Multicenter clinical trial of recombinant human insulin-like growth factor I in patients with acute renal failure

Renal repair and recovery

OBJECTIVE

To review the cellular and molecular mechanisms of renal repair and recovery after acute kidney injury (AKI).

DATA SOURCE

The data were summarized from published research articles.

RESULTS

In AKI, there is an acute inflammatory response, epithelial cell necrosis and apoptosis, and shedding of epithelial cells into the tubular lumen. Recent work demonstrates that repopulation of damaged renal tubules occurs primarily from proliferation of tubular epithelial cells and resident renal-specific stem cells, with some contribution of paracrine factors from bone marrow-derived mesenchymal stem cells. In addition, growth factors seem to play a critical role in the repair process in animal models of renal injury. However, attempts to use growth factors in the clinical setting to attenuate human AKI or accelerate renal repair have not yet been successful. The endothelium also plays a critical role in the pathogenesis of AKI. Lastly, in human studies, the effect of dialysis on renal recovery remains poorly understood.

CONCLUSIONS

Experimental animal models of AKI demonstrate that renal recovery and repair involves proliferation of tubular epithelial cells and stem cell populations and the coordinated contribution of multiple growth factors. Future efforts to improve recovery from AKI and improve patient outcomes may include novel therapies based on manipulation of populations of stem cells and augmenting repopulation of renal tubules.

Marked variation in the definition and diagnosis of delayed graft function: a systematic review

BACKGROUND

The term delayed graft function (DGF) is commonly used to describe the need for dialysis after receiving a kidney transplant. DGF increases morbidity after transplantation, prolongs hospitalization and may lead to premature graft failure. Various definitions of DGF are used in the literature without a uniformly accepted technique to identify DGF.

METHODS

We performed a systematic review of the literature to identify all of the different definitions and diagnostic techniques to identify DGF.

RESULTS

We identified 18 unique definitions for DGF and 10 diagnostic techniques to identify DGF.

CONCLUSIONS

The utilization of heterogeneous clinical criteria to define DGF has certain limitations. It will lead to delayed and sometimes inaccurate diagnosis of DGF. Hence a diagnostic test that identifies DGF reliably and early is necessary. Heterogeneity, in the definitions used for DGF, hinders the evolution of a diagnostic technique to identify DGF, which requires a gold standard definition. We are in need of a new definition that is uniformly accepted across the kidney transplant community. The new definition will be helpful in promoting better communication among transplant professionals and aids in comparing clinical studies of diagnostic techniques to identify DGF and thus may facilitate clinical trials of interventions for the treatment of DGF.

Emerging urinary biomarkers in the diagnosis of acute kidney injury

BACKGROUND: Acute kidney injury (AKI) represents a common and devastating problem in clinical medicine. The lack of early biomarkers for AKI has led to a delay in initiating potentially effective therapies. OBJECTIVE: Identification of novel urinary biomarkers for AKI that have progressed to the clinical phase of the biomarker discovery process. METHODS: A literature review (PubMed, MedLine) from 2000 to the present. RESULTS/CONCLUSIONS;: The most promising AKI biomarkers include neutrophil gelatinase-associated lipocalin, IL-18, kidney injury molecule-1 and liver-type fatty acid binding protein. Studies to validate the sensitivity and specificity of these biomarkers in clinical samples from large cohorts and from multiple clinical situations are in progress, facilitated by the development of commercial tools for their measurement.

Urine NGAL predicts severity of acute kidney injury after cardiac surgery: a prospective study

BACKGROUND AND OBJECTIVES

The authors have previously shown that urine neutrophil gelatinase-associated lipocalin (NGAL), measured by a research ELISA, is an early predictive biomarker of acute kidney injury (AKI) after cardiopulmonary bypass (CPB). In this study, whether an NGAL immunoassay developed for a standardized clinical platform (ARCHITECT analyzer, Abbott Diagnostics Division, Abbott Laboratories, Abbott Park, IL) can predict AKI after CPB was tested.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

In a pilot study with 136 urine samples (NGAL range, 0.3 to 815 ng/ml) and 6 calibration standards (NGAL range, 0 to 1000 ng/ml), NGAL measurements by research ELISA and by the ARCHITECT assay were highly correlated (r = 0.99). In a subsequent study, 196 children undergoing CPB were prospectively enrolled and serial urine NGAL measurements obtained by ARCHITECT assay. The primary outcome was AKI, defined as a > or = 50% increase in serum creatinine.

RESULTS

AKI developed in 99 patients (51%), but the diagnosis using serum creatinine was delayed by 2 to 3 d after CPB. In contrast, mean urine NGAL levels increased 15-fold within 2 h and by 25-fold at 4 and 6 h after CPB. For the 2-h urine NGAL measurement, the area under the curve was 0.95, sensitivity was 0.82, and the specificity was 0.90 for prediction of AKI using a cutoff value of 100 ng/ml. The 2-h urine NGAL levels correlated with severity and duration of AKI, length of stay, dialysis requirement, and death.

CONCLUSIONS

Accurate measurements of urine NGAL are obtained using the ARCHITECT platform. Urine NGAL is an early predictive biomarker of AKI severity after CPB.

