Acute kidney injury in neonates: from urine output to new biomarkers

Acute kidney injury surveillance in the high-risk neonatal population following implementation of creatinine screening protocol

AIM

Acute kidney injury (AKI) in neonates is associated with longer hospital stays and higher mortality rates. However, there is significant variability in prevalence rates of AKI and the true burden is incompletely understood. In November 2020, the University of Iowa Stead Family Children's Hospital Neonatal Intensive Care Unit implemented a creatinine screening protocol to enhance kidney function monitoring. We sought to evaluate adherence to the protocol to determine if increased surveillance led to increased detection of AKI events.

METHODS

A retrospective chart review was conducted for neonates born at <30 weeks' gestation admitted between 2015 and 2020. We reviewed 100 charts in both the pre (2015-2016) and post (2020-2021) implementation era of the AKI surveillance protocol. AKI was defined according to neonatal modified KDIGO criteria.

RESULTS

Following implementation of the protocol, neonates were significantly more likely to have creatinine checked (p < 0.001). Serum creatinine was drawn according to protocol guidelines 68% of the time, and 42% of patients (34/82) had an 80% or higher adherence to the protocol. There was a significant increase in detection of AKI in the post-protocol cohort (13/82, incidence of 16%) compared to the pre-protocol cohort (5/83, incidence of 6%), (p = 0.047).

CONCLUSION

The implementation of a serum creatinine screening protocol increased the frequency of creatinine draws and detection of AKI.

Immunoaffinity proteomics for kidney injury biomarkers in male beagle dogs

Drug-induced kidney injury (DIKI) is a cause of drug development failure. Dogs represent a common non-rodent animal model in pre-clinical safety studies; however, biomarker assays for detecting nephrotoxicity in dogs are limited. To identify novel proteins and gain insight into the molecular mechanisms involved in DIKI, we developed an assay to evaluate proteomic changes associated with DIKI in male beagle dogs that received nephrotoxic doses of tobramycin for 10 consecutive days. Label-free quantitative discovery proteomics analysis on representative kidney cortex tissues collected on Day 11 showed that the tobramycin-induced kidney injury led to a significant differential regulation of 94 proteins mostly associated with mechanisms of nephrotoxicity such as oxidative stress and proteasome degradation. For verification of the proteomic results, we developed a multiplex peptide-centric immunoaffinity liquid chromatography tandem mass spectrometry assay (IA LC-MS/MS) to evaluate the association of eight DIKI protein biomarker candidates using kidney cortices collected on Day 11 and urine samples collected on Days -4, 1, 3, 7 and 10. The results showed that most biomarkers evaluated were detected in the kidney cortices and their expression profile in tissue aligned with the label-free data. Cystatin C was the most consistent marker regardless of the magnitude of the renal injury while fatty acid-binding protein-4 (FABP4) and kidney injury molecule-1 (KIM-1) were the most affected biomarkers in response to moderate proximal tubular injury in absence of changes in serum-based concentrations of blood urea nitrogen or creatinine. In the urine, clusterin is considered the most consistent biomarker regardless of the magnitude and time of the renal injury. To our knowledge, this is the most comprehensive multiplex assay for the quantitative analysis of mechanism-based proximal tubular injury biomarkers in dogs.

Acute kidney injury in birth asphyxiated patients: A cross sectional study at Bahawal Victoria Hospital

BACKGROUND

The presence of perinatal asphyxia and its severity appear to correlate with increasing incidence of Acute kidney injury (AKI). The objective of this study is to determine the frequency of AKI and its outcome in birth asphyxia.

METHODS

This cross-sectional study was carried out in the Department of Pediatric Medicine from March 2019 to September 2019. A total of 111 newborns with birth asphyxia of gestational age 37-41 weeks were included. Neonates born to mothers having hypertension and diabetes mellitus, patients with congenital kidney anomalies like polycystic kidney disease and renal agenesis, and mothers taking nephrotoxic drugs or any other known cause of AKI like hypovolemic shock were excluded. Urine output (UOP) and final outcome of the patient were also noted. AKI was noted.

RESULTS

The mean gestational age was 38.29 ± 1.07 weeks. The mean weight of neonates was 3.08 ± 0.31 kg. The frequency of AKI in birth asphyxia was 20 (18.02%) neonates. Complete recovery in AKI patients was seen in 07 (35.0%) and death in 13 (65.0%) patients.

