Early detection of acute renal failure by serum cystatin C

Beneficial Effects of Sarpogrelate and Rosuvastatin in High Fat Diet/Streptozotocin-Induced Nephropathy in Mice

Chronic kidney disease (CKD) is a major complication of metabolic disorders such as diabetes mellitus, obesity, and hypertension. Comorbidity of these diseases is the factor exacerbating CKD progression. Statins are commonly used in patients with metabolic disorders to decrease the risk of cardiovascular complications. Sarpogrelate, a selective antagonist of 5-hydroxytryptamine (5-HT) 2A receptor, inhibits platelet aggregation and is used to improve peripheral circulation in diabetic patients. Here, we investigated the effects of sarpogrelate and rosuvastatin on CKD in mice that were subjected to a high fat diet (HFD) for 22 weeks and a single low dose of streptozotocin (STZ, 40 mg/kg). When mice were administrated sarpogrelate (50 mg/kg, p.o.) for 13 weeks, albuminuria and urinary cystatin C excretion were normalized and histopathological changes such as glomerular mesangial expansion, tubular damage, and accumulations in lipid droplets and collagen were significantly improved. Sarpogrelate treatment repressed the HFD/STZ-induced CD31 and vascular endothelial growth factor receptor-2 expressions, indicating the attenuation of glomerular endothelial proliferation. Additionally, sarpogrelate inhibited interstitial fibrosis by suppressing the increases in transforming growth factor-β1 (TGF-β1) and plasminogen activator inhibitor-1 (PAI-1). All of these functional and histological improvements were also seen in rosuvastatin (20 mg/kg) group and, notably, the combinatorial treatment with sarpogrelate and rosuvastatin showed additive beneficial effects on histopathological changes by HFD/STZ. Moreover, sarpogrelate reduced circulating levels of PAI-1 that were elevated in the HFD/STZ group. As supportive in vitro evidence, sarpogrelate incubation blocked TGF-β1/5-HT-inducible PAI-1 expression in murine glomerular mesangial cells. Taken together, sarpogrelate and rosuvastatin may be advantageous to control the progression of CKD in patients with comorbid metabolic disorders, and particularly, the use of sarpogrelate as adjunctive therapy with statins may provide additional benefits on CKD.

DDRGK1 in urine indicative of tubular cell injury in intensive care patients with serious infections

BACKGROUND

Acute kidney injury (AKI) is a life threatening condition. Despite intensive care treatment the occurrence cannot be predicted as very little indicators exist for direct measurement when tubular epithelial cell injury takes place. We therefore searched for novel peptide indicators expressed at intracellular level at the proximal kidney tubule for its appearance in urine samples.

OBJECTIVES

Establishing a test for urinary C20orf116 protein measurement.

PATIENTS AND METHODS

Generation of immunoreagents against C20orf116 also named DDRGK1. These were used to measure its presence in urine collected at 8-24 hours interval in a prospective study from 99 ICU patients at 4-6 time points. These patients received therapy because of serious infection and were categorized into 4 groups.

RESULTS

1) Ten tested highly for C20orf116 undergoing AKI graded Failure or Loss (3210 ± 4268 ng/mL) according to RIFLE criteria, all requiring renal replacement therapy (RRT) out of them 9 died. 2) Six patients with pre-existing kidney disease developed AKI and required RRT but had much lower C20orf116 levels of (33 ± 19), two of them died. 3) In contrast, out of 11 patients undergoing AKI grade Risk or Injury, four tested positive for C20orf116 but to much lower extent (66 ± 43) who recovered fully. 4) Out of 72 patients 25 tested positive (18 ± 12 ng/mL) not fulfilling criteria of AKI but with serum creatinine (sCr) rises of 1.2-1.4 (n = 52). Healthy donors (n = 48) showed no detectable C20orf116 at any time point.

CONCLUSIONS

C20orf116 excretion was detectable more than 24 hours before sCr rise could be measured; high level seemed to indicate severity of organ failure.

Renal markers cystatin C and neutrophil gelatinase-associated lipocalin (NGAL) in postmortem samples

PURPOSE

Renal markers may provide valuable information for cause of death (CoD) investigation when assessing the influence of impaired kidney function. A commonly used marker, creatinine (Cr), increases due to kidney injury and is known to be reasonably stable in postmortem (PM) samples. More sensitive markers are needed, as the increase of serum Cr level only occurs after relatively severe renal damage. We evaluated two markers, cystatin C and neutrophil gelatinase-associated lipocalin (NGAL), in addition to Cr. To the best of our knowledge this was the first study to investigate cystatin C and NGAL in a postmortem (PM) context.

METHODS

Cr, cystatin C, and NGAL were measured from PM blood in 39 autopsy cases. NGAL was also measured from urine in 16 cases. Cystatin C and NGAL were analyzed using ELISA, Cr measurements were performed with Jaffe method. Correlations of these markers were evaluated.

RESULTS AND CONCLUSIONS

Both, blood cystatin C and NGAL, levels showed significant correlation with Cr (p = 0.05 and p = 0.01, respectively). Cystatin C and NGAL in blood are promising markers for further studies with PM samples.

Effects of Sugammadex and Neostigmine on Renal Biomarkers

Background

Neostigmine, the currently commonly used agent for reversal of neuromuscular blockade. Sugammadex is a novel and unique compound designed as an antagonist of steroidal neuromuscular blockers. In this study, we evaluated the effects of sugammadex or neostigmine on kidney functions in patients scheduled for elective surgery.

Material/Methods

Patients scheduled for a surgical procedure under desflurane/opioid anesthesia received an intubating dose rocuronium. Patients were divided into 2 groups receiving either sugammadex or neostigmine atropine to reverse neuromuscular blockade. Cystatin C, creatinine, urea, blood urea nitrogen, sodium, potassium, and calcium levels in the blood and α₁microglobulin, β₂microglobulin, and microalbumin levels in the urine were measured.

Results

There was no significant difference between the groups with regard to the demographic data. In the Neostigmine Group, although β₂microglobulin and microalbumin were similar, a significant increase was found in the postoperative α₁microglobulin and cystatin C values. In the Sugammadex Group, although β₂-microglobulin and cystatin C were similar, a significant increase was found in the postoperative α₁-microglobulin and microalbumin values. The only significant difference was cystatin C value variation in the Neostigmine Group compared to the Sugammadex Group.

Conclusions

We believe that the use of more specific and sensitive new-generation markers like cystatin C to evaluate kidney function will provide a better understanding and interpretation of our results. Sugammadex has more tolerable effects on kidney function in patients than does neostigmine. However, when compared to preoperative values, there is a negative alteration of postoperative values. Neostigmine and sugammadex do not cause renal failure but they may affect kidney function.

