The future of pediatric acute kidney injury management--biomarkers

Intensive Care Management of Pediatric Acute Liver Failure

Pediatric acute liver failure is rare but life-threatening illness that occurs in children without preexisting liver disease. The rarity of the disease, along with its severity and heterogeneity, presents unique clinical challenges to the physicians providing care for pediatric patients with acute liver failure. In this review, practical clinical approaches to the care of critically ill children with acute liver failure are discussed with an organ system-specific approach. The underlying pathophysiological processes, major areas of uncertainty, and approaches to the critical care management of pediatric acute liver failure are also reviewed.

Kidney Injury Molecule-1 and Cardiovascular Diseases: From Basic Science to Clinical Practice

Despite the recent findings concerning pathogenesis and novel therapeutic strategies, cardiovascular disease (CVD) still stays the leading cause of morbidity and mortality in patients with renal dysfunction, especially acute kidney injury (AKI). Early detection of patients with impaired renal function with cardiovascular risk may help ensure more aggressive treatment and improve clinical outcome. Kidney injury molecule-1 (KIM-1) is a new, promising marker of kidney damage which is currently the focus of countless studies worldwide. Some recent animal and human studies established KIM-1 as an important marker of acute tubular necrosis (ATN) and reliable predictor of development and prognosis of AKI. Food and Drug Administration (FDA) in USA acclaimed KIM-1 as an AKI biomarker for preclinical drug development. Recent data suggest the importance of monitoring of KIM-1 for early diagnosis and clinical course not only in patients with various forms of AKI and other renal diseases but also in patients with cardiorenal syndrome, heart failure, cardiopulmonary bypass, cardiothoracic surgical interventions in the pediatric emergency setting, and so forth. The aim of this review article is to summarize the literature data concerning KIM-1 as a potential novel marker in the early diagnosis and prediction of clinical outcome of certain cardiovascular diseases.

Combining functional and tubular damage biomarkers improves diagnostic precision for acute kidney injury after cardiac surgery

BACKGROUND

Increases in serum creatinine (ΔSCr) from baseline signify acute kidney injury (AKI) but offer little granular information regarding its characteristics. The 10th Consensus Conference of the Acute Dialysis Quality Initiative (ADQI) suggested that combining AKI biomarkers would provide better precision for AKI course prognostication.

OBJECTIVES

This study investigated the value of combining a functional damage biomarker (plasma cystatin C [pCysC]) with a tubular damage biomarker (urine neutrophil gelatinase-associated lipocalin [uNGAL]), forming a composite biomarker for prediction of discrete characteristics of AKI.

METHODS

Data from 345 children after cardiopulmonary bypass (CPB) were analyzed. Severe AKI was defined as Kidney Disease Global Outcomes Initiative stages 2 to 3 (≥100% ΔSCr) within 7 days of CPB. Persistent AKI lasted >2 days. SCr in reversible AKI returned to baseline ≤48 h after CPB. The composite of uNGAL (>200 ng/mg urine Cr = positive [+]) and pCysC (>0.8 mg/l = positive [+]), uNGAL+/pCysC+, measured 2 h after CPB initiation, was compared to ΔSCr increases of ≥50% for correlation with AKI characteristics by using predictive probabilities, likelihood ratios (LR), and area under the curve receiver operating curve (AUC-ROC) values [Corrected].

RESULTS

Severe AKI occurred in 18% of patients. The composite uNGAL+/pCysC+ demonstrated a greater likelihood than ΔSCr for severe AKI (+LR: 34.2 [13.0:94.0] vs. 3.8 [1.9:7.2]) and persistent AKI (+LR: 15.6 [8.8:27.5] versus 4.5 [2.3:8.8]). In AKI patients, the uNGAL-/pCysC+ composite was superior to ΔSCr for prediction of transient AKI. Biomarker composites carried greater probability for specific outcomes than ΔSCr strata.

CONCLUSIONS

Composites of functional and tubular damage biomarkers are superior to ΔSCr for predicting discrete characteristics of AKI.

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.

