Kinetic estimated glomerular filtration rate as a predictor of successful continuous renal replacement therapy discontinuation

Weaning from Kidney Replacement Therapy in the Critically Ill Patient with Acute Kidney Injury

Around 10% of critically ill patients suffer acute kidney injury (AKI) requiring kidney replacement therapy (KRT), with a mortality rate approaching 50%. Although most survivors achieve sufficient renal recovery to be weaned from KRT, there are no recognized guidelines on the optimal period for weaning from KRT. A systematic review was conducted using a peer-reviewed strategy, combining themes of KRT (intermittent hemodialysis, CKRT: continuous veno-venous hemo/dialysis/filtration/diafiltration, sustained low-efficiency dialysis/filtration), factors predictive of successful weaning (defined as a prolonged period without new KRT) and patient outcomes. Our research resulted in studies, all observational, describing clinical and biological parameters predictive of successful weaning from KRT. Urine output prior to KRT cessation is the most studied variable and the most widely used in practice. Other predictive factors, such as urinary urea and creatinine and new urinary and serum renal biomarkers, including cystatin C and neutrophil gelatinase-associated lipocalin (NGAL), were also analyzed in the light of recent studies. This review presents the rationale for early weaning from KRT, the parameters that can guide it, and its practical modalities. Once the patient's clinical condition has stabilized and volume status optimized, a diuresis greater than 500 mL/day should prompt the intensivist to consider weaning. Urinary parameters could be useful in predicting weaning success but have yet to be validated.

Predictors for short-term successful weaning from continuous renal replacement therapy: a systematic review and meta-analysis

The systemic review and meta-analysis aimed to identify the predictors for short-term successful weaning from CRRT in severe AKI patients. PubMed, Embase, the Cochrane Library, and grey literature were searched for relevant studies investigating variables for short-term successful weaning from CRRT to August 2022. Our criteria included patients with AKI who required CRRT but excluded patients with kidney failure. The pooled odds ratios (OR) and 95% confidence intervals (CI) were calculated using fixed-effect (I²≤50% and P-value of the Q statistic > 0.1) or random-effect models (I²>50% or p-value of the Q statistic ≤ 0.1) as appropriate. Our search yielded 11 studies and described 11 variables. The pooled analysis showed that chronic kidney disease (OR = 0.638, 95% CI: 0.491-0.829), CRRT duration (OR = 0.913, 95% CI: 0.882-0.946), and urine output at the cessation of CRRT (per 100 mL/day increase) (OR = 1.084, 95% CI: 1.061-1.108) were predictive factors for short-term successful weaning from CRRT. Male (OR = 0.827, 95% CI: 0.627-1.092), diabetes mellitus (OR = 0.970, 95% CI: 0.761-1.237), and sepsis (OR = 0.911, 95% CI: 0.717-1.158) were unrelated to the short-term weaning from CRRT. The relationship between hypertension, use of vasopressors or inotropes at the starting of CRRT, use of vasopressors or inotropes at the cessation of CRRT, use of diuretics at the cessation of CRRT, serum creatinine at the cessation of CRRT, and short-term weaning from CRRT remains unclear. Additional prospective studies are needed to evaluate this relationship further.

When to discontinue renal replacement therapy. what do we know?

PURPOSE OF REVIEW

Acute kidney injury is common in intensive care patients. Supportive care involves the use of renal replacement therapies as organ support. Initiation of renal replacement therapy has been the subject of much interest over the last few years with several randomised controlled studies examining the optimal time to commence treatment. In contrast to this, little evidence has been generated regarding cessation of therapy. Given that this treatment is complex, not without risk and expensive it seems timely that efforts should be expended at examining this vexing issue.

RECENT FINDINGS

Although several studies have been reported examining the successful discontinuation of renal replacement therapies all studies reported to-date are observational in nature. Conventional biochemical criteria have been used as well as physiological parameters including urine output. More recently, more novel biomarkers of renal function have been studied. Although to-date no optimal variable nor threshold for discontinuation can be established.

SUMMARY

Several variables have been described which may have a role in determining which patients may be successfully weaned from renal replacement therapy. However, few have been exposed to vigorous examination and evidence is sparse in support of any potential approach although urine output currently is the most often described. More recently novel biomarkers have also been examined but again are limited by study design and heterogeneity. Further research is clearly needed focussing on proposed variables preferably in multivariate models to improve predictive ability and successful cessation of therapy.

