Prevention and nondialytic treatment of acute renal failure

Treatment of Acute Kidney Injury: A Review of Current Approaches and Emerging Innovations

Acute kidney injury (AKI) is a complex and life-threatening condition with multifactorial etiologies, ranging from ischemic injury to nephrotoxic exposures. Management is founded on treating the underlying cause of AKI, but supportive care-via fluid management, vasopressor therapy, kidney replacement therapy (KRT), and more-is also crucial. Blood pressure targets are often higher in AKI, and these can be achieved with fluids and vasopressors, some of which may be more kidney-protective than others. Initiation of KRT is controversial, and studies have not consistently demonstrated any benefit to early start dialysis. There are no targeted pharmacotherapies for AKI itself, but some do exist for complications of AKI; additionally, medications become a key aspect of AKI management because changes in renal function and dialysis support can lead to issues with both toxicities and underdosing. This review will cover existing literature on these and other aspects of AKI treatment. Additionally, this review aims to identify gaps and challenges and to offer recommendations for future research and clinical practice.

Perioperative considerations for kidney and pancreas-kidney transplantation

Kidney transplantation is the treatment of choice in patients with end-stage renal disease, as it improves survival and quality of life. Living donor kidney transplant prior to pancreas transplantation, or simultaneous pancreas and kidney transplantation are discussed. Patients usually present comorbidities and extensive preoperative workups are recommended, especially cardiac assessment, though type and frequency of surveillance is not established. Nephroprotective strategies include adequate fluid status and goal-directed therapy. The conventional use of diuretics has not demonstrated a real nephroprotective effect at follow-up. Thromboprophylaxis regimes, especially for the pancreatic graft outcome, are of importance. Notably, transplantation in the obese population has increased in recent decades. Strict preoperative evaluation and pulmonary considerations must be kept in mind. Finally, robotic kidney transplant is a recent approach that presents anesthetic challenges, mainly related to steep Trendelenburg position and fluid restriction.

Transaminase and Creatine Kinase Ratios for Differentiating Delayed Acetaminophen Overdose from Rhabdomyolysis

Introduction

Rhabdomyolysis and delayed acetaminophen hepatotoxicity may be associated with elevated serum transaminase values. Establishing the cause of elevated transaminases may be especially difficult because of limited or inaccurate histories of acetaminophen ingestion. We hypothesized that the comparative ratios of aspartate aminotransferase (AST), alanine aminotransferase (ALT), and creatine kinase (CK) can differentiate acetaminophen hepatotoxicity from rhabdomyolysis.

Methods

A retrospective chart review of patients in four hospitals from 2006 to 2011 with a discharge diagnosis of acetaminophen toxicity or rhabdomyolysis was performed. Subjects were classified into three groups: rhabdomyolysis, acetaminophen overdose (all), and acetaminophen overdose with undetectable serum acetaminophen concentrations [acetaminophen(delayed)]. Ratios of AST, ALT, and CK were compared using non-parametric statistical methods.

Results

1,353 subjects were identified and after applying our exclusion criteria there were 160 in the rhabdomyolysis group, 68 in the acetaminophen overdose (all) group, and 29 in the acetaminophen (delayed) group. The AST/ALT ratio for the rhabdomyolysis group was 1.66 (Interquartile range: 1.18–2.22), for the acetaminophen overdose (all) group was 1.38 (1.08–1.69, statistically lower than the rhabdomyolysis group, p = 0.018), and for the acetaminophen (delayed)group was 1.30 (1.06–1.63, p = 0.037). CK/AST ratios were 21.3 (12.8–42.2), 5.49 (2.52–15.1, p < 0.001), and 3.80 (1.43–13.8, p < 0.001) respectively. CK/ALT ratios were 37.1 (16.1–80.0), 5.77 (2.79–25.2, p < 0.001), and 5.03 (2.20–17.4, p < 0.001) respectively. Increasing CK to transaminase ratio cutoffs resulted in increasing test sensitivity but lower specificity.

Conclusion

AST/ALT, CK/AST and CK/ALT ratios are significantly larger in rhabdomyolysis when compared to patients with acetaminophen toxicity. This result suggests that the ratios could be used to identify patients with rhabdomyolysis who otherwise might have been diagnosed as delayed acetaminophen toxicity. Such patients may not require treatment with N-acetylcysteine, resulting in cost savings and improved resource utilization.