The cystatin C/creatinine ratio, a marker of glomerular filtration quality: associated factors, reference intervals, and prediction of morbidity and mortality in healthy seniors

The ratio of cystatin C (cysC) to creatinine (crea) is regarded as a marker of glomerular filtration quality associated with cardiovascular morbidities. We sought to determine reference intervals for serum cysC-crea ratio in seniors. Furthermore, we sought to determine whether other low-molecular weight molecules exhibit a similar behavior in individuals with altered glomerular filtration quality. Finally, we investigated associations with adverse outcomes. A total of 1382 subjectively healthy Swiss volunteers aged 60 years or older were enrolled in the study. Reference intervals were calculated according to Clinical & Laboratory Standards Institute (CLSI) guideline EP28-A3c. After a baseline exam, a 4-year follow-up survey recorded information about overall morbidity and mortality. The cysC-crea ratio (mean 0.0124 ± 0.0026 mg/μmol) was significantly higher in women and increased progressively with age. Other associated factors were hemoglobin A1c, mean arterial pressure, and C-reactive protein (P < 0.05 for all). Participants exhibiting shrunken pore syndrome had significantly higher ratios of 3.5-66.5 kDa molecules (brain natriuretic peptide, parathyroid hormone, β2-microglobulin, cystatin C, retinol-binding protein, thyroid-stimulating hormone, α1-acid glycoprotein, lipase, amylase, prealbumin, and albumin) and creatinine. There was no such difference in the ratios of very low-molecular weight molecules (urea, uric acid) to creatinine or in the ratios of molecules larger than 66.5 kDa (transferrin, haptoglobin) to creatinine. The cysC-crea ratio was significantly predictive of mortality and subjective overall morbidity at follow-up in logistic regression models adjusting for several factors. The cysC-crea ratio exhibits age- and sex-specific reference intervals in seniors. In conclusion, the cysC-crea ratio may indicate the relative retention of biologically active low-molecular weight compounds and can independently predict the risk for overall mortality and morbidity in the elderly.

Combination of Urinary Biomarkers Improves Early Detection of Acute Kidney Injury in Patients With Heart Failure

BACKGROUND

Acute kidney injury (AKI) is associated with morality and repeated hospitalization, and is frequently encountered in patients with acute decompensated heart failure (ADHF). However, few effective tools exist for early AKI identification and risk stratification.

METHODS AND RESULTS

This was a prospective observational study conducted in the coronary care unit (CCU) of a tertiary care university hospital. Patients with a diagnosis of ADHF and who were using diuretics were enrolled.Samples collected between December 2013 and February 2015 were tested for serum cystatin C (Cys-C), urinary neutrophil gelatinase-associated lipocalin, and kidney injury molecule-1 (KIM-1). Demographic, clinical, and laboratory data were evaluated. A total of 103 adult patients with a mean age of 68 years were investigated. AKI was diagnosed in 49 patients (47.6%). For predicting intrinsic AKI on the first day of CCU admission, a combination of Cys-C and urine KIM-1 yielded an excellent area under the receiver operating characteristic curve of 0.828, a sensitivity of 71.0%, and specificity of 43.0%, for an overall accuracy of 78%.

CONCLUSIONS

In this study, we found that combinations of the biomarker (Cys-C and KIM-1) were an effective clinical model for predicting AKI in patients with ADHF. The biomarker was also useful for differentiating subclinical AKI in patients with ADHF.

Can admission serum cystatin C level be an early marker subclinical acute kidney injury in critical care patients?

BACKGROUND

In critical care patients, the diagnosis of subclinical acute kidney injury (AKI) might be difficult with measurements of serum creatinine and estimated glomerular filtration rate (eGFR). Their 'sensitive kidneys' can easily be affected from sepsis, underlying diseases, medications and volume status and if they can be detected earlier, some preventive measures might be taken. In this study we aimed to determine whether admission serum cystatin C (sCys-C) and other clinical parameters can identify subclinical AKI in medical intensive care unit (ICU) patients with normal creatinine-based eGFR at admission.

METHODS

A prospective cohort study, performed in an adult ICU of a university hospital between January 2008 and March 2013. The blood samples were obtained within the first 24-48 hours of admission and sCys-C levels were analyzed with particle-enhanced immunonephelometric assay. AKI development was assessed according to RIFLE criteria. The cutoff value of sCys-C for the prediction of AKI was determined with receiver operating characteristic (ROC) curve analysis.

RESULTS

A total of 72 patients were included in the study and 19 (26%) of them developed AKI. Among the patients with AKI admission sCys-C levels were significantly higher when compared with non-AKI patients (1.06 ± 0.29 vs. 0.89 ± 0.28 respectively, p = 0.026). With ROC curve analysis, the threshold level for sCys-C was 0.94 mg/L with 63% sensitivity and 66% specificity [AUC: 0.67, p = 0.026]. With logistic regression analysis 'high sCys-C levels at admission' (OR = 4.73; 95%CI 1.03-21.5, p = 0.044) was found as one of the independent variables for the prediction of AKI development, in addition to 'being intubated before ICU admission' (OR = 10.2; 95%CI 1.72-60.4, p = 0.01) and 'hypotension during ICU follow-up' (OR = 12.3; 95%CI 2.5-60.1, p = 0.002).

CONCLUSION

In this cohort of patients, a high sCys-C level at admission was found to be a predictor of subclinical AKI arising during their ICU stay. If supported with further studies, it might be used to provide more accurate and earlier knowledge about renal dysfunction and to take appropriate preventive measures.

Urinary NGAL in patients with and without acute kidney injury in a cardiology intensive care unit

Objective

To assess the diagnostic and prognostic efficacy of urine neutrophil gelatinase-associated lipocalin in patients admitted to an intensive care unit.

Methods

Longitudinal, prospective cohort study conducted in a cardiology intensive care unit. The participants were divided into groups with and without acute kidney injury and were followed from admission to the intensive care unit until hospital discharge or death. Serum creatinine, urine output and urine neutrophil gelatinase-associated lipocalin were measured 24 and 48 hours after admission.

Results

A total of 83 patients admitted to the intensive care unit for clinical reasons were assessed, most being male (57.8%). The participants were divided into groups without acute kidney injury (N=18), with acute kidney injury (N=28) and with severe acute kidney injury (N=37). Chronic diseases, mechanical ventilation and renal replacement therapy were more common in the groups with acute kidney injury and severe acute kidney injury, and those groups exhibited longer intensive care unit stay and hospital stay and higher mortality. Serum creatinine did not change significantly in the group with acute kidney injury within the first 24 hours of admission to the intensive care unit, although, urine neutrophil gelatinase-associated lipocalin was high in the groups with acute kidney injury and severe acute kidney injury (p<0.001). Increased urine neutrophil gelatinase-associated lipocalin was associated with death.

Conclusion

An increase in urine neutrophil gelatinase-associated lipocalin precedes variations in serum creatinine in patients with acute kidney injury and may be associated with death.

Pyruvate Kinase M2: A Novel Biomarker for the Early Detection of Acute Kidney Injury

The identification of biomarkers for the early detection of acute kidney injury (AKI) is clinically important. Acute kidney injury (AKI) in critically ill patients is closely associated with increased morbidity and mortality. Conventional biomarkers, such as serum creatinine (SCr) and blood urea nitrogen (BUN), are frequently used to diagnose AKI. However, these biomarkers increase only after significant structural damage has occurred. Recent efforts have focused on identification and validation of new noninvasive biomarkers for the early detection of AKI, prior to extensive structural damage. Furthermore, AKI biomarkers can provide valuable insight into the molecular mechanisms of this complex and heterogeneous disease. Our previous study suggested that pyruvate kinase M2 (PKM2), which is excreted in the urine, is a sensitive biomarker for nephrotoxicity. To appropriately and optimally utilize PKM2 as a biomarker for AKI requires its complete characterization. This review highlights the major studies that have addressed the diagnostic and prognostic predictive power of biomarkers for AKI and assesses the potential usage of PKM2 as an early biomarker for AKI. We summarize the current state of knowledge regarding the role of biomarkers and the molecular and cellular mechanisms of AKI. This review will elucidate the biological basis of specific biomarkers that will contribute to improving the early detection and diagnosis of AKI.

