A multicenter comparison of dialysis membranes in the treatment of acute renal failure requiring dialysis

Novel method to recover Salmonella enterica cells for Tn-Seq approaches from lettuce leaves and agricultural environments using combination of sonication, filtration, and dialysis membrane

Salmonella enterica in agricultural environments has become an important concern, due to its potential transmission to humans and the associated public health risks. To identify genes contributing to Salmonella adaptation to such environments, transposon sequencing has been used in recent years. However, isolating Salmonella from atypical hosts, such as plant leaves, can pose technical challenges due to low bacterial content and the difficulty to separate an adequate number of bacteria from host tissues. In this study, we describe a modified methodology using a combination of sonication and filtration to recover S. enterica cells from lettuce leaves. We successfully recovered over a total of 3.5 × 106Salmonella cells in each biological replicate from two six-week old lettuce leaves, 7 days after infiltration with a Salmonella suspension of 5 × 107 colony forming units (CFU)/mL. Moreover, we have developed a dialysis membrane system as an alternative method for recovering bacteria from culture medium, mimicking a natural environment. Inoculating 107 CFU/mL of Salmonella into the media based on plant (lettuce and tomato) leaf and diluvial sand soil, a final concentration of 109.5 and 108.5 CFU/mL was obtained, respectively. One millilitre of the bacterial suspension after 24 h incubation at 28 °C using 60 rpm agitation was pelleted, corresponding to 109.5 and 108.5 cells from leaf- or soil-based media. The recovered bacterial population, from both lettuce leaves and environment-mimicking media, can adequately cover a presumptive library density of 106 mutants. In conclusion, this protocol provides an effective method to recover a Salmonella transposon sequencing library from in planta and in vitro systems. We expect this novel technique to foster the study of Salmonella in atypical hosts and environments, as well as other comparable scenarios.

Prescribing Continuous Kidney Replacement Therapy in Acute Kidney Injury: A Narrative Review

Severe acute kidney injury is a common complication in critically ill patients, often necessitating support with a modality of kidney replacement therapy. Continuous kidney replacement therapies (CKRTs) have become a mainstay in the management of patients with acute kidney injury in the intensive care unit. Understanding the fundamentals of CKRT is necessary to safely and effectively prescribe treatment. In this narrative review, we summarize critical aspects of CKRT management, including selection of the mode of therapy; choice of hemofilter/hemodialyzer used; determination of the blood flow rate, composition and flow rates of dialysate and/or replacement fluids, and the ultrafiltration rate; and use and methods of anticoagulation. Requirements for vascular access and appropriate monitoring and dose adjustment of medications and a plan for monitoring the delivery of therapy and ensuring appropriate nutritional management are also discussed.

Non-pharmacological interventions for preventing clotting of extracorporeal circuits during continuous renal replacement therapy

BACKGROUND

Acute kidney injury (AKI) is a common complication amongst people who are critically ill, and it is associated with an increased risk of death. For people with severe AKI, continuous kidney replacement therapy (CKRT), which is delivered over 24 hours, is needed when they become haemodynamically unstable. When CKRT is interrupted due to clotting of the extracorporeal circuit, the delivered dose is decreased and thus leading to undertreatment.

OBJECTIVES

This review assessed the efficacy of non-pharmacological measures to maintain circuit patency in CKRT.

SEARCH METHODS

We searched the Cochrane Kidney and Transplant Register of Studies up to 25 January 2021 which includes records identified through searches of CENTRAL, MEDLINE, and EMBASE, conference proceedings, the International Clinical Trials Register (ICTRP) Search Portal, and ClinicalTrials.gov.

SELECTION CRITERIA

We included all randomised controlled trials (RCTs) (parallel-group and cross-over studies), cluster RCTs and quasi-RCTs that examined non-pharmacological interventions to prevent clotting of extracorporeal circuits during CKRT.  DATA COLLECTION AND ANALYSIS: Three pairs of review authors independently extracted information including participants, interventions/comparators, outcomes, study methods, and risk of bias. The primary outcomes were circuit lifespan and death due to any cause at day 28. We used a random-effects model to perform quantitative synthesis (meta-analysis). We assessed risk of bias in included studies using the Cochrane Collaboration's tool for assessing risk of bias. Summary estimates of effect were obtained using a random-effects model, and results were expressed as risk ratios (RR) and their 95% confidence intervals (CI) for dichotomous outcomes, and mean difference (MD) and 95% CI for continuous outcomes. Confidence in the evidence was assessed using the Grading of Recommendations Assessment, Development and Evaluation (GRADE) approach.

MAIN RESULTS

A total of 20 studies involving 1143 randomised participants were included in the review. The methodological quality of the included studies was low, mainly due to the unclear randomisation process and blinding of the intervention. We found evidence on the following 11 comparisons: (i) continuous venovenous haemodialysis (CVVHD) versus continuous venovenous haemofiltration (CVVH) or continuous venovenous haemodiafiltration (CVVHDF); (ii) CVVHDF versus CVVH; (iii) higher blood flow (≥ 250 mL/minute) versus standard blood flow (< 250 mL/minute); (iv) AN69 membrane (AN69ST) versus other membranes; (v) pre-dilution versus post-dilution; (vi) a longer catheter (> 20 cm) placing the tip targeting the right atrium versus a shorter catheter (≤ 20 cm) placing the tip in the superior vena cava; (vii) surface-modified double-lumen catheter versus standard double-lumen catheter with identical geometry and flow design; (viii) single-site infusion anticoagulation versus double-site infusion anticoagulation; (ix) flat plate filter versus hollow fibre filter of the same membrane type; (x) a filter with a larger membrane surface area versus a smaller one; and (xi) a filter with more and shorter hollow fibre versus a standard filter of the same membrane type. Circuit lifespan was reported in 9 comparisons. Low certainty evidence indicated that CVVHDF (versus CVVH: MD 10.15 hours, 95% CI 5.15 to 15.15; 1 study, 62 circuits), pre-dilution haemofiltration (versus post-dilution haemofiltration: MD 9.34 hours, 95% CI -2.60 to 21.29; 2 studies, 47 circuits; I² = 13%), placing the tip of a longer catheter targeting the right atrium (versus placing a shorter catheter targeting the tip in the superior vena cava: MD 6.50 hours, 95% CI 1.48 to 11.52; 1 study, 420 circuits), and surface-modified double-lumen catheter (versus standard double-lumen catheter: MD 16.00 hours, 95% CI 13.49 to 18.51; 1 study, 262 circuits) may prolong circuit lifespan. However, higher blood flow may not increase circuit lifespan (versus standard blood flow: MD 0.64, 95% CI -3.37 to 4.64; 2 studies, 499 circuits; I² = 70%). More and shorter hollow fibre filters (versus standard filters: MD -5.87 hours, 95% CI -10.18 to -1.56; 1 study, 6 circuits) may reduce circuit lifespan. Death from any cause was reported in four comparisons We are uncertain whether CVVHDF versus CVVH, CVVHD versus CVVH or CVVHDF, longer versus a shorter catheter, or surface-modified double-lumen catheters versus standard double-lumen catheters reduced death due to any cause, in very low certainty evidence. Recovery of kidney function was reported in three comparisons. We are uncertain whether CVVHDF versus CVVH, CVVHDF versus CVVH, or surface-modified double-lumen catheters versus standard double-lumen catheters increased recovery of kidney function. Vascular access complications were reported in two comparisons. Low certainty evidence indicated using a longer catheter (versus a shorter catheter: RR 0.40, 95% CI 0.22 to 0.74) may reduce vascular access complications, however the use of surface-modified double lumen catheters versus standard double-lumen catheters may make little or no difference to vascular access complications.

AUTHORS' CONCLUSIONS

The use of CVVHDF as compared with CVVH, pre-dilution haemofiltration, a longer catheter, and surface-modified double-lumen catheter may be useful in prolonging the circuit lifespan, while higher blood flow and more and shorter hollow fibre filter may reduce circuit life. The Overall, the certainty of evidence was assessed to be low to very low due to the small sample size of the included studies. Data from future rigorous and transparent research are much needed in order to fully understand the effects of non-pharmacological interventions in preventing circuit coagulation amongst people with AKI receiving CKRT.

Lung Ultrasound: A "Biomarker" for Fluid Overload?