Biomarkers of renal recovery after acute kidney injury

Novel biomarkers can be suitable for early acute kidney injury diagnosis and the prediction of the need for dialysis. It remains unclear whether such biomarkers may also play a role in the prediction of recovery after established acute kidney injury or in aiding the decision of when to stop renal support therapy. PubMed, Web of Science and Google Scholar were searched for studies that reported on the epidemiology of renal recovery after acute kidney injury, the risk factors of recovery versus non-recovery after acute kidney injury, and potential biomarkers of acute kidney injury recovery. The reference lists of these articles and relevant review articles were also reviewed. Final references were selected for inclusion in the review based on their relevance. New biomarkers exhibited a potential role in the early diagnosis of acute kidney injury recovery. Urine HGF, IGFBP-7, TIMP-2 and NGAL may improve our ability to predict the odds and timing of recovery and eventually renal support withdrawal. Acute kidney injury recovery requires more study, and its definition needs to be standardized to allow for better and more powerful research on biomarkers because some of them show potential for the prediction of acute kidney injury recovery.

Nephroprotective Effects of Saponins from Leaves of Panax quinquefolius against Cisplatin-Induced Acute Kidney Injury

Although cisplatin is an anticancer drug that has activity against malignant tumor, it often causes nephrotoxicity. Previous reports have confirmed that the saponins from the leaves of P. quinquefolium (PQS) exerted many pharmacological activities. However, the renoprotective effects of PQS were still unknown. The purpose of the present research was to discuss renoprotective effect of PQS in a mouse model of cisplatin-induced acute kidney injury (AKI). The levels of blood urea nitrogen (BUN) and serum creatinine (CRE) were evidently increased in cisplatin-intoxicated mice, which were reversed by PQS. Renal oxidative stress, evidenced by increased malondialdehyde (MDA) level and decline of glutathione (GSH) and superoxide dismutase (SOD) activities, was significantly alleviated by PQS pretreatment. The suppression of inflammatory response by PQS was realized through the decrease the mRNA expression levels of tumor necrosis factor-α (TNF-α) and interleukin-1β (IL-1β) in kidney tissues, which were measured by quantitative real-time polymerase chain reaction (qRT-PCR). Simultaneously, the overexpression of cytochrome P450 E1 (CYP2E1) and heme oxygenase-1 (HO-1) were attenuated by PQS. Furthermore, the effects of Western blotting demonstrated that PQS administration significantly suppressed the protein expression levels of nicotinamide adenine dinucleotide phosphate oxidase type 4 (Nox4), cleaved Caspase-3, cleaved Caspase-9, Bax, nuclear factor-κB (NF-κB), cyclooxygenase-2 (COX-2), and inducible nitric oxide synthase (iNOS), suggesting the inhibition of apoptosis and inflammation response. Overall, PQS may possess protective effects in cisplatin-induced AKI through suppression of oxidative stress, inflammation and apoptosis.

HPLC-PDA Simultaneous Determination and Protective Effect of Anemarrhena asphodeloides Against Acute Renal Failure

We investigated the protective effects against acute renal failure (ARF) of Anemarrhena asphodeloides (AA) and performed simultaneous analysis of three compounds, neomangiferin (1), mangiferin (2), and isomangiferin (3) in AA using a high-performance liquid chromatography-photodiode array. To measure the protective effect of ARF, the levels of reactive oxygen species (ROS) and glutathione depletion were determined using a kit. HPLC analysis was performed using a Gemini C18 column at 40°C. The mobile phase used gradient elution with 1.0% (v/v) aqueous acetic acid (A) and 1.0% (v/v) acetic acid in acetonitrile (B). The flow rate was 1.0 mL/min. In our assay, AA extract inhibits cisplatin-induced production of intracellular ROS. Pre-incubation of AA extracts (10–200 μg/mL) markedly maintained cell viability compared with controls in the noncisplatin-treated cells. Calibration curves of all compounds showed good linearity ( r2  0.9992). Recoveries of the three compounds were 98.9–103.4%. The relative standard deviations of intra- and inter-day precision were 0.07–1.73% and 0.12–1.49%, respectively. The amounts of the three components were 1.22–20.63 mg/g. The AA extract has potential as a therapeutic agent for treatment of ARF. In addition, the established method will help to improve quality control of AA.

