Real-Time Acute Kidney Injury Risk Stratification-Biomarker Directed Fluid Management Improves Outcomes in Critically Ill Children and Young Adults

Kidney Injury Following Cardiac Surgery: A Review of Our Current Understanding

Around one-quarter of all patients undergoing cardiac procedures, particularly those on cardiopulmonary bypass, develop cardiac surgery-associated acute kidney injury (CSA-AKI). This complication increases the risk of several serious morbidities and of mortality, representing a significant burden for both patients and the healthcare system. Patients with diminished kidney function before surgery, such as those with chronic kidney disease, are at heightened risk of developing CSA-AKI and have poorer outcomes than patients without preexisting kidney injury who develop CSA-AKI. Several mechanisms are involved in the development of CSA-AKI; injury is primarily thought to result from an amplification loop of inflammation and cell death, with complement and immune system activation, cardiopulmonary bypass, and ischemia-reperfusion injury all contributing to pathogenesis. At present there are no effective, targeted pharmacological therapies for the prevention or treatment of CSA-AKI, although several preclinical trials have shown promise, and clinical trials are under way. Progress in the understanding of the complex pathophysiology of CSA-AKI is needed to improve the development of successful strategies for its prevention, management, and treatment. In this review, we outline our current understanding of CSA-AKI development and management strategies and discuss potential future therapeutic targets under investigation.

Neonatal Kidney Function, Injury and Drug Dosing: A Contemporary Review

In neonates, estimation of the glomerular filtration rate is problematic, and assessment of renal impairment is challenging. Serum creatinine is a widely used marker, and urine output is an important vital parameter monitored in intensive care settings, particularly in unwell neonates. However, the rapid changes after birth with adaptation to the extrauterine environment is a unique situation in which absolute serum creatinine is not a reliable indicator of renal function. A rise in serum creatinine from the previous value during the neonatal period can be a result of worsening renal function in neonates but is dependent on many other factors. In addition, urine output can be difficult to measure in sick neonates during their intensive care stay. Despite a high prevalence of acute kidney injury (AKI) in preterm and/or unwell infants, the current definitions are not straightforward and do not take postnatal adaptation processes into account. The management of AKI is challenging in very young and small patients because the assessment of fluid status as well as balancing nutritional needs with fluid restriction can be problematic. The Australian Neonatal Medicines Formulary provides advice on drug dosing in the face of reduced renal function in neonates. Predictors (or long-term outcome, or recovery) after AKI diagnosis are still poorly described. Therefore, the diagnosis of neonatal AKI needs to be documented and transferred to the paediatrician responsible for the follow-up of the child. This educational review aims to give a perspective on neonatal kidney function and AKI, the relation of fluid balance and creatinine, the management of neonatal AKI and the consequences for drug dosing and long-term outcomes.

Neutrophil Gelatinase-Associated Lipocalin: Biological Aspects and Potential Diagnostic Use in Acute Kidney Injury

Acute kidney injury (AKI) is a syndrome characterized by a rise in creatinine or a decrease in urinary flow, according to the Kidney Disease Improving Global Outcomes (KDIGO) definition. It is diagnosed in 15% of inpatients and 50% of patients in the intensive care unit (ICU), and it is related to increased mortality. As part of a global effort aimed at the elimination of preventable deaths from AKI, there is a growing interest in identifying biomarkers that can be point-of-care and that are not influenced by the variability in patient characteristics in a relevant way. Neutrophil gelatinase-associated lipocalin (NGAL), particularly in its 25 kDa form, which is exclusively released by renal tubules, has emerged as a promising biomarker with potential use in the diagnosis of AKI in the critically ill, including its use in guiding the initiation and/or weaning of renal replacement therapy (RRT). The objective of this review is to summarize the current understanding of NGAL in acute settings, emphasizing biological and genomic insights.