Fluid overload is associated with poor outcomes in patients with acute kidney injury as well as end-stage kidney disease. Lung ultrasound (LUS) has been used in many different settings and specialties including the emergency department, intensive care unit, trauma, cardiology, and nephrology. Although LUS has been a valuable tool in assessing pulmonary congestion, LUS findings may not always be pathognomonic for pulmonary congestion. Furthermore, the feasibility of doing an extensive LUS examination as has been done in research studies may be hard to implement within the clinical setting. This review will go over the use of LUS to evaluate for fluid overload, compare LUS with other markers of fluid overload, review limitations of LUS, and suggest potential future directions in the use of LUS in nephrology.

Neutrophil Activation and Neutrophil Extracellular Trap Formation in Dialysis Patients

Rationale & Objective

The removal of metabolic waste by passing blood through synthetic tubing and membranes generates an immune response, even with the most biocompatible materials available. We evaluated blood levels of neutrophil activation and cell death during dialysis to devise a set of markers by which future dialysis interventions might be measured for biocompatibility.

Study Design

Observational, case control.

Setting & Participants

30 patients with end-stage kidney disease in Seattle, WA, evaluated during 30 dialysis procedures in out- and inpatient settings were compared with 27 healthy (negative) controls and 20 nondialysis patients with systemic lupus erythematosus as positive controls.

Predictor(s)

Blood levels of neutrophil activation (calprotectin and peroxidase activity) and cell death (cell-free DNA and neutrophil extracellular traps) were assayed.

Outcome(s)

Markers of neutrophil activation and cell death can be used to assess immune response during dialysis.

Analytical Approach

Descriptive analysis and group comparisons.

Results

Intradialytic levels of neutrophil activation markers are higher than prehemodialysis levels (P < 0.05), demonstrating neutrophil activation during hemodialysis. Less neutrophil activation occurs with peritoneal dialysis (P < 0.05). Immunosuppressive treatment and anticoagulant therapy did not seem to affect the capacity of neutrophils to undergo activation with hemodialysis. Finally, levels of hemodialysis-induced neutrophil activation correlated with markers of endothelial activation (r = 0.44; P = 0.01).

Limitations

Low sample size with heterogeneous patient cohort.

Conclusions

Neutrophil activation occurs during hemodialysis, potentially contributing to endothelial inflammation and damage. Neutrophil activation markers are novel and sensitive measures of biocompatibility for improving dialysis.

Renal Replacement Therapy: Physical Properties of Hollow Fibers Influence Efficiency

Introduction

Physical properties of filters for continous renal replacement therapy have a great impact on biocompatibility. According to Poiseuille's law, a filter with more and shorter hollow fibers should offer a decreased pressure drop and, therefore, lower transmembrane pressure (TMP). The aim of this study was to study the effect of a new filter configuration in terms of TMP and clotting compared with the standard configuration.

Methods

In a prospective randomized cross-over study 2 polysulphone hollow fiber hemofilters, one handmade, which differed only in length and number of hollow fibers were compared. In each group 12 filters were investigated during continous venovenous hemofiltration in patients with acute renal failure due to septic shock. Pressures were measured every 3 hours and running time until filter clotting was documented. Mediators before and after the filter, at the end of treatment and in filtrate were assessed.

Results

The standard filter with longer hollow fibers had significantly lower TMPs (106 vs.194 mmHg, p=0.02) and longer running times (1276 vs. 851 min, p=0,04). There were no differences in hematocrit, total protein, cellular and plasmatic coagulation or blood temperature. No significant elimination of mediators was shown.

Conclusion

In contrast to our expectations, the filter with the longer hollow fibers had a better performance, as it ran longer and had lower TMP. This may be due to slower blood flow leading to an increase in blood viscosity in a filter with a larger cross section.

Effect of Frequent Dialysis on Renal Recovery: Results From the Acute Renal Failure Trial Network Study

INTRODUCTION

The optimal frequency of intermittent hemodialysis (IHD) in the treatment of acute kidney injury (AKI) remains unclear. Increasing the frequency of IHD, while offering the possible advantage of reduced ultrafiltration requirement and less hemodynamic instability per session, amplifies patient contact with an extracorporeal circuit with possible deleterious cardiovascular and immunological consequences. A recent study suggested that intensive renal replacement therapy (RRT) is associated with a decrease in urine output during AKI. We hypothesized that increased frequency of IHD may be associated with delayed renal recovery.

METHODS

This is a post hoc analysis of the Acute Renal Failure Trial Network (ATN) study. The ATN study was a large randomized multicenter trial of intensive versus less-intensive RRT in critically ill patients with AKI. This study used either continuous RRT or IHD, depending on the hemodynamic status of the patient. Of 1124 patients, 246 were treated solely with IHD during the study period and were included in this analysis. The participants were randomized to receive IHD 3 days per week (L-IntRRT) or 6 days per week (IntRRT). The primary outcome of interest was renal recovery at day 28.

RESULTS

L-IntRRT was associated with higher number of RRT-free days through day 28 than IntRRT (mean difference 2.5 days; 95% confidence interval [CI]: -4.79 to -0.27 days; P = 0.028). The likelihood for renal recovery at day 28 was lower in the IntRRT group (OR: 0.49; 95% CI: 0.28-0.87; P = 0.016).

CONCLUSION

In hemodynamically stable patients with AKI, intensifying the frequency of IHD from 3 to 6 days per week may be associated with impaired renal recovery.

Issues of Acute Kidney Injury Staging and Management in Sepsis and Critical Illness: A Narrative Review

Acute kidney injury (AKI) has a high incidence on intensive care units around the world and is a major complication in critically ill patients suffering from sepsis or septic shock. The short- and long-term complications are thereby devastating and impair the quality of life. Especially in terms of AKI staging, the determination of kidney function and the timing of dialytic AKI management outside of life-threatening indications are ongoing matters of debate. Despite several studies, a major problem remains in distinguishing between beneficial and unnecessary "early" or even harmful renal replacement therapy (RRT). The latter might prolong disease course and renal recovery. AKI scores, however, provide an insufficient outcome-predicting ability and the related estimation of kidney function via serum creatinine or blood urea nitrogen (BUN)/urea is not reliable in AKI and critical illness. Kidney independent alterations of creatinine- and BUN/urea-levels further complicate the situation. This review critically assesses the current AKI staging, issues and pitfalls of the determination of kidney function and RRT timing, as well as the potential harm reflected by unnecessary RRT. A better understanding is mandatory to improve future study designs and avoid unnecessary RRT for higher patient safety and lower health care costs.

Clinical profile and outcome of patients with acute kidney injury requiring dialysis-an experience from a haemodialysis unit in a developing country

Background

The first government funded and sustainable dialysis unit was established in Ethiopia at Saint Paul’s Hospital Millennium Medical College (SPHMMC). This has led to the development of a unique cohort of patients about which very little is known. This study was conducted to describe the clinical profile and outcome of adult Acute Kidney Injury (AKI) patients treated with intermittent haemodialysis at the dialysis center of SPHMMC.

Methods

A retrospective review of clinical records of cases of AKI who required haemodialysis support during the time period from August 1, 2013 to February 1, 2015 was conducted.

Results

A total of 151 cases AKI requiring dialysis were included for the study. Overall, the patients were generally younger with a mean age of 36.7 years and thus with few premorbid conditions. The most common causes of AKI were hypovolemia (22.5 %), acute glomerulonephritis (AGN) (21.9 %) and pregnancy related causes (18.5 %). Nearly a third (29.1 %) of patients succumbed to the AKI.

Conclusion

Infections, AGN, obstetric causes and nephrotoxins were the primary causes of dialysis requiring AKI. Most of these causes can be prevented with simple interventions such as health education on oral rehydration, quality prenatal and emergency obstetric care, appropriate management of infections and taking appropriate precautions when prescribing potentially nephrotoxic medications.

Update on Dialytic Management of Acute Renal Failure

The potential impact of renal replacement therapy on clinical outcomes in acute renal failure (ARF) remains a subject of ongoing investigation and controversy. This article reviews in depth the clinical trials to date that have examined the effect of dialysis-related variables on outcomes of patients with hospital-acquired ARF. In particular, the role of the dialysis modality, dialyzer characteristics, and dosing strategies are discussed. Clinical trials comparing intermittent hemodialysis (HD) to continuous renal replacement therapies (CRRT) have failed to demonstrate a survival difference when adjusting for disease severity. Similarly, studies evaluating dialyzer membrane biocompatibility and flux properties had no impact on survival. Efforts aimed at measuring dialysis adequacy in patients with ARF receiving HD using urea kinetic modeling are hindered by a lack of understanding of solute kinetics in this setting. However, dosing strategies during CRRT are promising. Finally, the application of cell therapy to the successful substitution of renal function shows promise for the future.

