics have been found in several clinical studies of patients with AKI to be potentially detrimental or, at the least, lack effectiveness for improving clinical outcomes. This contradiction between clinical practice and available evidence would suggest there is equipoise and need for higher-quality evidence to better characterize the role of loop diuretics in ICU patients with AKI.