Diuretics are frequently given to treat acute oliguric renal failure, but the response to diuretics in this setting may actually be a marker for severe disease rather than a valid response to therapy. Mehta and colleagues hypothesize that the use of diuretics for treatment of acute renal failure is associated with increased mortality, increased hospital stay, and nonrecovery of renal function caused by a direct toxic effect or as an indirect effect secondary to a delay in dialysis.

Acute renal failure was defined by an increased blood urea nitrogen level (40 mg per dL or higher [14.3 mmol per L or higher]) or a sustained rise in serum creatinine (1 mg per dL [88.4 μmol per L] or more). The main outcome measure was all-cause hospital mortality, with the combined end point of mortality or nonrecovery of renal function and lengths of intensive care unit and hospital stay. The authors defined characteristics of patients with acute renal failure taking diuretics and calculated propensity scores to predict the likelihood of diuretic use based on the listed characteristics.

Of 552 patients, 294 (53 percent) died in the hospital, with 56 (19) of these patients recovering renal function before death. Of the 258 surviving patients (47 percent), 17 (7 percent) were dependent on dialysis after discharge. Diuretic use was associated with a 68 percent increase in in-hospital mortality and a 77 percent increase in the odds of death or nonrecovery of renal function. There was no difference in hospital length of stay when diuretics were used on the first day of consultation. However, subsequent use of diuretics was associated with significantly longer lengths of stay (median difference, four to 10 days). The median time from consultation to first dialysis was also significantly prolonged among patients given diuretics (median difference, one to two days).

While there was no difference in these findings with single versus combination diuretic use, patients given higher-dose equivalents (arbitrarily set at a per milliliter ratio greater than or equal to 1) had higher odds of death or nonrecovery than nonusers of diuretics. Patients with a lower dose equivalent experienced no increase in risk.

In this study, diuretic use was significantly associated with in-hospital mortality and non-recovery of renal function, even after adjustment for nonrandom treatment assignment using propensity scores as a guide. The increased risk related primarily to patients who were relatively resistant to diuretics, with blood urea nitrogen levels rising faster in these patients than in diuretic-responsive patients. The authors conclude that widespread use of high-dose diuretics in critically ill patients with acute renal failure should be discouraged.