Ulinastatin Protects against Acute Kidney Injury in Infant Piglets Model Undergoing Surgery on Hypothermic Low-Flow Cardiopulmonary Bypass

Objective

Infants are more vulnerable to kidney injuries induced by inflammatory response syndrome and ischemia-reperfusion injury following cardiopulmonary bypass especially with prolonged hypothermic low-flow (HLF). This study aims to evaluate the protective role of ulinastatin, an anti-inflammatory agent, against acute kidney injuries in infant piglets model undergoing surgery on HLF cardiopulmonary bypass.

Methods

Eighteen general-type infant piglets were randomly separated into the ulinastatin group (Group U, n = 6), the control group (Group C, n = 6), and the sham operation group (Group S, n = 6), and anaesthetized. The groups U and C received following experimental procedure: median thoracotomy, routine CPB and HLF, and finally weaned from CPB. The group S only underwent sham median thoracotomy. Ulinastatin at a dose of 5,000 units/kg body weight and a certain volume of saline were administrated to animals of the groups U and C at the beginning of CPB and at aortic declamping, respectively. Venous blood samples were collected at 3 different time points: after anesthesia induction in all experimental groups, 5 minutes, and 120 minutes after CPB in the Groups U and C. Markers for inflammation and acute kidney injury were tested in the collected plasma. N-acetyl-β-D-glucosaminidase (NAG) from urine, markers of oxidative stress injury and TUNEL-positive cells in kidney tissues were also detected.

Results

The expressions of plasma inflammatory markers and acute kidney injury markers increased both in Group U and Group C at 5 min and 120 min after CPB. Also, numbers of TUNEL-positive cells and oxidative stress markers in kidney rose in both groups. At the time point of 120-min after CPB, compared with the Group C, some plasma inflammatory and acute kidney injury markers as well as TUNEL-positive cells and oxidative stress markers in kidney were significantly reduced in the Group U. Histologic analyses showed that HLF promoted acute tubular necrosis and dilatation.

Conclusions

HLF cardiopulmonary bypass surgery could intensify systemic inflammatory responses and oxidative stress on infant piglets, thus causing acute kidney injury. Ulinastatin might reduce such inflammatory response and oxidative stress and the extent of kidney injury.

A comparison of RIFLE, AKIN, KDIGO, and Cys-C criteria for the definition of acute kidney injury in critically ill patients

PURPOSE

AKI is a major clinical problem and predictor of prognosis in critically ill patients. The aim of our study was to determine whether the new Cys-C criteria for identification and prognosis of AKI were superior to the RIFLE, AKIN, and KDIGO criteria.

METHODS

In the retrospective and multicenter study, the incidence of AKI was identified by the four criteria. Receiver operating characteristic (ROC) curve was applied to compare the predictive ability for 28-day mortality, and logistic regression analysis was used for the calculation of odds ratios and 95 % confidence intervals.

RESULTS

In the 1036 patients enrolled, the incidences of AKI were 26.4, 34.1, 37.8, and 36.1 %, respectively, under the four criteria. Patients with AKI had higher mortality and longer length of stay than those without in all definitions. Concordance in AKI diagnosis between Cys-C and KDIGO criteria was 95.9 %, higher than AKIN and RIFLE criteria (p < 0.0001). The area under ROC curves was 0.7023 for Cys-C criteria, which was a significantly greater discrimination (p < 0.05).

CONCLUSION

KDIGO criteria identified significantly more AKI and AKI patients had significantly higher 28-day mortality than patients without AKI. The Cys-C criteria were more predictive for short-term outcomes than other three criteria among critically ill patients.

Early Acute Kidney Injury based on Serum Creatinine or Cystatin C in Intensive Care Unit after Major Trauma

BACKGROUND

Acute kidney injury (AKI) is a common problem in critically ill patients and is independently associated with increased morbidity and mortality. Recently, serum cystatin C has been shown to be superior to creatinine in early detection of renal function impairment. We compared estimated GFR based on serum cystatin C with estimated GFR based on serum creatinine for early detection of renal dysfunction according to the RIFLE criteria.

METHODS

During 9 months, three hundred post trauma patients that were referred to the intensive care unit of a referral trauma hospital were recruited. Serum creatinine and serum cystatin C were measured and the estimated GFR within 24 hours of ICU admission was calculated. The primary outcome was the incidence of AKI according to the RIFLE criteria within 2(nd) to 7(th) day of admission.

RESULTS

During the first week of ICU admission, 21% of patients experienced AKI. After adjusting for major confounders, only the patients with first day's serum cystatin level higher than 0.78 mg/l were at higher risk of first week AKI (OR=6.14, 95% CI: 2.5-14.7, P<0.001). First day's serum cystatin C and injury severity score were the major risk factors for ICU mortality (OR=3.54, 95% CI: 1.7-7.4, P=0.001) and (OR=4.6, 95% CI: 1.5-14, P=0.007), respectively.

CONCLUSION

Within 24 hours after admission in ICU due to multiple trauma, high serum cystatin C level may have prognostic value in predicting early AKI and mortality during ICU admission. However, such correlation was not seen neither with creatinine nor cystatin C based GFR.

Paradoxical effects of thyroid function on glomerular filtration rate estimated from serum creatinine or standardized cystatin C in patients with Japanese Graves' disease

BACKGROUND

Estimated glomerular filtration rate (eGFR) is clinically valuable for evaluating renal function. Recently, serum cystatin C (sCysC) measurement has been standardized and has demonstrated utility as a novel indicator of renal function. Thyroid hormone is known to affect serum creatinine (sCr) and sCysC, however, the clinical significance of post-treatment renal function evaluation is yet to be completely elucidated. This study examined the effects of thyroid hormones on eGFR by sCr (eGFRCr), and standardized sCysC (eGFRCysC) in patients with Japanese Graves' disease (GD).

METHODS

Serum samples were obtained from 113 outpatients with GD. Following pharmacotherapy, 41 of the 113 outpatients with GD achieved remission. Renal function was evaluated by eGFRCr and eGFRCysC. Reference method used Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equations.

RESULTS

eGFRCr levels significantly increased whereas eGFRCysC levels significantly decreased with elevated FT3 and FT4 levels in patients with GD. In the remission group, eGFRCr levels significantly decreased and eGFRCysC levels significantly increased. No significant differences between eGFRCr and eGFRCysC levels were observed. Furthermore, CKD-EPI equations show a similar trend and eGFRCr-CysC levels were no significant differences regardless of before and after treatment.

CONCLUSIONS

Renal function evaluation by eGFRCr and eGFRCysC had clinical utility in post-treatment euthyroidism.

The performance of contemporary cystatin C-based GFR equations in predicting gentamicin clearance

AIMS

We aimed to compare the performances of contemporary cystatin C (Cys)-based GFR equations, and the creatinine only Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equation for predicting gentamicin clearance.

METHODS

The bias and imprecision of the CKD-EPI, CKD-EPI_Cys and creatinine-cystatin C CKD-EPI (CKD-EPI_CrCys) equations for predicting gentamicin clearances, were assessed in 260 patients treated with gentamicin during 2012-2013. The creatinine-cystatin C Berlin Initiative Study equation (BIS_CrCys) was examined in the ≥70 year subgroup. The reference gentamicin clearance was calculated using post-dose plasma concentrations.

RESULTS

The CKD-EPI_CrCys equation had the highest percentage of estimates within 30% of the reference gentamicin clearance (70%, P = 0.003) and lowest root mean square error (95% CI) of 29 (25, 23) ml min(-1) of the three equations for the entire cohort. There was no significant improvement in the performances of the equations with the exclusion of 41 patients with abnormal thyroid function tests or steroid co-prescription at the time of the index gentamicin dose. Of the remaining 219 patients, adjustment for individual BSA improved the performances of all GFR equations (P ≤ 0.003) in those with body mass indices (BMI) <18.5 or ≥30 kg m(-2) , but not those with BMI 18.5-29.9 kg m(-2) . There was no advantage of the BIS_CrCys over the CKD-EPI_CrCys equation in the ≥70 year subgroup.