Renal replacement therapy in adult and pediatric intensive care : Recommendations by an expert panel from the French Intensive Care Society (SRLF) with the French Society of Anesthesia Intensive Care (SFAR) French Group for Pediatric Intensive Care Emergencies (GFRUP) the French Dialysis Society (SFD)

Acute renal failure (ARF) in critically ill patients is currently very frequent and requires renal replacement therapy (RRT) in many patients. During the last 15 years, several studies have considered important issues regarding the use of RRT in ARF, like the time to initiate the therapy, the dialysis dose, the types of catheter, the choice of technique, and anticoagulation. However, despite an abundant literature, conflicting results do not provide evidence on RRT implementation. We present herein recommendations for the use of RRT in adult and pediatric intensive care developed with the Grading of Recommendations Assessment, Development, and Evaluation (GRADE) system by an expert group of French Intensive Care Society (SRLF), with the participation of the French Society of Anesthesia and Intensive Care (SFAR), the French Group for Pediatric Intensive Care and Emergencies (GFRUP), and the French Dialysis Society (SFD). The recommendations cover 4 fields: criteria for RRT initiation, technical aspects (access routes, membranes, anticoagulation, reverse osmosis water), practical aspects (choice of the method, peritoneal dialysis, dialysis dose, adjustments), and safety (procedures and training, dialysis catheter management, extracorporeal circuit set-up). These recommendations have been designed on a practical point of view to provide guidance for intensivists in their daily practice.

Acute kidney injury: effect of hemodialysis membrane on Hgf and recovery of renal function

OBJECTIVES

Acute kidney injury (AKI) is associated with a high mortality and morbidity rate. In this study we investigated whether dialysis membranes influence the recovery of renal function, through the regulation of hepatocyte growth factor (HGF).

DESIGN AND METHODS

21 patients were enrolled and assigned to hemodialysis (HD) with cellulose (CE, N=11) versus polymethylacrylate (PMMA, N=10) membranes in alternating order. HGF and IL-1 were measured in serum and in peripheral blood mononuclear cells (PBMC) supernatants collected immediately before the first HD session (T0), at 15 minutes (T15), at 240 minutes (T240) and after the last HD, when renal recovery occurred. Eight healthy volunteers were the controls (CON).

RESULTS

Time to renal function recovery was lower in CE than in PMMA patients. Serum HGF in HD patients was significantly higher than in CON. HGF levels were higher in CE than in PMMA patients at T15 (13.4±2.7 vs 8.9±3.0 ng/mL, P=0.004) and T240. At recovery, HGF levels decreased. IL-1 serum levels showed a similar trend (at T15 CE: 20.5±2.9 vs PMMA: 16.9±3.2 pg/mL, P=0.005). HGF release significantly increased in the course of HD, resulting in higher levels in CE than that in PMMA patients. Considering all the patients, basal HGF release negatively correlated with time to renal recovery (r2=0.42, P<0.01).

CONCLUSIONS

Here we demonstrated that dialysis membranes influence the cytokine profile in AKI patients, HGF release being higher in patients treated with the CE membrane, in comparison to PMMA. Our results suggest that treatment with CE might improve clinical outcomes, possibly through increased release of HGF.

High-flux versus low-flux membranes for end-stage kidney disease

BACKGROUND

Clinical practice guidelines regarding the use of high-flux haemodialysis membranes vary widely.

OBJECTIVES

We aimed to analyse the current evidence reported for the benefits and harms of high-flux and low-flux haemodialysis.

SEARCH METHODS

We searched Cochrane Renal Group's specialised register (July 2012), the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE (1948 to March 2011), and EMBASE (1947 to March 2011) without language restriction.

SELECTION CRITERIA

We included randomised controlled trials (RCTs) that compared high-flux haemodialysis with low-flux haemodialysis in people with end-stage kidney disease (ESKD) who required long-term haemodialysis.

DATA COLLECTION AND ANALYSIS

Data were extracted independently by two authors for study characteristics (participants and interventions), risks of bias, and outcomes (all-cause mortality and cause-specific mortality, hospitalisation, health-related quality of life, carpal tunnel syndrome, dialysis-related arthropathy, kidney function, and symptoms) among people on haemodialysis. Treatment effects were expressed as a risk ratio (RR) or mean difference (MD), with 95% confidence intervals (CI) using the random-effects model.

MAIN RESULTS

We included 33 studies that involved 3820 participants with ESKD. High-flux membranes reduced cardiovascular mortality (5 studies, 2612 participants: RR 0.83, 95% CI 0.70 to 0.99) but not all-cause mortality (10 studies, 2915 participants: RR 0.95, 95% CI 0.87 to 1.04) or infection-related mortality (3 studies, 2547 participants: RR 0.91, 95% CI 0.71 to 1.14). In absolute terms, high-flux membranes may prevent three cardiovascular deaths in 100 people treated with haemodialysis for two years. While high-flux membranes reduced predialysis beta-2 microglobulin levels (MD -12.17 mg/L, 95% CI -15.83 to -8.51 mg/L), insufficient data were available to reliably estimate the effects of membrane flux on hospitalisation, carpal tunnel syndrome, or amyloid-related arthropathy. Evidence for effects of high-flux membranes was limited by selective reporting in a few studies. Insufficient numbers of studies limited our ability to conduct subgroup analyses for membrane type, biocompatibility, or reuse. In general, the risk of bias was either high or unclear in the majority of studies.

AUTHORS' CONCLUSIONS

High-flux haemodialysis may reduce cardiovascular mortality in people requiring haemodialysis by about 15%. A large well-designed RCT is now required to confirm this finding.

Effect of hemodialysis before transplant surgery on renal allograft function--a pair of randomized controlled trials

BACKGROUND

Hemodialysis immediately before kidney transplant surgery has been suggested to adversely affect early graft function. On the other hand, considering its profound antiinflammatory effects, a beneficial impact of regional citrate anticoagulation on the evolution of graft function can be speculated. We sought to assess the clinical impact of preoperative hemodialysis and dialysis anticoagulation in two related randomized trials.

METHODS

Eligible kidney transplant candidates with a serum potassium less than or equal to 5.0 mEq/L were randomized to receive dialysis or no dialysis before deceased donor transplantation. Patients with a potassium more than 5.0 mEq/L were randomized to receive dialysis with heparin or citrate anticoagulation. The primary endpoint was the estimated glomerular filtration rate (eGFR) at posttransplant day 5.

RESULTS

The first comparison (56 vs. 54 patients) revealed no effect of dialysis on eGFR at day 5 (primary endpoint, 12 [interquartile range 5-36] vs. 13 [5-37] mL/min/1.73 m2, P=0.98), rates of delayed graft function (22% vs. 27%, P=0.66), cellular rejection (20% vs. 24%, P=0.65), and C4d-positive dysfunction (2% vs. 9%, P=0.11) or 1-year death-censored graft survival (89% vs. 91%, P=0.51). Comparing citrate with heparin anticoagulation (44 vs. 66 patients), no differences in eGFR at day 5 (17 [8-31] vs. 14 [6-38] ml/min/1.73 m2, P=0.57), delayed graft function (21% vs. 30%, P=0.28), cellular rejection (23% vs. 33%, P=0.29), and graft survival (90% vs. 88%, P=0.44) were found. For citrate anticoagulation, less C4d-positive rejection episodes (P=0.08) and higher 1-year eGFR levels (P=0.03) were observed.

CONCLUSION

Pretransplant hemodialysis and anticoagulation may not affect early graft function in a meaningful way.