External Validation, Re-Calibration, and Extension of a Prediction Model of Early Acute Kidney Injury in Critically Ill Children using Multi-Center Data

Background

Acute kidney injury (AKI) is common among children with critical illness and is associated with high morbidity and mortality. Risk prediction models designed for clinical decision support implementation offer an opportunity to identify and proactively mitigate AKI risks. Existing models have been primarily validated on single-center data, owing partly to the lack of appropriately detailed multicenter datasets.

Objective

To determine the accuracy of a single-center model to predict new AKI at 72 hours of ICU admission across two multicenter datasets and extend this model to improve prediction accuracy while maintaining acceptable alert burden.

Derivation and Validation Cohorts

We separately derived models in two datasets: PEDSNET-VPS, created through the linkage of PEDSnet electronic health record (EHR) extraction with Virtual Pediatric Systems (VPS); and the PICU Data Collaborative dataset, created through EHR extraction and harmonization from eight participating institutions. Derivation datasets comprised temporal and location-specific spit of these datasets (80%), while the holdout test split comprised the remaining (20%).

Prediction Model

We recalibrated an existing single-center model and measured discrimination and accuracy. We then add features guided by precision and recall measures. All features were available at 12 hours of ICU admission. We measure discrimination and accuracy at multiple cut-points and identify the features contributing most to the risk score.

Results

In two datasets comprising 186,540 ICU admissions, we report an incidence of early AKI of 2.2 - 2.7%. Initial recalibration of an existing single-center model demonstrated poor discrimination (AUROC 0.60 - 0.78). Following the addition of new features, we report higher AUROC values of 0.79 - 0.80 and AUPRC values of 0.13 - 0.21 in both datasets. We report accuracy at several cutpoints as well as cross-validate between datasets.

Conclusions

In this first use of two new multicenter datasets, we report improved discrimination and accuracy in a model designed specifically for implementation, balancing sensitivity and precision to predict patients at risk for AKI development.

Acute kidney injury

Acute kidney injury (AKI) is a common, heterogeneous, multifactorial condition, which is part of the overarching syndrome of acute kidney diseases and disorders. This condition's incidence highest in low-income and middle-income countries. In the short term, AKI is associated with increased mortality, an increased risk of complications, extended stays in hospital, and high health-care costs. Long-term complications include chronic kidney disease, kidney failure, cardiovascular morbidity, and an increased risk of death. Several strategies are available to prevent and treat AKI in specific clinical contexts. Otherwise, AKI care is primarily supportive, focused on treatment of the underlying cause, prevention of further injury, management of complications, and short-term renal replacement therapy in case of refractory complications. Evidence confirming that AKI subphenotyping is necessary to identify precision-oriented interventions is growing. Long-term follow-up of individuals recovered from AKI is recommended but the most effective models of care remain unclear.

Determination of Urinary Neutrophil Gelatinase-Associated Lipocalin (uNGAL) Reference Intervals in Healthy Adult and Pediatric Individuals Using a Particle-Enhanced Turbidimetric Immunoassay

Background: The current gold standards for diagnosing acute kidney injury (AKI) are an increase in serum creatinine and a decrease in urine output, which are inadequate for rapid diagnosis. Neutrophil gelatinase-associated lipocalin (NGAL) is a 25-kDa protein produced and secreted by injured kidney tubule epithelial cells, and can serve as an early urinary biomarker for AKI. ProNephro AKI (NGAL) is an immunoassay for the quantitative determination of NGAL in urine (uNGAL) that recently received FDA clearance. A multisite, cross-sectional study was conducted to establish reference intervals for uNGAL in apparently healthy individuals. Methods: Urine samples were collected from apparently healthy individuals aged ≥3 months who met all inclusion criteria and no exclusion criteria. Specimens were temporarily stored at room temperature or 2-8 °C, then transferred into urinalysis tubes before being frozen and shipped for testing. uNGAL testing was performed using the ProNephro AKI (NGAL) immunoassay on a Roche cobas c501 analyzer. Results: Of the 688 individuals screened, 677 were eligible, and 629 (91.4%) of those were deemed evaluable. The 95th and 97.5th percentile uNGAL values for all pediatric participants were below the clinical cutoff of 125 ng/mL. uNGAL values were statistically significantly higher for female vs. male participants in both adult (p = 0.003) and pediatric groups (p < 0.001), while differences were not statistically significant for age, site location, race, or ethnicity. Conclusions: This study provides normal reference intervals for uNGAL with the ProNephro AKI (NGAL) clinical chemistry immunoassay that may be useful for interpreting patient results.

