Dynamic Biomarker Assessment: A Diagnostic Paradigm to Match the AKI Syndrome

Urine Quantification Following Furosemide for Severe Acute Kidney Injury Prediction in Critically Ill Children

A standardized, quantified assessment of furosemide responsiveness predicts acute kidney injury (AKI) in children after cardiac surgery and AKI progression in critically ill adults. The purpose of this study was to determine if response to furosemide is predictive of severe AKI in critically ill children outside of cardiac surgery. We performed a multicenter retrospective study of critically ill children. Quantification of furosemide response was based on urine flow rate (normalized for weight) measurement 0 to 6 hours after the dose. The primary outcome was presence of creatinine defined severe AKI (Kidney Disease Improving Global Outcomes stage 2 or greater) within 7 days of furosemide administration. Secondary outcomes included mortality, duration of mechanical ventilation and length of stay. A total of 110 patients were analyzed. Severe AKI occurred in 20% ( n  = 22). Both 2- and 6-hour urine flow rate were significantly lower in those with severe AKI compared with no AKI ( p  = 0.002 and p  < 0.001). Cutoffs for 2- and 6-hour urine flow rate for prediction of severe AKI were <4 and <3 mL/kg/hour, respectively. The adjusted odds of developing severe AKI for 2-hour urine flow rate of <4 mL/kg/hour was 4.3 (95% confidence interval [CI]: 1.33-14.15; p  = 0.02). The adjusted odds of developing severe AKI for 6-hour urine flow rate of <3 mL/kg/hour was 6.19 (95% CI: 1.85-20.70; p  = 0.003). Urine flow rate in response to furosemide is predictive of severe AKI in critically ill children. A prospective assessment of urine flow rate in response to furosemide for predicting subsequent severe AKI is warranted.

Acute Kidney Injury: Gaps and Opportunities for Knowledge and Growth

Acute kidney injury (AKI) occurs frequently in hospitalized patients, regardless of age or prior medical history. Increasing awareness of the epidemiologic problem of AKI has directly led to increased study of global recognition, diagnostic tools, both reactive and proactive management, and analysis of long-term sequelae. Many gaps remain, however, and in this article we highlight opportunities to add significantly to the increasing bodies of evidence surrounding AKI. Practical considerations related to initiation, prescription, anticoagulation, and monitoring are discussed. In addition, the importance of AKI follow-up evaluation, particularly for those surviving the receipt of renal replacement therapy, is highlighted as a push for global equity in the realm of critical care nephrology is broached. Addressing these gaps presents an opportunity to impact patient care directly and improve patient outcomes.

Usefulness of urinary calprotectin as a novel marker differentiating functional from structural acute kidney injury in the critical care setting

BACKGROUND

Biomarkers are fundamental tools for differentiating between types of acute kidney injury (AKI) and may thus be crucial in management and prognosis. We report on a recently described biomarker, calprotectin, that appears to be a promising candidate in differentiating hypovolemic/functional AKI from intrinsic/structural AKI, whose acknowledgement may play a role in improving outcomes. We aimed to study the efficacy of urinary calprotectin in differentiating these two forms of AKI. The effect of fluid administration on the subsequent clinical course of AKI, its severity and the outcomes were also studied.

METHODOLOGY

Children who presented with conditions predisposing to AKI or with diagnosis of AKI were included. Urine samples for calprotectin analysis were collected and stored at - 20 ºC for analysis at the end of the study. Fluids were administered as per clinical conditions, followed by intravenous furosemide 1 mg/kg, and patients were observed closely for at least 72 h. Children with serum creatinine normalization and clinical improvement were classified as with functional AKI, while those with no response were classified as with structural AKI. Urine calprotectin levels between these two groups were compared. Statistical analysis was performed with SPSS 21.0 software.

RESULTS

Of the 56 children enrolled, 26 were classified as with functional AKI and 30 as with structural AKI. Stage 3 AKI was observed in 48.2% of patients and stage 2 AKI in 33.8%. Mean urine output, creatinine and stage of AKI improved with fluid and furosemide or furosemide alone (OR 6.08, 95% CI 1.65-27.23) (p < 0.01). A positive response to fluid challenge was in favor of functional AKI (OR 6.08, 95% CI 1.65-27.23) (p = 0.008). Presence of edema, sepsis and need for dialysis were hallmarks of structural AKI (p < 0.05). Urine calprotectin/creatinine values were 6 times higher in structural AKI compared to functional AKI. Urine calprotectin/creatinine ratio showed the best sensitivity (63.3%) and specificity (80.7%) at a cut-off value of 1 mcg/mL in differentiating the two types of AKI.