CONCLUSION

This study has shown that the frequency of AKI in birth asphyxia was found in 18.02% neonates with complete recovery seen in 35.0% and death in 65.0% patients.

Clinical impact of severe acute kidney injury on post-operative and brain injury outcomes in preterm infants following surgical necrotizing enterocolitis

BACKGROUND

To evaluate post-operative outcomes and white matter injury (WMI) using brain MRI at term equivalent in neonates with and without severe acute kidney injury (AKI) following surgical necrotizing enterocolitis (NEC).

METHODS

A retrospective cohort study comparing neonates with severe (Stage 2/3) vs. other (no AKI/Stage 1) AKI using KDIGO classification with multivariable models assessing this association in the context of multiple systemic comorbidities.

RESULTS

Of 103 neonates with surgical NEC, 60 (58%) had severe AKI. Those with severe AKI had lower birth weight (BW; 715 vs. 950 g; p = .023), more frequently treated with indomethacin (18.3 vs. 2.4%); p = .014), higher CRP levels at 24 h after NEC onset (14.4 [6.4-19.8] vs. 4.8 [1.6-13.4]; p = .005), higher presence of cholestasis (73.3 vs. 51.2%); p = .023), later age of NEC onset (14 vs. 7 d); p = .004), longer length of bowel resected (14.9 vs. 4.3 cm); p = .011), longer post-operative ileus days (14 vs. 9 d); p < .001), longer post-operative days at starting enteral feedings (15 vs. 10 d; p < .001), longer days of attainment of full enteral feedings (75 vs. 44.5 d; p = .008) and longer length of stay (140.5 vs. 94 d; p = .028) compared to those without severe AKI. Compared to infants without AKI by serum creatinine, those with AKI had significantly more cases of white matter abnormality (WMA; 90 vs. 36.6%; p < .001) and retinopathy of prematurity (63.9 vs. 35.3%; p = .017). In addition, the presence of AKI Stage 2 and 3 by serum creatinine was independently associated with higher odds of sustaining severe WMI level on an ordinal scale (OR = 6.2; 95% CI = (1.1-35.5); p = .041).

CONCLUSIONS

Neonates with severe AKI following surgical NEC were more likely to experience longer post-operative morbidity and higher WMI by MRI at term.

Effects of aminophylline on the levels of neutrophil gelatinase-associated lipocalin (NGAL) in asphyxiated term neonates

OBJECTIVE

Our study evaluates the effects of aminophylline in the reduction of NGAL levels in perinatal asphyxia.

METHODS

Term neonates with hypoxic ischaemic encephalopathy who were divided into two groups, the treatment and placebo. Urine NGAL levels were measured on day one and four of the treatment using BIOPORTO kits in both the groups.

RESULTS

Day 1 NGAL levels were not statistically different in either group irrespective of the age, gender and the mode of delivery. on 4^th day, NGAL in treatment group significantly decreased as compared to day 1 levels and placebo day-4 levels. significant differences were seen between first and fourth day NGAL levels among children with normal and caesarean birth and among female and male neonates.

CONCLUSIONS

Following the treatment with aminophylline, NGAL levels in asphyxiated neonates are likely to reduce. Further studies based on other kidney dysfunction parameters can lead to the better and accurate conclusions.

Tubular and glomerular biomarkers of renal tissue function in the urine of fetuses with posterior urethral valves

INTRODUCTION

Posterior urethral valve (PUV) is a congenital malformation characterized by a membranous structure located in the prostatic portion of the male posterior urethra that obstructs the urinary flow. Efforts have been made to determine the degree of impairment of fetal kidney function in this condition.

OBJECTIVE

This study aimed to measure the levels of urinary biomarkers of glomerular and tubular functions in fetuses with PUV and to compare with the levels of the same molecules in healthy male premature newborns.

STUDY DESIGN

Urine samples from 43 fetuses with PUVs were collected and compared with urine samples from 40 healthy male newborns of the same gestational age (controls). Tubular and glomerular biomarkers levels were measured in urine samples by MILLIPLEX® assay kits. Levels of the molecules were related to creatinine (Cr) measurements at same urine samples and expressed as pg/mg Cr. Results were analysed with Graphpad Prism version 7.0 and SPSS version 20.0.