Different Roles of Functional and Structural Renal Markers Measured at Discontinuation of Renal Replacement Therapy for Acute Kidney Injury

INTRODUCTION

Severe acute kidney injury (AKI) requiring renal replacement therapy (RRT) has been associated with an unacceptably high mortality of 50% or more. Successful discontinuation of RRT is thought to be linked to better outcomes. Although functional and structural renal markers have been evaluated in AKI, little is known about their roles in predicting outcomes at the time of RRT discontinuation.

METHODS

In this prospective single-center cohort study, we analyzed patients who received continuous RRT (CRRT) for AKI between August 2016 and March 2018 in the intensive care unit of the University of Tokyo Hospital (Tokyo, Japan). Clinical parameters and urine samples were obtained at CRRT discontinuation. Successful CRRT discontinuation was defined as neither resuming CRRT for 48 h nor receiving intermittent hemodialysis for 7 days from the CRRT termination. Major adverse kidney events (MAKEs) were defined as death, requirement for dialysis, or a decrease in the estimated glomerular filtration rate (eGFR) of more than 25% from the baseline at day 90.

RESULTS

Of 73 patients, who received CRRT for AKI, 59 successfully discontinued CRRT and 14 could not. Kinetic eGFR, urine volume, urinary neutrophil gelatinase-associated lipocalin (NGAL), and urinary L-type fatty acid binding protein were predictive for CRRT discontinuation. Of these factors, urine volume had the highest area under the curve (AUC) 0.91 with 95% confidence interval [0.80-0.96] for successful CRRT discontinuation. For predicting MAKEs at day 90, the urinary NGAL showed the highest AUC 0.76 [0.62-0.86], whereas kinetic eGFR and urine volume failed to show statistical significance (AUC 0.49 [0.35-0.63] and AUC 0.59 [0.44-0.73], respectively).

CONCLUSIONS

Our prospective study confirmed that urine volume, a functional renal marker, predicted successful discontinuation of RRT and that urinary NGAL, a structural renal marker, predicted long-term renal outcomes. These observations suggest that the functional and structural renal makers play different roles in predicting the outcomes of severe AKI requiring RRT.

A clinical model to predict successful renal replacement therapy (RRT) discontinuation in patients with Acute Kidney Injury (AKI)

INTRODUCTION

Ideal timing of Renal Replacement Therapy (RRT) discontinuation in Acute Kidney Injury (AKI) is still unknown. We aimed to study the role of creatinine-related variables in predicting RRT successful discontinuation and to propose a clinical predictive score.

METHODS

In this single-centre retrospective study, we evaluated all AKI patients in whom RRT was interrupted for at least 48 hours. Patients who were still RRT-independent 7 days after initial RRT cessation were included in the "Success" group and opposed to the "Failure" group. We evaluated baseline characteristics and variables collected at the time of RRT interruption, as well as the Kinetic estimated Glomerular Filtration Rate (KeGFR), the simple variation in serum Creatinine (ΔsCr), and the incremental creatinine ratio on the first three days after RRT interruption. Multivariable analysis was performed to evaluate prediction of success. Internal validation using a simple binomial generalized regression model with Lasso estimation and 5-fold cross validation method was performed.

RESULTS

We included 124 patients, 49 in the "Failure" group and 75 in the "Success" group. All creatinine-related variables predicted success in simple and multiple logistic regression models. The best model generated a clinical score based on the odds ratio obtained for each variable and included urine output, non-renal SOFA score, fluid balance, serum urea, serum potassium, blood pH, and the variation in sCr values after RRT discontinuation. The score presented an area under the ROC of 0.86 (95% CI 0.76‒1.00).

CONCLUSION

Creatinine variation between the first 2 consecutive days after RRT discontinuation might predict success in RRT discontinuation. The developed clinical score based on these variables might be a useful clinical decision tool to guide hemodialysis catheter safe removal.

Prolonged exposure to continuous renal replacement therapy in patients with acute kidney injury

BACKGROUND

Little is known about the process of deciding to discontinue continuous renal replacement therapy (CRRT) in patients with acute kidney injury (AKI) and the impact of CRRT duration on outcomes.