Furosemide stress test to predict acute kidney injury progression in critically ill children

BACKGROUND

Furosemide stress test (FST) is a novel functional biomarker for predicting severe acute kidney injury (AKI); however, pediatric studies are limited.

METHODS

Children 3 months to 18 years of age admitted to the intensive care unit (ICU) of a tertiary care hospital from Nov 2019 to July 2021 were screened and those who developed AKI stage 1 or 2 within 7 days of admission underwent FST (intravenous furosemide 1 mg/kg). Urine output was measured hourly for the next 6 h; a value > 2 ml/kg within the first 2 h was deemed furosemide responsive. Other biomarkers like plasma neutrophil gelatinase-associated lipocalin (NGAL) and proenkephalin (PENK) were also evaluated.

RESULTS

Of the 480 admitted patients, 51 developed AKI stage 1 or 2 within 7 days of admission and underwent FST. Nine of these patients were furosemide non-responsive. Thirteen (25.5%) patients (eight of nine from FST non-responsive group) developed stage 3 AKI within 7 days of FST, nine (17.6%) of whom (seven from non-responsive group) required kidney support therapy (KST). FST emerged as a good biomarker for predicting stage 3 AKI and need for KST with area-under-the-curve (AUC) being 0.93 ± 0.05 (95% CI 0.84-1.0) and 0.96 ± 0.03 (95% CI 0.9-1.0), respectively. FST outperformed NGAL and PENK in predicting AKI stage 3 and KST; however, the combination did not improve the diagnostic accuracy.

CONCLUSIONS

Furosemide stress test is a simple, inexpensive, and robust biomarker for predicting stage 3 AKI and KST need in critically ill children. Further research is required to identify the best FST cut-off in children.

Prediction of cardiac surgery associated acute kidney injury using response to loop diuretic and urine neutrophil gelatinase associated lipocalin

BACKGROUND

Cardiac surgery associated acute kidney injury (CS-AKI) is common. Urine response to loop diuretic and urine neutrophil gelatinase associated lipocalin (uNGAL) are separately associated with CS-AKI. We aimed to determine whether urine response to loop diuretic and uNGAL together were associated with postoperative day 2-4 CS-AKI.

METHODS

Two-center prospective observational study (ages 0-18 years). uNGAL (8-12 h after admission) (ng/mL) and urine response to loop diuretic (6 h for bolus furosemide and 12 h for infusion bumetanide) (mL/kg/hr) were measured. All diuretic doses were converted to furosemide equivalents. The primary outcome was day 2-4 CS-AKI. Patients were sub-phenotyped using a priori cutoffs (uNGAL +  ≥ 100 ng/mL and UOP +  < 1.5 mL/kg/hr) and optimal cutoffs (uNGAL +  ≥ 127 ng/mL and UOP +  ≤ 0.79 mL/kg/hr): 1) uNGAL-/UOP-, 2) uNGAL-/UOP + , 3) uNGAL + /UOP-, and 4) uNGAL + /UOP + . Multivariable regression was used to assess the association of uNGAL, UOP and each sub-phenotype with outcomes.