Management of acute renal failure in the elderly patient: a clinician's guide

Numerous anatomical and functional changes occurring in the aging kidney lead to reduced glomerular filtration rate, lower renal blood flow and impaired renal autoregulation. The elderly are especially vulnerable to the development of renal dysfunction and in this population acute renal failure (ARF) is a common problem. ARF is often iatrogenic and multifactorial; common iatrogenic combinations include pre-existing renal dysfunction and exposure to nephrotoxins such as radiocontrast agents or aminoglycosides, use of NSAIDs in patients with congestive cardiac failure and use of ACE inhibitors and diuretics in patients with underlying atherosclerotic renal artery stenosis. The aetiology of ARF is classically grouped into three categories: prerenal, intrinsic and postrenal. Prerenal ARF is the second most common cause of ARF in the elderly, accounting for nearly one-third of all hospitalized cases. Common causes can be grouped into true volume depletion (e.g. decreased fluid intake), decreased effective blood volume (e.g. systemic vasodilation) and haemodynamic (e.g. renal artery stenosis, NSAID use). Acute tubular necrosis (ATN) is the most common cause of intrinsic ARF and is responsible for over 50% of ARF in hospitalized patients, and up to 76% of cases in patients in intensive care units. ATN usually occurs after an acute ischaemic or toxic event. The pathogenesis of ATN involves an interplay of processes that include endothelial injury, microvascular flow disruption, tubular hypoxia, dysfunction and apoptosis, tubular obstruction and trans-tubular back-leak. Vasculitis causing ARF should not be missed as this condition is potentially life threatening. The likelihood of a postrenal cause for ARF increases with age. Benign prostatic hypertrophy, prostatic carcinoma and pelvic malignancies are all important causes. Early identification of ARF secondary to obstruction with renal imaging is essential, and complete or partial renal recovery usually ensues following relief of the obstruction.A comprehensive medical and drug history and physical examination are all invaluable. Particular attention should be paid to the fluid status of the patient (skin turgor, jugular venous pressure, lying and standing blood pressure, urine output). Urinalysis should be performed to detect evidence of proteinuria and haematuria, which will aid diagnosis. Fractional excretion of sodium and urine osmolality may be measured but the widespread use of diuretics in the elderly gives rise to unreliable results. Renal imaging, usually ultrasound scanning, is routinely performed for assessment of renal size and to exclude urinary obstruction. In some cases, renal biopsy is necessary to provide specific diagnostic information. The general principles of managing ARF include treatment of life-threatening features such as shock, respiratory failure, hyperkalaemia, pulmonary oedema, metabolic acidosis and sepsis; stopping and avoiding administration of nephrotoxins; optimization of haemodynamic and fluid status; adjustment of drug dosage appropriate to glomerular filtration rate; early nutritional support; and early referral to nephrologists for diagnosis of ARF cause, timely initiation of dialysis and initiation of specific treatment. The treatment of prerenal and ATN ARF is largely supportive with little evidence of benefit from current pharmacological therapies. Despite advances in critical care medicine and renal replacement therapy, the mortality of ARF has not changed significantly over the last 40 years, with current mortality rates being up to 75%.

Outcome comparisons of intermittent and continuous therapies in acute kidney injury: what do they mean?

Despite the fact that no new clinical outcome studies comparing intermittent hemodialysis (IHD) and continuous renal replacement therapy (CRRT) for acute kidney injury (AKI) have been published in the past year, two meta-analyses addressing the topic (Bagshaw et al, Crit Care Med 2008; 36: 610-7, and Pannu et al, JAMA 2008; 299: 793-805) have been published recently. With respect to randomized controlled trials (RCTs), there was a substantial overlap between the studies considered in the analysis by Bagshaw et al and those considered in the analysis by Pannu et al. Although neither metaanalysis showed a benefit for either modality with respect to mortality or renal recovery, the two publications offered vastly different conclusions. Bagshaw et al concluded it is impossible to make any definitive recommendations about dialysis modality choice in AKI because previous studies were not adequately powered and failed to standardize for treatment dose. On the other hand, because the metaanalysis of Pannu et al demonstrated equivalent patient outcomes, and in light of the lower costs of IHD, they suggested that alternate-day hemodialysis should become the preferred therapy in many critically ill patients. As the clinical practice recommendations made by Pannu and colleagues have very important implications, we believe their analysis should be critically assessed. In this review, the weaknesses of the RCTs considered in the meta-analysis by Pannu et al are presented. Furthermore, the assumption by Pannu et al that IHD is associated with lower costs than CRRT is challenged, as they did not consider adequately both the short-term and long-term costs associated with the dialytic management of AKI patients. Based on our critical analysis, we believe the AKI dialytic treatment approach recommended by the JAMA investigators (Pannu et al) is not supported by the aggregate of the available clinical outcome data and, therefore, remains highly controversial. We would like to join with others in the AKI field by strongly recommending that investigators and other clinicians stop trying to make conclusive determinations about dialysis modalities when robust supportive data simply are not available. Instead of additional intermodality comparisons, the focus of future clinical research should be toward generating high-quality data on intramodality interventions, such as treatment dose and timing of treatment initiation. In this regard, at least for CRRT, we anxiously await the results of the ongoing RCTs evaluating the effect of CRRT dose on patient outcome.

Intermittent versus continuous renal replacement therapy: a matter of controversy

BACKGROUND

Acute Renal Failure (ARF) requiring some form of replacement therapy is a frequent complication in the critically ill patient. Despite potential therapeutic advantages the expectation of an improvement in patient outcomes using Continuous Renal Replacement Therapy (CRRT) compared to conventional Intermittent Haemodialysis (IHD) remains controversial.

AIMS AND METHOD

This article will review the literature on the issues surrounding the use of IHD versus CRRT in the management of the critically ill patient. Articles were selected according to level of evidence with priority given to meta-analyses and randomised controlled trials.

DISCUSSION

Several operational features of CRRT allow this technique to be tolerated more easily in critical illness than IHD. The gradual removal of fluid reduces the incidence of hypotension and the risk of volume overload. Decreased variability in the concentration of solutes enables greater azotemia control. However, CRRT is required to operate uninterrupted to achieve a treatment dose that is equivalent to a conventional IHD treatment schedule. In the absence of definitive evidence to validate superior patient survival and return of renal function there is disagreement as to the most appropriate form of Renal Replacement Therapy (RRT) for the critically ill patient. The introduction of 'hybrid' therapies offers a further alternative treatment strategy, which combine favourable aspects of IHD and CRRT.

CONCLUSION

The decision to use IHD or CRRT should be guided by the therapeutic needs of the patient rather than the operational differences between the two techniques. The resources and expertise available at the organisation are also important in determining the mode best able to manage the critically ill patient at any stage and may change according to the severity of illness. The emergence of hybrid therapies provides a compromise option which encompasses many of the features of both systems, but does not embrace all options of either approach.

Timing of renal replacement therapy in critically ill patients with acute kidney injury

PURPOSE OF REVIEW

Timing of renal replacement therapy in critically ill patients with acute kidney injury is highly subjective, and may influence outcome. We discuss renal and nonrenal criteria for timing considering the recent literature.

RECENT FINDINGS

Two randomized and four nonrandomized controlled trials investigated the effects of timing on patient outcome. All but one randomized controlled trial indicated better outcome with early renal replacement therapy but had poor methodological quality. The heterogeneity of timing definition, study population and mode of therapy, however, hampered comparison among studies.

SUMMARY

In the absence of large randomized controlled trials we can make no firm recommendations for timing of renal replacement therapy in acute kidney injury. Since rapid recovery of renal function is unlikely when other organ failure persists and the consequences of acute kidney injury may be more severe in critically ill patients, we suggest other organ failure is also considered. Patients with acute kidney injury, persisting shock and poorly recovering functions of other organs may benefit from early therapy. For future studies, we recommend describing renal replacement therapy timing according to the 'RIFLE' classification, as modified by the Acute Kidney Injury Network, and quantifying the severity of other organ failure. Biomarkers may refine acute kidney injury and timing definitions in the future.

Withholding and withdrawing dialysis in the intensive care unit: benefits derived from consulting the renal physicians association/american society of nephrology clinical practice guideline, shared decision-making in the appropriate initiation of and withdrawal from dialysis

Despite advances in the technology of dialysis, mortality in patients who develop acute renal failure remains high. Scoring systems have been developed to improve the ability to define prognosis in seriously ill patients with acute renal failure but predicting outcomes for individual patients is uncertain. Decisions to withhold or withdraw dialysis in seriously ill patients are difficult for patients, families, and health care providers. The clinical practice guideline, Shared Decision-Making in the Appropriate Initiation of and Withdrawal from Dialysis, provides evidence-based recommendations to aid nephrologists in discussions and the process of medical decision-making about starting and stopping dialysis. Estimating prognosis and addressing the issues of advance directives and patient and family preferences through the process of shared decision-making can clarify appropriate strategies for clinical management and interventions. Time-limited trials of dialysis may be an invaluable tool in this process. Increasing nephrologists' awareness of the guideline may facilitate decision-making around the issues of withholding and withdrawing dialysis in part by clarifying patients and situations in which it may be appropriate to withhold or withdraw dialysis.