CONCLUSIONS

The CKD-EPI_CrCys equation provided the best estimate of gentamicin clearance. If used for guiding gentamicin dosing, the results from GFR equations should be adjusted for individual BSA at the extremes of body size.

Comparison between Cystatin C- and Creatinine-Estimated Glomerular Filtration Rate in Cardiology Patients

OBJECTIVE

Estimation of the glomerular filtration rate (GFR) is essential for identification, evaluation and risk prediction in patients with kidney disease. Estimated GFR (eGFR) is also needed for the correct dosing of drugs eliminated by the kidneys and to identify high-risk individuals in whom coronary angiography or other procedures may lead to kidney failure. Both cystatin C and creatinine are used for the determination of GFR, and we aimed to investigate if eGFR by the two methods differ in cardiology patients.

METHODS

We compared cystatin C and creatinine (CKD-EPI) eGFR calculated from the same request from a cardiology outpatient unit (n = 2,716), a cardiology ward (n = 980), a coronary care unit (n = 1,464), and an advanced coronary care unit (n = 518) in an observational, cross-sectional study.

RESULTS

The median creatinine eGFR results are approximately 10 ml/min/1.73 m(2) higher than the median cystatin C eGFR that is up to 90 ml/min/1.73 m(2), irrespective of the level of care. Creatinine eGFR resulted in a less advanced eGFR category in the majority of patients with a cystatin C eGFR <60 ml/min/1.73 m(2).

CONCLUSIONS

Our study demonstrates a difference between creatinine and cystatin C eGFR in cardiology patients. It is important to be aware of which marker is used for the reported eGFR to minimize erroneous interpretations of the test results, as this could lead to under- or overmedication. Further studies are needed to determine the best method of estimating the GFR in cardiology units.

Biomarkers of delayed graft function as a form of acute kidney injury in kidney transplantation

Renal transplantation ensures distinct advantages for patients with end-stage kidney disease. However, in some cases early complications can lead to allograft dysfunction and consequently graft loss. One of the most common early complications after kidney transplantation is delayed graft function (DGF). Unfortunately there is no effective treatment for DGF, however early diagnosis of DGF and therapeutic intervention (eg modification of immunosuppression) may improve outcome. Therefore, markers of acute kidney injury are required. Creatinine is a poor biomarker for kidney injury due principally to its inability to help diagnose early acute renal failure and complete inability to help differentiate among its various causes. Different urinary and serum proteins have been intensively investigated as possible biomarkers in this setting. There are promising candidate biomarkers with the ability to detect DGF. We focused on emerging biomarkers of DGF with NGAL is being the most studied followed by KIM-1, L-FABP, IL-18, and others. However, large randomized studies are needed to establish the value of new, promising biomarkers, in DGF diagnosis, prognosis and its cost-effectiveness.

From the nephrologist's point of view: diversity of causes and clinical features of acute kidney injury

Acute kidney injury (AKI) is a clinical syndrome with multiple entities. Although AKI implies renal damage, functional impairment or both, diagnosis is solely based on the functional parameters of serum creatinine and urine output. The latest definition was provided by the Kidney Disease Improving Global Outcomes (KDIGO) working group in 2012. Independent of the underlying disease, and even in the case of full recovery, AKI is associated with an increased morbidity and mortality. Awareness of the patient's individual risk profile and the diversity of causes and clinical features of AKI is pivotal for optimization of prophylaxes, diagnosis and therapy of each form of AKI. A differentiated and individualized approach is required to improve patient mortality, morbidity, long-term kidney function and eventually the quality of life. In this review, we provide an overview of the different clinical settings in which specific forms of AKI may occur and point out possible diagnostic as well as therapeutic approaches. Secifically AKI is discussed in the context of non-kidney organ failure, organ transplantation, sepsis, malignancy and autoimmune disease.

Cost-effectiveness analysis of acute kidney injury biomarkers in pediatric cardiac surgery

Introduction

Acute kidney injury (AKI) is significant problem in children with congenital heart disease (CHD) who undergo cardiac surgery. The economic impact of a biomarker-based diagnostic strategy for AKI in pediatric populations undergoing CHD surgery is unknown. The aim of this study was to perform the cost effectiveness analysis of using serum cystatin C (sCysC), urine neutrophil gelatinase-associated lipocalin (uNGAL) and urine liver fatty acid-binding protein (uL-FABP) for the diagnosis of AKI in children after cardiac surgery compared with current diagnostic method (monitoring of serum creatinine (sCr) level).

Materials and methods

We developed a decision analytical model to estimate incremental cost-effectiveness of different biomarker-based diagnostic strategies compared to current diagnostic strategy. The Markov model was created to compare the lifetime cost associated with using of sCysC, uNGAL, uL-FABP with monitoring of sCr level for the diagnosis of AKI. The utility measurement included in the analysis was quality-adjusted life years (QALY). The results of the analysis are presented as the incremental cost-effectiveness ratio (ICER).

Results

Analysed biomarker-based diagnostic strategies for AKI were cost-effective compared to current diagnostic method. However, uNGAL and sCys C strategies yielded higher costs and lower effectiveness compared to uL-FABP strategy. uL-FABP added 1.43 QALY compared to current diagnostic method at an additional cost of $8521.87 per patient. Therefore, ICER for uL-FABP compared to sCr was $5959.35/QALY.

Conclusions

Our results suggest that the use of uL-FABP would represent cost effective strategy for early diagnosis of AKI in children after cardiac surgery.

Association of definition of acute kidney injury by cystatin C rise with biomarkers and clinical outcomes in children undergoing cardiac surgery

IMPORTANCE

Research has identified improved biomarkers of acute kidney injury (AKI). Cystatin C (CysC) is a better glomerular filtration rate marker than serum creatinine (SCr) and may improve AKI definition.

OBJECTIVE

To determine if defining clinical AKI by increases in CysC vs SCr alters associations with biomarkers and clinical outcomes.

DESIGN, SETTING, AND PARTICIPANTS

Three-center prospective cohort study of intensive care units in New Haven, Connecticut, Cincinnati, Ohio, and Montreal, Quebec, Canada. Participants were 287 patients 18 years or younger without preoperative AKI or end-stage renal disease who were undergoing cardiac surgery. The study dates were July 1, 2007, through December 31, 2009.

EXPOSURES

For biomarker vs clinical AKI associations, the exposures were first postoperative (0-6 hours after surgery) urine interleukin 18, neutrophil gelatinase-associated lipocalin, kidney injury molecule 1, and liver fatty acid-binding protein. For clinical AKI outcome associations, the exposure was Kidney Disease: Improving Global Outcomes AKI definition (based on SCr or CysC).

MAIN OUTCOMES AND MEASURES

Clinical AKI, length of stay, and length of mechanical ventilation. We determined areas under the receiver operating characteristic curve and odds ratios for first postoperative biomarkers to predict AKI.