Diagnosis, epidemiology and outcomes of acute kidney injury

Acute kidney injury is an increasingly common and potentially catastrophic complication in hospitalized patients. Early observational studies from the 1980s and 1990s established the general epidemiologic features of acute kidney injury: the incidence, prognostic significance, and predisposing medical and surgical conditions. Recent multicenter observational cohorts and administrative databases have enhanced our understanding of the overall disease burden of acute kidney injury and trends in its epidemiology. An increasing number of clinical studies focusing on specific types of acute kidney injury (e.g., in the setting of intravenous contrast, sepsis, and major surgery) have provided further details into this heterogeneous syndrome. Despite our sophisticated understanding of the epidemiology and pathobiology of acute kidney injury, current prevention strategies are inadequate and current treatment options outside of renal replacement therapy are nonexistent. This failure to innovate may be due in part to a diagnostic approach that has stagnated for decades and continues to rely on markers of glomerular filtration (blood urea nitrogen and creatinine) that are neither sensitive nor specific. There has been increasing interest in the identification and validation of novel biomarkers of acute kidney injury that may permit earlier and more accurate diagnosis. This review summarizes the major epidemiologic studies of acute kidney injury and efforts to modernize the approach to its diagnosis.

Do stem cells exist in the adult kidney?

Adult stem cells exist in many organs and play a critical role in normal cell turnover and the response to injury. The existence of adult stem cells in the mammalian kidney remains controversial. Kidney stem cells have been isolated and characterized by many groups, often with discrepant results. This article will review the current state of knowledge regarding adult kidney stem cells and discuss future directions for kidney stem cell research.

Proteomics for biomarker discovery in acute kidney injury

Acute kidney injury (AKI), previously referred to as acute renal failure, represents a common and devastating problem in clinical medicine. Despite significant improvements in therapeutics, the mortality and morbidity associated with AKI remain high. A major reason for this is the lack of early markers for AKI, and hence an unacceptable delay in initiating therapy. Fortunately, the application of innovative technologies such as functional genomics and proteomics to human and animal models of AKI has uncovered several novel biomarkers and therapeutic targets. The most promising of these are chronicled in this review. These include the identification of biomarker panels in plasma (neutrophil gelatinase-associated lipocalin and cystatin C) and urine (neutrophil gelatinase-associated lipocalin, kidney injury molecule-1, interleukin-18, cystatin C, alpha1-microglobulin, Fetuin-A, Gro-alpha, and meprin). It is likely that the AKI panels will be useful for timing the initial insult, and assessing the duration and severity of AKI. It is also probable that the AKI panels will distinguish between the various etiologies of AKI and predict clinical outcomes. It will be important in future studies to validate the sensitivity and specificity of these biomarker panels in clinical samples from large cohorts and from multiple clinical situations. Such studies will be facilitated markedly by the development of commercial tools for the reproducible measurement of biomarkers across different laboratories.

Urinary biomarkers for acute kidney injury: perspectives on translation

Acute kidney injury (previously known as acute renal failure) is a common complication in hospitalized patients, and its incidence has risen significantly in the past 15 yr. Despite significant technical advances in therapeutics, the mortality and morbidity rates associated with acute kidney injury remain dismally high and have not appreciably improved during the past four decades. Although the serum creatinine concentration performs fairly well for estimating kidney function in patients with stable chronic kidney disease, it performs poorly in the setting of acute disease. An ideal biomarker for acute kidney injury would help clinicians and scientists diagnose the most common form of acute kidney injury in hospitalized patients, acute tubular necrosis, early and accurately and may aid to risk-stratify patients with acute kidney injury by predicting the need for renal replacement therapy, the duration of acute kidney injury, the length of stay, and mortality. Herein is reviewed the diagnostic and prognostic performance of several types of urinary biomarkers for the diagnosis and risk stratification of acute kidney injury. The major types of urinary biomarkers fall into three classes: (1) Inflammatory, (2) renal tubular proteins that are excreted into the urine after injury, and (3) surrogate markers of tubular injury. Also discussed are statistical issues in evaluating the accuracy of biomarkers as diagnostic tests. It is likely that a panel of biomarkers, rather than a single biomarker, will be needed to perform extremely well in these three situations.

Fenoldopam reduces the need for renal replacement therapy and in-hospital death in cardiovascular surgery: a meta-analysis

OBJECTIVE

Acute renal failure is a common and threatening complication in patients undergoing cardiovascular surgery. To determine the efficacy of fenoldopam in the prevention of acute renal failure, the authors performed a systematic review of randomized, controlled trials and propensity-matched studies in patients undergoing cardiovascular surgery.

DESIGN

Meta-analysis.

SETTING

Hospitals.

PARTICIPANTS

A total of 1,059 patients from 13 randomized and case-matched studies were included in the analysis.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Google Scholar, PubMed, and scientific sessions were searched (updated November 2006). Authors and external experts were contacted. Four unblinded reviewers selected controlled trials that used fenoldopam in the prevention or treatment of acute renal failure in cardiovascular surgery. Four reviewers independently abstracted patient data, treatment characteristics, and outcomes. Pooled estimates showed that fenoldopam consistently and significantly reduced the need for renal replacement therapy (odds ratio = 0.37 [0.23-0.59], p < 0.001) and in-hospital death (odds ratio = 0.46 [0.29-0.75], p = 0.01). These benefits were associated with shorter intensive care unit stay (weighted mean difference [WMD] = -0.93 days [-1.27; -0.58], p = 0.002). Sensitivity analyses, tests for small study bias, and heterogeneity assessment further confirmed the main analysis.

CONCLUSIONS

This meta-analysis provides evidence that fenoldopam may confer significant benefits in preventing renal replacement therapy and reducing mortality in patients undergoing cardiovascular surgery.