RESULTS

Fetuses with PUV showed a significant reduction in urine levels of Epidermal Growth Factor (EGF), Calbindin, Osteoactivin, Molecule Renal Injury 1 (KIM-1 and Factor of trefoil 3 (TFF-3) when compared to controls. On the other hand, urine levels of cystatin C and renin were higher in PUV fetuses. The levels of molecules also differed according to urine osmolality and grade of hydronephrosis.

DISCUSSION

Some urinary excreted molecules may indicate kidney damage in several segments along the nephron, while others may exert important functions. Mechanical and immunological mechanisms related to PUV might significantly modulate the synthesis of cytokines related to glomerular and tubular physiology, leading to alterations in urinary concentrations of those molecules. These biomarkers can be used as future diagnostic and prognostic markers in clinical practice.

CONCLUSION

Early kidney structural and functional impairment influenced the synthesis of glomerular and tubular molecules related to kidney physiological processes in fetuses with PUV.

Impact of nephrotoxic drugs on urinary biomarkers of renal function in very preterm infants

BACKGROUND

Following preterm birth, the immature kidney is exposed to several harmful conditions, with an increased risk of renal impairment. We aimed to assess urinary biomarkers of renal function in very preterm infants during early nephrotoxic treatments.

METHODS

Infants ≤32 weeks' gestation and ≤1500 g were enrolled in this observational prospective study. Urine samples were collected on day 1(T1), 2-4(T2), 5-7(T3), 8-10(T4), 11-13(T5). The following urinary biomarkers were determined: osteopontin (uOPN), epidermal growth factor (uEGF), neutrophil gelatinase-associated lipocalin (uNGAL), cystatin C (uCysC). The infants were grouped according to their exposure to amikacin or ibuprofen during the study period and a between-group comparison of urinary biomarkers at each time point was performed.

RESULTS

Thirty-six infants were included. Urinary CysC, uOPN, and uNGAL rose significantly during ibuprofen or amikacin treatment, while no difference was observed for uEGF. After adjustment for possible influencing factors, amikacin administration was associated with higher uCysC at T1 (p = 0.007) and T2 (p = 0.016), whereas ibuprofen increased uOPN (p = 0.001) and uNGAL concentration (p = 0.009) at T3.

CONCLUSION

Nephrotoxic therapies induce molecule-specific change patterns of renal function biomarkers in treated preterm infants. Serial assessments of these biomarkers may aid to identify neonates at risk of renal impairment and to develop tailored therapeutic approaches.

IMPACT

Despite the wide use of nephrotoxic therapies in neonatal settings, little is known on their effect on renal function biomarkers in preterm infants. This study describes molecule-specific change patterns of urinary biomarkers during ibuprofen and amikacin administration, suggesting underlying pathophysiological effects on renal function. Given their low analytical costs and non-invasive collection, the urinary biomarkers investigated in this study represent a promising strategy for serial monitoring of renal function in at-risk neonates and may aid the early detection of renal function impairment at different kidney levels during nephrotoxic treatments.

Development of Physiologically Based Pharmacokinetic Model and Assessment of the Impact of Renal Underdevelopment in Preterm Infants on the Pharmacokinetics of Aminophylline

Objective:

To develop a physiologically based pharmacokinetic (PBPK) model for individualization of the dosing regimen considering the physiological requirements of these preterm neonates.

Methods:

The study comprised preterm newborns with fewer than 34 weeks of gestation and six apneic episodes in 24 h. A PBPK model was created using PK-SIM (version 9, update 1, GitHub, San Francisco, CA, USA). A PBPK model is built using a typical loading dosage of 5 mg/kg and a maintenance dose of 1.5 mg/kg. Based on the verified base model, a PBPK model representing renal underdevelopment based on nRIFLE/pRIFLE categorization was developed.

Results:

The PK parameters of Aminophylline were computed using the PBPK model. As per the model prediction, T1/2 and area under the curve reduced as postnatal age increased, and in the event of renal underdevelopment, even while C max for patients under R (RISK), I (injury) was within the therapeutic range; it was greater compared to preterm without any renal complications. Mean C max (mol/L) was 59.53 and for R, I, and F (FAILURE) categories the values were 83.04, 99.69, and 126.98, respectively.