RESULTS

The SCr-defined vs CysC-defined AKI incidence differed substantially (43.6% vs 20.6%). Percentage agreement was 71% (κ = 0.38); stage 2 or worse AKI percentage agreement was 95%. Interleukin 18 and kidney injury molecule 1 discriminated for CysC-defined AKI better than for SCr-defined AKI. For interleukin 18 and kidney injury molecule 1, the areas under the receiver operating characteristic curve were 0.74 and 0.65, respectively, for CysC-defined AKI, and 0.66 and 0.58, respectively, for SCr-defined AKI. Fifth (vs first) quintile concentrations of both biomarkers were more strongly associated with CysC-defined AKI. For interleukin 18 and kidney injury molecule 1, the odds ratios were 16.19 (95% CI, 3.55-73.93) and 6.93 (95% CI, 1.88-25.59), respectively, for CysC-defined AKI vs 6.60 (95% CI, 2.76-15.76) and 2.04 (95% CI, 0.94-4.38), respectively, for SCr-defined AKI. Neutrophil gelatinase-associated lipocalin and liver fatty acid-binding protein associations with both definitions were similar. The CysC definitions and SCr definitions were similarly associated with clinical outcomes of resource use.

CONCLUSIONS AND RELEVANCE

Compared with the SCr-based definition, the CysC-based definition is more strongly associated with urine interleukin 18 and kidney injury molecule 1 in children undergoing cardiac surgery. Consideration should be made for defining AKI based on CysC in clinical care and future studies.

Novel biomarkers of acute kidney injury: Evaluation and evidence in urologic surgery

Patients undergoing urologic surgery are at risk of acute kidney injury (AKI) and consequently long-term deterioration in renal function. AKI is further associated with significantly higher odds of perioperative complications, prolonged hospital stay, higher mortality and costs. Therefore, better awareness and detection of AKI, as well as identification of AKI determinants in the urological surgery setting is warranted to pre-empt and mitigate further deterioration of renal function in patients at special risk. New consensus criteria provide precise definitions of diagnosis and description of the severity of AKI. However, they rely on serum creatinine (SCr), which is known to be an inaccurate marker of early changes in renal function. Therefore, several new urinary and serum biomarkers promise to address the gap associated with the use of SCr. Novel biomarkers may complement SCr measurement or most likely improve the diagnostic accuracy of AKI when used in combinations. However, novel biomarkers have to prove their clinical applicability, accuracy, and cost effectiveness prior to implementation into clinical practice. Most preferably, novel biomarkers should help to positively improve a patient’s long-term renal functional outcomes. The purpose of this review is to discuss currently available biomarkers and to review their clinical evidence within urologic surgery settings.

Cystatin C in acute kidney injury diagnosis: early biomarker or alternative to serum creatinine?

BACKGROUND

Early acute kidney injury (AKI) diagnosis is needed to pursue treatment trials. We evaluated cystatin C (CysC) as an early biomarker of serum creatinine (SCr)-AKI and an alternative to define AKI.

METHODS

We studied 160 non-cardiac children in the intensive care unit (ICU). We measured daily CysC and SCr. AKI was staged by KDIGO (Kidney Disease: Improving Global Outcomes) guidelines using SCr and CysC (CysC-AKI). We calculated area under the curve (AUC) for (1) neutrophil gelatinase-associated lipocalin (NGAL), interleukin-18 (IL-18), kidney injury molecule-1 (KIM-1) and urine CysC to diagnose SCr- and CysC-AKI; and (2) for CysC to diagnose SCr-AKI. We evaluated AKI associations with length of stay and ventilation duration.

RESULTS

We found that 44 % of patients developed SCr-AKI; 32 % developed CysC-AKI. Early ICU NGAL was most diagnostic of CysC-AKI (AUC 0.69, 95% CI 0.54-0.84); IL-18 was most diagnostic for SCr-AKI (AUC 0.69 95% CI 0.55-0.82). Combining SCr and CysC-AKI definition led to higher biomarker diagnostic AUC's. CysC-AKI was not more strongly associated with clinical outcomes. Early ICU CysC predicted SCr-AKI development (AUC 0.70, 95 % CI 0.53-0.89).

CONCLUSIONS

Our findings do not support replacing SCr by CysC to define AKI. Early ICU CysC predicts SCr-AKI development and combined SCr-CysC-AKI definition leads to stronger AKI biomarker associations.

Pediatric reference ranges for acute kidney injury biomarkers

BACKGROUND

Novel urinary biomarkers are useful for the prediction of acute kidney injury (AKI). Most promising are the urine markers NGAL, IL-18, KIM-1, and LFABP. Each of these has shown considerable promise diagnosing AKI earlier than serum creatinine (Scr) using disease controls. We set out to determine reference levels of these markers in a healthy pediatric population.

METHODS

Urine was collected from 368 healthy children and assayed for NGAL, IL-18, KIM-1, and LFABP using commercially available kits or assay materials. Analysis of biomarkers by linear regression and according to age groups (3-<5 years; 5-<10; 10-<15; 15-<18) was performed to determine if biomarker levels differed with age and gender.

RESULTS

Median values were: NGAL (6.6 ng/ml; IQR 2.8-17), IL-18 (21.6 pg/ml; IQR 13.6-32.9), KIM-1 (410 pg/ml; IQR 226-703), LFABP (3.4 ng/ml; IQR 1.6-6.0). Significant gender differences were found with NGAL and IL-18 and significant age differences were found with all markers. 95th percentile values for each marker varied with age and gender greater than median values.

CONCLUSIONS

This is the largest pediatric reference range study for the urinary measurement of NGAL, IL-18, KIM-1, and LFABP and highlights age and gender differences in these markers. This information is essential for rational interpretation of studies and clinical trials utilizing these emerging AKI biomarkers.

Novel biomarkers in heart failure with preserved ejection fraction

Heart failure with preserved ejection fraction (HFPEF) is a common subtype of heart failure with morbidity and mortality similar to that of heart failure with systolic dysfunction. This article discusses the numerous biomarkers that promise to play a substantial role in terms of our ability to understand the mechanisms of HFPEF and discern possible phenotypes that respond to targeted therapies: natriuretic peptides, high-sensitivity troponins, galectin-3, soluble ST2, neutrophil gelatinase-associated lipocalin, and cystatin C.

Acute Kidney Injury in the Critically Ill Patient: A Current Review of the Literature

PURPOSE

A comprehensive review of the literature to provide a focused and thorough update on the issue of acute kidney injury (AKI) in the surgical patient.

METHODS

A PubMed and Medline search was performed and keywords included AKI, renal failure, critically ill, and renal replacement therapy (RRT).

PRINCIPAL FINDINGS

A common clinical problem encountered in critically ill patients is AKI. The recent consensus definitions for the diagnosis and classification of AKI (ie, Risk, Injury, Failure, Loss of kidney function, and End-stage kidney disease/Acute Kidney Injury Network) have enabled us to standardize the severity of AKI and facilitate strategies for prevention. These strategies as well as treatment modalities of AKI are discussed. We provide a concise overview of the issue of renal failure. We describe strategies for prevention including types of fluids used for resuscitation, timing of initiation of RRT, and different treatment modalities currently available for clinical practice.

CONCLUSIONS

Acute kidney injury is a common problem in the critically ill patient and is associated with worse clinical outcomes. A standardized definition and staging system has led to improved diagnosis and understanding of the pathophysiology of AKI. There are many trials leading to improved prevention and management of the disease.