Potential interventions in sepsis-related acute kidney injury

Sepsis is an important cause of morbidity and mortality. Acute kidney injury often complicates sepsis, leading to greater complexity, cost of care, and worsening prognosis. In recent years, a consensus definition of acute kidney injury has been developed, facilitating research into the pathophysiology and epidemiology of this disorder. New and emerging biomarkers to recognize kidney injury before functional abnormalities are manifest may allow early recognition and facilitate prevention or treatment. Furthermore, advances in the clinical management of sepsis may have secondary benefits with respect to renal outcomes. Existing and hybrid extracorporeal therapies are being investigated not only as means to replace lost kidney function but also to modulate the immune response to sepsis. For those who have more advanced forms of kidney injury, strategies to promote renal recovery are being sought to minimize the long-term consequences of impaired kidney function. This review provides an update on the current state of the science and a glimpse toward the future of intervention in sepsis-related acute kidney injury.

Technology Insight: biomarker development in acute kidney injury--what can we anticipate?

Early diagnosis has been the 'Achilles heel' of acute kidney injury (AKI) that has prevented successful implementation of treatment strategies. To date, pharmacological intervention has been largely unsuccessful or equivocal, and morbidity and mortality associated with AKI have remained unacceptably high. Despite their well-known limitations, the most widely used biomarkers for the early diagnosis of AKI are serum creatinine, blood urea nitrogen and urine output. Development of new biomarkers is imperative. A variety of methods have been employed to discover new biomarkers of AKI, including transcriptomics, proteomics, gene arrays, lipidomics and imaging technologies. Clinical trials are underway to establish the validity of the biomarkers discovered using these techniques. This Review summarizes the importance of biomarkers of AKI, from their discovery to clinical practice, from the current perspective and that of what to expect in the future. Great strides forward are being made in breaking down important barriers to the successful prevention and treatment of this devastating disorder.

Biomarkers for the early detection of acute kidney injury

Acute kidney injury (AKI), previously referred to as acute renal failure (ARF), represents a persistent problem in clinical medicine. Despite significant improvements in therapeutics, the mortality and morbidity associated with AKI remain high. A major reason for this is the lack of early markers for AKI, akin to troponins in acute myocardial disease, and hence an unacceptable delay in initiating therapy. Fortunately, the application of innovative technologies such as functional genomics and proteomics to human and animal models of AKI has uncovered several novel genes and gene products that are emerging as biomarkers. The most promising of these are chronicled in this article. These include a plasma panel [neutrophil gelatinase-associated lipocalin (NGAL) and cystatin C] and a urine panel [NGAL, interleukin 18 (IL-18), and kidney injury molecule 1 (KIM)-1]. As they represent sequentially expressed biomarkers, it is likely that the AKI panels will be useful for timing the initial insult and assessing the duration of AKI. Based on the differential expression of the biomarkers, it is also likely that the AKI panels will distinguish between the various types and etiologies of AKI. It will be important in future studies to validate the sensitivity and specificity of these biomarker panels in clinical samples from large cohorts and from multiple clinical situations.

The prognostic importance of a small acute decrement in kidney function in hospitalized patients: a systematic review and meta-analysis

BACKGROUND

Recently, acute kidney injury defined by small changes in serum creatinine levels was associated with worse short-term outcomes; however, the precision and variability of this association was not fully explored.

STUDY DESIGN

Systematic review and meta-analysis.

SETTING & PARTICIPANTS

Hospitalized patients.

SELECTION CRITERIA FOR STUDIES

MEDLINE and EMBASE databases were searched for observational cohort studies and randomized controlled trials published from 1990 through February 2007 that provided information for small changes in serum creatinine levels.

PREDICTOR

Small acute changes in serum creatinine levels by absolute and percentage of changes in serum creatinine levels (lower threshold for increase in serum creatinine <0.5 mg/dL or <25%).

OUTCOME

Short-term mortality (<or=30 days).

RESULTS

Compared with controls, patients with a 10% to 24% increase in creatinine levels had a relative risk (RR) of death of 1.8 (95% confidence interval [CI], 1.3 to 2.5). By comparison, subjects with a 25% to 49% acute change in creatinine levels had an RR of death of 3.0 (95% CI, 1.6 to 5.8), and those with the largest change (>or=50%) had the greatest RR of death (RR, 6.9; 95% CI, 2.0 to 24.5). Results were similar when absolute changes in creatinine levels were considered and when pooled estimates of adjusted RR were used.

LIMITATIONS

Individual patient data were unavailable; thus, only group-level data were pooled for meta-analysis. Results showed a significant degree of statistical heterogeneity that was only partially ameliorated by separating studies into subsets based on clinical setting.

CONCLUSIONS

Short-term mortality and acute decreases in renal function are associated through a graded relationship such that even mild changes in serum creatinine levels portend worse outcome in a variety of clinical settings and patient-types.

Insulin-like growth factor-1 sustains stem cell mediated renal repair

In mice with cisplatin-induced acute kidney injury, administration of bone marrow-derived mesenchymal stem cells (MSC) restores renal tubular structure and improves renal function, but the underlying mechanism is unclear. Here, we examined the process of kidney cell repair in co-culture experiments with MSC and cisplatin-injured proximal tubular epithelial cells (PTEC). Exposure of PTEC to cisplatin markedly reduced cell viability at 4 days, but co-culture with MSC provided a protective effect by promoting tubular cell proliferation. This effect was mediated by insulin-like growth factor-1 (IGF-1), highly expressed by MSC as mRNA and protein, since blocking the growth factor's function with a specific antibody attenuated cell proliferation of PTEC. Confirming this, knocking down IGF-1 expression in MSC by small interfering-RNA also resulted in a significant decrease in PTEC proliferation and increased apoptosis. Furthermore, in the murine model of cisplatin-induced kidney injury, administering IGF-1 gene-silenced MSC limited their protective effect on renal function and tubular structure. These findings indicate that MSC exert beneficial effects on tubular cell repair in acute kidney injury by producing the mitogenic and pro-survival factor IGF-1.