Conclusion:

The model was created using appropriate drug, study subject, and dosage protocol inputs. The established PBPK model could help in individualizing aminophylline dose in preterm babies.

Use of non-conventional biomarkers in the early diagnosis of acute kidney injury in preterm newborns with sepsis

Acute kidney injury (AKI) is a common finding in Neotatal Intensive Care Units (NICU). Sepsis is one the main causes of AKI in preterm newborns. AKI has been associated with significant death rates. Early detection of the condition is the first step to improving prevention, treatment, and outcomes, while decreasing length of hospitalization, care costs, and morbimortality. AKI may progress to chronic kidney disease (CKD), a condition linked with dialysis and greater risk of cardiovascular disease. This review article aims to discuss cases of AKI in preterm newborns with sepsis, the use of biomarkers in lab workup, and the use of non-conventional biomarkers for the early identification of AKI.

Nephrotoxicity in Neonates

Acute kidney injury (AKI) is classified based on prerenal, intrinsic, and postrenal causes. In the newborn, AKI can occur after an insult during the prenatal, perinatal, or postnatal period. AKI is usually an underrecognized condition and its true incidence is unknown. AKI may result from the administration of a number of different nephrotoxic medications, which are often used concurrently in critically ill neonates, exponentially increasing the risk of renal injury. Drug toxicity may also compromise the formation and development of nephrons, and this is particularly important in preterm infants, who have incomplete nephrogenesis. Little is known about the pharmacokinetics and pharmacodynamics of different medications used in neonates, especially for the most immature infant, and the use of most medications in this population is off label. Strategies to prevent AKI include the avoidance of hypotension, hypovolemia, fluid imbalances, hypoxia, and sepsis as well as judicious use of nephrotoxic medications. Treatment strategies aim to maintain fluids and electrolytic and acid-base homeostasis, along with an adequate nutritional status. Neonates are especially prone to long-term sequelae of AKI and benefit from long-term follow-up. This review summarizes the most relevant aspects of nephrotoxicity in neonates and describes the prevention, treatment, and follow-up of AKI in neonates.

Can urinary biomarkers predict acute kidney injury in newborns with critical congenital heart disease?

Background/aim

Congenital heart disease (CHD) is the most common congenital malformation group and is the leading cause of newborn mortality in developed countries. Most of the infants with CHD develop preoperative or postoperative acute kidney injury (AKI). Acute kidney injury may develop before the serum creatinine rise and oliguria. Urinary biomarkers such as kidney injury molecule-1 (KIM-1), neutrophil gelatinase-associated lipocalin (NGAL), interleukin (IL)-18, and cystatin C may predict AKI in patients with critical CHD (CCHD) before the serum creatinine rise. In this study, we aimed to determine the AKI incidence among newborn patients with CCHD and investigate the predictivity of urinary biomarkers for AKI.

Materials and methods

Newborns with a gestational age >34 weeks and birth weight >1500 g with a diagnosis of CCHD were enrolled in the study. Blood and urine samples were collected at birth, during the first 24–48 h, and in the preoperative and postoperative periods.

Results

A total of 53 CCHD patients requiring surgery during the neonatal period were enrolled in the study. The 24–48 h KIM-1 levels of the cases with exitus were higher (P = 0.007). The 24–48 h cystatin C and preoperative NGAL levels were higher in patients with postoperative AKI (P = 0.02).

Conclusion

In newborns with CCHD, high KIM-1 levels may predict mortality, whereas high cystatin C and preoperative NGAL levels may be indicative of AKI. These biomarkers deserve further investigation in larger study populations.

Urinary netrin-1 concentration in healthy full-term newborns

INTRODUCTION

Monitoring of renal function in acute kidney injury in the pediatric population is complicated by the lack of age-related reference values of new biomarkers. Urinary netrin-1 is a new marker to demonstrate early kidney damage. Netrin-1 has a molecular mass of 72 kDa. It is therefore unlikely that it is filtered by the glomerulus under normal conditions. However, netrin-1 is highly induced after acute and chronic kidney injury and excreted in urine in humans. The aim of the study was to determine the normal concentrations of urinary netrin-1 in healthy full-term newborns.

MATERIAL AND METHODS

The study included 88 healthy full-term neonates (51 boys and 37 girls) born from normal, uncomplicated pregnancies. The concentration of netrin-1 was determined in urine obtained on the first or second day of life with a commercially available ELISA kit.