Biocompatible hemodialysis membranes for acute renal failure

BACKGROUND

Acute renal failure (ARF) is associated with substantial morbidity and mortality. Some studies have reported a survival advantage among patients dialyzed with biocompatible membranes (BCM) compared to bioincompatible membranes (BICM). These findings were not consistently observed in subsequent studies.

OBJECTIVES

To ascertain whether the use of BCM confers an advantage in either survival or recovery of renal function over the use of BICM in adult patients with ARF requiring intermittent hemodialysis.

SEARCH STRATEGY

We searched the Cochrane Central Register of Controlled Trials (CENTRAL, in The Cochrane Library), MEDLINE (from 1966), EMBASE (from 1980), the Mexican Index of Latin American Biomedical Journals IMBIOMED (from 1990), the Latin American and Caribbean Health Sciences Literature Database LILACS (from 1982), and reference lists of articles. Search date: January 2007

SELECTION CRITERIA

Randomized and quasi-randomized controlled trials comparing the use of a BCM with a BICM in patients > 18 years of age with ARF requiring intermittent hemodialysis.

DATA COLLECTION AND ANALYSIS

Two authors extracted the data independently. Cellulose-derived dialysis membranes were classified as BICM, and synthetic dialyzers were considered as BCM. The main outcomes were all-cause mortality and recovery of renal function by type of dialyzer. We further explored these outcomes according to the flux properties (high-flux or low-flux) of each of these dialyzers. A meta-analysis was conducted by combining data using a random-effects model.

MAIN RESULTS

Ten studies were included in the primary analysis of mortality, with a total of 1100 patients. None of the pooled risk ratios (RRs) reached statistical significance. The pooled RR for mortality was 0.93 (95% confidence interval (CI) 0.81 to 1.07). The overall RR for recovery of renal function, which was inclusive of 1038 patients from nine studies, was 1.09 (95% CI 0.90 to 1.31). The pooled RR for mortality by dialyzer flux property was 1.05 (95% CI 0.81 to 1.37). The pooled RR for recovery of renal function by flux property was 1.30 (95% CI 0.83 to 2.02). A meta-analysis of mortality among kidney transplant recipients was not possible, however the analysis of recovery of renal function in this patient population revealed an RR of 1.05 (95% CI 0.87 to 1.26). Results of sensitivity analyses did not differ significantly from the primary analyses.

AUTHORS' CONCLUSIONS

There is no demonstrable clinical advantage to the use of BCM versus BICM in patients with ARF who require intermittent hemodialysis.

Continuous renal replacement therapy: a worldwide practice survey. The beginning and ending supportive therapy for the kidney (B.E.S.T. kidney) investigators

OBJECTIVE

Little information is available regarding current practice in continuous renal replacement therapy (CRRT) for the treatment of acute renal failure (ARF) and the possible clinical effect of practice variation.

DESIGN

Prospective observational study.

SETTING

A total of 54 intensive care units (ICUs) in 23 countries.

PATIENTS AND PARTICIPANTS

A cohort of 1006 ICU patients treated with CRRT for ARF.

INTERVENTIONS

Collection of demographic, clinical and outcome data.

MEASUREMENTS AND RESULTS

All patients except one were treated with venovenous circuits, most commonly as venovenous hemofiltration (52.8%). Approximately one-third received CRRT without anticoagulation (33.1%). Among patients who received anticoagulation, unfractionated heparin (UFH) was the most common choice (42.9%), followed by sodium citrate (9.9%), nafamostat mesilate (6.1%), and low-molecular-weight heparin (LMWH; 4.4%). Hypotension related to CRRT occurred in 19% of patients and arrhythmias in 4.3%. Bleeding complications occurred in 3.3% of patients. Treatment with LMWH was associated with a higher incidence of bleeding complications (11.4%) compared to UFH (2.3%, p = 0.0083) and citrate (2.0%, p = 0.029). The median dose of CRRT was 20.4 ml/kg/h. Only 11.7% of patients received a dose of > 35 ml/kg/h. Most (85.5%) survivors recovered to dialysis independence at hospital discharge. Hospital mortality was 63.8%. Multivariable analysis showed that no CRRT-related variables (mode, filter material, drug for anticoagulation, and prescribed dose) predicted hospital mortality.

CONCLUSIONS

This study supports the notion that, worldwide, CRRT practice is quite variable and not aligned with best evidence.

[Extracorporeal blood purification in the intensive care units]

Mortality remains high in intensive care patients with renal failure requiring extra corporeal blood purification. This article reviews the recent data that have led to the improvement of the care for such patients. We will discuss the criteria to determine the choice of the technique (intermittent or continuous), of the membrane, of the prescribing dose, and the type of anticoagulation and when to initiate such a treatment.

Epidemiology of renal recovery after acute renal failure

PURPOSE OF REVIEW

Recovery of renal function after acute renal failure is an important clinical determinant of patient morbidity. Herein, the epidemiology of renal recovery after acute renal failure will be described, along with potential predictive factors and interventions.

RECENT FINDINGS

Renal recovery has been variably defined, most often as recovery to independence from renal replacement therapy. A recent consensus definition for acute renal failure has been published and included provisions for defining renal recovery. Renal recovery to renal replacement therapy independence occurs in the majority by hospital discharge and peaks by 90 days. All of older age, female sex, co-morbid illnesses, especially chronic kidney disease, and late initiation of renal replacement therapy or conventional intermittent renal replacement therapy have been coupled with non-recovery. Analysis of the literature suggests several interventions may influence recovery.

SUMMARY

The prognosis is generally good for recovery after acute renal failure. Most patients will be independent of renal replacement therapy by 90 days. Additional research is necessary, however, to understand recovery rates not only to independence from renal replacement therapy, but also to complete and partial recovery. Future studies need to consider the health economic implications for survival and non-recovery. Finally, questions on the role of various interventions require characterization in randomized controlled trials to determine how they may influence renal prognosis.

Continuous renal replacement therapy in the treatment of acute renal failure: critical assessment is required

A continuous approach to renal replacement therapy (CRRT) for critically ill patients was introduced in 1977 and was hailed almost immediately as an improved alternative to intermittent hemodialysis (IHD). Now that CRRT has been in clinical practice for three decades, it is fair to ask whether research-based evidence (rather than expert opinion) supports the use of this complex technology in comparison to IHD. Several randomized clinical trials have compared the outcomes of CRRT and IHD. In one trial, patients assigned to CRRT had a significantly higher intensive-care mortality rate. In other recent trials, there has been no significant difference in outcome. A meta-analysis of observational studies similarly shows no benefit of CRRT versus IHD, with recent trends actually favoring IHD. While considerable attention has been focused on perceived benefits of CRRT compared to IHD, comparatively less attention has been focused on the potential for increased risks. When examining the totality of evidence from recent observational studies and clinical trials, there is no convincing evidence to support superiority of CRRT over IHD in the treatment of critically ill patients with ARF.

Perioperative fluid management in renal transplantation: a narrative review of the literature

Adequate volume maintenance is essential to prevent acute renal failure during major surgery or to ensure graft function after renal transplantation. The various recommendations on the optimum fluid therapy are based, at best, on sparse evidence only from observational studies. This article reviews the literature on perioperative fluid management in renal transplantation. Crystalloid solutions not exerting any specific side-effects are the first choice for volume replacement in kidney transplantation. The use of colloids should be restricted to patients with severe intravascular volume deficits necessitating high volume restoration. The routine application of albumin, dopamine, and high dose diuretics is no longer warranted. Mannitol given immediately before removal of the vessel clamps reduces the requirement of post-transplant dialysis, but has no effects on graft function in the long term. There is insufficient evidence on the best use of dialysis, but it seems peritoneal dialysis pretransplant is associated with less delayed graft function, whereas the preference of dialysis post-transplant is not yet well-founded. This review article should provide better guidance for fluid management in kidney transplantation until best-evidence guidelines can be established based upon more research.