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.

Pharmacologic treatment of acute kidney injury: why drugs haven't worked and what is on the horizon

Current strategies to limit the extent of injury in acute renal failure are based on extensive studies that identified cellular and molecular mechanisms of acute kidney injury. Despite successes in various animal models, translation to human studies has failed or studies are inconclusive. This review describes past failures and barriers to successful clinical trials. It also focuses on promising preclinical studies using novel compounds that currently are in or close to human investigation. Implementation of previous or novel compounds in well-designed clinical trials provides hope for the successful treatment of this devastating disorder.

Beneficial impact of fenoldopam in critically ill patients with or at risk for acute renal failure: a meta-analysis of randomized clinical trials

BACKGROUND

Acute kidney injury is common in critically ill patients. Fenoldopam mesylate is a potent dopamine A-1 receptor agonist that increases blood flow to the renal cortex and outer medulla. Because there is uncertainty about the benefits of fenoldopam in such a setting, we performed a systematic review of randomized controlled trials of intensive care unit patients or those undergoing major surgery.

METHODS

BioMedCentral, CENTRAL, PubMed, and conference proceedings were searched (updated October 2005). Investigators and external experts were contacted. Two unblinded reviewers selected randomized controlled trials that used fenoldopam in the prevention or treatment of acute kidney injury in postoperative or intensive care patients. Studies involving the prevention of contrast nephropathy or containing duplicate data were excluded from analysis. Two reviewers independently abstracted patient data, treatment characteristics, and outcomes.

RESULTS

A total of 1,290 patients from 16 randomized studies were included in the analysis. Pooled estimates showed that fenoldopam consistently and significantly reduced the risk for acute kidney injury (odds ratio [OR], 0.43; 95% confidence interval [CI], 0.32 to 0.59; P < 0.001), need for renal replacement therapy (OR, 0.54; 95% CI, 0.34 to 0.84; P = 0.007), and in-hospital death (OR, 0.64; 95% CI, 0.45 to 0.91; P = 0.01). These benefits were associated with shorter intensive care unit stay (weighted mean difference, -0.61 days; 95% CI, -0.99 to -0.23; P = 0.002). Sensitivity analyses, tests for small-study bias, and heterogeneity assessment further confirmed the main analysis.

CONCLUSION

This analysis suggests that fenoldopam reduces the need for renal replacement and mortality in patients with acute kidney injury. A large, multicenter, appropriately powered trial will need to be performed to confirm these results.

Elevated plasma concentrations of IL-6 and elevated APACHE II score predict acute kidney injury in patients with severe sepsis

Acute kidney injury (AKI) is common in critically ill patients with severe sepsis (SS), and the predictors of AKI in this population have not been well characterized. The study group was the placebo group of the Prospective Recombinant Human Activated Protein C Worldwide Evaluation in Severe Sepsis (PROWESS) data set. PROWESS is a prospective, randomized, controlled study of the use of drotrecogin alpha (activated) for the treatment of SS. Placebo patients who had an admission renal sepsis organ failure score of 2 or more were excluded. AKI was defined as an increase in serum creatinine of 25% or 0.3 mg/dl during the first week postbaseline. The incidence of relevant parameters was then compared in patients with and without AKI. Half of the patients were randomly assigned to a model-building data set, and multivariable Cox regression was used to determine risk factors. Factors that remained significant in the remaining "model validation" data set were considered significant. Of the 840 patients in the placebo group, 547 met inclusion criteria. Of the 547 patients, 127 (23.2%) patients met criteria for AKI. The mean age of the 547 patients was 59.8 +/- 17.0, and 43.3% of the cohort were female. The ethnicity breakdown was as follows: White 83.2%, black 5.9%, and other 11%. Univariate analyses indicated that patients with AKI had a higher incidence of a dependence on the basis of activity of daily living scale (38.6 versus 26.7%; P = 0.01), a lower baseline platelet count (193,000 versus 222,000; P = 0.02), a higher baseline respiratory Sepsis Organ Failure Assessment score (2.9 versus 2.7; P = 0.02), higher preinfusion Acute Physiology and Chronic Health Evaluation II (APACHE II) score (24.8 versus 22.0; P = 0.0002), older age (63.7 versus 58.7 yr; P = 0.008), and higher log IL-6 (6.6 versus 5.8; P = 0.0006). In a multivariable Cox regression, the predictors of AKI were log IL-6 (P < 0.0001) and APACHE II (P = 0.0008). Increased log IL-6 and APACHE II score are significant risk factors of AKI in patients with SS. IL-6 data and the absence of correlation with measures of hypotension (e.g., mean arterial pressure, dosage of vasopressors) support the notion that inflammation is a significant component of AKI in SS.

Mechanistic biomarkers for cytotoxic acute kidney injury

Acute kidney injury is a common condition and is associated with a high mortality rate. It has been recognised that routinely used measures of renal function, such as levels of blood urea nitrogen and serum creatinine, increase significantly only after substantial kidney injury occurs and then with a time delay. Insensitivity of such tests delays the diagnosis in humans, making it particularly challenging to administer putative therapeutic agents in a timely fashion. Furthermore, this insensitivity affects the evaluation of toxicity in preclinical studies by allowing drug candidates, which have low, but nevertheless important, nephrotoxic side effects in animals, to pass the preclinical safety criteria only to be found to be clinically nephrotoxic with great human costs. This review presents the current status of sensitive and specific biomarkers to detect preclinical and clinical renal injury and summarises the techniques used to quantitate these biomarkers in biological fluids.