RESULTS

The urinary concentration of netrin-1 in newborns was independent of gender and time of urine collection. We found a negative correlation between both the urinary netrin-1 concentration and urinary netrin-1 concentration after normalization for urinary creatinine and the birth weight.

CONCLUSIONS

This is the first study showing the urinary netrin-1 concentration in healthy full-term newborns. Future investigation is needed to confirm its potential role as a marker of kidney function in this age group.

Cystatin C compared to serum creatinine as a marker of acute kidney injury in critically ill neonates

BACKGROUND

Acute kidney injury (AKI) is one of the most common causes of neonatal morbidity and mortality. Diagnosing AKI in neonates is challenging as it lacks specific signs, symptoms, and biomarkers. However, detecting AKI in critically ill neonates is crucial to determine appropriate management and prevent complications. Cystatin C (CysC) has been recognized as a superior kidney biomarker reflecting kidney function in neonates. The objective of this study is to evaluate the diagnostic value of CysC as an AKI biomarker in critically ill neonates.

METHODS

We performed a diagnostic test between cystatin C-based estimated glomerular filtration rate (eGFR-CysC) and serum creatinine-based estimated glomerular filtration rate (eGFR-SCr) as the gold standard to diagnose AKI in 135 critically ill neonates treated in Cipto Mangunkusumo National Hospital from July 2017 to January 2018.

RESULTS

Prevalence of AKI was 23.7% predominantly in neonates with a very preterm gestational age, low birthweight, probable sepsis, and those receiving invasive oxygen therapy or nephrotoxic drugs. The proportion of AKI based on neonate RIFLE criteria was 72.7% risk, 18.9% injury, and 9% failure. eGFR-CysC had the following parameters: sensitivity, 84.8%; specificity, 61.8%; PPV, 41.8%; NPV, 89.7%; LR(+), 2.2; LR(-), 0.24; and accuracy, 67.4%. The AUROC for CysC was 84.9%. The optimal cut-off value for CysC was 1.605 mg/l.

CONCLUSIONS

CysC may be used as a screening biomarker of AKI in critically ill neonates; yet, it was not superior to serum creatinine. Graphical abstract.

NEUTROPHIL GELATINASE-ASSOCIATED LIPOCALIN AS AN EARLY BIOMARKER OF ACUTE KIDNEY INJURY IN NEWBORNS

The aim of the study was to determine the incidence, risk factors and efficiency of the neutrophil gelatinase-associated lipocalin (NGAL) biomarker in early diagnosis of acute kidney injury (AKI) in newborns. The study was designed as a prospective, clinical, epidemiological investigation conducted in the period of three years, which included 50 newborns with AKI hospitalized in the Neonatal Intensive Care Unit, University Children’s Hospital in Skopje. The estimated prevalence of AKI was 6.4%, while the prevalence according to RIFLE classification was 8.7%. Perinatal asphyxia was a common predisposing factor associated to kidney injury. The mortality rate was 32% and was significantly higher in the group of newborns with congenital heart diseases. There was a significant difference between NGAL values and creatinine values on the day of admission. There was a significant difference in NGAL values between newborns with AKI and lethal outcome and newborns without lethal outcome (p<0.001). In conclusion, AKI is a life-threatening condition. It is an independent contributor to mortality. Urinary NGAL is an early predictive biomarker of AKI in critically ill newborns.

A New Approach to Recognize Neonatal Impaired Kidney Function

Introduction

Previous studies in term newborns with hypoxic ischemic encephalopathy showed that the rate of serum creatinine (SCr) decline during the first week of life could be used to identify newborns with impaired kidney function (IKF) who are missed by standard definitions of neonatal acute kidney injury (nAKI).

Methods

Retrospective review of the medical records of 329 critically ill newborns ≥27 weeks of gestational age (GA) admitted to a level 4 neonatal intensive care unit (NICU). We tested the hypothesis that the rate of SCr decline combined with SCr thresholds provides a sensitive approach to identify term and preterm newborns with IKF during the first week of life.