Survival by Dialysis Modality in Critically Ill Patients with Acute Kidney Injury

Among critically ill patients, acute kidney injury (AKI) requiring dialysis is associated with mortality rates generally in excess of 50%. Continuous renal replacement therapies (CRRT) often are recommended and widely used, although data to support its superiority over intermittent hemodialysis (IHD) are lacking. Data from the Program to Improve Care in Acute Renal Disease (PICARD), a multicenter observational study of AKI, were analyzed. Among 398 patients who required dialysis, the risk for death within 60 d was examined by assigned initial dialysis modality (CRRT [n = 206] versus IHD [n = 192]) using standard Kaplan-Meier product limit estimates, proportional hazards ("Cox") regression methods, and a propensity score approach to account for selection effects. Crude survival rates were lower for patients who were treated with CRRT than IHD (survival at 30 d 45 versus 58%; P = 0.006). Adjusted for age, hepatic failure, sepsis, thrombocytopenia, blood urea nitrogen, and serum creatinine and stratified by site, the relative risk for death associated with CRRT was 1.82 (95% confidence interval 1.26 to 2.62). Further adjustment for the propensity score did not materially alter the association (relative risk 1.92; 95% confidence interval 1.28 to 2.89). Among critically ill patients with AKI, CRRT was associated with increased mortality. Although the results could reflect residual confounding by severity of illness, these data provide no evidence for a survival benefit afforded by CRRT. Larger, prospective, randomized clinical trials to compare CRRT and IHD in severe AKI are needed.

Consensus development in acute renal failure: The Acute Dialysis Quality Initiative

PURPOSE OF REVIEW

Although acute renal failure is both common and highly lethal in the intensive care unit, our understanding of the epidemiology and pathophysiology of acute renal failure is limited, and treatment for acute renal failure is extremely variable around the world. The general lack of consensus with regard to definitions, prevention, and treatment of acute renal failure has limited progress in this field.

RECENT FINDINGS

Consensus in acute renal failure requires establishing a framework in which intensivists, nephrologists, pharmacologists, and others who care for critically ill patients with or at risk for acute renal failure can reach consensus and develop evidence-based practice guidelines. The Acute Dialysis Quality Initiative seeks to provide an objective, dispassionate distillation of the literature and description of the current state of practice of dialysis and related therapies as they are applied to acutely ill patients. The purposes of Acute Dialysis Quality Initiative are first, to develop a consensus of opinion, with evidence where possible, on best practice; and second, to articulate a research agenda to focus on important unanswered questions.

SUMMARY

Broad consensus in the diagnosis and management of acute renal failure and in the use of blood purification in nonrenal critical illness is achievable. Standardization of definitions, practice, and research methodology is urgently needed, and specific proposals have been made by an international, interdisciplinary group.

Renal replacement therapy and the kidney: minimizing the impact of renal replacement therapy on recovery of acute renal failure

PURPOSE OF REVIEW

Although renal replacement therapy is the mainstay of supportive care in patients with severe acute renal failure, its performance can have untoward effects that contribute to the prolongation of renal failure or impede the ultimate recovery of renal function. In this review, we categorize the major complications associated with renal replacement therapy and assess their impact on recovery of renal function.

RECENT FINDINGS

The major mechanisms by which renal replacement therapy is postulated to delay renal recovery include treatment-associated hemodynamic instability, vascular catheter-related bacteremia and sepsis, and cytokine activation by bioincompatible membranes. Clinical data regarding the role of dialysis catheter infections in delay of renal recovery are lacking. The data regarding the role of membrane biocompatibility and the modality and dose of renal replacement therapy are limited and conflicting.

SUMMARY

Clinical recommendations must be limited to the broad admonishment that complications during renal replacement therapy, including hemodynamic instability and catheter-related bacteremia, be minimized by using best clinical practices, while recognizing that the impact of specific practices on recovery of renal function have not been evaluated. The data do not support recommendations regarding utilization of specific membranes or the modality or dose of renal replacement therapy on the basis of their impact on recovery of renal function.

Management of early acute renal failure: focus on post-injury prevention

PURPOSE OF REVIEW

In this review, we describe our current understanding of various aspects of secondary renal injury and its prevention. Secondary renal injury indicates any injury to the kidney, which occurs after an initial event has already triggered injury to the organ.

RECENT FINDINGS

Analysis of the literature reveals several important fields of possible intervention. First, blood pressure is considered important and hypotension is associated with renal injury. Avoiding hypotension is an important mechanism of renal protection from secondary injury. Similarly, a low cardiac output state should be promptly treated or prevented. Adequate volume resuscitation is also considered important although strong direct evidence for this intervention is not available. There is insufficient evidence to suggest that any drug can specifically increase renal blood flow in man independent of an effect on blood pressure or cardiac output. Specific kidney protective approaches have not yet been identified. Intensive insulin therapy possibly delivers renal protection and deserves further investigation. Modulation of the stress response appears attractive in experimental models but it has not been shown effective in man. Ischemic preconditioning is a useful strategy for renal protection in the experimental setting. An understanding of the mechanisms involved in ischemic preconditioning might assist in developing novel and effective interventions in man.

SUMMARY

The pillars of protection from secondary renal injury are similar to those needed to protect the kidney from primary injury: maintenance of adequate intravascular volume, cardiac output, and arterial blood pressure. Novel protective strategies such as intensive insulin therapy require further investigation.

Renal failure secondary to acute tubular necrosis: epidemiology, diagnosis, and management

Acute tubular necrosis (ATN) is a form of acute renal failure (ARF) that is common in hospitalized patients. In critical care units, it accounts for about 76% of cases of ARF. Despite the introduction of hemodialysis > 30 years ago, the mortality rates from ATN in hospitalized and ICU patients are about 37.1% and 78.6%, respectively. The purpose of this review is to discuss briefly the cause, diagnosis, and epidemiology of ARF, and to review in depth the clinical trials performed to date that have examined the influence of growth factors, hormones, antioxidants, diuretics, and dialysis. In particular, the role of the dialysis modality, dialyzer characteristics, and dosing strategies are discussed.

Epidemiology and natural history of acute renal failure in the ICU

This article focuses on the incidence, risk factors, and mortality of acute renal failure (ARF) in critically ill patients. Accurate epidemiologic assessment of ARF is still a problem; as long as there is neither a uniquely accepted definition of ARF nor definitions for end points to measure, results will remain heterogeneous and hard to compare. Mortality of ARF has remained high throughout the last decades, despite further development of modern treatment modalities. This indicates that ARF is not just a matter of loss of organ function that can easily be replaced easily by extracorporeal therapies, but is a condition additionally accompanied by systemic consequences which significantly impact on prognosis.

Biocompatible hemodialysis membranes for acute renal failure

BACKGROUND

Acute renal failure (ARF) is associated with substantial morbidity and mortality. Some trials have reported a survival advantage among patients dialyzed with biocompatible membranes (BCM) compared to bioincompatible membranes (BICM). These findings were not consistently observed in subsequent studies.

OBJECTIVES

To ascertain whether the use of BCM confers an advantage in either survival or recovery of renal function over the use of BICM in adult patients with ARF requiring intermittent hemodialysis.

SEARCH STRATEGY

We searched the Cochrane Central Register of Controlled Trials (CENTRAL, in The Cochrane Library - Issue 1, 2004), MEDLINE (1966 to January 2004), EMBASE (1980 to January 2004), the Mexican Index of Latin American Biomedical Journals IMBIOMED (1990 to January 2004), the Latin American and Caribbean Health Sciences Literature Database LILACS (1982 to January 2004), and reference lists of articles.

SELECTION CRITERIA

Randomized and quasi-randomized controlled trials comparing the use of a BCM with a BICM in patients > 18 years of age with ARF requiring intermittent hemodialysis.

DATA COLLECTION AND ANALYSIS

Two authors extracted the data independently. Cellulose-derived dialysis membranes were classified as BICM, and synthetic dialyzers were considered as BCM. The main outcomes were all-cause mortality and recovery of renal function by type of dialyzer. We further explored these outcomes according to the flux properties (high-flux or low-flux) of each of these dialyzers. A meta-analysis was conducted by combining data using a random-effects model.