Clinical analysis of cause, treatment and prognosis in acute kidney injury patients

Acute kidney injury (AKI) is characterized by an abrupt decline in renal function, resulting in an inability to secrete waste products and maintain electrolyte and water balance, and is associated with high risks of morbidity and mortality. This study retrospectively analyzed clinical data, treatment, and prognosis of 271 hospitalized patients (172 males and 99 females) diagnosed with AKI from December, 2008 to December, 2011. In addition, this study explored the association between the cause of AKI and prognosis, severity and treatment of AKI. The severity of AKI was classified according to the Acute Kidney Injury Network (AKIN) criteria. Renal recovery was defined as a decrease in a serum creatinine level to the normal value. Prerenal, renal, and postrenal causes accounted for 36.5% (99 patients), 46.5% (126 patients) and 17.0% (46 patients), respectively, of the incidence of AKI. Conservative, surgical, and renal replacement treatments were given to 180 (66.4%), 30 (11.1%) and 61 patients (22.5%), respectively. The overall recovery rate was 21.0%, and the mortality rate was 19.6%. Levels of Cl⁻, Na⁺ and carbon dioxide combining power decreased with increasing severity of AKI. Cause and treatment were significantly associated with AKI prognosis. Likewise, the severity of AKI was significantly associated with cause, treatment and prognosis. Multivariate logistic regression analysis found that respiratory injury and multiple organ dysfunction syndrome (MODS) were associated with AKI patient death. Cause, treatment and AKIN stage are associated with the prognosis of AKI. Respiratory injury and MODS are prognostic factors for death of AKI patients.

Higher diastolic blood pressure at admission and antiedema therapy is associated with acute kidney injury in acute ischemic stroke patients

Antiedema therapy with mannitol and furosemide is widely used for prevention and management of cerebral edema, elevated intracranial pressure, and cerebral hernia. There are some reports about mannitol and furosemide as risk factors of acute kidney injury (AKI). We investigated the risk factors for AKI including antiedema therapy in acute ischemic stroke patients. The subjects were 129 patients with acute ischemic stroke including 56 females and 73 males with a mean age 68.16±12.29 years. Patients were divided into two groups: patients with AKI and without AKI according to Acute Kidney Injury Network criteria. All patients had undergone cranial, carotid, and vertebral artery evaluation with magnetic resonance imaging. The number of patients with AKI was 14 (10.9%). Subjects experiencing atrial fibrillation (P=0.043) and higher diastolic blood pressure (DBP) (P=0.032) treated with mannitol (P=0.019) and furosemide (P=0.019) disclosed significant association with AKI. Regression analysis revealed that higher DBP (P=0.029) and management with mannitol (P=0.044) were the risk factors for AKI. Higher DBP at admission is the most important risk factor for AKI. However antiedema therapy should be used carefully in patients with acute ischemic stroke. Serum creatinine levels or estimated glomerular filtration rate should be watched frequently to prevent AKI.

Renal ischaemia/reperfusion injury: possible role of aquaporins

Renal ischaemia/reperfusion (I/R) injury is a common problem that occurs when blood flow is interrupted to the kidney in case of kidney transplantation, aortic cross-clamping and shock with subsequent resuscitation. Renal I/R injury is a complex conditions which includes the onset of an inflammatory process, which is associated with impairment of concentrating ability of the kidney and impairment of solute transport. Characteristically, renal I/R injury is associated with marked reduction in the protein expression of renal aquaporins (AQPs) mainly (AQP1, AQP2 and AQP3), and solute transporters were observed in this condition and could account for the impaired urinary concentration that observed in this condition. Recently, many agents were tested for a possible protective effect against this insult such as erythropoietin (EPO), α-melanocyte-stimulating hormone (α-MSH) and α-lipoic acid which were proved to prevent downregulation of AQPs and solute transporters. The aim of this short review is to outline the potential pathophysiological role of AQPs in renal I/R injury and to put a spotlight on the modulation of renal functions impairment in renal ischaemia by new drugs that prevent downregulation of AQPs.