Results

Excluding neonates with nAKI, an SCr decline <31% by the seventh day of life, combined with an SCr threshold ≥0.7 mg/dl, recognized newborns of 40 to 31 weeks of GA with IKF. An SCr decline <21% combined with an SCr threshold ≥0.8 mg/dl identified newborns of 30 to 27 weeks of GA with IKF. Neonates with IKF (∼17%), like those with nAKI (7%), showed a more prolonged hospital stay and required more days of mechanical ventilation, vasoactive drugs, and diuretics, when compared with the controls. Changes in urine output did not distinguish newborns with IKF.

Conclusion

The rate of SCr decline combined with SCr thresholds identifies newborns with IKF during the first week of life. This distinctive group of newborns that is missed by standard definitions of nAKI, warrants close monitoring in the NICU to prevent further renal complications.

Risk factors and outcomes of acute kidney injury in ventilated newborns

Purpose: This study aimed to investigate the occurrence and risk factors of acute kidney injury (AKI) in ventilated newborns.

Methods: In total, 139 newborns receiving mechanical ventilation (MV) were reviewed in this retrospective study. The demographic and clinical data were collected. Then, the independent risk factors for AKI were evaluated using univariate and multivariate logistic regression analyses.

Results: The incidence rate of AKI was 15.11% (21/139) in ventilated newborns. Univariate analysis showed significant differences in gestational age, birth weight, Apagar scores, the highest oxygen concentration, serum creatinine levels at admission and 48 h after MV, history of asphyxia, urine output at 48 h after MV, invasive MV, noninvasive MV, and outcomes between AKI and non-AKI groups (all p < .05). The lower gestational age (odd ratio (OR): 1.194, 95% confidence interval (CI): 1.013–1.407, p = .035), the increased use of invasive mechanical ventilation (IMV) (OR: 4.790, 95% CI: 1.115–20.575, p = .035), and lower birth weight (OR: 0.377, 95% CI: 0.178–0.801, p = .011) were independent risk factors for the occurrence of AKI. Additionally, higher stage of AKI was significantly associated with poor prognosis of AKI (p = .018).

Conclusion: In this retrospective study, it was found that lower gestational age, birth weight, and increased use of IMV were independent risk factors for AKI in ventilated newborns. The poor prognosis might be indicated by the higher AKI stage.

The effectiveness of urinary TIMP-2 and IGFBP-7 in predicting acute kidney injury in critically ill neonates

BACKGROUD

Urinary tissue inhibitor of metalloproteinase-2 (TIMP-2), insulin-like growth factor binding protein-7 (IGFBP-7) and the combination of TIMP-2 and IGFBP-7 ([TIMP-2]•[IGFBP7]) are proposed to be predictive biomarkers for acute kidney injury (AKI). The intention of our study was to determine whether there is any significant predictive value of these biomarkers for the occurrence of AKI and severe AKI in critically ill neonates.

METHODS

Urinary samples were serially collected in 237 neonates during neonatal intensive care unit (NICU) stay for measurements of TIMP-2 and IGFBP-7 in this prospective study. AKI diagnosis was based on KDIGO classification without urine output or serum creatinine >1.2 mg/dL.

RESULTS

Twenty neonates developed AKI, including 11 with KDIGO stage 1, defined as mild AKI, and 9 with stages 2 and 3, defined as severe AKI. Urinary IGFBP-7 and [TIMP-2]•[IGFBP7] remained associated with AKI after adjustment for gestational age, gender and illness severity. Urinary [TIMP-2]•[IGFBP7] achieved an AUC of 0.71 (P = 0.034) and displayed a sensitivity of 88.9% and a specificity of 50.9% for discriminating severe AKI at the optimal cut-off value of 0.045.

CONCLUSION

The combination of TIMP-2 and IGFBP-7 had independent discriminative value for severe AKI in critically ill neonates.

Variation in clinical usefulness of biomarkers of acute kidney injury in young children undergoing cardiac surgery

BACKGROUND

Acute kidney injury (AKI) is one of the most significant postoperative complications of pediatric cardiac surgery. Because serum creatinine has limitations as a diagnostic marker of AKI, new biomarkers including neutrophil gelatinase-associated lipocalin (NGAL), kidney injury molecule-1 (KIM-1), and interleukin-18 (IL-18) are being evaluated to overcome these limitations and detect AKI at an early stage after cardiac surgery.

PURPOSE

This study aimed to investigate the clinical usefulness of these biomarkers in young children.