CONCLUSION

Urinary calprotectin is a promising biomarker that may help differentiating structural from functional AKI in children.

Incidence and factors associated with acute kidney injury among children with type 1 diabetes hospitalized with diabetic ketoacidosis: A prospective study

BACKGROUND AND OBJECTIVES

Acute kidney injury (AKI) is frequent among critically ill children. This study aimed to assess the incidence and factors associated with AKI among children with type 1 diabetes mellitus (T1DM) hospitalized with diabetic ketoacidosis (DKA).

METHODS

This prospective observational study was conducted at Sohag University Hospital, Egypt over 1 year. Children aged 6 months to 12 years, diagnosed with T1DM and hospitalized with the criteria of DKA were included. The study participants received intravenous fluid therapy and intravenous insulin infusion for DKA management. Serum creatinine levels were measured at admission, 24 and 48 h after admission. AKI was defined and staged using the Kidney Disease Improving Global Outcomes serum creatinine criteria.

RESULTS

The study included 265 DKA episodes in 240 participants. AKI was found in 110 (41.5%) DKA episodes. Moderated to severe AKI developed in 41 (15.5%) episodes. Multivariate regression analysis revealed that age (adjusted odds ratio = 0.78, 95% confidence interval (CI): 0.69-0.89, p < 0.001), Glasgow-Coma scale (GCS) < 14 at admission (adjusted odds ratio = 4.66, 95% CI: 1.66-13.14, p = 0.004) and serum chloride level at 12 h (adjusted odds ratio = 1.10, 95% CI: 1.02-1.18, p = 0.01) were the most significant factors associated with moderate to severe AKI development.

CONCLUSIONS

AKI is common among T1DM children hospitalized with DKA. Younger age, low GCS at hospital admission and increased serum chloride level during DKA management were associated with increased risk for moderate to severe AKI development.

Diagnostic accuracy of renal angina index alone or in combination with biomarkers for predicting acute kidney injury in children

Early recognition of patients at risk for severe acute kidney injury (AKI) by renal angina index (RAI) may help in the early institution of preventive measures. Objective was to evaluate performance of RAI alone or in combination with biomarkers in predicting severe AKI (KDIGO stage 2 and 3 or equivalent) and receipt of kidney replacement therapy (KRT) in critically ill children. We searched PubMed, EMBASE, Web of Sciences, and CENTRAL for studies published till May 2021. Search terms included acute kidney injury, pediatrics, adolescent, renal angina index, and biomarker. Proceedings of relevant conferences and references of included studies were also scrutinized. Two reviewers independently assessed the study eligibility. Cohort and cross-sectional studies evaluating the diagnostic performance of RAI in predicting AKI or receipt of KRT in children were included. Eligible participants were the children less than 18 years with RAI assessment on day 0 ofadmission. We followed PRISMA-DTA guidelines and used the QUADAS-2 tool for quality assessment. A bivariate model for meta-analysis was used to calculate the summary estimates of diagnostic parameters. Major outcomes were the diagnostic accuracy of RAI (≥ 8) alone or with biomarkers in predicting severe AKI and KRT receipt. Diagnostic accuracy was reported using summary sensitivity, specificity, and area under the curve (AUC). Overall, 22 studies (24 reports, 14,001 participants) were included. RAI ≥ 8 on day 0 has summary sensitivity, specificity, and AUC of 0.86 (95% CI, 0.77-0.92), 0.77 (0.68-0.83), and 0.88 (0.85-0.91) respectively for prediction of severe AKI on day 3. In comparison, a combination of RAI and urinary neutrophil gelatinase-associated lipocalin (NGAL) showed summary sensitivity, specificity, and AUC of 0.76 (0.62-0.85), 0.89 (0.74-0.96), and 0.87 (0.84-0.90) respectively for predicting severe AKI. The sensitivity, specificity, and AUC of RAI for predicting receipt of KRT were 0.82 (0.71-0.90), 0.74 (0.66-0.81), and 0.85 (0.81-0.88) respectively. In meta-regression, only the study setting (sepsis vs. heterogenous) was associated with heterogeneity. We observed substantial heterogeneity among eligible studies. Five studies had concerns in patient selection, and seven studies also had applicability concerns in patient selection for this review. Moderate certainty evidence showed that RAI ≥ 8 has good predicting ability in recognizing children at risk of severe AKI and receipt of KRT. The combination of urinary NGAL and RAI further improves the predicting ability (low-certainty evidence). Further studies are required on the context-driven assessment of novel biomarkers in the early prediction of AKI in RAI-positive children. Systematic review registration number: CRD4202122268. A higher resolution version of the Graphical abstract is available as Supplementary information.