MAIN RESULTS

Nine studies were included in the primary analysis of mortality, with a total of 1062 patients. None of the pooled RR's reached statistical significance. The pooled relative risk (RR) for mortality was 0.93 (95% confidence interval (CI) = 0.81 to 1.07). The overall RR for recovery of renal function, inclusive of 1038 patients from nine studies was 1.09 (95% CI 0.90 to 1.31). The pooled RR for mortality by dialyzer flux property was 1.03 (95% CI 0.82 to 1.30). The RR for recovery of renal function by flux property was 0.85 (95% CI 0.55 to 1.31). A meta-analysis of mortality of kidney transplant recipients was not possible, but the analysis of recovery of renal function in this patient population was 1.09 (95% CI 0.91to 1.31). Results of sensitivity analyses did not differ significantly from the primary analyses.

AUTHORS' CONCLUSIONS

There is no demonstrable clinical advantage to the use of BCM versus BICM in patients with ARF who require intermittent hemodialysis.

Acute renal failure - definition, outcome measures, animal models, fluid therapy and information technology needs: the Second International Consensus Conference of the Acute Dialysis Quality Initiative (ADQI) Group

INTRODUCTION

There is no consensus definition of acute renal failure (ARF) in critically ill patients. More than 30 different definitions have been used in the literature, creating much confusion and making comparisons difficult. Similarly, strong debate exists on the validity and clinical relevance of animal models of ARF; on choices of fluid management and of end-points for trials of new interventions in this field; and on how information technology can be used to assist this process. Accordingly, we sought to review the available evidence, make recommendations and delineate key questions for future studies.

METHODS

We undertook a systematic review of the literature using Medline and PubMed searches. We determined a list of key questions and convened a 2-day consensus conference to develop summary statements via a series of alternating breakout and plenary sessions. In these sessions, we identified supporting evidence and generated recommendations and/or directions for future research.

RESULTS

We found sufficient consensus on 47 questions to allow the development of recommendations. Importantly, we were able to develop a consensus definition for ARF. In some cases it was also possible to issue useful consensus recommendations for future investigations. We present a summary of the findings. (Full versions of the six workgroups' findings are available on the internet at http://www.ADQI.net)

CONCLUSION

Despite limited data, broad areas of consensus exist for the physiological and clinical principles needed to guide the development of consensus recommendations for defining ARF, selection of animal models, methods of monitoring fluid therapy, choice of physiological and clinical end-points for trials, and the possible role of information technology.

Acute renal failure - definition, outcome measures, animal models, fluid therapy and information technology needs: the Second International Consensus Conference of the Acute Dialysis Quality Initiative (ADQI) Group

INTRODUCTION

There is no consensus definition of acute renal failure (ARF) in critically ill patients. More than 30 different definitions have been used in the literature, creating much confusion and making comparisons difficult. Similarly, strong debate exists on the validity and clinical relevance of animal models of ARF; on choices of fluid management and of end-points for trials of new interventions in this field; and on how information technology can be used to assist this process. Accordingly, we sought to review the available evidence, make recommendations and delineate key questions for future studies.

METHODS

We undertook a systematic review of the literature using Medline and PubMed searches. We determined a list of key questions and convened a 2-day consensus conference to develop summary statements via a series of alternating breakout and plenary sessions. In these sessions, we identified supporting evidence and generated recommendations and/or directions for future research.

RESULTS

We found sufficient consensus on 47 questions to allow the development of recommendations. Importantly, we were able to develop a consensus definition for ARF. In some cases it was also possible to issue useful consensus recommendations for future investigations. We present a summary of the findings. (Full versions of the six workgroups' findings are available on the internet at http://www.ADQI.net)

CONCLUSION

Despite limited data, broad areas of consensus exist for the physiological and clinical principles needed to guide the development of consensus recommendations for defining ARF, selection of animal models, methods of monitoring fluid therapy, choice of physiological and clinical end-points for trials, and the possible role of information technology.

Dialysis strategies in critically ill acute renal failure patients

PURPOSE OF REVIEW

Acute renal failure requiring dialysis is a frequent complication in critically ill patients, with a high morbidity and mortality. Until now, no evidence-based guidelines on the optimal treatment of acute renal failure on the ICU are available. This article reviews recent publications that shed light on several specific topics, like optimal treatment modality, dose of dialysis, type of dialysis membrane, and new developments such as slow extended daily dialysis.

RECENT FINDINGS

For a long time, it has been claimed that continuous renal replacement therapies were superior to intermittent hemodialysis. Several recent articles addressed this topic, but none of them could demonstrate superiority of one of the two modalities. A meta-analysis confirmed this lack of differences in outcome. A landmark study underscored the importance of dose of dialysis in continuous renal replacement therapy. Although a comparable study in intermittent hemodialysis is still lacking, it was shown that daily dialysis is an absolute prerequisite for adequate intermittent hemodialysis. A meta-analysis further demonstrated that the use of biocompatible membranes can influence patient survival positively, without effect on recovery of renal function. Slow extended daily dialysis emerged as a hybrid renal replacement therapeutic modality and has promising features because it combines the advantages of both continuous renal replacement therapy and intermittent hemodialysis.

SUMMARY

Adequate dialysis is needed to reduce mortality related to acute renal failure in ICU patients. This necessitates an approach that is completely different from that in chronic renal failure.

Dose of Dialysis in Acute Renal Failure

Acute renal failure (ARF) is a cause of significant morbidity and mortality. Despite advances in supportive care, outcomes in ARF have improved little over the past decades. The primary goals in management of patients with ARF are to optimize hemodynamic and volume status, minimize further renal injury, correct metabolic abnormalities, and permit adequate nutrition. Renal replacement therapy (RRT) is often required to achieve these goals while awaiting renal recovery, but the optimal dose of dialysis in patients with ARF is not known. Extrapolation of required dialysis dose from recommendations in chronic dialysis is unlikely to be appropriate because of the lack of a steady state and differences in distribution volume of urea that are intrinsic to ARF. The prescribed dialysis dose in ARF is often low, and actual delivered dose is often even less than prescribed. Delivery of dialysis in ARF is often hampered by the patient's hypercatabolic state, hemodynamic instability, and volume status, as well as suboptimal vascular access with temporary venous catheters. The impact of intermittent hemodialysis (IHD) versus continuous renal replacement therapy (CRRT) on outcomes in ARF is also not clear. Patient disease severity impacts more than dialysis modality in patient outcome, but when patients are stratified for equal disease severity, CRRT may have potential benefits over IHD in terms of patient survival, fluid and metabolic control, and renal recovery. Strategies associated with improved outcomes that have emerged thus far in ARF are to aim for a time-averaged blood urea nitrogen (BUN) of less than 60 mg/dl with IHD, varying IHD frequency as necessary, or to achieve a minimum ultrafiltration rate of 35 ml/kg/hr with CRRT.

Special issues in the patient with renal failure

Renal failure commonly occurs in an ICU as part of the evolution of an underlying disease process. Appropriate and rapid resuscitation and treatment prevents or reverses prerenal insults. Patients usually make a complete recovery if the disease process is reversible and the renal injury mild or moderate. More severe degrees of renal injury initially require conservative management with attention to maintaining a diuresis, preventing fluid, electrolyte, and acid-base imbalances, and ensuring adequate nutrition. Renal replacement therapy is required for the more severe forms of renal failure. Continuous forms of RRT are gaining favor as they are associated with less hemodynamic instability, though current evidence does not demonstrate any clear outcome benefit. Mortality is high when the severe form of ARF is established. ARF may have some attributable mortality, but the poor outcome is usually related more to the underlying medical problems and concurrent multisystem derangements.

Selection of endpoints for clinical trials of acute renal failure in critically ill patients

The selection of appropriate outcome measures is essential to the design of clinical trials of the prevention or treatment of acute renal failure in critically ill patients. In this paper, we present the consensus opinion from the second Acute Dialysis Quality Initiative Conference held in Vicenza, Italy, in May 2002, regarding the issues that should guide the selection of endpoints in clinical intervention trials of acute renal failure. Important criteria for the selection of these outcome measures include their clinical importance, responsiveness to experimental intervention, precision of definition, accuracy of measurement, and completeness of ascertainment. Although the most appropriate endpoints for individual studies are dependent on specific hypotheses and study designs, the primary endpoint in prevention trials should be based on an assessment of renal function, whereas mortality or renal functional assessment may serve as the primary endpoint in studies of established acute renal failure.

Dosing patterns for continuous renal replacement therapy at a large academic medical center in the United States

PURPOSE

We sought to retrospectively review the dosing patterns of continuous renal replacement therapy (CRRT) in patients with acute renal failure (ARF) and determine their actual delivered dosage of CRRT.