METHODS

We report the clinical parameters of prolonged CRRT exposure and predictors of doubling of serum creatinine or need for dialysis at 90 days after CRRT with propensity score matching, including covariates that were likely to influence patients in the prolonged CRRT group.

RESULTS

Among 104 survey responders, most use urine output (87%) to guide CRRT discontinuation, 24% use improvement in clinical or hemodynamic status. In the cohort study, of 854 included patients, 465 participated in the assessment of kidney recovery. Patients with prolonged CRRT had higher SOFA scores (11.9 vs. 11.2) and were more likely to be mechanically ventilated (99% vs. 84%) at CRRT initiation compared to patients without prolonged CRRT, p-value < 0.05. In multivariable logistic regression, daily urine output and cumulative fluid balance leading to CRRT discontinuation or day seven were independently associated with lower [OR 0.87 per 200 ml/day increase] and higher odds [OR 1.03 per 1-L increase] of requiring prolonged CRRT, respectively. After propensity score matching, prolonged exposure to CRRT was independently associated with increased risk of doubling serum creatinine or dialysis at 90 days, OR 3.1 (95% CI 1.23-8.3 p = 0.017).

CONCLUSIONS

Resolution of critical illness and signs of kidney recovery are important factors when considering CRRT discontinuation. Prolonged CRRT exposure may be associated with less chance of kidney recovery among survivors.

Continuous Renal Replacement Therapy Liberation and Outcomes of Critically Ill Patients With Acute Kidney Injury

OBJECTIVE

To examine the association between continuous renal replacement therapy (CRRT) liberation and clinical outcomes among patients with acute kidney injury (AKI) requiring CRRT.

METHODS

This single-center, retrospective cohort study included adult patients admitted to intensive care units with AKI and treated with CRRT from January 1, 2007, to May 4, 2018. Based on the survival and renal replacement therapy (RRT) status at 72 hours after the first CRRT liberation, we classified patients into liberated, reinstituted, and those who died. We observed patients for 90 days after CRRT initiation to compare the major adverse kidney events (MAKE₉₀).

RESULTS

Of 1135 patients with AKI, 228 (20%), 437 (39%), and 470 (41%) were assigned to liberated, reinstituted, and nonsurvival groups, respectively. The MAKE₉₀, mortality, and RRT independence rates of the cohort were 62% (707 cases), 59% (674 cases), and 40% (453 cases), respectively. Compared with reinstituted patients, the liberated group had a lower MAKE₉₀ (29% vs 39%; P=.009) and higher RRT independence rate (73% vs 65%; P=.04) on day 90, but without significant difference in 90-day mortality (26% vs 33%; P=.05). After adjustments for confounders, successful CRRT liberation was not associated with lower MAKE₉₀ (odds ratio, 0.71; 95% CI, 0.48 to 1.04; P=.08) but was independently associated with improved kidney recovery at 90-day follow-up (hazard ratio, 1.81; 95% CI, 1.41 to 2.32; P<.001).

CONCLUSION

Our study demonstrated a high occurrence of CRRT liberation failure and poor 90-day outcomes in a cohort of AKI patients treated with CRRT.

Predicting successful continuous renal replacement therapy liberation in critically ill patients with acute kidney injury

PURPOSE

No standardized criteria for continuous renal replacement therapy (CRRT) liberation have been established. We sought to develop and internally validate prediction models for successful CRRT liberation in critically ill patients with acute kidney injury (AKI).

MATERIALS AND METHODS

This single-center, retrospective cohort study included adult patients admitted to intensive care units (ICUs) with AKI and treated with CRRT from January 1, 2007, to May 4, 2018, at a tertiary referral hospital. The cohort was randomly divided into derivation and validation sets. The outcomes were successful CRRT liberation, defined as renal replacement therapy (RRT)-free survival within 72 h after the liberation and hospital discharge. Multivariate logistic regression models were developed and internally validated.