RESULTS

476 patients were included. CS-AKI occurred in 52 (10.9%). uNGAL was associated with 2.59-fold greater odds (95%CI: 1.52-4.41) of CS-AKI. UOP was not associated with CS-AKI. Compared with uNGAL + alone, uNGAL + /UOP + improved prediction of CS-AKI using a priori and optimal cutoffs respectively (AUC 0.70 vs. 0.75). Both uNGAL + /UOP + (IQR OR:4.63, 95%CI: 1.74-12.32) and uNGAL + /UOP- (IQR OR:5.94, 95%CI: 2.09-16.84) were associated with CS-AKI when compared with uNGAL-/UOP-.

CONCLUSIONS

uNGAL is associated with CS-AKI. The sub-phenotype association was largely driven by uNGAL. Future studies standardizing diuretic dose and timing may be needed to refine the combined performance for clinical decision making.

Pediatric acute kidney injury and adverse health outcomes: using a foundational framework to evaluate a causal link

Acute kidney injury (AKI) is a major global health problem, expensive to manage, and its associations with negative pediatric health outcomes have been clearly demonstrated. One of the most fundamental questions to consider as we use previous epidemiological information to advance research and care paradigms is the strength of the causal link between pediatric AKI and health outcomes. In this review, we apply the foundational framework of the Bradford Hill criteria to evaluate the extent to which a causal link exists between AKI and the associated adverse outcomes in children. Available data in children support a causal link between AKI and short-term outcomes including mortality, length of stay, and ventilation time. Clarifying the causal nature of longer term associations requires further high-quality observational studies in children, careful consideration of what defines the most meaningful and measurable longer term outcomes after pediatric AKI, and integration of evolving biological data related to mechanisms of disease. Preventing or mitigating AKI should lead to improved outcomes. Demonstrating such reversibility will solidify confidence in the causal relationship, improve child health, and highlight an aspect which is highly relevant to clinicians, scientists, and policy makers.

10 tips on how to use dynamic risk assessment and alerts for AKI

Acute kidney injury (AKI) is a common syndrome in hospitalized patients and is associated with increased morbidity and mortality. The focus of AKI care requires a shift away from strictly supportive management of established injury to the early identification and timely prevention of worsening renal injury. Identifying patients at risk for developing or progression of severe AKI is crucial for improving patient outcomes, reducing the length of hospitalization and minimizing resource utilization. Implementation of dynamic risk scores and incorporation of novel biomarkers show promise for early detection and minimizing progression of AKI. Like any risk assessment tools, these require further external validation in a variety of clinical settings prior to widespread implementation. Additionally, alerts that may minimize exposure to a variety of nephrotoxic medications or prompt early nephrology consultation are shown to reduce the incidence and progression of AKI severity and enhance renal recovery. While dynamic risk scores and alerts are valuable, implementation requires thoughtfulness and should be used in conjunction with the overall clinical picture in certain situations, particularly when considering the initiation of fluid and diuretic administration or renal replacement therapy. Despite the contemporary challenges encountered with alert fatigue, implementing an alert-based bundle to improve AKI care is associated with improved outcomes, even when implementation is incomplete. Lastly, all alert-based interventions should be validated at an institutional level and assessed for their ability to improve institutionally relevant and clinically meaningful outcomes, reduce resource utilization and provide cost-effective interventions.

Diagnostic Validation of the Updated Pediatric Sepsis Biomarker Risk II for Acute Kidney Injury Prediction Model in Pediatric Septic Shock

OBJECTIVES

We previously derived the updated Pediatric Sepsis Biomarker Risk for Acute Kidney Injury (PERSEVERE-II AKI) prediction model, which had robust diagnostic test characteristics for severe AKI on day 3 (D3 severe AKI) of septic shock. We now sought to validate this model in an independent cohort of children to the one in which the model was developed.

DESIGN

A secondary analysis of a multicenter, prospective, observational study carried out from January 2019 to December 2022.

SETTING

Ten PICUs in the United States.