MATERIALS AND METHODS

Computerized records of patients (n = 115) who received CRRT for ARF at a single, large, academic, tertiary care hospital from September 1, 1999 through August 31, 2000 were reviewed. The delivered dose of CRRT for each patient/day was calculated from the hourly effluent flow rate, the patient's weight, and the duration (in hours) of CRRT for that day. A mean effluent flow rate (in L/h) for each patient was then calculated.

RESULTS

The average number of hours/day on CRRT was 16.1 +/- 3.53 (mean +/- SD), with a mean flow rate (averaged over 24 h) of 1.36 +/- 0.31 L/h. The mean CRRT dose prescribed for these patients was 24.46 +/- 6.73 mL/Kg/h, but the mean dose delivered was only 16.55 +/- 5.41 mL/Kg/h (68% of the prescribed dose, P <.000001).

CONCLUSIONS

Many patients are prescribed low doses of CRRT. Furthermore, the dose delivered is considerably lower than that prescribed. Methods and procedures to extend CRRT system life may improve the dose delivery.

Influence of dialysis membranes on outcomes in acute renal failure: a meta-analysis

BACKGROUND

Considerable controversy exists as to whether synthetic (more biocompatible) dialysis membranes improve outcome in patients with acute renal failure (ARF) compared to cellulose-based membranes. Numerous trials conducted have yielded inconsistent results. Although the discordant results of existing studies could be explained by the varying degrees of biocompatibility among the different membranes used, these studies also had low statistical power. Thus, we sought to determine whether combining results from all published trials would provide a better estimate of the effect of membrane composition on survival in ARF.

METHODS

We performed a meta-analysis of all previously published prospective trials comparing the use of synthetic membranes with cellulose-based membranes for hemodialysis in patients with ARF.

RESULTS

Of the 10 prospective trials identified, eight trials (867 patients) provided survival data and six trials (641 patients) provided data on recovery of renal function. We used the Mantel-Haenszel test based on a fixed effects model to analyze the data. The cumulative odds ratio (OR) for survival in favor of synthetic membranes was 1.37 (95% CI: 1.02 to 1.83), P = 0.03 and that for renal recovery was 1.23 (95% CI: 0.90 to 1.68), P = 0.18. We performed a sensitivity analysis by stratifying studies on the basis of control group membrane type (unsubstituted or substituted cellulose) and found that the survival advantage for synthetic membranes was mainly limited to comparison with the unsubstituted cellulose group [OR 1.64 (95% CI: 1.10 to 2.45) vs. OR 1.20 (95% CI: 0.73 to 1.97)].

CONCLUSIONS

Synthetic membranes appear to confer a significant survival advantage over cellulose-based membranes. We could not demonstrate a similar benefit with use of synthetic membranes over cellulose-based membranes for recovery of renal function but sample size was limited. Finally, our results suggest that the survival disadvantage for cellulose-based membranes may be limited to unsubstituted cellulose (cuprophane) membranes.

The first international consensus conference on continuous renal replacement therapy

BACKGROUND

Management of acute renal failure (ARF) in the critically ill is extremely variable and there are no published standards for the provision of renal replacement therapy in this population. We sought to review the available evidence, make evidence-based practice recommendations, and delineate key questions for future study.

METHODS

We undertook an evidence-based review of the literature on continuous renal replacement therapy (CRRT) using MEDLINE searches. We determined a list of key questions and convened a 2-day consensus conference to develop summary statements via a series of alternating breakout and plenary sessions. In these sessions, we identified supporting evidence and generated practice guidelines and/or directions for future research.

RESULTS

Of the 46 questions considered, we found consensus for 20. We found inadequate evidence for 21 questions and for the remaining five we found data but no consensus. Full versions of workgroup findings are available on the Internet at http://www.ADQI.net.

CONCLUSIONS

Despite limited data, broad areas of consensus exist for use of CRRT and guideline development appears feasible. Equally broad areas of disagreement also exist and additional basic and applied research in acute renal failure is needed.

The Acute Dialysis Quality Initiative--part II: patient selection for CRRT

The delivery of optimal acute dialytic support requires that the correct patients be selected for such treatment in a timely fashion and that such treatment be delivered at the appropriate dose, for an appropriate length of time, and for the appropriate indications. The Acute Dialysis Quality Initiative sought to address these issues through an expert-enhanced review of the literature. This article represents a condensation of its findings with regard to patients selection for CRRT, indications for initiation of treatment, transition to other treatments, cessation of treatment, and availability of continuous therapy. The article offers recommendations for clinical practice based on the findings of the expert group. It also offers suggestions and sets priorities for future research in this important area of critical care nephrology.

Strategies for Treatment and Prevention of Acute Renal Failure

Acute renal failure (ARF) is a potentially life-threatening medical condition that often complicates the hospitalization of critically ill patients. A variety of therapeutic strategies has been studied for both preventing ischemic and nephrotoxic injury to the kidney and improving renal function in established ARF. This article summarizes the role of pharmacologic therapy in the treatment of ARF. Strategies to reduce extracellular fluid volume and preserve renal function with loop diuretics, low-dose dopamine, and renal replacement therapy will be discussed. The value of preventative therapy has increased, and identifying patients at high risk for development of ARF is critical. Modification of drug regimens, administration of less nephrotoxic medications, and volume expansion prior to nephrotoxin administration can minimize toxicity to the kidney. The search for new agents that can improve survival, decrease the need for renal replacement therapy, and hasten the recovery of renal function in ARF is ongoing.

Effects of early high-volume continuous venovenous hemofiltration on survival and recovery of renal function in intensive care patients with acute renal failure: a prospective, randomized trial

OBJECTIVE

To study the effects of the initiation time of continuous venovenous hemofiltration and of the ultrafiltrate rate in patients with circulatory and respiratory insufficiency developing early oliguric acute renal failure. The primary end points were mortality at 28 days and recovery of renal function.

DESIGN

A randomized, controlled, two-center study.

SETTING

The closed-format multidisciplinary intensive care units of a university hospital (30 beds) and a teaching hospital (18 beds).

PATIENTS AND INTERVENTIONS

A total of 106 ventilated severely ill patients who were oliguric despite massive fluid resuscitation, inotropic support, and high-dose intravenous diuretics were randomized into three groups. Thirty-five patients were treated with early high-volume hemofiltration (72-96 L per 24 hrs), 35 patients with early low-volume hemofiltration (24-36 L per 24 hrs), and 36 patients with late low-volume hemofiltration (24-36 L per 24 hrs).

RESULTS

Median ultrafiltrate rate was 48.2 (42.3-58.7) mL.kg(-1).hr(-1) in early high-volume hemofiltration, 20.1 (17.5-22.0) mL.kg(-1).hr(-1) in early low-volume hemofiltration, and 19.0 (16.6-21.1) mL.kg(-1).hr(-1) in late low-volume hemofiltration. Survival at day 28 was 74.3% in early high-volume hemofiltration, 68.8% in early low-volume hemofiltration, and 75.0% in late low-volume hemofiltration (p =.80). On average, hemofiltration started 7 hrs after inclusion in the early groups and 42 hrs after inclusion in the late group. All hospital survivors had recovery of renal function at hospital discharge, except for one patient in the early low-volume hemofiltration group. Median duration of renal failure in hospital survivors was 4.3 (1.4-7.8) days in early high-volume hemofiltration, 3.2 (2.4-5.4) days in early low-volume hemofiltration, and 5.6 (3.1-8.5) days in late low-volume hemofiltration (p =.25).

CONCLUSIONS

In the present study of critically ill patients with oliguric acute renal failure, survival at 28 days and recovery of renal function were not improved using high ultrafiltrate volumes or early initiation of hemofiltration.

The Acute Dialysis Quality Initiative--part IV: membranes for CRRT

The extracorporeal membrane used in a continuous renal replacement therapy (CRRT) for the treatment of a critically ill patient with acute renal failure (ARF) is vitally important for several reasons, including its influence on biocompatibility and filter performance. The clinical relevance of membrane-related biocompatibility markers traditionally used in chronic hemodialysis remains unclear in CRRT. Numerous approaches may be used to assess membrane and filter performance in CRRT, but no specific methodology is accepted widely at present. Although a potential benefit of certain membranes used for CRRT is adsorptive removal of inflammatory mediators, this issue has not been assessed carefully in well-designed clinical trials. These and other issues should be the subject of future clinical research efforts.