METHODS

Thirty patients with congenital heart diseases who underwent cardiac surgery using cardiopulmonary bypass (CPB) were selected, and their urine and blood samples were collected at baseline and 6, 24, and 48 hours after surgery. Serum creatinine and blood urea nitrogen levels as well as NGAL, KIM-1, and IL-18 levels in urine samples were measured, and clinical parameters were evaluated.

RESULTS

Of the 30 patients, 12 developed AKI within 48 hours after cardiac surgery. In the AKI group, 8 of 12 (66.6%) met AKI criteria after 24 hours, and urine KIM-1/creatinine (Cr) level (with adjustment of urine creatinine) peaked at 24 hours with significant difference from baseline level. Additionally, urine KIM-1/Cr level in the AKI group was significantly higher than in the non-AKI group at 6 hours. However, urine NGAL/Cr and IL-18/Cr levels showed no specific trend with time for 48 hours after cardiac surgery.

CONCLUSION

It is suggested that urine KIM-1/Cr concentration could be considered a good biomarker for early AKI prediction after open cardiac surgery using CPB in young children with congenital heart diseases.

Echocardiographic predictors of acute kidney injury in neonates with a patent ductus arteriosus

OBJECTIVE

To investigate acute kidney injury (AKI) in neonates with a patent ductus arteriosus (PDA) including incidence, risk factors, and possible correlations between PDA-related echocardiographic measurements and AKI incidence.

STUDY DESIGN

We conducted a single-center retrospective cohort study of infants admitted to the neonatal intensive care unit with a diagnosis of a PDA between July 2015 and July 2017. Infants were evaluated for development of AKI based on the KDIGO criteria and a multivariable logistic regression analysis was performed.

RESULTS

A total of 142 neonates with moderate or large PDAs were included, 43 (30%) developed AKI. Patients who developed AKI had longer length of stay, lower birth weights, lengths, and gestational ages. No echocardiographic measurements were predictive of an increased risk for developing AKI.

CONCLUSION

There are no significant differences in commonly measured echocardiographic markers of PDA hemodynamic significance in neonates who develop AKI.

Renal functional markers in extremely premature infants with and without twin-twin transfusion syndrome

OBJECTIVE

Describe renal function of preterm infants <29 weeks of gestational age (GA) with twin-twin transfusion syndrome (TTTS) who received laser therapy.

DESIGN

Retrospective analysis of premature TTTS compared with dichorionic-diamniotic (di-di) twins from 2006 to 2015. Primary outcome was biomarkers of renal injury.

RESULTS

Thirty-three TTTS-laser and 101 di-di newborns with similar GA at birth (26.4 ± 1.4 vs 26.9 ± 1.6 weeks, p = 0.07) were included. Creatinine and urea levels were higher in TTTS-laser group at day of life (DOL) 2-7 (123.5 ± 12.4 vs 75.8 ± 2 μmol/L, p = 0.0001 and 11.9 ± 1.1 mmol/L vs 8.7 ± 0.3 mmol/L, p = 0.0001) and DOL 8-14, (98.1 ± 14.2 vs 64.8 ± 2.3 μmol/L, p = 0.0001 and 9.1 ± 1.2 vs 5.4 ± 0.3 mmol/L, p = 0.0001). There was a significant effect of TTTS status on creatinine level at DOL 8-14.

CONCLUSION

In extremely preterm with TTTS treated by laser, biomarkers of renal function were higher compared with di-di twins in the first 2 weeks of life.

Oct-4 Enhanced the Therapeutic Effects of Mesenchymal Stem Cell-Derived Extracellular Vesicles in Acute Kidney Injury

BACKGROUND/AIMS

Acute kidney injury (AKI) is a common clinical condition that can lead to chronic kidney failure. Although mesenchymal stem cell-derived extracellular vesicles (MSC EVs) are regarded as a potent AKI treatment, the mechanisms underlying their beneficial effects remain unclear. Oct-4 may play an important role in tissue injury repair. We thus hypothesized that oct-4 overexpression might enhance the therapeutic effects of MSC EVs in AKI treatment.

