Comparison of Urine Output among Patients Treated with More Intensive Versus Less Intensive RRT: Results from the Acute Renal Failure Trial Network Study

Abstract

Background and objectives Intensive RRT may have adverse effects that account for the absence of benefit observed in randomized trials of more intensive versus less intensive RRT. We wished to determine the association of more intensive RRT with changes in urine output as a marker of worsening residual renal function in critically ill patients with severe AKI.Design, setting, participants, & measurements The Acute Renal Failure Trial Network Study (n=1124) was a multicenter trial that randomized critically ill patients requiring initiation of RRT to more intensive (hemodialysis or sustained low-efficiency dialysis six times per week or continuous venovenous hemodiafiltration at 35 ml/kg per hour) versus less intensive (hemodialysis or sustained low-efficiency dialysis three times per week or continuous venovenous hemodiafiltration at 20 ml/kg per hour) RRT. Mixed linear regression models were fit to estimate the association of RRT intensity with change in daily urine output in survivors through day 7 (n=871); Cox regression models were fit to determine the association of RRT intensity with time to $50% decline in urine output in all patients through day 28.Results Mean age of participants was 60615 years old, 72% were men, and 30% were diabetic. In unadjusted models, among patients who survived $7 days, mean urine output was, on average, 31.7 ml/d higher (95% confidence interval, 8.2 to 55.2 ml/d) for the less intensive group compared with the more intensive group (P50.01). More intensive RRT was associated with 29% greater unadjusted risk of decline in urine output of $50% (hazard ratio, 1.29; 95% confidence interval, 1.10 to 1.51).Conclusions More intensive versus less intensive RRT is associated with a greater reduction in urine output during the first 7 days of therapy and a greater risk of developing a decline in urine output of $50% in critically ill patients with severe AKI.

Does Changing the Volume Matter? The Relationship of Urine Volume and Dialysis Intensity

“…In fact, even in the ATN Study, urine output of .30 ml/h (720 ml/d) was one of the clinical criteria used to identify patients who might have renal recovery; these patients subsequently underwent a timed creatinine clearance to assess renal function (15). However, in this subgroup analysis of the ATN Study by McCausland et al (17), there were no reported differences in rates of dialysis dependence and presumably, no difference in time to renal recovery (although these data were not shown). Thus, it is not clear that the lower urine output observed here associates with less residual renal function.…”

“…Although this is a well executed study, we believe that some caution needs to be applied to the statement that the findings of this study are "consistent with a potentially early adverse effect of more intensive RRT on residual renal function" (17). There is no doubt that urine output is lower in those receiving more intensive RRT, and there is no doubt that clinicians often use urine output as a surrogate for early renal recovery.…”

“…They hypothesized that more intensive RRT would be associated with lower urine volumes (17). To avoid the competing risk of death, they focused on only those patients who survived to day 7 (n5871) (17). In line with the original study findings, there were no differences in the baseline characteristics of the two treatment arms in this subgroup.…”

“…Given the prior studies suggesting a potential relationship between lower urine volumes and adverse outcomes, McCausland et al (17) sought to explore the relationship of more intensive RRT with urine volume in the ATN Study. They hypothesized that more intensive RRT would be associated with lower urine volumes (17).…”

“…They hypothesized that more intensive RRT would be associated with lower urine volumes (17). To avoid the competing risk of death, they focused on only those patients who survived to day 7 (n5871) (17).…”