Prognostic Biomarkers and AKI: Potential to Enhance the Identification of Post-Operative Patients at Risk of Loss of Renal Function

Acute kidney injury (AKI) is a common complication after surgery and the more complex the surgery, the greater the risk. During surgery, patients are exposed to a combination of factors all of which are associated with the development of AKI. These include hypotension and hypovolaemia, sepsis, systemic inflammation, the use of nephrotoxic agents, tissue injury, the infusion of blood or blood products, ischaemia, oxidative stress and reperfusion injury. Given the risks of AKI, it would seem logical to conclude that early identification of patients at risk of AKI would translate into benefit. The conventional markers of AKI, namely serum creatinine and urine output are the mainstay of defining chronic kidney disease but are less suited to the acute phase. Such concerns are compounded in surgical patients given they often have significantly reduced mobility, suboptimal levels of nutrition and reduced muscle bulk. Many patients may also have misleadingly low serum creatinine and high urine output due to aggressive fluid resuscitation, particularly in intensive care units. Over the last two decades, considerable information has accrued with regard to the performance of what was termed "novel" biomarkers of AKI, and here, we discuss the most examined molecules and performance in surgical settings. We also discuss the application of biomarkers to guide patients' postoperative care.

Current Knowledge of Selected Cardiovascular Biomarkers in Pediatrics: Kidney Injury Molecule-1, Salusin-α and -β, Uromodulin, and Adropin

Cardiovascular diseases are the leading cause of morbidity and mortality in the modern world. Their common denominator is atherosclerosis, a process beginning in childhood. In pediatrics, the aim of preventive measures is to recognize children and adolescents at risk for accelerated atherosclerosis and possible premature cardiovascular events in adulthood. Several diagnostic procedures and biomarkers are available for cardiovascular risk assessment in adults. However, reliable markers in pediatrics are still insufficiently studied. In this contribution, we discuss five potential biomarkers of particular interest: kidney injury molecule-1, salusin-α and -β, uromodulin, and adropin. Studies regarding the pediatric population are scarce, but they support the evidence from studies in the adult population. These markers might entail both a prognostic and a therapeutic interest.

Potential Prognostic Markers of Acute Kidney Injury in the Early Phase of Acute Pancreatitis

Acute kidney injury (AKI) is a serious complication of acute pancreatitis (AP), which occurs in up to 70% of patients with severe AP and significantly increases the risk of mortality. At present, AKI is diagnosed based on dynamic increase in serum creatinine and decreased urine output; however, there is a need for earlier and more accurate biomarkers. The aim of the study was to review current evidence on the laboratory tests that were studied as the potential biomarkers of AKI in AP. We also briefly summarized the knowledge coming from the studies including sepsis or ICU patients since severe acute pancreatitis is associated with systemic inflammation and organ failure. Serum cystatin C and serum or urine NGAL have been shown to predict or diagnose AKI in AP; however, this evidence come from the single center studies of low number of patients. Other markers, such as urinary kidney injury molecule-1, cell cycle arrest biomarkers (tissue inhibitor metalloproteinase-2 and urine insulin-like growth factor-binding protein 7), interleukin-18, liver-type fatty acid-binding protein, or calprotectin have been studied in other populations suffering from systemic inflammatory states. In AP, the potential markers of AKI may be significantly influenced by either dehydration or inflammation, and the impact of these factors may be difficult to distinguish from kidney injury. The subject of AKI complicating AP is understudied. More studies are needed, for both exploratory (to choose the best markers) and clinical (to evaluate the diagnostic accuracy of the chosen markers in real clinical settings).

Why Have Detection, Understanding and Management of Kidney Hypoxic Injury Lagged Behind those for the Heart?

The outcome of patients with acute myocardial infarction (AMI) has dramatically improved over recent decades, thanks to early detection and prompt interventions to restore coronary blood flow. In contrast, the prognosis of patients with hypoxic acute kidney injury (AKI) remained unchanged over the years. Delayed diagnosis of AKI is a major reason for this discrepancy, reflecting the lack of symptoms and diagnostic tools indicating at real time altered renal microcirculation, oxygenation, functional derangement and tissue injury. New tools addressing these deficiencies, such as biomarkers of tissue damage are yet far less distinctive than myocardial biomarkers and advanced functional renal imaging technologies are non-available in the clinical practice. Moreover, our understanding of pathogenic mechanisms likely suffers from conceptual errors, generated by the extensive use of the wrong animal model, namely warm ischemia and reperfusion. This model parallels mechanistically type I AMI, which properly represents the rare conditions leading to renal infarcts, whereas common scenarios leading to hypoxic AKI parallel physiologically type II AMI, with tissue hypoxic damage generated by altered oxygen supply/demand equilibrium. Better understanding the pathogenesis of hypoxic AKI and its management requires a more extensive use of models of type II-rather than type I hypoxic AKI.