Neonatal Acute Kidney Injury: Understanding of the Impact on the Smallest Patients

The study of neonatal acute kidney injury (AKI) has transitioned from small, single-center studies to the development of a large, multicenter cohort. The scope of research has expanded from assessment of incidence and mortality to analysis of more specific risk factors, novel urinary biomarkers, interplay between AKI and other organ systems, impact of fluid overload, and quality improvement efforts. The intensification has occurred through collaboration between the neonatology and nephrology communities. This review discusses 2 case scenarios to illustrate the clinical presentation of neonatal AKI, important risk factors, and approaches to minimize AKI events and adverse long-term outcomes.

Fluid management, electrolytes imbalance and renal management in neonates with neonatal encephalopathy treated with hypothermia

Kidney dysfunction and acute kidney injury (AKI) frequently accompanies neonatal encephalopathy and contributes to neonatal morbidity and mortality. While there are currently no proven therapies for the treatment of AKI, understanding the pathophysiology along with early recognition and treatment of alterations in fluid, electrolyte and metabolic homeostasis that accompany AKI offer opportunity to reduce associated morbidity. Promising new tests and technologies, including urine and serum biomarkers and renal near-infrared spectroscopy offer opportunities to improve diagnosis and monitoring of neonates at risk for kidney injury. Furthermore, recent advances in neonatal kidney supportive therapies such as hemofiltration and hemodialysis may further improve outcomes in this population. This chapter provides an overview of disorders of fluid balance, electrolyte homeostasis and kidney function associated with neonatal encephalopathy and therapeutic hypothermia. Recommendations for fluid and electrolyte management based upon published literature and authors' opinions are provided.

Utility of Kinetic GFR for Predicting Severe Persistent AKI in Critically Ill Children and Young Adults

Kinetic eGFR can be part of a multidimensional approach for AKI prediction combined with biomarkers, fluid corrected creatinine, and renal angina.Kinetic eGFR on day 1 is not independently associated with severe day-3 AKI in children and young adults who are critically ill.

Kidney Biomarkers and Major Adverse Kidney Events in Critically Ill Patients

Background

Several biomarkers of AKI have been examined for their ability to predict AKI before serum creatinine. Few studies have focused on using kidney biomarkers to better predict major adverse kidney events (MAKE), an increasingly used composite outcome in critical care nephrology research.

Methods

Single-center prospective study collecting blood and urine samples from critically ill patients with AKI Kidney Disease Improving Global Outcomes stage 2 or above, and matched controls from a single, tertiary care intensive care unit (ICU). Samples were collected at 24-48 hours after AKI diagnosis (patients) or ICU admission (controls), 5-7 days later, and 4-6 weeks after discharge for patients with AKI. The primary outcome of interest was MAKE at hospital discharge (MAKE-DC), consisting of the composite end point of death, RRT dependence, or a decrease in estimated glomerular filtration to <75% of baseline.

Results

Serum/urinary neutrophil gelatinase-associated lipocalin (NGAL), serum/urinary cystatin C, and urinary kidney injury molecule-1 early in the AKI or ICU course were all significantly higher in patients with MAKE-DC compared with those not experiencing MAKE-DC. Additionally, serum/urinary NGAL and serum cystatin C measurements at the first time point remained significantly associated with MAKE events at 3, 6, and 12 months. Serum cystatin C, and to a lesser extent serum NGAL, significantly improved upon a logistic regression clinical prediction model of MAKE-DC (AUROC 0.94 and 0.87 versus 0.83; P=0.001 and P=0.02, respectively). Patients without MAKE-DC experienced a greater decline in serum NGAL from first to second measurement than those patients experiencing MAKE-DC.

Conclusions

Early measures of kidney biomarkers in patients who are critically ill are associated with MAKE-DC. This relationship appears to be greatest with serum NGAL and cystatin C, which display additive utility to a clinical prediction model. Trending serum NGAL may also have utility in predicting MAKE-DC.