Enhancement of electric field-mediated gene delivery through pretreatment of tumors with a hyperosmotic mannitol solution

Pulsed electric fields can enhance interstitial transport of plasmid DNA (pDNA) in solid tumors. However, the extent of enhancement is still limited. To this end, effects of cellular resistance to electric field-mediated gene delivery were investigated. The investigation used two tumor cell lines (4T1 and B16.F10) either in suspensions or implanted in two in vivo models (dorsal skin-fold chamber (DSC) and hind leg). The volume fraction of cells was altered by pretreatment with a hyperosmotic mannitol solution (1 M). It was observed that the pretreatment reduced the volumes of 4T1 and B16.F10 cells, suspended in an agarose gel, by 50% and 46%, respectively, over a 20-min period but did not cause significant changes ex vivo in volumes of hind leg tumor tissues grown from the same cells in mice. The mannitol pretreatment in vivo improved electric field-mediated gene delivery in the hind leg tumor models, in terms of reporter gene expression, but resulted in minimal enhancement in pDNA electrophoresis over a few micron distance in the DSC tumor models. These data demonstrated that hyperosmotic mannitol solution could effectively improve electric field-mediated gene delivery around individual cells in vivo through increasing the extracellular space.

Outcome definitions in non-dialysis intervention and prevention trials in acute kidney injury (AKI)

BACKGROUND

The risk, injury, failure, loss-of-function, end-stage-renal-failure (RIFLE) and acute kidney injury network (AKIN) consensus definitions of acute kidney injury (AKI) were established in part to facilitate comparison of trials. Contrast-induced nephropathy (CIN) has traditionally used a less demanding definition.

OBJECTIVES

To review use of RIFLE and AKIN as AKI trial outcome variables and contrast these with outcomes for CIN.

METHODS

We conducted a search of PubMed from 1 January 2005 to 31 December 2008 and 9 trial registries for randomized control trials for preventional or interventional treatment of AKI and CIN.

RESULTS

RIFLE or AKIN were outcome variables in 36% (n = 8) of the published (n = 22) and 18% (n = 4) of the current (n = 22) AKI trials. RIFLE was used to triage to intervention in three trials. The urine output definition of RIFLE and AKIN was an outcome in only two trials. In 18% (n = 8) of AKI trials, the CIN definition (increase in serum creatinine of > or =25% and/or > or =44 micromol/l) was the primary outcome. This was also the primary outcome in 56% (n = 13) of published (n = 12) and current (n = 11) CIN trials. Three published CIN trials used RIFLE or AKIN as an outcome (13%). The duration over which outcomes were determined varied from 24 h to 7 days.

CONCLUSIONS

Considerable heterogeneity remains in outcome variables of AKI and CIN clinical trials. Even when the RIFLE or AKIN criteria were used, they were not applied consistently. There is a need for further consensus on surrogate outcome variables.

Torsemide Versus Furosemide After Continuous Renal Replacement Therapy Due to Acute Renal Failure in Cardiac Surgery Patients

Diuretic therapy in ARF (acute renal failure) is mainly done with loop diuretics, first of all furosemide. Torsemide has a longer duration of action and does not accumulate in renal failure. In chronic and acute renal failure, both diuretics have been effectively applied, with a more pronounced diuretic effect for torsemide. In this study, the effects of torsemide versus furosemide on renal function in cardiac surgery patients recovering from ARF after continuous renal replacement therapy (CRRT) were studied. Twenty-nine critically ill patients admitted to an intensive care unit at a university teaching hospital after cardiac surgery recovering from ARF after CRRT were included in this prospective, controlled, single-center, open-labeled, randomized clinical trial. Inclusion criteria were urine output >0.5 mL/kg/h over 6 h under CRRT. Torsemide and furosemide dosages were adjusted with the target urine output being 0.8-1.5 mL/kg/h. Hemodynamic data, urine output, volume balance, serum creatinine clearance, electrolytes, blood urea nitrogen, serum creatinine, renin, and aldosterone concentrations were measured. Fourteen patients were included in the furosemide group and 15 patients in the torsemide group. Dosages of 29 (0-160) mg torsemide and a dosage of 60 (0-240) mg furosemide were given every 6 h in each group, respectively. The dosage given at the end of the study decreased significantly in furosemide and torsemide treated patients. Urine output, 24 h balance, and serum creatinine clearance did not differ significantly between groups. Urine output decreased in both groups, mostly dose-dependent in the torsemide group. The intragroup comparison of the first time-interval after inclusion with the last time-interval showed a significant increase in serum creatinine and blood urea nitrogen in the furosemide group. Renin and aldosterone concentrations did not show significant differences. In conclusion, torsemide and furosemide were effective in increasing urine output. Torsemide might show a better dose-dependent diuretic effect in ARF patients after CRRT treatment. Serum creatinine and blood urea nitrogen elimination were less pronounced in the furosemide group.