A comparison of the effects of ketamine and remifentanil on renal functions in coronary artery bypass graft surgery

We have investigated the effects of ketamine-based and remifentanil-based anesthetic protocol on perioperative serum cystatin-C levels, and creatinine and/or cystatin-C-based eGFR equations in terms of acute kidney injury in coronary artery bypass graft (CABG) surgery. Using a simple randomization method (coin tossing), patients were divided into the two groups and not-blinded to the anesthetist. Remifentanil-midazolam-propofol or ketamine-midazolam-propofol-based anesthetic regimen was chosen. Different eGFR formulas using creatinine (MDRD, CKD-EPI, Cockrauft Gault); cystatin-C (eGFR1, eGFR2) or a combination of creatinine and cystatin-C (eGFR 3) were used to calculate estimated glomerular filtration rates (eGFRs). High-sensitive troponin T was used to determine if ketamine use in coronary surgery contributed to myocardial cell damage. Thirty-seven patients were included in the study (remifentanil group = 19, ketamine Group = 18). Urea, creatinine, cystatin-C levels were comparable between the groups in all the measurement times and also postoperative day 2 samples showed statistically higher results compared to baseline (p < 0.001). Effects of ketamine and remifentanil on renal functions were found similar. Creatinine and cystatin-C-based eGFR equations resulted similar in our study. Reversible stage 1 acute kidney injury (AKI) was observed on postoperative day 2 in seven patients from the remifentanil group and six patients from the ketamine group. Hs-troponin T was found to be higher in postoperative day 1 samples; there were no significant difference between the groups. Our results indicated that patients who have normal renal functions undergoing on-pump coronary bypass surgery, effects of ketamine and remifentanil on renal functions in terms of AKI were found to be similar.

Urine interleukin-18 in prediction of acute kidney injury: a systemic review and meta-analysis

BACKGROUND

Interleukin-18 (IL-18) mediates ischemic acute tubular necrosis; it has been proved as a rapid, reliable, and affordable test marker for the early detection of acute kidney injury (AKI), but its predictive accuracy varies greatly.

METHODS

MEDLINE and EMBASE, Cochrane Library, Ovid, and Springerlink (from inception to November 15, 2013) were searched for relevant studies (in English) investigating diagnostic accuracy of urine IL-18 to predict AKI in various clinical settings. The text index was increasing or increased urine IL-18 level and the main outcome was the development of AKI, which was primarily based on serum creatinine level [using risk, injury, failure, loss and end-stage renal disease (RIFLE), acute kidney injury network, or modified pediatric RIFLE criteria in pediatric patients]. Pooled estimates of diagnostic odds ratio (OR), sensitivity and specificity were calculated. Summary receiver operating characteristic curves were used to calculate the measures of accuracy and Q point value (Q*). Remarkable heterogeneity was explored further by subgroup analysis based on the different clinical settings.

RESULTS

We analyzed data from 11 studies of 3 countries covering 2,796 patients. These studies were marked by limitations of threshold and non-threshold effect heterogeneity. Across all settings, the diagnostic OR for urine IL-18 level to predict AKI was 5.11 [95% confidence interval (CI) 3.22-8.12], with sensitivity and specificity respectively at 0.51 and 0.79. The area under the ROC curve of urine IL-18 level to predict AKI was 0.77 (95% CI 0.71-0.83). Subgroup analysis showed that urine IL-18 level in pediatric patients (<18 years) and early AKI predictive time (<12 h) were more effective in predicting AKI, with diagnostic ORs of 7.51 (2.99-18.88), 8.18 (2.19-30.51), respectively.

CONCLUSION

Urine IL-18 holds promise as a biomarker in the prediction of AKI but has only moderate diagnostic value.

Glomerular filtration rate, urine production, and fractional clearance of electrolytes in acute kidney injury in dogs and their association with survival

Background

Acute kidney injury (AKI) is common in dogs. Few studies have assessed sequential changes in indices of kidney function in dogs with naturally occurring AKI.

Objective

To document sequential changes of conventional indices of renal function, to better define the course of AKI, and to identify a candidate marker for recovery.

Animals

Ten dogs with AKI.

Methods

Dogs were prospectively enrolled and divided into surviving and nonsurviving dogs. Urine production was measured with a closed system for 7 days. One and 24‐hour urinary clearances were performed daily to estimate solute excretion and glomerular filtration rate (GFR). Solute excretion was calculated as an excretion ratio (ER) and fractional clearance (FC) based on both the 1‐ and 24‐hour urine collections.

Results

Four dogs survived and 6 died. At presentation, GFR was not significantly different between the outcome groups, but significantly (P = .03) increased over time in the surviving, but not in the nonsurviving dogs. Fractional clearance of Na decreased significantly over time (20.2–9.4%, P < .0001) in the surviving, but not in the nonsurviving dogs. The ER and FC of solutes were highly correlated (r, 0.70–0.95).

Conclusion and Clinical Impact

Excretion ratio might be used in the clinical setting as a surrogate marker to follow trends in solute excretion. Increased GFR, urine production, and decreased FC of Na were markers of renal recovery. The FC of Na is a simple, noninvasive, and cost‐effective method that can be used to evaluate recovery of renal function.

Combination of biomarkers for diagnosis of acute kidney injury after cardiopulmonary bypass

Novel acute kidney injury (AKI) biomarkers offer promise of earlier diagnosis and risk stratification, but have yet to find widespread clinical application. We measured urinary α and π glutathione S-transferases (α-GST and π-GST), urinary l-type fatty acid-binding protein (l-FABP), urinary neutrophil gelatinase-associated lipocalin (NGAL), urinary hepcidin and serum cystatin c (CysC) before surgery, post-operatively and at 24 h after surgery in 93 high risk patient undergoing cardiopulmonary bypass (CPB) and assessed the ability of these biomarkers alone and in combination to predict RIFLE-R defined AKI in the first 5 post-operative days. Twenty-five patients developed AKI. π-GST (ROCAUC = 0.75), lower urine Hepcidin:Creatine ratio at 24 h (0.77), greater urine NGAL:Cr ratio post-op (0.73) and greater serum CysC at 24 h (0.72) best predicted AKI. Linear combinations with significant improvement in AUC were: Hepcidin:Cr 24 h + post-operative π-GST (AUC = 0.86, p = 0.01), Hepcidin:Cr 24 h + NGAL:Cr post-op (0.84, p = 0.03) and CysC 24 h + post-operative π-GST (0.83, p = 0.03), notably these significant biomarkers combinations all involved a tubular injury and a glomerular filtration biomarker. Despite statistical significance in receiver-operator characteristic (ROC) analysis, when assessed by ability to define patients to two groups at high and low risk of AKI, combinations failed to significantly improve classification of risk compared to the best single biomarkers. In an alternative approach using Classification and Regression Tree (CART) analysis a model involving NGAL:Cr measurement post-op followed by Hepcidin:Cr at 24 h was developed which identified high, intermediate and low risk groups for AKI. Regression tree analysis has the potential produce models with greater clinical utility than single combined scores.

Cystatin C and Its Role in Patients with Type 1 and Type 2 Diabetes Mellitus

Diabetes mellitus is the commonest cause of CKD. It is the leading cause of new patients requiring renal replacement therapy, accounting for 40%, 34%, and 30% of cases in United States, Germany, and Australia, respectively. Recent studies have shown that a low-molecular weight protein, cystatin C, freely filtered by the kidneys is a novel biomarker that may be used for detection of early renal dysfunction in patients with type 1 or type 2 diabetes. Cystatin C has also been shown to detect cardiovascular disease in patients with diabetes and it may also be linked with incident type 2 diabetes in obese patients. We aim to review current evidence based literature on use of cystatin C for early detection of diabetic nephropathy due to type 1 and type 2 diabetes in comparison to conventional methods and explore its association with other comorbidities.