Interleukin 18 as a marker of chronic nephropathy in children after anticancer treatment

Novel markers of nephrotoxicity, including kidney injury molecule 1 (KIM-1), interleukin 18 (IL-18), and beta-2 microglobulin, were used in the detection of acute renal injury. The aim of the study was to establish the frequency of postchemotherapy chronic kidney dysfunction in children and to assess the efficacy of IL-18, KIM-1, and beta-2 microglobulin in the detection of chronic nephropathy. We examined eighty-five patients after chemotherapy (median age of twelve years). The median age at the point of diagnosis was 4.2 years, and the median follow-up time was 4.6 years. We performed classic laboratory tests assessing kidney function and compared the results with novel markers (KIM-1, beta-2 microglobulin, and IL-18). Features of subclinical renal injury were identified in forty-eight children (56.3% of the examined group). Nephropathy, especially tubulopathy, appeared more frequently in patients treated with ifosfamide, cisplatin, and/or carboplatin, following nephrectomy or abdominal radiotherapy (P = 0.14, P = 0.11, and P = 0.08, resp.). Concentrations of IL-18 and beta-2 microglobulin were comparable with classic signs of tubulopathy (P = 0.0001 and P = 0.05). Concentrations of IL-18 were also significantly higher in children treated with highly nephrotoxic drugs (P = 0.0004) following nephrectomy (P = 0.0007) and abdominal radiotherapy (P = 0.01). Concentrations of beta-2 microglobulin were higher after highly toxic chemotherapy (P = 0.004) and after radiotherapy (P = 0.02). ROC curves created utilizing IL-18 data allowed us to distinguish between children with nephropathy (value 28.8 pg/mL) and tubulopathy (37.1 pg/mL). Beta-2 microglobulin and IL-18 seem to be promising markers of chronic renal injury in children after chemotherapy.

Serum cystatin C predicts acute kidney injury in preterm neonates with respiratory distress syndrome

BACKGROUND

We aimed to compare serum cystatin C levels (sCysC) in preterm neonates with respiratory distress syndrome (RDS) with a control group and to investigate whether it could be used as a predictor for acute kidney injury (AKI).

METHODS

sCysC was measured in 62 neonates with RDS (n = 28) and control neonates without RDS (n = 34), whose gestational ages (GA) were between 27 and 29 weeks (subgroup 1) and 30-32 weeks (subgroup 2). AKI was defined as oliguria and/or increase of serum creatinine. Blood samples were obtained on postnatal days (PND) 3 and 30. sCysC levels were determined by particle-enhanced nephelometric immunoassay.

RESULTS

There were six neonates with AKI (RDS-AKI subgroup) and 22 neonates without AKI (RDS-no AKI subgroup) during the first 7 days. Although sCysC levels were lower in neonates with RDS than controls on PND3 in both GA subgroups, the differences were not significant. However, in neonates with RDS and AKI, sCysC levels were significantly higher than neonates with RDS but no AKI and neonates in the control group on PND3. sCysC level was found to have a statistically significant association with AKI development in preterm neonates with RDS.

CONCLUSIONS

sCysC is an independent predictor of AKI in preterm neonates with RDS.

The kidney in pediatric liver transplantation: an updated perspective

CKD continues to detract from the success of improved survival in pediatric liver transplantation, and its presence is likely under recognized. Here we review the literature regarding the prevalence, etiology, and management of renal dysfunction in pediatric liver transplant recipients. Long-term studies suggest the prevalence of CKD to be 25-38% by 5-10 yr post-transplant. While important, sole use of serum creatinine overestimates renal function in this population. Screening for and treatment of persistent proteinuria and hypertension as well as minimization of nephrotoxic insults are the mainstays to delay or prevent CKD progression. Office-based blood pressure measures are less sensitive than ABPM, which is specifically recommended by the American Heart Association for its ability to diagnose masked hypertension in pediatric liver transplant recipients. Long-term risk of CKD is predominantly secondary to CNI toxicity. CNI minimization protocols have shown promise in slowing progression of CKD while maintaining graft function, but large-scale randomized control trials with long-term follow-up are needed.