The syndrome of rhabdomyolysis: complications and treatment

Rhabdomyolysis is a syndrome of skeletal muscle cell damage that leads to the release of toxic intracellular material into the systemic circulation. The pathogenesis of rhabdomyolysis is based on an increase in free ionized calcium in the cytoplasm. Its main complications include (a) acute renal failure, which is triggered by renal vasoconstriction and ischemia, (b) myoglobin cast formation in the distal convoluted tubules, and (c) direct renal toxic effect of myoglobin on the epithelial cells of proximal convoluted tubules. Other major complications include electrolyte disorders, such as hyperkalemia, which may cause cardiac arrhythmias, metabolic acidosis, hyperphosphatemia, early hypocalcemia, and late hypercalcemia. Compartmental syndrome and disseminated intravascular coagulopathy may also emerge. The management of myoglobinuric acute renal failure includes aggressive fluid administration to restore the hypovolemia and urine alkalization. The concomitant electrolyte and metabolic disorders should also be treated appropriately; hemodialysis should be considered when life-threatening hyperkalemia and metabolic acidosis exist. In the case of compartmental syndrome, it is important to monitor the intra-compartmental pressure and to perform fasciotomy, if required. When diagnosed early and if the appropriate treatment is initiated promptly, the complications of rhabdomyolysis are preventable and the syndrome has a good prognosis.

Renal hypoxia and dysoxia after reperfusion of the ischemic kidney

Ischemia is the most common cause of acute renal failure. Ischemic-induced renal tissue hypoxia is thought to be a major component in the development of acute renal failure in promoting the initial tubular damage. Renal oxygenation originates from a balance between oxygen supply and consumption. Recent investigations have provided new insights into alterations in oxygenation pathways in the ischemic kidney. These findings have identified a central role of microvascular dysfunction related to an imbalance between vasoconstrictors and vasodilators, endothelial damage and endothelium-leukocyte interactions, leading to decreased renal oxygen supply. Reduced microcirculatory oxygen supply may be associated with altered cellular oxygen consumption (dysoxia), because of mitochondrial dysfunction and activity of alternative oxygen-consuming pathways. Alterations in oxygen utilization and/or supply might therefore contribute to the occurrence of organ dysfunction. This view places oxygen pathways' alterations as a potential central player in the pathogenesis of acute kidney injury. Both in regulation of oxygen supply and consumption, nitric oxide seems to play a pivotal role. Furthermore, recent studies suggest that, following acute ischemic renal injury, persistent tissue hypoxia contributes to the development of chronic renal dysfunction. Adaptative mechanisms to renal hypoxia may be ineffective in more severe cases and lead to the development of chronic renal failure following ischemia-reperfusion. This paper is aimed at reviewing the current insights into oxygen transport pathways, from oxygen supply to oxygen consumption in the kidney and from the adaptation mechanisms to renal hypoxia. Their role in the development of ischemia-induced renal damage and ischemic acute renal failure are discussed.

Renal hypoxia and dysoxia after reperfusion of the ischemic kidney

Ischemia is the most common cause of acute renal failure. Ischemic-induced renal tissue hypoxia is thought to be a major component in the development of acute renal failure in promoting the initial tubular damage. Renal oxygenation originates from a balance between oxygen supply and consumption. Recent investigations have provided new insights into alterations in oxygenation pathways in the ischemic kidney. These findings have identified a central role of microvascular dysfunction related to an imbalance between vasoconstrictors and vasodilators, endothelial damage and endothelium-leukocyte interactions, leading to decreased renal oxygen supply. Reduced microcirculatory oxygen supply may be associated with altered cellular oxygen consumption (dysoxia), because of mitochondrial dysfunction and activity of alternative oxygen-consuming pathways. Alterations in oxygen utilization and/or supply might therefore contribute to the occurrence of organ dysfunction. This view places oxygen pathways' alterations as a potential central player in the pathogenesis of acute kidney injury. Both in regulation of oxygen supply and consumption, nitric oxide seems to play a pivotal role. Furthermore, recent studies suggest that, following acute ischemic renal injury, persistent tissue hypoxia contributes to the development of chronic renal dysfunction. Adaptative mechanisms to renal hypoxia may be ineffective in more severe cases and lead to the development of chronic renal failure following ischemia-reperfusion. This paper is aimed at reviewing the current insights into oxygen transport pathways, from oxygen supply to oxygen consumption in the kidney and from the adaptation mechanisms to renal hypoxia. Their role in the development of ischemia-induced renal damage and ischemic acute renal failure are discussed.