Renal Safety Pharmacology in Drug Discovery and Development

The kidney is a complex excretory organ playing a crucial role in various physiological processes such as fluid and electrolyte balance, control of blood pressure, removal of waste products, and drug disposition. Drug-induced kidney injury (DIKI) remains a significant cause of candidate drug attrition during drug development. However, the incidence of renal toxicities in preclinical studies is low, and the mechanisms by which drugs induce kidney injury are still poorly understood. Although some in vitro investigational tools have been developed, the in vivo assessment of renal function remains the most widely used methodology to identify DIKI. Stand-alone safety pharmacology studies usually include assessment of glomerular and hemodynamic function, coupled with urine and plasma analyses. However, as renal function is not part of the ICH S7A core battery, such studies are not routinely conducted by pharmaceutical companies. The most common approach consists in integrating renal/urinary measurements in repeat-dose toxicity studies. In addition to the standard analyses and histopathological examination of kidneys, novel promising urinary biomarkers have emerged over the last decade, offering greater sensitivity and specificity than traditional renal parameters. Seven of these biomarkers have been qualified by regulatory agencies for use in rat toxicity studies.

Sepsis and Acute Kidney Injury

Acute kindney injury (AKI) is a clinical syndrome which is generally defined as an abrupt decline in glomerular filtration rate, causing accumulation of nitrogenous products and rapid development of fluid, electrolyte and acid base disorders. In intensive care unit sepsis and septic shock are leading causes of AKI. Sepsis-induced AKI literally acts as a biologic indicator of clinical deterioration. AKI triggers variety of immune, inflammatory, metabolic and humoral patways; ultimately leading distant organ dysfunction and increases morbidity and mortality. Serial mesurements of creatinine and urine volume do not make it possible to diagnose AKI at early stages. Serum creatinine influenced by age, weight, hydration status and become apparent only when the kidneys have lost 50% of their function. For that reason we need new markers, and many biomarkers in the diagnosis of early AKI activity is assessed. Historically "Risk-Injury-Failure-Loss-Endstage" (RIFLE), "Acute Kidney Injury Netwok" (AKIN) and "The Kidney Disease/ Improving Global Outcomes" (KDIGO) classification systems are used for diagnosing easily in clinical practice and research and grading disease. Classifications including diagnostic criteria are formed for the identification of AKI. Neutrophil gelatinase associated lipocalin (NGAL), cystatin-C (Cys-C), kidney injury molecule-1 (KIM-1) and also "cell cycle arrest" molecules has been concerned for clinical use. In this review the pathophysiology of AKI, with the relationship of sepsis and the importance of early diagnosis of AKI is evaluated.

The role of drug transporters in the kidney: lessons from tenofovir

Tenofovir disoproxil fumarate, the prodrug of nucleotide reverse transcriptase inhibitor tenofovir, shows high efficacy and relatively low toxicity in HIV patients. However, long-term kidney toxicity is now acknowledged as a modest but significant risk for tenofovir-containing regimens, and continuous use of tenofovir in HIV therapy is currently under question by practitioners and researchers. Co-morbidities (hepatitis C, diabetes), low body weight, older age, concomitant administration of potentially nephrotoxic drugs, low CD4 count, and duration of therapy are all risk factors associated with tenofovir-associated tubular dysfunction. Tenofovir is predominantly eliminated via the proximal tubules of the kidney, therefore drug transporters expressed in renal proximal tubule cells are believed to influence tenofovir plasma concentration and toxicity in the kidney. We review here the current evidence that the actions, pharmacogenetics, and drug interactions of drug transporters are relevant factors for tenofovir-associated tubular dysfunction. The use of creatinine and novel biomarkers for kidney damage, and the role that drug transporters play in biomarker disposition, are discussed. The lessons learnt from investigating the role of transporters in tenofovir kidney elimination and toxicity can be utilized for future drug development and clinical management programs.

Cystatin C for early detection of acute kidney injury after laparoscopic partial nephrectomy

Introduction and Objectives:

Mortality due to AKI has not changed significantly over the past 50 years. This is due in part to failure to detect early AKI and to initiate appropriate therapeutic measures. There is therefore a need to identify biomarkers that would improve the early detection of AKI. The objective of this study was to assess whether cystatin C levels obtained at specific timepoints during laparoscopic partial nephrectomy (PN) could be early predictors of AKI.

Materials and Methods:

Twenty-five patients underwent laparoscopic PN for organ-confined tumors. All procedures were performed by two surgeons in a single institution. Plasma samples were collected preoperatively, and post-unclamping at 5, 20, 120 min and on the day following surgery. Plasma cystatin C was measured by enzyme-linked immunosorbent assay. Correlation between levels of cystatin C and other parameters of interest were assessed in order to define cystatin C ability to predict AKI and loss of renal function following laparoscopic PN.

Results:

The mean baseline eGFR was 93 ml/min/1.73 m². Warm ischemia time varied between 16 and 44 min. Post-operative day 1 (POD1) cystatin C levels compared to baseline were increased in 13 (52%) of the patients. There was a high correlation between the difference of POD 1 and baseline value, and eGFR in the immediate postoperative period (r = −0.681; P = 0.0002) and at 12-month follow-up (r = −0.460, P = 0.048). However, the variation in cystatin C levels at earlier timepoints were not associated to AKI nor renal function.

Conclusions:

High increase in POD 1 cystatin C levels from baseline may help identify patients with AKI and those at higher risk of chronic kidney disease, following laparoscopic PN.

Clinical relevance of biomarkers in heart failure and cardiorenal syndrome: the role of natriuretic peptides and troponin

In recent years, numerous biomarkers have been studied in heart failure to improve diagnostic accuracy and identify patients at higher risk. The overall outcome remains fairish despite improvements in therapy, with mean survival after first hospitalization, around 5 years. We therefore need surrogate end points to better understand the pathogenetic mechanisms of the disease, including interplays with other organs. The kidney plays an important role in the initiation and progression of HF, and around one-third of patients with HF show some degree of renal dysfunction. In addition, treatment for HF often worsens renal function, consequently to hemodynamic and clinical improvement do not correspond an effective improvement in HF prognosis. Association between HF and renal impairment (RI) is now classified as cardiorenal syndrome (CRS) pointing out the bidirectional nature of this vicious circle leading to a mutual and progressive damage of both organs. The clinicians can rely on circulating biomarkers that give insights into the underlying pathogenetic mechanisms and help in risk stratification. Recently, a multimarker strategy including biomarker tool to traditional risk scores has been purposed and applied: Although each biomarker provided incremental outcome benefit, the combination of multiple biomarkers should offer the greatest improvement in risk prediction. Natriuretic peptides (NP) and cardiac troponins (TN) are the two biomarkers most studied in this setting, probably because of their organ-specific nature. However, both NP and TN cutoffs in presence of renal dysfunction need to be revised and discussed in relation to age, gender and stage of RI. In this context, the biomarkers are a unique opportunity to elucidate pathophysiological mechanisms, tailor clinical management to the single patient and improve outcomes. Specific studies about the exact role of biomarkers as in HF as in CRS should be planned and considered for future trials.

Comparison of Serum Cystatin C and Creatinine Level Changes for Prognosis of Patients After Peripheral Arterial Angiography

We compared changes in serum cystatin C (Cys C) and creatinine (sCr) levels for detecting contrast-induced acute kidney injury; 350 consecutive patients who underwent peripheral arterial angiography were prospectively enrolled. Serum Cys C and sCr levels were assayed at predefined time points after contrast-media exposure. During 1-year follow-up, major adverse events (MAEs) including all-cause mortality and dialysis were assessed. A sCr increase ≥25% was not associated with MAEs, whereas a serum Cys C increase ≥5% at 24 hours was associated with higher probability of MAEs ( P = .010). The independent predictors of 1-year MAEs were older age ( P = .004), lower prealbumin levels ( P = .022), and serum Cys C increase ≥5%. In patients who underwent peripheral angiography, a serum Cys C increase ≥5% was an independent predictor of 1-year MAEs.