RESULTS

Of 1135 AKI patients requiring CRRT, successful CRRT liberation and RRT-free survival at hospital discharge were observed in 228 (20%) and 395 (35%) individuals, respectively. The independent predictors included mean hourly urine output within 12 h before liberation, mean serum creatinine value within 24 h before liberation, cumulative fluid balance from ICU admission to liberation, CRRT duration before liberation, and the requirement of vasoactive agents within 24 h before liberation. The models demonstrated good discrimination (AUROC, 0.76 and 0.78; positive predictive value, 36% and 48%; negative predictive value, 92% and 94%; respectively) and calibration in the validation set.

CONCLUSIONS

These validated models could assist the decision-making related to the CRRT liberation in critically ill patients with AKI.

In creatinine kinetics, the glomerular filtration rate always moves the serum creatinine in the opposite direction

INTRODUCTION

When the serum [creatinine] is changing, creatinine kinetics can still gauge the kidney function, and knowing the kinetic glomerular filtration rate (GFR) helps doctors take care of patients with renal failure. We wondered how the serum [creatinine] would respond if the kinetic GFR were tweaked. In every scenario, if the kinetic GFR decreased, the [creatinine] would increase, and vice versa. This opposing relationship was hypothesized to be universal.

METHODS

Serum [creatinine] and kinetic GFR, along with other parameters, are described by a differential equation. We differentiated [creatinine] with respect to kinetic GFR to test if the two variables would change oppositely of each other, throughout the gamut of all allowable clinical values. To remove the discontinuities in the derivative, limits were solved.

RESULTS

The derivative and its limits were comprehensively analyzed and proved to have a sign that is always negative, meaning that [creatinine] and kinetic GFR must indeed move in opposite directions. The derivative is bigger in absolute value at the higher end of the [creatinine] scale, where a small drop in the kinetic GFR can cause the [creatinine] to shoot upward, making acute kidney injury similar to chronic kidney disease in that regard.

CONCLUSIONS

All else being equal, a change in the kinetic GFR obligates the [creatinine] to change in the opposite direction. This does not negate the fact that an increasing [creatinine] can be compatible with a rising kinetic GFR, due to differences in how the time variable is treated.

A Scoring Model with Simple Clinical Parameters to Predict Successful Discontinuation of Continuous Renal Replacement Therapy

BACKGROUND

Continuous renal replacement therapy (CRRT) is the standard treatment for severe acute kidney injury in critically ill patients. However, a practical consensus for discontinuing CRRT is lacking. We aimed to develop a prediction model with simple clinical parameters for successful discontinuation of CRRT.

METHODS

Adult patients who received CRRT at Samsung Medical Center from 2007 to 2017 were included. Patients with preexisting ESRD and patients who progressed to ESRD within 1 year or died within 7 days after CRRT were excluded. Successful discontinuation of CRRT was defined as no requirement for renal replacement therapy for 7 days after discontinuing CRRT. Patients were assigned to either a success group or failure group according to whether discontinuation of CRRT was successful or not.

RESULTS

A total of 1,158 patients were included in the final analyses. The success group showed greater urine output on the day before CRRT discontinuation (D-1) and the discontinuation day (D0). Multivariable analysis identified that urine output ≥300 mL on D-1, and mean arterial pressure 50∼78 mm Hg, serum potassium <4.1 mmol/L, and BUN <35 mg/dL (12.5 mmol/L) on D0 were predictive factors for successful discontinuation of CRRT. A scoring system using the 4 variables above (area under the receiver operating curve: 0.731) was developed.

CONCLUSIONS

Scoring system composed of urine output ≥300 mL/day on D-1, and adequate blood pressure, serum potassium <4.1 mmol/L, and BUN <35 mg/dL (12.5 mmol/L) on D0 was developed to predict successful discontinuation of CRRT.