Effects of mannitol alone and mannitol plus furosemide on renal oxygen consumption, blood flow and glomerular filtration after cardiac surgery

OBJECTIVE

Imbalance of the renal medullary oxygen supply/demand relationship can cause hypoxic medullary damage and ischaemic acute renal failure (ARF). The use of mannitol for prophylaxis/treatment of clinical ischaemic ARF is controversial and the effect of mannitol on renal oxygenation in man has not yet been investigated. We evaluated the effects of mannitol on renal oxygen consumption (RVO(2))(,) renal blood flow (RBF) and glomerular filtration rate (GFR) in postoperative patients.

DESIGN

Prospective interventional study.

SETTING

University hospital cardiothoracic ICU.

PATIENTS

Ten uncomplicated mechanically ventilated and sedated postcardiac surgery patients with preoperatively normal renal function.

INTERVENTIONS

Mannitol infusion (225 mg/kg + 75 mg/kg/h) and combined mannitol and furosemide infusion (0.25 mg/kg + 0.25 mg/kg/h).

MEASUREMENTS AND RESULTS

Systemic haemodynamics were evaluated by a pulmonary artery catheter. RBF and GFR were measured by the renal vein thermodilution technique and by renal extraction of (51)Cr-EDTA, respectively. Mannitol increased urine flow (60%), GFR (20%) and filtration fraction (FF) (20%) with no change in RBF. This was accompanied by an increase in renal sodium reabsorption (18%), RVO(2) (19%) and renal oxygen extraction (21%). When combined with mannitol, furosemide normalised sodium reabsorption, RVO(2), renal oxygen extraction with no change in RBF, while GFR and FF were still elevated compared to control.

CONCLUSIONS

In patients with normal renal function, mannitol increases GFR, which increases tubular sodium load, sodium reabsorption and RVO(2) after cardiac surgery. The lack of effect on RBF, indicates that mannitol impairs the renal oxygen supply/demand relationship. Furosemide normalised renal oxygenation when combined with mannitol.

The efficacy of loop diuretics in acute renal failure: assessment using Bayesian evidence synthesis techniques

OBJECTIVE

To quantify the therapeutic efficacy of loop diuretics in acute renal failure using Bayesian evidence synthesis, because despite widespread use, the role of diuretics is controversial.

DATA SOURCE

Randomized controlled trials or nonrandomized studies, 1966 to January 2007, identified from MEDLINE and EMBASE databases and manual bibliographic search.

STUDY SELECTION

Studies with assessable predefined end points, exclusive of those pertaining to acute renal failure prophylaxis or chronic renal failure.

DATA EXTRACTION

Data extraction was performed jointly by the first two authors; independent study assessment was via standard checklist, unblinded.

DATA SYNTHESIS

The primary outcome was mortality; secondary outcomes were time to renal function normalization and total number of dialyses. Bayesian hierarchical random effects estimates of treatment effects were determined as risk ratio for mortality, incidence rate ratio for dialysis number, and mean difference for continuous measures. Bayesian outcome probabilities were calculated as probability (P) that risk ratio or incidence rate ratio of loop diuretics >1 and probability that mean difference >0. Five randomized controlled trials and eight nonrandomized studies were identified. Loop diuretics were not associated with decreased mortality in either randomized controlled trials or nonrandomized studies: overall risk ratio 1.10; 95% credible interval 0.85, 1.42; P(risk ratio >1) > 83.8%. The oliguric period was decreased by loop diuretics: overall mean difference -7.70 days; 95% credible interval -12.51, -2.08; P (mean difference >0) = 0.7%. Although the dialysis rate credible interval, loop diuretics vs. control, spanned unity (incidence rate ratio 0.71; 95% credible interval 0.47, 1.06), the probability that the incidence rate ratio exceeded unity indicated a substantial benefit: P (incidence rate ratio >1 = 4.1%. Uremic duration was not substantially different, loop diuretics vs. control: overall mean difference -1.54 days; 95% credible interval -5.62, 2.46; P [mean difference >0] = 17.8%).