PATIENTS

Children with septic shock 1 week to 18 years old admitted to the PICU.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Seventy-nine of 363 patients (22%) had D3 severe AKI, defined as Kidney Disease Improving Global Outcomes stage 2 or higher. Patients were assigned a probability of D3 severe AKI using the PERSEVERE-II AKI model. The model predicted D3 severe AKI with an area under the receiver operating characteristic curve of 0.89 (95% CI, 0.85-0.93), sensitivity of 77% (95% CI, 66-86%), specificity of 88% (95% CI, 84-92%), positive predictive value of 65% (95% CI, 54-74%), and negative predictive value of 93% (95% CI, 89-96%). These data represent an increase in post-test probability of D3 severe AKI with a positive test from 22% to 65%, and a prevalence threshold of 28%. On multivariable regression, the PERSEVERE-II AKI prediction model demonstrated greater adjusted odds ratio (aOR) for D3 severe AKI (aOR, 11.2; 95% CI, 4.9-25.3) and lesser aOR for failure of D3 renal recovery from early AKI (aOR, 0.31; 95% CI, 0.13-0.69).

CONCLUSIONS

The PERSEVERE-II AKI model demonstrates consistently robust performance for prediction of new or persistent D3 severe AKI in children with septic shock. A major limitation is that actual D3 severe AKI prevalence is below the prevalence threshold for the test, and thus future work should focus on evaluating use in enriched populations.

Fluid deresuscitation in critically ill children: comparing perspectives of intensivists and nephrologists

Introduction

Fluid accumulation, presently defined as a pathologic state of overhydration/volume overload associated with clinical impact, is common and associated with worse outcomes. At times, deresuscitation, the active removal of fluid via diuretics or ultrafiltration, is necessary. There is no consensus regarding deresuscitation in children admitted to the pediatric intensive care unit. Little is known regarding perceptions and practices among pediatric intensivists and nephrologists regarding fluid provision and deresuscitation.

Methods

Cross-sectional electronic survey of pediatric nephrologists and intensivists from academic societies in the United States designed to better understand fluid management between disciplines. A clinical vignette was used to characterize the perceptions of optimal timing and method of deresuscitation initiation at four timepoints that correspond to different stages of shock.

Results

In total, 179 respondents (140 intensivists, 39 nephrologists) completed the survey. Most 75.4% (135/179) providers believe discussing fluid balance and initiating fluid deresuscitation in pediatric intensive care unit (PICU) patients is "very important". The first clinical vignette time point (corresponding to resuscitation phase of early shock) had the most dissimilarity between intensivists and nephrologists (p = 0.01) with regards to initiation of deresuscitation. However, providers demonstrated increasing agreement in their responses to initiate deresuscitation as the clinical vignette progressed. Compared to intensivists, nephrologists were more likely to choose "dialysis or ultrafiltration" as a deresuscitation method during the optimization [10.3 vs. 2.9% (p = 0.07)], stabilization [18.0% vs. 3.6% (p < 0.01)], and evacuation [48.7% vs. 23.6% (p < 0.01)] phases of shock. Conversely, intensivists were more likely to utilize scheduled diuretics than nephrologists [47.1% vs. 28.2% (p = 0.04)] later on in the patient course.

Discussion

Most physicians believe that discussing fluid balance and deresuscitation is important. Nevertheless, when to initiate deresuscitation and how to accomplish it differed between nephrologist and intensivists. Widely understood and operationalizable definitions, further research, and eventually evidence-based guidelines are needed to help guide care.