More than a simple biomarker: the role of NGAL in cardiovascular and renal diseases

Neutrophil gelatinase-associated lipocalin (NGAL) is a small circulating protein that is highly modulated in a wide variety of pathological situations, making it a useful biomarker of various disease states. It is one of the best markers of acute kidney injury, as it is rapidly released after tubular damage. However, a growing body of evidence highlights an important role for NGAL beyond that of a biomarker of renal dysfunction. Indeed, numerous studies have demonstrated a role for NGAL in both cardiovascular and renal diseases. In the present review, we summarize current knowledge concerning the involvement of NGAL in cardiovascular and renal diseases and discuss the various mechanisms underlying its pathological implications.

Novel acute kidney injury biomarkers: their characteristics, utility and concerns

Acute kidney injury (AKI) consists of a rapid renal function decline which usually increases serum urea and creatinine levels. Since kidney injury begins by inducing biological and molecular changes which evolve to cellular damage, biomarkers could be used as tools for monitoring early AKI appearance, and predicting its recovery. Among the main AKI biomarkers the neutrophil gelatinase-associated lipocalin, cystatin C, kidney injury molecule-1, monocyte chemotactic peptide-1, N-acetyl-β-D-glucosaminidase, interleukin-18, liver-type fatty acid-binding protein, netrin-1, cycle arrest markers, endogenous ouabain, selenium-binding protein 1, and BPIFA2 marker, have been described. Even though novel biomarkers seem to be more helpful to early detect AKI and/or predict the need for renal replacement, and mortality compared to serum creatinine, more comprehensive studies are still required to determine their clinical utility.

Biomarkers of acute kidney injury: the pathway from discovery to clinical adoption

Acute kidney injury (AKI) is a common complication of critical illnesses and has a significant impact on outcomes, including mortality and morbidities. Unfortunately, apart from prophylactic measures, no effective treatment for this syndrome is known. Therefore, early recognition of AKI not only can provide better opportunities for preventive interventions, but also opens many gates for research and development of effective therapeutic options. Over the last few years, several new AKI biomarkers have been discovered and validated to improve early detection, differential diagnosis, and differentiation of patients into risk groups for progressive renal failure, need for renal replacement therapy (RRT), or death. These novel AKI biomarkers complement serum creatinine (SCr) and urine output, which are the standard diagnostic tools for AKI detection. In this article, we review the available literature on characteristics of promising AKI biomarkers that are currently the focus of preclinical and clinical investigations. These biomarkers include neutrophil gelatinase-associated lipocalin (NGAL), kidney injury molecule 1 (KIM-1), liver-type fatty acid-binding protein, interleukin 18 (lL-18), insulin-like growth factor-binding protein 7, tissue inhibitor of metalloproteinase 2 (TIMP-2), calprotectin, urine angiotensinogen (AGT), and urine microRNA. We then describe the clinical performance of these biomarkers for diagnosis and prognostication. We also appraise each AKI biomarker's advantages and limitations as a tool for early AKI recognition and prediction of clinical outcomes after AKI. Finally, we review the current and future states of implementation of biomarkers in the clinical practice.

High dose statin prophylaxis in cardiopulmonary bypass related surgery: clinical utility

Background

Previous studies from our group demonstrated the anti-inflammatory properties of statins on cardiopulmonary bypass (CPB), through inhibition of neutrophil transendothelial migration. We sought to determine the utility of preoperative statin on patients undergoing cardiac surgery, to investigate any moderating effects on the systemic inflammatory response (SIRS) with CPB, and to evaluate any clinical impact on our patients.

Methods

This is a prospective, randomised controlled trial with national regulatory body approval. Eligible patients were already on oral statin therapy. They were then randomly assigned to either investigation arm (n = 15, atorvastatin 80 mg for 2 weeks before surgery) or control arm (n = 15, no change to current statin therapy). Blood and urine samples were collected at 3 timepoints. Postoperative clinical measures were documented.

Results

Patients in the investigation arm have significantly lower troponin level (p = 0.016), and lower level of urine neutrophil gelatinase-associated lipocalin (NGAL; p = 0.002); thus demonstrating a lesser degree of cardiac and renal injury in these patients. Higher level of Interleukin-8 (IL-8) at baseline (p = 0.036) and 4 h post cross-clamp removal (p = 0.035) in the investiation arm. A similar trend is also observed in Matrix Metalloproteinase-9 (MMP-9; p > 0.05). There were however no differences in clinical outcomes.

Conclusions

Maximizing the dose of statin in patients waiting for cardiac surgery has measurable biological effects. There is evidence of less cardiac and renal damage. The use of preoperative statins and in particular, high dose preoperative statin therapy, may prove a useful new tool for optimal preparation of patients for cardiac surgery.