CONCLUSIONS

Loop diuretics were not associated with improved survival benefit in acute renal failure, despite reduction in oliguric period and high probability of a significant reduction in dialysis numbers. Further studies to clarify this dichotomy appear mandated.

[Acute renal failure. Extracorporeal therapy]

Acute renal failure is increasingly found in critically ill patients as part of the multiple organ dysfunction syndrome. Intermittent hemodialysis and continuous renal replacement therapy are standard extracorporeal replacement therapies. Continuous therapies are thought to be especially useful in cardiovascularly instable patients in the intensive care unit. Recently, slow, extended daily dialysis was introduced as a hybrid method, combining the advantages of intermittent and continuous renal replacement therapy. While controlled studies have uniformly shown that a high dose of such replacement therapy increases survival, studies have failed to support a definitive advantage for any method in terms of patient survival. Therefore, the choice of renal replacement therapy should be based on personal experience, the available resources/infrastructure as well as the needs of the individual patient.

Acute and delayed renal protection against renal ischemia and reperfusion injury with A1adenosine receptors

We showed previously that activation of A1adenosine receptors (AR) protects against renal ischemia-reperfusion (IR) injury in rats and mice. In the heart, transient A1AR activation produces biphasic protective effects: acute protection wanes after several hours but protective effects return 24–72 h later (second window of protection). In this study, we determined whether A1AR activation produces delayed renal protection and elucidated the mechanisms of acute and delayed renal protection. A1AR wild-type mice were subjected to 30-min renal ischemia and 24 h of reperfusion to produce acute renal failure. Pretreatment with a selective A1AR agonist 2-chloro- N6-cyclopentyladenosine (CCPA; 0.1 mg/kg bolus ip) either 15 min or 24 h before renal ischemia protected against renal IR injury and reduced renal corticomedullary necrosis, apoptosis, and inflammation. Transient A1AR activation led to phosphorylation of extracellular signal-regulated protein kinase mitogen-activated protein kinase (ERK MAPK), Akt, and heat shock protein 27 (HSP27). Moreover, induction of HSP27 and Akt occurred with CCPA treatment. Inhibition of PKC with chelerythrine prevented acute but not delayed renal protection with A1AR activation. Moreover, deletion of PI3Kγ or inhibition of Akt, but not inhibition of ERK, prevented delayed and acute renal protection with A1AR activation. Inhibition of Gi/owith pertussis toxin obliterated both acute and delayed A1AR-mediated renal protection. In contrast to renal protection with delayed ischemic preconditioning, nitric oxide synthase activity was not induced with delayed A1AR-mediated renal protection. Therefore, transient activation of renal A1AR led to acute as well as delayed protective effects against renal IR injury via distinct signaling pathways.

N-Acetylcysteine for the Prevention of Kidney Injury in Abdominal Aortic Surgery: A Randomized, Double-Blind, Placebo-Controlled Trial

In this prospective, randomized, placebo-controlled, double-blind trial we studied the effects of IV N-acetylcysteine for prevention of renal injury in patients undergoing abdominal aortic surgery. Seventy patients without previously documented renal dysfunction were randomly allocated to receive either N-acetylcysteine (150 mg/kg mixed in 250 mL of 5% dextrose infused in 20 min, followed by an infusion of 150 mg/kg in 250 mL of 5% dextrose over 24 h) or placebo. The infusion was started after the induction of anesthesia. The primary outcome measure was renal injury as measured by the increases in urinary N-acetyl-beta-d-glucosaminidase (NAG)/creatinine ratio (indicator of renal tubular injury) and urinary albumin/creatinine ratio (indicator of glomerular injury). Renal function was assessed by measuring plasma creatinine and serum cystatin C concentrations. The urinary NAG/creatinine ratio increased significantly from baseline to before crossclamp and remained increased on day 5 in both groups. The urinary albumin/creatinine ratio increased significantly from baseline to 6 h after declamping in the N-acetylcysteine group. However, the changes in the NAG/creatinine ratio and the albumin/creatinine ratio were not significantly different between the two groups. Plasma creatinine and serum cystatin C values remained unchanged during the study period in both groups. In conclusion, N-acetylcysteine did not offer any significant protection from renal injury during elective aortic operation in patients with normal preoperative renal function, and some degree of tubular injury seems to occur before aortic crossclamp.