Predictors of successful discontinuation from renal replacement therapy during AKI: A meta-analysis

The predictors of weaning time of renal replacement therapy (RRT) remain controversial for special patients suffering from acute kidney injury (AKI). The present work aims to perform a meta-analysis to evaluate proper predictors of RRT weaning in AKI patients. We systematically searched EMBASE, PubMed, and Cochrane Central Register of Controlled trials for literatures between 1984 and June 2019. Studies evaluating predictors of weaning success of RRT in patients of AKI were included. Random-effects model or fixed-effects model meta-analyses were performed to compute a standard mean difference (SMD). Newcastle-Ottawa Scale was employed to assess the risk of bias. We included 10 observational trials including 1453 patients. Twelve predictors including urine output, serum creatinine, serum urea, mean arterial pressure, central venous pressure, lactate, serum potassium, serum bicarbonate, pH value, SOFA score, urinary urea, and urinary creatinine were identified, showing urine output (p = 0.0000), serum creatinine (p = 0.008), serum potassium (p = 0.02), serum bicarbonate (p = 0.01), pH value (p = 0.03), urinary urea (p = 0.002), and urinary creatinine (p = 0.02) were significantly associated with weaning success. With the limited evidence, we speculate that urine output, serum creatinine, serum potassium, serum bicarbonate, pH value, urinary urea, and urinary creatinine might be associated with successful weaning.

The need for disruptive innovation in acute kidney injury

Acute kidney injury (AKI) is a threatening medical condition associated with poor outcomes at different settings. The development of standardized diagnostic criteria and new biomarkers addressed significant clinical impacts of AKI and the need for an early AKI detection, respectively. There have been some breakthroughs in understanding the pathogenesis of AKI through basic research; however, treatments against AKI aside from renal replacement therapy (RRT) have not shown adequate successful results. Biomarkers that could identify good responders to certain treatment are expected to facilitate translation of basic research findings. Most patients with severe AKI treated with RRT died due to multiple-organ failure, not renal dysfunction. Hence, it is essential to identify other organ dysfunctions induced by AKI as organ crosstalk. Also, a multidisciplinary approach of critical care nephrology is needed to evaluate a complex organ crosstalk in AKI. For disruptive innovation for AKI, we further explore these new aspects of AKI, which previously were considered outside the scope of nephrology.

Current Approach to Successful Liberation from Renal Replacement Therapy in Critically Ill Patients with Severe Acute Kidney Injury: The Quest for Biomarkers Continues

Recovery of sufficient kidney function to liberate patients with severe acute kidney injury (AKI-D) from renal replacement therapy (RRT) is recognized as a vital patient-centred outcome. However, no clinical consensus guideline provides specific recommendations on when and how to stop RRT in anticipation of renal recovery from AKI-D. Currently, wide variations in clinical practice regarding liberation from RRT result in early re-start of RRT to treat uraemia after premature liberation or in the unnecessary prolonged exposure of unwell patients after late liberation. Observational studies, predominantly retrospective in nature, have attempted to assess numerous surrogate markers of kidney function or of biomarkers of kidney damage to predict successful liberation from RRT. However, a substantial heterogeneity in the timing of measurement and cut-off values of most biomarkers across studies allows no pooling of data, and impedes the comparison of outcomes from such studies. The accuracy of most traditional and novel biomarkers cannot be assessed reliably. Currently, the decision to discontinue RRT in AKI-D patients relies on daily clinical assessments of the patient’s status supplemented by measurement of creatinine clearance (> 15 ml/min) and 24-h urine output (> 2000 ml/min with diuretics). Clinical trials objectively comparing the success of validated biomarkers for guiding optimal timed liberation from RRT in AKI-D will be required to provide high-quality evidence for guidelines.

Estimating Creatinine Clearance in the Nonsteady State: The Determination and Role of the True Average Creatinine Concentration

Creatinine clearance is a tenet of nephrology practice. However, with just a single creatinine concentration included in the denominator of the creatinine clearance equation, the resulting value seems to apply only in the steady state. Does the basic clearance formula work in the nonsteady state, and can it recapitulate the kinetic glomerular filtration rate (GFR) equation? In the kinetic state, a nonlinear creatinine trajectory is reducible into a “true average” value that can be found using calculus, proceeding from a differential equation based on the mass balance principle. Using the fundamental theorem of calculus, we prove definitively that the true average is the correct creatinine to divide by, even as the mathematical model accommodates clinical complexities such as volume change and other factors that affect creatinine kinetics. The true average of a creatinine versus time function between 2 measured creatinine values is found by a definite integral. To use the true average to compute kinetic GFR, 2 techniques are demonstrated, a graphical one and a numerical one. We apply this concept to a clinical case of an individual with acute kidney injury requiring dialysis; despite the effects of hemodialysis on serum creatinine concentration, kinetic GFR was able to track the underlying kidney function and provided critical information regarding kidney function recovery. Finally, a prior concept of the maximum increase in creatinine per day is made more clinically objective. Thus, the clearance paradigm applies to the nonsteady state as well when the true average creatinine is used, providing a fundamentally valid strategy to deduce kinetic GFRs from serum creatinine trends occurring in real-life acute kidney injury and kidney recovery.

