Association between Net Ultrafiltration Rate and Renal Recovery among Critically Ill Adults with Acute Kidney Injury Receiving Continuous Renal Replacement Therapy: An Observational Cohort Study

Abstract

<b><i>Introduction:</i></b> Higher net ultrafiltration (UF<sub>NET</sub>) rates are associated with mortality among critically ill patients with acute kidney injury (AKI) and treated with continuous renal replacement therapy (CRRT). <b><i>Objective:</i></b> The aim of the study was to discover whether UF<sub>NET</sub> rates are associated with renal recovery and independence from renal replacement therapy (RRT). <b><i>Methods:</i></b> Retrospective cohort study using data from the Randomized Evaluation of Normal versus Augmented Level of Renal Replacement Therapy trial that enrolled 1,433 critically ill patients with AKI and treated with CRRT between December 2005 and November 2008 across 35 intensive care units in Australia and New Zealand. We examined the association between UF<sub>NET</sub> rate and time to independence from RRT by day 90 using competing risk regression after accounting for mortality. The UF<sub>NET</sub> rate was defined as the volume of fluid removed per hour adjusted for patient body weight. <b><i>Results and Conclusions:</i></b> Median age was 67.3 (interquartile range [IQR], 57–76.3) years, 64.4% were male, median Acute Physiology and Chronic Health Evaluation-III score was 100 (IQR, 84–118), and 634 (44.2%) died by day 90. Kidney recovery occurred in 755 patients (52.7%). Using tertiles of UF<sub>NET</sub> rates, 3 groups were defined: high, >1.75; middle, 1.01–1.75; and low, <1.01 mL/kg/h. Proportion of patients alive and independent of RRT among the groups were 47.8 versus 57.2 versus 53.0%; <i>p</i> = 0.01. Using competing risk regression, higher UF<sub>NET</sub> rate tertile compared with middle (cause-specific hazard ratio [csHR], 0.79, 95% CI, 0.66–0.95; subdistribution hazard ratio [sHR], 0.80, 95% CI, 0.67–0.97) and lower (csHR, 0.69, 95% CI, 0.56–0.85; sHR, 0.78, 95% CI 0.64–0.95) tertiles were associated with a longer time to independence from RRT. Every 1.0 mL/kg/h increase in rate was associated with a lower probability of kidney recovery (csHR, 0.81, 95% CI, 0.74–0.89; and sHR, 0.87, 95% CI, 0.80–0.95). Using the joint model, longitudinal increases in UF<sub>NET</sub> rates were also associated with a lower renal recovery (β = −0.29, <i>p</i> < 0.001). UF<sub>NET</sub> rates >1.75 mL/kg/h compared with rates 1.01–1.75 and <1.01 mL/kg/h were associated with a longer duration of dependence on RRT. Randomized clinical trials are required to confirm this UF<sub>NET</sub> rate-outcome relationship.

Acute kidney injury-associated delirium: a review of clinical and pathophysiological mechanisms

“…Ultrafiltration may be an intuitive approach to addressing AKI-associated delirium, due to fluid overload; however, any potential benefits of ultrafiltration need to be balanced with the concerns related to cerebral hypoperfusion [ 95 ] and worsened renal recovery [ 96 ]. Although delirium has not been specifically evaluated in prior studies using ultrafiltration, prior studies have shown improved rates of extracerebral organ dysfunction with lower compared to higher rates of ultrafiltration [ 96 ]. Future studies are needed to examine the viability of ultrafiltration in hypervolemic patients with AKI to mitigate delirium.…”

Association of Intradialytic Hypotension and Ultrafiltration with AKI-D Outcomes in the Outpatient Dialysis Setting

“…Murugan et al undertook two studies on the same cohort of critically ill AKI-D patients treated with CRRT in Australia and New Zealand (n = 1433) to determine the association between net UF rate and time to renal recovery [ 18 , 19 ]. The studies showed that higher net UF (>1.75 mL/kg/hour) correlated with more time to renal recovery and lower incidence of patient survival.…”

“…Modifiable factors that may play a role in predicting and hence promoting better care of AKI-D include the dialysis prescription and the dialysis procedure in the outpatient setting. However, most studies assessing the role of dialysis prescriptions on AKI-D patient outcomes have been conducted in the inpatient setting [ 18 , 19 , 20 , 21 , 22 ].…”

A Case Series: Continuous Kidney Replacement Therapy in Neonates With Low Body Weight

“…However, another study revealed an association between higher net ultrafiltration and improved survival rate ( 32 ). Similarly, the association between net ultrafiltration rate and renal recovery rate has yet to be established ( 33 ). Other factors, such as fluid overload status and input fluid volumes, may influence clinical outcomes and should also be carefully considered ( 34 ).…”