Trial registration

EudraCT no. 2012-003396-20. Registered 05 November 2012

Ideal Hematocrit to Minimize Renal Injury on Cardiopulmonary Bypass

OBJECTIVE

Renal dysfunction after cardiopulmonary bypass (CBP) ranges from subclinical injury to established renal failure requiring dialysis. The pathophysiology is multifactorial, and recently, hemodilution during CBP has been thought to be an important determinant of postoperative renal injury. In this study, we attempted to assess the independent effect of hemodilution on renal function. We also aimed to identify the optimal hematocrit where hemodilution-induced renal injury is minimal.

METHODS

A prospective observational study was conducted on 200 patients between February 2012 and July 2013. One hundred fifty patients were included in the study group, who were further subdivided on the basis of lowest hemodilution as mild hemodilution (>25%), moderate hemodilution (21%-25%), and severe hemodilution (<21%) categories. The primary outcome of the study was renal outcome measure, which was assessed by comparing the creatinine clearance across the groups.

RESULTS

The creatinine clearance decreased over a period in all three groups. When compared with mild or moderate hemodilution, the reduction in creatinine clearance was significantly higher in the group with severe hemodilution (P ≤ 0.0001). However, there was no significant difference in creatinine clearance reduction between the mild and moderate hemodilution groups (P = 0.813; 95% confidence interval, -8.41 to 10.68).

CONCLUSIONS

Based on our observations, we would like to propose that a hematocrit of 21% should be considered the critical threshold. Hematocrit below this value of 21% during CBP is associated with the most significant deterioration in renal function.

[Acute kidney injury and tubular biomarkers after hematopoietic stem cell transplantation]

AIM

To determine the value of molecular biomarkers (BMs) associated with tubular epithelial damage in developing and predicting acute kidney injury (AKI) after hematopoietic stem cell transplantation (HSCT).

SUBJECTS AND METHODS

The open-label observational prospective study enrolled 90 patients (46 males and 44 females) who had undergone HSCT. The concentrations of BMs (calbindin, clusterin, interleukin-18 (IL-18), kidney injury molecules-1 (KIM-1), glutathione S-transferase-π (GST-π), and monocyte chemoattractant protein-1 (MCP-1) were measured in urinary samples 7 days before HSCT (week 0) and at weeks 1, 2, 3, 4, and 5. Main clinical parameters were simultaneously monitored. AKI was diagnosed and stratified according to the Kidney Disease Improving Global Outcomes (KDIGO) guidelines.

RESULTS

At weeks 1, 2, 3, 4, and 5 after HSCT, the proportion of AKI cases was 7.8, 8.9, 12.5, 27.3, and 35.9%, respectively. The elevated urinary levels of BMs (above the median) were found to be substantially more common than AKI cases. The urinary excretion of the majority of BMs dramatically increased in the early HSCT period. The median number of simultaneously elevated BMs was 3 (2; 5) during the entire follow-up period. Clusterin, MCP-1 and KIM-1 positively and significantly correlated with serum creatinine at the week following the determination of BMs in the multivariate linear regression models adjusted for other confounders. The higher urinary KIM-1 and/or MCP-1 excretion regardless of other clinical indicators was associated with the higher relative risk (RR) of AKI, which increased by 2.3 times with a rise in one of these indicators and by 3.4 times with a rise in both indicators.

CONCLUSION

Multiple renal toxic effects after HSCT result in a substantial and simultaneous elevation of urinary excretion of BMs for tubular damage. Among the BMs studied, KIM-1 and MCP-1 seem to be the most suitable molecules for assessing the risk of AKI in this cohort of patient within the predictive diagnostic approach.

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.

Are perioperative near-infrared spectroscopy values correlated with clinical and biochemical parameters in cyanotic and acyanotic infants following corrective cardiac surgery?

Background:

Near-infrared spectroscopy (NIRS) is a useful non-invasive tool for monitoring infants undergoing cardiac surgery. In this study, we aimed to determine the NIRS values in cyanotic and acyanotic patients who underwent corrective cardiac surgery for congenital heart diseases.

Methods:

Thirty consecutive infants who were operated on with the diagnosis of ventricular septal defect (n=15) and tetralogy of Fallot (n=15) were evaluated retrospectively. A definitive repair of the underlying cardiac pathology was achieved in all cases. A total of six measurements of cerebral and renal NIRS were performed at different stages of the perioperative period. The laboratory data, mean urine output and serum lactate levels were evaluated along with NIRS values in each group.

Results:

The NIRS values differ in both groups, even after the corrective surgical procedure is performed. The recovery of renal NIRS values is delayed in the cyanotic patients.

Conclusion:

Even though definitive surgical repair is performed in cyanotic infants, recovery of the renal vasculature may be delayed by up to two days, which is suggestive of a vulnerable period for renal dysfunction.