Advances in acute kidney injury associated with cardiac surgery: the unfolding revolution in early detection

Cardiac surgery-associated acute kidney injury (CSA-AKI) is important because it remains common and serious. A major limitation in the management of CSA-AKI has been ongoing delayed diagnosis by standard clinical approaches, including serum creatinine and calculated glomerular filtration rate. Recent advances in the understanding of CSA-AKI have highlighted the utility of novel biomarkers that diagnose CSA-AKI within the first 24 hours. The biomarkers that have been evaluated in clinical trials include neutrophil gelatinase-associated lipocalin (NGAL), cystatin C, kidney injury molecule 1 and interleukin-18. The biomarker with the greatest clinical promise is NGAL. Although it has multiple advantages over serum creatinine, it is still not the ideal biomarker for CSA-AKI. It is likely that a panel of early biomarkers will be developed to facilitate rapid and reliable detection of CSA-AKI, combining their different characteristics to optimize patient management. Future clinical trials likely will focus on whether these biomarkers predict adverse outcomes independent of serum creatinine fluctuations and whether therapies guided by biomarker profiles improve renal salvage and overall clinical outcomes. Given their clinical utility, these novel biomarkers have been evaluated beyond cardiac surgery for AKI in multiple clinical environments, including the emergency department, the operating room, the cardiac catheterization laboratory, and the intensive care unit. Their integration into clinical practice seems likely in the near future.

Biomarkers and clinical tools in critically ill children: are we heading toward tailored drug therapy?

In pediatric critical care, validated biomarkers are essential for guiding drug therapy. The aim of this article is to present examples of current biomarker developments in its full breadth, including biochemical substances, physiological measurements and clinical scoring tools, with a focus on the field of circulatory, renal and neurophysiologic failure. Within each field we consecutively discuss the rationale for the selected biomarkers, studies in critically ill children, biomarker validation stage and biomarker use or potential use in drug studies and clinical drug dosing. This article demonstrates that there is paucity of properly validated biomarkers. Nevertheless, recent developments in, for instance, the field of sepsis, point us toward a future wherein, for critically ill children, drug therapy may be personalized using proteomic profiling instead of a small number of biomarkers, in order to establish a personal and dynamic disease profile.

Urine interleukin-18 and cystatin-C as biomarkers of acute kidney injury in critically ill neonates

BACKGROUND

Urinary interleukin-18 and cystatin-C are suggested to be biomarkers for predicting acute kidney injury (AKI). The aims of this study are to examine whether the urinary concentrations of interleukin-18 and cystatin-C vary with gestational age and other factors in non-AKI control neonates, and to determine whether urinary interleukin-18 and cystatin-C can predict AKI development in non-septic critically ill neonates, independently of potential confounders.

METHODS

We enrolled 62 non-septic critically ill neonates. Urine was collected every 48-72 h during the first 10 days of life.

RESULTS

Urinary concentration of cystatin-C, but not interleukin-18, decreased with increasing gestational age and body weight, but not with increasing postnatal age in non-AKI control neonates. Both urinary interleukin-18 and cystatin-C were associated with AKI, even after controlling for gestational and postnatal age, birth weight, gender, Apgar score and the score for neonatal acute physiology in non-septic critically ill neonates. Urinary interleukin-18 and cystatin-C had odds ratios of 2.27 and 2.07, and achieved the area under-the-receiver-operating-characteristic curve of 0.72 and 0.92, respectively, for predicting AKI.

CONCLUSIONS

The urinary concentration of cystatin-C, but not interleukin-18, may decrease with increasing renal maturity. Both urinary interleukin-18 and cystatin-C are independently predictive of AKI in non-septic critically ill neonates.

Clearance and beyond: the complementary roles of GFR measurement and injury biomarkers in acute kidney injury (AKI)

Acute kidney injury (AKI) is a common and frequently fatal illness in critically ill patients. The reliance on daily measurements of serum creatinine as a surrogate of glomerular filtration rate (GFR) not only delays diagnosis and development of successful therapies but also hinders insight into the pathophysiology of human AKI. Measurement of GFR under non-steady-state conditions remains an elusive gold standard against which biomarkers of renal injury need to be judged. Approaches to the rapid (near real-time) measurement of GFR are explored. Even if real-time GFR was available, absent baseline information will always limit diagnosis of AKI based on GFR or serum creatinine to a detection of change. Biomarkers of renal cellular injury have provided new strategies to facilitate detection and early intervention in AKI. However, the diagnostic and predictive performance of urinary biomarkers of injury vary, depending on both the time after renal injury and on the preinjury GFR. Progress in understanding the role of each novel biomarker in the causal pathways of AKI promises to enhance their diagnostic potential. We predict that combining rapid measures of GFR with biomarkers of renal injury will yield substantive progress in the treatment of AKI.