Fluid Overload in Children Following Hematopoietic Cell Transplant: A Comprehensive Review

Fluid overload significantly increases morbidity and mortality in critically ill children. Following hematopoietic cell transplant (HCT), children are at a high risk of fluid accumulation due to essential increased fluid intake for nutrition, blood products, and antimicrobials. In addition, many complications predispose these children to capillary leak and fluid overload (FO), such as sinusoidal obstruction syndrome, engraftment syndrome, sepsis, and acute kidney injury (AKI). FO > 10% occurs in nearly half of children following HCT and is associated with a lower PICU survival rate. In addition, in children with acute respiratory failure post HCT, each 1% increase in cumulative fluid balance on d 3 increases the odds of PICU mortality by 3%. Furthermore, FO worsens AKI. Tools such as the renal angina index and urinary biomarkers such as neutrophil gelatinase-associated lipocalin can help identify patients at risk of AKI and FO. Early detection, prevention, and intervention are crucial to improving outcomes in this population. Management strategies include fluid restriction, diuretics, and continuous kidney replacement therapy (CKRT) when FO exceeds 10% and other measures have failed.

Recommendations for clinical trial design in acute kidney injury from the 31st acute disease quality initiative consensus conference. A consensus statement

PURPOSE

Novel interventions for the prevention or treatment of acute kidney injury (AKI) are currently lacking. To facilitate the evaluation and adoption of new treatments, the use of the most appropriate design and endpoints for clinical trials in AKI is critical and yet there is little consensus regarding these issues. We aimed to develop recommendations on endpoints and trial design for studies of AKI prevention and treatment interventions based on existing data and expert consensus.

METHODS

At the 31st Acute Disease Quality Initiative (ADQI) meeting, international experts in critical care, nephrology, involving adults and pediatrics, biostatistics and people with lived experience (PWLE) were assembled. We focused on four main areas: (1) patient enrichment strategies, (2) prevention and attenuation studies, (3) treatment studies, and (4) innovative trial designs of studies other than traditional (parallel arm or cluster) randomized controlled trials. Using a modified Delphi process, recommendations and consensus statements were developed based on existing data, with > 90% agreement among panel members required for final adoption.

RESULTS

The panel developed 12 consensus statements for clinical trial endpoints, application of enrichment strategies where appropriate, and inclusion of PWLE to inform trial designs. Innovative trial designs were also considered.

CONCLUSION

The current lack of specific therapy for prevention or treatment of AKI demands refinement of future clinical trial design. Here we report the consensus findings of the 31st ADQI group meeting which has attempted to address these issues including the use of predictive and prognostic enrichment strategies to enable appropriate patient selection.

Derivation and Validation of an Optimal Neutrophil Gelatinase-Associated Lipocalin Cutoff to Predict Stage 2/3 Acute Kidney Injury (AKI) in Critically Ill Children

Introduction

Acute kidney injury (AKI) defined by changes in serum creatinine (SCr), or oliguria is associated with increased morbidity and mortality in children who are critically ill. We derived and validated a clinical cutoff value for urine neutrophil gelatinase-associated lipocalin (NGAL), in a prospective multicenter study of children who were critically ill. We report the clinical performance of urine NGAL (uNGAL) to aid in pediatric AKI risk assessment.

Methods

Eligible subjects were aged ≥ 90 days to < 22 years, admitted to an intensive care unit (ICU), and had 1 or more of the following: mechanical ventilation, vasoactive medication administration, solid organ or bone marrow transplantation, or hypotension within 24-hours of admission. uNGAL was assessed within 24-hours of admission. The primary outcome was SCr-based stage 2/3 AKI presence at 48- to 72-hours.

Results

Twenty-five (12.3%) derivation study patients had stage 2/3 AKI at 48- to 72-hours. uNGAL concentration of 125 ng/ml was the optimal cutoff. Forty-seven (9.1%) validation study patients had stage 2/3 AKI at 48- to 72-hours. The area under the curve of a receiver operator characteristics curve (AUC-ROC) for uNGAL performance was 0.83 (95% confidence interval [CI]: 0.77-0.90). Performance characteristics were sensitivity 72.3% (95% CI: 57.4%-84.4%), specificity 86.3% (95% CI: 82.8%-89.3%), positive predictive value 34.7% (95% CI: 28.5%-41.5%), and negative predictive value 96.9% (95% CI: 95.1%-98.0%).