A1adenosine receptor knockout mice are protected against acute radiocontrast nephropathy in vivo

The role of renal A1adenosine receptors (A1AR) in the pathogenesis of radiocontrast nephropathy is controversial. We aimed to further elucidate the role of A1AR in the pathogenesis of radiocontrast nephropathy and determine whether renal proximal tubule A1AR contribute to the radiocontrast nephropathy. To induce radiocontrast nephropathy, A1AR wild-type (WT) or knockout (KO) mice were injected with a nonionic radiocontrast (iohexol, 1.5–3 g iodine/kg). Some A1WT mice were pretreated with 8-cyclopentyl-1,3-dipropylxanthine (DPCPX; a selective A1AR antagonist) before iohexol injection. A1AR contribute to the pathogenesis of radiocontrast nephropathy in vivo as the A1WT mice developed significantly worse acute renal failure, more renal cortex vacuolization, and had lower survival 24 h after iohexol treatment compared with the A1KO mice. DPCPX pretreatment also protected the A1WT mice against radiocontrast-induced acute renal failure. No differences in renal cortical apoptosis or inflammation were observed between A1WT and A1KO mice. To determine whether the proximal tubular A1AR mediate the direct renal cytotoxicity of radiocontrast, we treated proximal tubules in culture with iohexol with or without 2-chloro- N6-cyclopentyladenosine (a selective A1AR agonist) or DPCPX pretreatment. We also subjected cultured proximal tubule cells overexpressing A1AR or lacking A1AR to radiocontrast injury. Iohexol caused a direct dose-dependent reduction in proximal tubule cell viability as well as proliferation. Neither the A1AR agonist nor the antagonist treatment affected proximal tubule viability or proliferation. Moreover, overexpression or lack of A1AR failed to impact the iohexol toxicity on proximal tubule cells. Therefore, we conclude that radiocontrast causes acute renal failure via mechanisms dependent on A1AR; however, renal proximal tubule A1AR do not contribute to the direct tubular toxicity of radiocontrast.

Cellular and molecular derangements in acute tubular necrosis

PURPOSE OF REVIEW

Acute tubular necrosis secondary to ischemic acute renal failure remains a common clinical problem with serious consequences and unsatisfactory therapeutic options. The purpose of this review is to summarize recent advances that have provided an improved understanding of the underlying cellular and molecular derangements, and have resulted in the design of novel therapeutic approaches.

RECENT FINDINGS

Sophisticated morphologic studies have identified apoptosis and vascular changes as significant novel findings in human acute tubular necrosis. Promising roles for inhibitors of apoptosis have been proposed. Activation of tubuloglomerular feedback, previously thought to contribute to acute tubular necrosis, has now emerged as a potentially beneficial phenomenon. The role of reactive oxygen molecules has been further elucidated, and novel antioxidants and iron chelators have been identified. Genome-wide screening techniques have identified the molecular mechanisms underlying the regeneration and repair processes, and have provided clues towards accelerating recovery from acute renal failure. An improved understanding of the role of inflammation has suggested strategies to target this previously underappreciated aspect of acute tubular necrosis.

SUMMARY

The cellular and molecular tools of modern science have provided critical new insights into the roles of apoptosis, oxidant and iron-mediated injury, endothelial changes, regeneration, and the inflammatory response in the pathogenesis of acute tubular necrosis. Novel strategies that modulate these pathways hold tremendous promise for the proactive treatment of human acute renal failure.

Acute renal failure in cancer patients

Acute renal failure (ARF) is defined as a sudden decrease in glomerular filtration rate leading to an acute rise in blood urea nitrogen and serum creatinine levels. It is a serious complication of cancer and constitutes a major source of morbidity and mortality. Current data suggest that ARF has the potential to substantially jeopardize the chances of cancer patients receiving optimal treatment and a potential cure. The pathways leading to ARF in cancer patients are common to the development of ARF in other conditions. However, ARF may also develop due to aetiologies arising from cancer treatment or the disease itself, including: nephrotoxic chemotherapy agents, post-renal obstruction, compression and infiltration by malignancy, tumour lysis syndrome, uric acid, sepsis and contrast agent nephropathy. This review provides a comprehensive overview of the causes of ARF in patients with cancer and guidance on how to prevent and treat this condition. Ultimately, the key to managing ARF in cancer patients is to ensure that a multidisciplinary approach provides adequate assessment, appropriate preventative measures and early intervention.