Delayed administration of darbepoetin or erythropoietin protects against ischemic acute renal injury and failure

Administration of human recombinant erythropoietin (EPO) at time of acute ischemic renal injury (IRI) inhibits apoptosis, enhances tubular epithelial regeneration, and promotes renal functional recovery. The present study aimed to determine whether darbepoetin-alfa (DPO) exhibits comparable renoprotection to that afforded by EPO, whether pro or antiapoptotic Bcl-2 proteins are involved, and whether delayed administration of EPO or DPO 6 h following IRI ameliorates renal dysfunction. The model of IRI involved bilateral renal artery occlusion for 45 min in rats (N = 4 per group), followed by reperfusion for 1-7 days. Controls were sham-operated. Rats were treated at time of ischemia or sham operation (T0), or post-treated (6 h after the onset of reperfusion, T6) with EPO (5000 IU/kg), DPO (25 mug/kg), or appropriate vehicle by intraperitoneal injection. Renal function, structure, and immunohistochemistry for Bcl-2, Bcl-XL, and Bax were analyzed. DPO or EPO at T0 significantly abrogated renal dysfunction in IRI animals (serum creatinine for IRI 0.17 +/- 0.05 mmol/l vs DPO-IRI 0.08 +/- 0.03 mmol/l vs EPO-IRI 0.04 +/- 0.01 mmol/l, P = 0.01). Delayed administration of DPO or EPO (T6) also significantly abrogated subsequent renal dysfunction (serum creatinine for IRI 0.17 +/- 0.05 mmol/l vs DPO-IRI 0.06 +/- 0.01 mmol/l vs EPO-IRI 0.03 +/- 0.03 mmol/l, P = 0.01). There was also significantly decreased tissue injury (apoptosis, P < 0.05), decreased proapoptotic Bax, and increased regenerative capacity, especially in the outer stripe of the outer medulla, with DPO or EPO at T0 or T6. These results reaffirm the potential clinical application of DPO and EPO as novel renoprotective agents for patients at risk of ischemic acute renal failure or after having sustained an ischemic renal insult.

Acute renal failure: much more than a kidney disease

Acute renal failure is a frequent clinical problem with an increasing incidence, an unacceptably high mortality rate that has not improved in more than 40 years, and no specific treatment, yet renal failure is not the usual cause of death. The role of inflammation has been documented in both acute renal injury and cardiac dysfunction. Several investigators have shown that congestive heart failure is associated with increased mortality in patients with acute renal failure. This article reviews some of the cardiac and other distant organ effects of acute renal injury that may be important in the morbidity and mortality observed clinically. Cardiac changes after experimental renal ischemia include cytokine induction, leukocyte infiltration, cell death by apoptosis, and impaired function. I propose that the extrarenal effects of kidney injury must be considered in designing therapies. Acute renal failure has systemic consequences and must be thought of as more than a kidney disease.

Erythropoietin and Acute Renal Failure

The hemopoietic growth factor erythropoietin (EPO) has been recognized to be a multifunctional cytokine that plays a key role in ischemic preconditioning in the brain and heart. The EPO receptor is expressed widely in the kidney, and we review the important findings from the use of EPO in experimental models of acute renal failure that show that EPO reduces tubular cell death and hence the dysfunction induced by ischemia reperfusion injury, and we explore how these observations may be translated into the clinical arena.

Perioperative acute renal failure

PURPOSE OF REVIEW

Recent biochemical evidence increasingly implicates inflammatory mechanisms as precipitants of acute renal failure. In this review, we detail some of these pathways together with potential new therapeutic targets.

RECENT FINDINGS

Neutrophil gelatinase-associated lipocalin appears to be a sensitive, specific and reliable biomarker of renal injury, which may be predictive of renal outcome in the perioperative setting. For estimation of glomerular filtration rate, cystatin C is superior to creatinine. No drug is definitively effective at preventing postoperative renal failure. Clinical trials of fenoldopam and atrial natriuretic peptide are, at best, equivocal. As with pharmacological preconditioning of the heart, volatile anaesthetic agents appear to offer a protective effect to the subsequently ischaemic kidney.

SUMMARY

Although a greatly improved understanding of the pathophysiology of acute renal failure has offered even more therapeutic targets, the maintenance of intravascular euvolaemia and perfusion pressure is most effective at preventing new postoperative acute renal failure. In the future, strategies targeting renal regeneration after injury will use bone marrow-derived stem cells and growth factors such as insulin-like growth factor-1.

Acute renal failure in the critically ill

PURPOSE OF REVIEW

Acute renal failure occurs frequently in hospitalized patients and is associated with significant morbidity and mortality. An effort to better understand the epidemiology and pathophysiology of this disease will hopefully lead to improvement in patient outcomes. Considerable effort has been expended to develop techniques to prevent acute renal failure or to facilitate its resolution. In this review we attempt to summarize some of these recent advances.

RECENT FINDINGS

Attempts have been made to clearly define acute renal failure. Among the available pharmacologic agents, current evidence suggests that with the possible exception of radio-contrast-induced acute renal failure, no drugs are capable of preventing the condition or hastening its recovery. Advances in techniques and understanding of how to best provide renal replacement therapy appear to have improved patient outcomes and several newer treatments are under preclinical evaluation and may hold promise for the future.