An update and review of acute kidney injury in pediatrics

OBJECTIVES

To inform the pediatric intensivist of recent advancements in acute kidney injury diagnosis and management.

DATA SOURCES

Studies were identified from MEDLINE (OVID), PubMed, and the Cochrane Library for topics relevant to acute kidney injury. We also reviewed bibliographies of relevant studies. DATA EXTRACTION, SYNTHESIS, AND OUTLINE REVIEW: Because of the lack of prospective trials, a majority of information is extracted from observational and retrospective data. The pathophysiology section reviews acute kidney injury mechanisms and highlights data regarding distal injury from experimental acute kidney injury. The epidemiology section focuses on incidence and outcomes of acute kidney injury, highlighting new strategies for diagnosis. The management section cites studies investigating hemodynamic optimization, nutrition, and fluid management, including the indications and impact of continuous renal replacement therapy in fluid overload.

CONCLUSIONS

There is limited data-driven evidence in pediatrics regarding effective therapy for acute kidney injury, a significant problem in the pediatric intensive care unit extending length of stay, ventilator days, and overall mortality. Sublethal kidney injury may be contributing to overall morbidity. We conclude that prospective clinical trials are needed to evaluate specific diagnostic aids, such as biomarkers, and therapeutic strategies, such as early initiation of continuous renal replacement therapy in children with fluid overload.

Heart failure treatment in the intensive care unit in children

Although pediatric heart failure is generally a chronic, progressive disorder, recovery of ventricular function may occur with some forms of cardiomyopathy. Guidelines for the management of chronic heart failure in adults and children have recently been published by the International Society for Heart and Lung Transplantation the American College of Cardiology, and the American Heart Association. The primary aim of heart failure therapy is to reduce symptoms, preserve long-term ventricular performance, and prolong survival primarily through antagonism of the neurohormonal compensatory mechanisms. Because some medications may be detrimental during an acute decompensation, physicians who manage these patients as inpatients must be knowledgeable about the medications and therapeutic goals of chronic heart failure treatment. Understanding the mechanisms of chronic heart failure may foster improved understanding of the treatment of decompensated heart failure.

Acute kidney injury post neonatal asphyxia

Acute kidney injury (AKI) is a common consequence of perinatal asphyxia, occurring in up to 56% of these infants. A major difficulty in diagnosing this condition is the lack of a consensus definition of neonatal AKI, largely because of a dearth of specific measurable variables and biochemical markers. This review will discuss the current evidence regarding the epidemiology, investigation, and treatment of AKI in the asphyxiated neonate. Particular emphasis will be given to the investigation of renal function in the neonate and to potential biomarkers that may aid the clinician in the diagnosis of renal injury in this population.

Acute kidney injury: can we improve prognosis?

The incidence of pediatric acute kidney injury (AKI) is increasing. AKI has been found to be independently associated with increased mortality, and current management options are limited in that they are mainly supportive. The use of various definitions of AKI can still be found in the literature, making it difficult to discern the epidemiology behind pediatric AKI. The use of a more uniform definition is a necessary first step to clarify AKI epidemiology and direct our research efforts, and it will ultimately improve prognosis. There is evidence that neonates and infants may be at higher risk for AKI than adults. However, the least amount of research is found for this youngest age group, and more focused efforts on this population are necessary. This paper reviews existing data on and definitions for pediatric AKI, general preventive and treatment strategies, as well as ongoing research efforts on AKI. We are hopeful that the prognosis of AKI will improve with collaboration on a multicenter, multinational scale in the form of prospective, long-term studies on pediatric AKI.