Bedside biomarkers in pediatric cardio renal injuries in emergency

Point of care testing (POCT) using biomarkers in the emergency department reduces turnaround time for clinical decision making. An ideal biomarker should be accurate, reliable and easy to measure with a standard assay, non-invasive, sensitive and specific with defined cutoff values. Conventional biomarkers for renal injuries include rise in serum creatinine and fluid overload. Recently, neutrophil gelatinase associated lipocalin (NGAL), kidney injury molecule-1 (KIM-1), cystatin C, interleukin-18 (IL-18) and liver fatty acid binding protein (L-FABP) have been studied extensively for their role in acute kidney injury associated with various clinical entities. Biochemical markers of ischaemic cardiac damage commonly used are plasma creatine kinase and cardiac troponins (cTn). Clinically valuable cardiac markers for myocardial injury in research at present comprise BNP/NT-proBNP and to a lesser extent, CRP, which are independent predictors of adverse events including death and heart failure. Current status of point of care biomarkers for diagnosis and prognostication of renal and cardiac injuries in pediatric emergency care is appraised in this review.

Effect of aging on renal function plus monitoring and support

Several anatomic changes and physiologic alterations occur in the aging kidney, awareness of which is essential for the early recognition of acute kidney injury (AKI) to improve outcomes in hospitalized geriatric patients. There are no unique diagnostic methods or treatment modalities in the care of the geriatric patient with AKI. Therapy is mainly supportive, and the full spectrum of treatment options, including renal replacement therapy (RRT), should not be withheld from a patient based on age. More studies need to be performed to determine the optimal timing, intensity, and modality of RRT in the geriatric population.

Do intravenous N-acetylcysteine and sodium bicarbonate prevent high osmolal contrast-induced acute kidney injury? A randomized controlled trial

BACKGROUND

N-acetylcysteine (NAC) or sodium bicarbonate (NaHCO3), singly or combined, inconsistently prevent patients exposed to radiographic contrast media from developing contrast-induced acute kidney injury (CI-AKI).

OBJECTIVE

We asked whether intravenous isotonic saline and either NaHCO3 in 5% dextrose or else a high dose of NAC in 5% dextrose prevent CI-AKI in outpatients exposed to high-osmolal iodinated contrast medium more than does saline alone.

METHODS

This completed prospective, parallel, superiority, open-label, controlled, computer-randomized, single-center, Brazilian trial (NCT01612013) hydrated 500 adult outpatients (214 at high risk of developing CI-AKI) exposed to ioxitalamate during elective coronary angiography and ventriculography. From 1 hour before through 6 hours after exposure, 126 patients (group 1) received a high dose of NAC and saline, 125 (group 2) received NaHCO3 and saline, 124 (group 3) received both treatments, and 125 (group 4) received only saline.

RESULTS

Groups were similar with respect to age, gender, weight, pre-existing renal dysfunction, hypertension, medication, and baseline serum creatinine and serum cystatin C, but diabetes mellitus was significantly less prevalent in group 1. CI-AKI incidence 72 hours after exposure to contrast medium was 51.4% (257/500), measured as serum creatinine > (baseline+0.3 mg/dL) and/or serum cystatin C > (1.1 · baseline), and 7.6% (38/500), measured as both serum creatinine and serum cystatin C > (baseline+0.3 mg/dL) or > (1.25 · baseline). CI-AKI incidence measured less sensitively was similar among groups. Measured more sensitively, incidence in group 1 was significantly (p<0.05) lower than in groups 2 and 3 but not group 4; adjustment for confounding by infused volume equalized incidence in groups 1 and 3.

CONCLUSION

We found no evidence that intravenous isotonic saline and either NaHCO3 or else a high dose of NAC prevent CI-AKI in outpatients exposed to high osmolal iodinated contrast medium more than does saline alone.

TRIAL REGISTRATION

ClinicalTrials.gov NCT01612013.

Comparison of serum creatinine and serum cystatin C as biomarkers to detect sepsis-induced acute kidney injury and to predict mortality in CD-1 mice

Acute kidney injury (AKI) dramatically increases sepsis mortality, but AKI diagnosis is delayed when based on serum creatinine (SCr) changes, due in part, to decreased creatinine production. During experimental sepsis, we compared serum cystatin C (sCysC), SCr, and blood urea nitrogen (BUN) to inulin glomerular filtration rate (iGFR) before or 3-18 h after cecal ligation and puncture (CLP)-induced sepsis in CD-1 mice. sCysC had a faster increase and reached peak levels more rapidly than SCr in both sepsis and bilateral nephrectomy (BiNx) models. sCysC was a better surrogate of iGFR than SCr during sepsis. Combining sCysC with SCr values into a composite biomarker improved correlation with iGFR better than any biomarker alone or any other combination. We determined the renal contribution to sCysC handling with BiNx. sCysC and SCr were lower post-BiNx/CLP than post-BiNx alone, despite increased inflammatory and nonrenal organ damage biomarkers. Sepsis decreased CysC production in nephrectomized mice without changing body weight or CysC space. Sepsis decreased sCysC production and increased nonrenal clearance, similar to effects of sepsis on SCr. sCysC, SCr, and BUN were measured 6 h postsepsis to link AKI with mortality. Mice with above-median sCysC, BUN, or SCr values 6 h postsepsis died earlier than mice with below-median values, corresponding to a substantial AKI association with sepsis mortality in this model. sCysC performs similarly to SCr in classifying mice at risk for early mortality. We conclude that sCysC detects AKI early and better reflects iGFR in CLP-induced sepsis. This study shows that renal biomarkers need to be evaluated in specific contexts.

Pediatric acute kidney injury: A syndrome under paradigm shift

The recent standardization and validation of definitions of pediatric acute kidney injury (pAKI) has ignited new dimensions of pAKI epidemiology and its risk factors. pAKI causes increased morbidity and mortality in critically ill-children. Among the hospitalized patients incidence of pAKI ranges from 1% to 31%, while mortality ranges from 28% to 82%, presenting a broad range due to lack of uniformly acceptable pAKI definition. In addition, cumulative data regarding the progression of pAKI to chronic kidney disease in children is rising. Despite these alarming figures, treatment modalities have failed to deliver significantly. In this review, we will summarize the latest developments of pAKI and highlight important aspects of pAKI management.

Measuring renal function in critically ill patients: tools and strategies for assessing glomerular filtration rate

PURPOSE OF REVIEW

Alterations in kidney function are common in critically ill patients and are generally assessed by changes in serum creatinine (sCr) or urine output, which are considered surrogates for glomerular filtration rate (GFR) but do not reflect the overall kidney function. There is a great need for more reliable measurements of glomerular filtration in order to guide diagnosis and therapy for acute kidney injury. In this review, we will focus on recent advances to measure GFR that could help to better evaluate kidney function and improve patient care.

RECENT FINDINGS

Standardized assays for sCr measurements, the use of a more precise scale with more frequent measurements, and the interpretation of the results based on patient's characteristics can increase the clinical value of sCr. New endogenous and exogenous markers will provide a more precise estimation. Imaging techniques are being developed and will probably be available in the near future. New gold standards for glomerular filtration will help in the development and improvement in the use of new biomarkers of kidney injury.