SUMMARY

Preventing acute renal failure, improving clinical outcomes of the condition and attempts to hasten renal recovery have all been very attractive but difficult propositions. Recent efforts to explore the underlying pathophysiology and insight into mechanisms leading to acute renal failure have triggered investigators to evaluate novel therapeutic agents and enhance existing dialytic techniques. These hold great promise for improving patient outcomes in the near future.

Identifying critically ill patients at high risk for developing acute renal failure: a pilot study

BACKGROUND

Acute renal failure (ARF) occurs commonly in the intensive care unit (ICU), but predicting which patients will develop ARF is difficult. We set out to determine which risk factors would predict the development of ARF in critically ill patients who are admitted to the ICU without ARF.

METHODS

From August 2002 to April 2003, we enrolled medical-surgical ICU admissions into a cohort using a sampling tool based on their risk factor (RF) profile. The risk factors we identified were separated into 3 categories: chronic major, chronic minor, and acute RFs. Combinations of these RFs were used to create a sampling tool and identify patients to enroll into our cohort. Patients with end-stage renal disease and ARF upon admission to the ICU were excluded.

RESULTS

We enrolled 194 patients over a 14-month period. The mean age of the cohort was 64.6 +/- 14.7 years. The percentage of Caucasians, African Americans, and Hispanics was 40.7%, 50.5%, and 3.6%, respectively. In a univariate analysis of the entire cohort, increasing APACHE II quartile, increased A-a gradient, presence of systemic inflammatory response syndrome (SIRS), decreased levels of serum albumin, and presence of active cancer predicted ARF. In a multiple logistic regression analysis, decreased serum albumin (high levels of serum albumin were protective), increased A-a gradient, and cancer were associated with development of ARF (OR 2.17, 1.04, and 2.86, respectively).

CONCLUSION

Decreased levels of serum albumin concentration, increased A-a gradient, and presence of active cancer predict which patients who are admitted to the ICU will develop ARF.

Prophylactic fenoldopam for renal protection in sepsis: a randomized, double-blind, placebo-controlled pilot trial

OBJECTIVE

Acute renal failure is common in septic patients. Fenoldopam, a dopamine-1 receptor agonist, increases renal blood flow and may, therefore, reduce the risk of acute renal failure in such patients. Accordingly, we sought to determine the safety and efficacy of fenoldopam for the prevention of acute renal failure in septic patients.

DESIGN

Prospective, double-blind, placebo-controlled trial.

SETTING

Three multidisciplinary intensive care units at a university hospital.

PATIENTS

Three hundred septic patients with baseline serum creatinine concentrations <150 micromol/L.

INTERVENTIONS

We randomized patients to a continuous infusion of either fenoldopam (n = 150) at 0.09 microg x kg x min or placebo (n = 150) while in the intensive care unit. The primary outcome measure was the incidence of acute renal failure, defined as a serum creatinine concentration increase to >150 micromol/L, during study drug infusion.

MEASUREMENTS AND MAIN RESULTS

The incidence of acute renal failure was significantly lower in the fenoldopam group compared with the control group (29 vs. 51 patients; p = .006). The odds ratio of developing acute renal failure for patients treated with fenoldopam was estimated to be 0.47 (p = .005). The difference in the incidence of severe acute renal failure (creatinine >300 mumol/L), however, failed to achieve statistical significance (10 vs. 21; p = .056). The length of intensive care unit stay in surviving patients was significantly lower in the fenoldopam group compared with the control group (10.64 +/- 9.3 vs. 13.4 +/- 14.0; p < .001). There were no complications of fenoldopam infusion. A direct effect of treatment on the probability of death, beyond its effect on acute renal failure, was not significant (odds ratio = 0.68, p = .1).

CONCLUSIONS

Compared with placebo, low-dose fenoldopam resulted in a smaller increase in serum creatinine in septic patients. The clinical significance of this finding is uncertain. A large multiple-center trial is now needed to confirm these findings.

Mechanisms of Disease: cell death in acute renal failure and emerging evidence for a protective role of erythropoietin

Acute renal failure--characterized by a sudden loss of the ability of the kidneys to excrete nitrogenous waste, and to maintain electrolyte homeostasis and fluid balance--is a frequently encountered clinical problem, particularly in the intensive care unit. Unfortunately, advances in supportive interventions have done little to reduce the high mortality associated with this condition. Might erythropoietin (EPO) have utility as a therapeutic agent in acute renal failure? This hormone mediates anti-apoptotic effects in the bone marrow, facilitating maturation and differentiation of erythroid progenitors. New evidence indicates that EPO also exerts anti-apoptotic effects in the brain, heart and vasculature, which can limit the degree of organ damage. Here, we review the emerging biological role of EPO in the kidney and the pathophysiology of ischemia-reperfusion injury in an attempt to understand the therapeutic potential of EPO in acute renal failure.

La reprise retardée de fonction : une complication fréquente, non résolue, en transplantation rénale

Delayed graft function (DGF) is a frequent and well-known complication of renal transplantation, which occurs in 30% of cadaver kidney allografts. It has an economic cost that is the result of prolonged patient hospitalization and the need for hemodialysis sessions; it also increases the risk of acute allograft rejection and may affect long-term graft survival. Lots of risk factors were identified, like donor hemodynamic compromise or prolonged cold ischemia time; however, incidence of DGF remains high due to the frequent use of marginal donors due to organ shortage. Recent advances in the pathophysiology of DGF point the importance of the ischemia-reperfusion injury mechanisms and some therapeutics that may reduce them are under investigation, like the use of new solutions to improve organ preservation and the use of some antioxidant and anti-inflammatory drugs.

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.