A meta-analysis of clinical predictors for renal recovery and overall mortality in acute kidney injury requiring continuous renal replacement therapy

PURPOSE

To determine clinical predictors for continuous renal replacement therapy (CRRT) discontinuation in patients with acute kidney injury (AKI).

MATERIALS AND METHODS

Ovid MEDLINE, EMBASE, and Cochrane Library were searched. The protocol is registered on researchregistry.com (reviewregistry909). Our criteria included non-end-stage kidney disease adults who required CRRT for AKI. Renal recovery was defined by CRRT discontinuation. Risk of bias was assessed using ROBINS-I tool.

RESULTS

We classified our analyses into renal recovery cohort and overall mortality cohort. All studies were observational. For renal recovery cohort, increasing urine output at time of CRRT discontinuation, elevated initial SOFA score and serum creatinine at CRRT initiation were predictive of renal recovery with OR 1.021 (95%CI = 1.011-1.031), 0.869 (95%CI = 0.811-0.932) and 0.995 (95%CI = 0.996-0.999), respectively. For overall mortality cohort, age and presence of sepsis were significantly associated with overall mortality with OR of 1.028 (95%CI = 1.008-1.048) and 2.160 (95%CI = 0.973-1.932), respectively.

CONCLUSIONS

Urine output at CRRT discontinuation, lower initial SOFA score, and lower serum creatinine levels at CRRT initiation were associated with higher likelihood of renal recovery. Increasing age and the presence of sepsis were associated with increased overall mortality from AKI on CRRT. However, there were limited data on co-morbidities which might preclude their inclusion in our analysis.

Determining the optimal time for liberation from renal replacement therapy in critically ill patients: a systematic review and meta-analysis (DOnE RRT)

INTRODUCTION

Renal replacement therapy (RRT) is associated with high mortality and costs; however, no clinical guidelines currently provide specific recommendations for clinicians on when and how to stop RRT in recovering patients. Our objective was to systematically review the current evidence for clinical and biochemical parameters that can be used to predict successful discontinuation of RRT.

METHODS

A systematic review and meta-analysis were performed with a peer-reviewed search strategy combining the themes of renal replacement therapy (IHD, CRRT, SLED), predictors of successful discontinuation or weaning (defined as an extended period of time free from further RRT), and patient outcomes. Major databases were searched and citations were screened using predefined criteria. Studied parameters were reported and, where possible, data was analyzed in the pooled analysis.

RESULTS

Our search yielded 23 studies describing 16 variables for predicting the successful discontinuation of RRT. All studies were observational in nature. None were externally validated. Fourteen studies described conventional biochemical criteria used as surrogates of glomerular filtration rate (serum urea, serum creatinine, creatinine clearance, urine urea excretion, urine creatinine excretion). Thirteen studies described physiologic parameters such as urine output before and after cessation of RRT, and 13 studies reported on newer kidney biomarkers, such as serum cystatin C and serum neutrophil gelatinase-associated lipocalin (NGAL). Six studies reported sensitivity and specificity characteristics of multivariate models. Urine output prior to discontinuation of RRT was the most-studied variable, with nine studies reporting. Pooled analysis found a sensitivity of 66.2% (95% CI, 53.6-76.9%) and specificity of 73.6% (95% CI, 67.5-79.0%) for urine output to predict successful RRT discontinuation. Due to heterogeneity in the thresholds of urine output used across the studies, an optimal threshold value could not be determined.

CONCLUSIONS

Numerous variables have been described to predict successful discontinuation of RRT; however, available studies are limited by study design, variable heterogeneity, and lack of prospective validation. Urine output prior to discontinuation of RRT was the most commonly described and robust predictor. Further research should focus on the determination and validation of urine output thresholds, and the evaluation of additional clinical and biochemical parameters in multivariate models to enhance predictive accuracy.