Conclusion

These prospective, pediatric, multicenter studies demonstrate that uNGAL in the first 24-hours performs very well to predict Kidney Disease Improving Global Outcomes (KDIGO) stage 2/3 AKI at 48- to 72-hours into an ICU course. We suggest that a uNGAL cut point of 125 ng/ml can aid in the risk assessment for stage 2/3 AKI persistence or development.

The Road to Precision Medicine for Acute Kidney Injury

OBJECTIVES

Acute kidney injury (AKI) is a common form of organ dysfunction in the ICU. AKI is associated with adverse short- and long-term outcomes, including high mortality rates, which have not measurably improved over the past decade. This review summarizes the available literature examining the evidence of the need for precision medicine in AKI in critical illness, highlights the current evidence for heterogeneity in the field of AKI, discusses the progress made in advancing precision in AKI, and provides a roadmap for studying precision-guided care in AKI.

DATA SOURCES

Medical literature regarding topics relevant to precision medicine in AKI, including AKI definitions, epidemiology, and outcomes, novel AKI biomarkers, studies of electronic health records (EHRs), clinical trial design, and observational studies of kidney biopsies in patients with AKI.

STUDY SELECTION

English language observational studies, randomized clinical trials, reviews, professional society recommendations, and guidelines on areas related to precision medicine in AKI.

DATA EXTRACTION

Relevant study results, statements, and guidelines were qualitatively assessed and narratively synthesized.

DATA SYNTHESIS

We synthesized relevant study results, professional society recommendations, and guidelines in this discussion.

CONCLUSIONS

AKI is a syndrome that encompasses a wide range of underlying pathologies, and this heterogeneity has hindered the development of novel therapeutics for AKI. Wide-ranging efforts to improve precision in AKI have included the validation of novel biomarkers of AKI, leveraging EHRs for disease classification, and phenotyping of tubular secretory clearance. Ongoing efforts such as the Kidney Precision Medicine Project, identifying subphenotypes in AKI, and optimizing clinical trials and endpoints all have great promise in advancing precision medicine in AKI.

Perioperative Acute Renal Injury: Revisiting Pathophysiology

BACKGROUND

Acute renal dysfunction and subsequent acute renal failure after cardiac surgery are associated with high mortality and morbidity. Early therapeutic or preventive intervention is hampered by the lack of an early biomarker for acute renal injury. Recent studies showed that urinary neutrophil gelatinase-associated lipocalin (NGAL or lipocalin 2) is upregulated early (within 1 to 3 h) after murine renal injury and in pediatric acute renal dysfunction after cardiac surgery. The authors hypothesized that postoperative urinary NGAL concentrations are increased in adult patients developing acute renal dysfunction after cardiac surgery compared with patients without acute renal dysfunction.

METHODS

After institutional review board approval, 81 cardiac surgical patients were prospectively studied. Urine samples were collected immediately before incision and at various time intervals after surgery for NGAL analysis by quantitative immunoblotting. Acute renal dysfunction was defined as peak postoperative serum creatinine increase by 50% or greater compared with preoperative serum creatinine.

RESULTS

Sixteen of 81 patients (20%) developed postoperative acute renal dysfunction, and the mean urinary NGAL concentrations in patients who developed acute renal dysfunction were significantly higher early after surgery (after 1 h, mean ± SD, 4,195 ± 6,520 vs. 1,068 ± 2,129 ng/ml; P < 0.01) compared with patients who did not develop acute renal dysfunction. Mean urinary NGAL concentrations continued to increase and remained significantly higher at 3 and 18 h after cardiac surgery in patients with acute renal dysfunction. In contrast, urinary NGAL in patients without acute renal dysfunction decreased rapidly after cardiac surgery.