External validation of severity scoring systems for acute renal failure using a multinational database

OBJECTIVE

Several different severity scoring systems specific to acute renal failure have been proposed. However, most validation studies of these scoring systems were conducted in a single center or in a small number of centers, often the same ones used for their development. Therefore, it is not known whether such severity scoring systems may be widely applied.

DESIGN

Prospective clinical investigation.

SETTING

Intensive care units.

PATIENTS

One thousand seven hundred and forty-two intensive care unit patients with acute renal failure who were either treated with renal replacement therapy or fulfilled predefined criteria.

INTERVENTIONS

Demographic and clinical information and outcomes were measured.

MEASUREMENTS AND MAIN RESULTS

Scores for four acute renal failure-specific scoring systems and two general scoring systems (Simplified Acute Physiology Score II and Sequential Organ Failure Assessment) were calculated, and their discrimination and calibration were tested with receiver operating characteristic curves and Hosmer-Lemeshow goodness-of fit-tests. For the receiver operating characteristic curves, blood lactate levels were also used as a reference. All scores had an area under the receiver operating characteristic curve <0.7 (Mehta 0.670, Liano 0.698, Chertow 0.610, Paganini 0.643, Simplified Acute Physiology Score II 0.645, Sequential Organ Failure Assessment 0.675, lactate 0.639). For scores that can calculate predicted mortality, the Hosmer-Lemeshow goodness-of-fit test showed poor calibration.

CONCLUSIONS

None of the scoring systems tested had a high level of discrimination or calibration to predict mortality for patients with acute renal failure when tested in a broad cohort of patients from multiple countries. A large, multiple-center database might be needed to improve the discrimination and calibration of acute renal failure scoring system.

Fenoldopam Mesylate in Early Acute Tubular Necrosis: A Randomized, Double-Blind, Placebo-Controlled Clinical Trial

BACKGROUND

Acute tubular necrosis (ATN) occurs commonly in critically ill patients and is associated with increased morbidity and mortality. Fenoldopam is a dopamine receptor alpha1-specific agonist that increases renal blood flow in patients with kidney failure. We hypothesized that administration of low-dose fenoldopam during early ATN would decrease the need for dialysis therapy and/or incidence of death at 21 days.

METHODS

We conducted a prospective, randomized, double-blind, placebo-controlled, clinical trial in 155 patients with early ATN. Patients were considered eligible for enrollment if serum creatinine level increased to 50% greater than admission levels within 24 hours and mean arterial pressure was greater than 70 mm Hg. Patients were randomly assigned to the administration of placebo or fenoldopam for 72 hours.

RESULTS

Overall, 22 of 80 patients (27.5%) in the fenoldopam group reached the primary end point compared with 29 of 75 patients (38.7%) in the placebo group (P = 0.235). This 11% absolute reduction in the primary end point was not statistically significant (P = 0.23). Similarly, there was no difference in the incidence of dialysis therapy between patients randomly assigned to fenoldopam (13 of 80 patients; 16.25%) versus the placebo group (19 of 75 patients; 25.3%; P = 0.163). Moreover, there was no statistically significant difference in 21-day mortality rates between the 2 groups (fenoldopam, 13.8% versus placebo, 25.3%; P = 0.068). In secondary analyses, fenoldopam tended to reduce the primary end point in patients without diabetes and postoperative cardiothoracic surgery patients with early ATN (fenoldopam patients without diabetes, 14 of 54 patients [25.9%] versus placebo patients without diabetes, 23 of 52 patients [44.2%]; P = 0.048) and postoperative cardiothoracic patients (6 of 34 patients [17.6%] versus 14 of 36 patients [38.8%]; P = 0.049). Conversely, fenoldopam did not improve the primary end point in patients with diabetes or those with acute renal failure from other causes. A larger multicenter trial using separate randomizations for patients with and without diabetes will be needed to determine the efficacy of fenoldopam mesylate in specific subpopulations with ATN.

CONCLUSION

Fenoldopam does not reduce the incidence of death or dialysis therapy in intensive care unit patients with early ATN.

Emerging drugs for renal failure

Renal failure involves a significant impairment of the essential functions of the kidney, which can be either acute with sudden and rapid onset (acute renal failure [ARF]) or chronic with gradual onset (chronic renal failure [CRF]). ARF, if detected early, may be halted or reversed, whereas CRF is generally irreversible. Without treatment or intervention, both forms of renal failure lead to end stage renal failure (ESRF) or end stage renal disease (ESRD), requiring renal replacement therapy (RRT) in the form of dialysis or renal transplantation for survival. However, provision of RRT requires expert teams working in specialised units, making therapy of patients with renal failure expensive; furthermore, RRT is complex, with its own complications. Although pharmacological interventions have shown promise in experimental models, these have not been as successful in the clinical setting (e.g., administration of atrial natriuretic peptide, low-dose dopamine). At present, drugs are administered during CRF to either reduce one of the many risk factors of CRF (e.g., angiotensin-converting enzyme inhibitors, statins) or to deal with the consequences of CRF (e.g., erythropoietin, calcitriol). Recent evidence suggests that some of these interventions may provide further direct beneficial effects via reduction of renal inflammation. Although these interventions have greatly improved the prospects for patients suffering ESRF, the development of novel drugs and therapies with which to reduce the consequences of renal failure and ESRD remain topics of great interest. This article reviews the therapies available for the prevention and management of renal failure in adults and describes, in detail, emerging drugs and novel interventions that may soon become available for the treatment or prevention of ESRF.