Theophylline dosing and pharmacokinetics for renal protection in neonates with hypoxic-ischemic encephalopathy undergoing therapeutic hypothermia

BACKGROUND

Theophylline, a non-selective adenosine receptor antagonist, improves renal perfusion in the setting of hypoxia-ischemia and may offer therapeutic benefit in neonates with hypoxic-ischemic encephalopathy (HIE) undergoing hypothermia. We evaluated the pharmacokinetics and dose-exposure relationships of theophylline in this population to guide dosing strategies.

METHODS

A population pharmacokinetic analysis was performed in 22 neonates with HIE undergoing hypothermia who were part of a prospective study or retrospective chart review. Aminophylline (intravenous salt form of theophylline) was given per institutional standard of care for low urine output and/or rising serum creatinine (5 mg/kg intravenous (i.v.) load then 1.8 mg/kg i.v. q6h). The ability of different dosing regimens to achieve target concentrations (4-10 mg/L) associated with clinical response was examined.

RESULTS

Birth weight was a significant predictor of theophylline clearance and volume of distribution (p < 0.05). The median half-life was 39.5 h (range 27.2-50.4). An aminophylline loading dose of 7 mg/kg followed by 1.6 mg/kg q12h was predicted to achieve target concentrations in 84% of simulated neonates.

CONCLUSIONS

In neonates with HIE undergoing hypothermia, theophylline clearance was low with a 50% longer half-life compared to full-term normothermic neonates without HIE. Dosing strategies need to consider the unique pharmacokinetic needs of this population.

IMPACT

Theophylline is a potential renal-protective therapy in neonates with HIE undergoing therapeutic hypothermia; however, the pharmacokinetics and dose needs in this population are not known. Theophylline clearance was low in neonates with HIE undergoing therapeutic hypothermia with a 50% longer half-life compared to full-term normothermic neonates without HIE. As theophylline is advanced in clinical development, dosing strategies will need to consider the unique pharmacokinetic needs of neonates with HIE undergoing therapeutic hypothermia.

Ability of different assay platforms to measure renal biomarker concentrations during ischaemia-reperfusion acute kidney injury in dogs

Several protein biomarkers have been shown to be useful for the early diagnosis of acute kidney injury (AKI) in animals and people. Multiplex assays for measurement of a panel of renal biomarkers in canine samples have recently become available. This study compared the use of two such assays, versus previously validated ELISAs, to measure five biomarkers in canine samples during ischaemia-reperfusion (IR) AKI. Blood and urine was collected from six male anaesthetised greyhounds that underwent 1-h of renal ischaemia (severe hypotension induced by acute haemorrhage) and 2-h of reperfusion (intravenous fluid resuscitation). Histology confirmed presence of acute tubular injury at 2 h of reperfusion. Concentrations of clusterin, cystatin C, kidney-injury molecule 1 (KIM-1), monocyte chemoattractant protein 1, and neutrophil gelatinase-associated lipocalin (NGAL) at baseline and following IR, measured by two different multiplex assays and previously-validated single analyte immunoassays, were compared. Only NGAL was significantly elevated following IR with all assays investigated. Whether concentrations of the other four biomarkers were significantly increased following IR depended on the assay used. Concentrations of cystatin C and KIM-1 measured with the multiplex assays were of a vast magnitude lower than those measured with the corresponding single analyte ELISAs. We conclude that further validation is required before these assays can reliably be used to measure AKI biomarkers in canine samples.

Diagnostics, Risk Factors, Treatment and Outcomes of Acute Kidney Injury in a New Paradigm

Acute kidney injury (AKI) is a common clinical condition among patients admitted in the hospitals. The condition is associated with both increased short-term and long-term mortality. With the development of a standardized definition for AKI and the acknowledgment of the impact of AKI on patient outcomes, there has been increased recognition of AKI. Two advances from past decades, the usage of computer decision support and the discovery of AKI biomarkers, have the ability to advance the diagnostic method to and further management of AKI. The increasingly widespread use of electronic health records across hospitals has substantially increased the amount of data available to investigators and has shown promise in advancing AKI research. In addition, progress in the finding and validation of different forms of biomarkers of AKI within diversified clinical environments and has provided information and insight on testing, etiology and further prognosis of AKI, leading to future of precision and personalized approach to AKI management. In this this article, we discussed the changing paradigms in AKI: from mechanisms to diagnostics, risk factors, and management of AKI.