CONCLUSIONS

Patients developing postoperative acute renal dysfunction had significantly higher urinary NGAL concentrations early after cardiac surgery. Urinary NGAL may therefore be a useful early biomarker of acute renal dysfunction after cardiac surgery. These findings may facilitate the early detection of acute renal injury and potentially prevent progression to acute renal failure.

Evaluating fluid overload in critically ill children

PURPOSE OF REVIEW

To review the evaluation and management of fluid overload in critically ill children.

RECENT FINDINGS

Emerging evidence associates fluid overload, i.e. having a positive cumulative fluid balance, with adverse outcome in critically ill children. This is most likely the result of impaired organ function due to increased extravascular water content. The combination of a number of parameters, including physical, laboratory and radiographic markers, may aid the clinician in monitoring and quantifying fluid status, but all have important limitations, in particular to discriminate between intra- and extravascular water volume. Current guidelines advocate a restrictive fluid management, initiated early during the disease course, but are hampered by the lack of high quality evidence.

SUMMARY

Recent advances in early evaluation of fluid status and (tailored) restrictive fluid management in critically ill children may decrease complications of fluid overload, potentially improving outcome. Further clinical trials are necessary to provide the clinician with solid recommendations.

Time to Continuous Renal Replacement Therapy Initiation and 90-Day Major Adverse Kidney Events in Children and Young Adults

Importance

In clinical trials, the early or accelerated continuous renal replacement therapy (CRRT) initiation strategy among adults with acute kidney injury or volume overload has not demonstrated a survival benefit. Whether the timing of initiation of CRRT is associated with outcomes among children and young adults is unknown.

Objective

To determine whether timing of CRRT initiation, with and without consideration of volume overload (VO; <10% vs ≥10%), is associated with major adverse kidney events at 90 days (MAKE-90).

Design, Setting, and Participants

This multinational retrospective cohort study was conducted using data from the Worldwide Exploration of Renal Replacement Outcome Collaborative in Kidney Disease (WE-ROCK) registry from 2015 to 2021. Participants included children and young adults (birth to 25 years) receiving CRRT for acute kidney injury or VO at 32 centers across 7 countries. Statistical analysis was performed from February to July 2023.

Exposure

The primary exposure was time to CRRT initiation from intensive care unit admission.

Main Outcomes and measures

The primary outcome was MAKE-90 (death, dialysis dependence, or persistent kidney dysfunction [>25% decline in estimated glomerular filtration rate from baseline]).

Results

Data from 996 patients were entered into the registry. After exclusions (n = 27), 969 patients (440 [45.4%] female; 16 (1.9%) American Indian or Alaska Native, 40 (4.7%) Asian or Pacific Islander, 127 (14.9%) Black, 652 (76.4%) White, 18 (2.1%) more than 1 race; median [IQR] patient age, 8.8 [1.7-15.0] years) with data for the primary outcome (MAKE-90) were included. Median (IQR) time to CRRT initiation was 2 (1-6) days. MAKE-90 occurred in 630 patients (65.0%), of which 368 (58.4%) died. Among the 601 patients who survived, 262 (43.6%) had persistent kidney dysfunction. Of patients with persistent dysfunction, 91 (34.7%) were dependent on dialysis. Time to CRRT initiation was approximately 1 day longer among those with MAKE-90 (median [IQR], 3 [1-8] days vs 2 [1-4] days; P = .002). In the generalized propensity score-weighted regression, there were approximately 3% higher odds of MAKE-90 for each 1-day delay in CRRT initiation (odds ratio, 1.03 [95% CI, 1.02-1.04]).

Conclusions and Relevance

In this cohort study of children and young adults receiving CRRT, longer time to CRRT initiation was associated with greater risk of MAKE-90 outcomes, in particular, mortality. These findings suggest that prospective multicenter studies are needed to further delineate the appropriate time to initiate CRRT and the interaction between CRRT initiation timing and VO to continue to improve survival and reduce morbidity in this population.