Spectrum of acute renal failure in the intensive care unit: the PICARD experience

BACKGROUND

Acute renal failure (ARF) in the critically ill is associated with extremely high mortality rates. Understanding the changing spectrum of ARF will be necessary to facilitate quality improvement efforts and to design successful interventional trials.

METHODS

We conducted an observational cohort study of 618 patients with ARF in intensive care units at five academic medical centers in the United States. Participants were required to sign (or have a proxy sign) informed consent for data collection. A comprehensive data collection instrument captured more than 800 variables, most on a daily basis, throughout the course of ARF. Patient characteristics, dialysis status, and major outcomes were determined and stratified by clinical site.

RESULTS

The mean age was 59.5 years, 41% were women, and 20% were of minority race or ethnicity. There was extensive comorbidity; 30% had chronic kidney disease, 37% had coronary artery disease, 29% had diabetes mellitus, and 21% had chronic liver disease. Acute renal failure was accompanied by extrarenal organ system failure in most patients, even those who did not require dialysis. Three hundred and ninety-eight (64%) patients required dialysis. The in-hospital mortality rate was 37%, and the rate of mortality or nonrecovery of renal function was 50%. The median hospital length of stay was 25 days (26 days, excluding patients who died).

CONCLUSION

There is a changing spectrum of ARF in the critically ill, characterized by a large burden of comorbid disease and extensive extrarenal complications, obligating the need for dialysis in the majority of patients. There is wide variation across institutions in patient characteristics and practice patterns. These differences highlight the need for additional multicenter observational and interventional studies in ARF.

Renal protection strategies in the perioperative period

The development of acute renal failure (ARF) in the perioperative period continues to be a vexing condition associated with high morbidity and mortality rates which have been unchanged for several decades. In this article I briefly review recent research categorizing pathogenesis of ARF and mechanisms of recovery. Once ARF is established, its maintenance phase is dependent on several mechanisms that interact with cellular integrity. The main focus of the article is on assessing clinical and experimental interventions to prevent ARF. Unfortunately, existing pharmacological and other interventions show a rather limited efficacy in preventing ARF.

Biologic markers for the early detection of acute kidney injury

PURPOSE OF REVIEW

This review discusses the current status of several biomarkers as potential diagnostic tools in patients with acute kidney disease.

RECENT FINDINGS

Although the term "acute renal failure" has generally been used to describe acute kidney dysfunction that runs the spectrum from mild prerenal azotemia with no renal pathologic changes and no functional failure to severe oliguric renal dysfunction associated with tubular necrosis with failure of function, this spectrum is better described by the term "acute kidney injury." The mortality rate of hospitalized patients with severe acute kidney disease has not decreased significantly over the past 50 years despite advances in supportive care. The absence of sensitive and specific biomarkers for detecting injury early, grading the severity of the injury, and monitoring the response to therapy has impaired progress in the field and has had a very detrimental effect on the design and outcome of clinical trials in acute kidney disease. As a result of reliance on serum creatinine as a marker for injury and diagnosis, the institution of therapy is markedly delayed.

SUMMARY

The search for new biomarkers for acute kidney injury is evolving rapidly with advancement in modern technologies. With better biomarkers we will have the ability to detect injury earlier, identify subclinical injury, provide prognostic information on the course of renal impairment, identify the nephron segments most affected, provide a rationale for segmentation of patients for clinical studies, guide timing of therapy, assess response to therapy, and screen patients at risk for renal injury.

Delayed graft function in kidney transplantation

Delayed graft function is a form of acute renal failure resulting in post-transplantation oliguria, increased allograft immunogenicity and risk of acute rejection episodes, and decreased long-term survival. Factors related to the donor and prerenal, renal, or postrenal transplant factors related to the recipient can contribute to this condition. From experimental studies, we have learnt that both ischaemia and reinstitution of blood flow in ischaemically damaged kidneys after hypothermic preservation activate a complex sequence of events that sustain renal injury and play a pivotal part in the development of delayed graft function. Elucidation of the pathophysiology of renal ischaemia and reperfusion injury has contributed to the development of strategies to decrease the rate of delayed graft function, focusing on donor management, organ procurement and preservation techniques, recipient fluid management, and pharmacological agents (vasodilators, antioxidants, anti-inflammatory agents). Several new drugs show promise in animal studies in preventing or ameliorating ischaemia-reperfusion injury and possibly delayed graft function, but definitive clinical trials are lacking. The goal of monotherapy for the prevention or treatment of is perhaps unattainable, and multidrug approaches or single drug targeting multiple signals will be the next step to reduce post-transplantation injury and delayed graft function.

New concepts: growth hormone, insulin-like growth factor-I and the kidney

Both growth hormone (GH) and IGF-1 have major effects on normal kidney growth, structure and function and participate in the pathogenesis of certain kidney diseases. Furthermore when the kidneys fail there are profound changes in the circulating GH-IGF-1 system and the renal and systemic responses to these hormones. In this brief review we address the advances that have been made in our understanding of the relationship between growth hormone GH and IGF-1 and the kidney in health and the systemic and local perturbations that occur in kidney disease and identify key unanswered questions.

Acute renal failure: definitions, diagnosis, pathogenesis, and therapy

Acute renal failure (ARF), characterized by sudden loss of the ability of the kidneys to excrete wastes, concentrate urine, conserve electrolytes, and maintain fluid balance, is a frequent clinical problem, particularly in the intensive care unit, where it is associated with a mortality of between 50% and 80%. In this review, the epidemiology and pathophysiology of ARF are discussed, including the vascular, tubular, and inflammatory perturbations. The clinical evaluation of ARF and implications for potential future therapies to decrease the high mortality are described.