METHODS

Renal tubular epithelial cells were cultured in a low oxygen environment, then cocultured with MSC EVs or control medium for 48 h. BrdU and transferase-mediated dUTP nick-end labeling (TUNEL) staining were used to assess cell proliferation and apoptosis. Mice subjected to ischemia reperfusion were randomly divided into 4 groups, then injected with either phosphate-buffered saline (vehicle), EVs, EVs overexpressing oct-4 (EVs+Oct-4), and EVs not expressing Oct-4 (EVs-Oct-4). Blood creatinine (CREA) and urine nitrone levels were assessed 48 h and 2 weeks after injection. After ischemia reperfusion, renal tissues from each group were stained with TUNEL and proliferating cell nuclear antigen (PCNA) to determine the degree of apoptosis and proliferation. Masson trichrome staining was used to evaluate renal fibrosis progression. Snail gene expression was assessed using polymerase chain reaction (PCR).

RESULTS

At 48 h after hypoxic treatment, TUNEL and BrdU staining indicated that the EVs+Oct-4 group had the least apoptosis and the most proliferation, respectively. Treatment with EVs overexpressing Oct-4 significantly decreased serum Crea and blood urea nitrogen levels and rescued kidney fibrosis, as indicated by the low proportion of Masson staining, high number of PCNA-positive cells, and low number of TUNEL-positive cells. PCR analysis indicated that Snail was most upregulated in the vehicle group and least upregulated in the EVs+Oct-4 group.

CONCLUSIONS

MSC EVs had a pronounced therapeutic effect on ischemic reperfusion injury-related AKI, and Oct-4 overexpression enhanced these therapeutic effects. Our results may inspire a new direction for AKI treatment with MSC EVs.

Length of gestation and birth weight are associated with indices of combined kidney biomarkers in early childhood

Infants born prematurely or with low birth weights are more susceptible to kidney dysfunction throughout their lives. Multiple proteins measured in urine are noninvasive biomarkers of subclinical kidney damage, but few studies have examined the joint effects of multiple biomarkers. We conducted an exploratory study of 103 children in the Programing Research in Obesity, Growth, Environment, and Social Stressors (PROGRESS) longitudinal birth cohort, and measured nine proteins selected a priori in banked spot urine samples collected at ages 4-6. The goal of our study was to explore the combined effects of kidney damage biomarkers previously associated with birth outcomes. To do this, we generated kidney biomarker indices using weighted quantile sum regression and assessed associations with length of gestation or birth weight. A decile increase in each kidney biomarker index was associated with 2-day shorter gestations (β = -2.0, 95% CI: -3.2, -0.9) and 59-gram lower birth weights (β = -58.5, 95% CI: -98.3, -18.7), respectively. Weights highlighting the contributions showed neutrophil gelatinase-associated lipocalin (NGAL) (60%) and osteopontin (19%) contributed most to the index derived for gestational age. NGAL (66%) and beta-2-microglobulin (10%) contributed most to the index derived for birth weight. Joint analyses of multiple kidney biomarkers can provide integrated measures of kidney dysfunction and improved statistical assessments compared to biomarkers assessed individually. Additionally, shorter gestations and lower birth weights may contribute to subclinical kidney damage measurable in childhood.

Prenatal Use of Sildenafil in Fetal Growth Restriction and Its Effect on Neonatal Tissue Oxygenation-A Retrospective Analysis of Hemodynamic Data From Participants of the Dutch STRIDER Trial

Objective: Sildenafil is under investigation as a potential agent to improve uteroplacental perfusion in fetal growth restriction (FGR). However, the STRIDER RCT was halted after interim analysis due to futility and higher rates of persistent pulmonary hypertension and mortality in sildenafil-exposed neonates. This hypothesis-generating study within the Dutch STRIDER trial sought to understand what happened to these neonates by studying their regional tissue oxygen saturation (rSO₂) within the first 72 h after birth. Methods: Pregnant women with FGR received 25 mg placebo or sildenafil thrice daily within the Dutch STRIDER trial. We retrospectively analyzed the cerebral and renal rSO₂ monitored with near-infrared spectroscopy (NIRS) in a subset of neonates admitted to two participating neonatal intensive care units, in which NIRS is part of standard care. Secondarily, blood pressure and heart rate were analyzed to aid interpretation. Differences in oxygenation levels and interaction with time (slope) between placebo- and sildenafil-exposed groups were tested using mixed effects analyses with multiple comparisons tests. Results: Cerebral rSO₂ levels were not different between treatment groups (79 vs. 77%; both n = 14) with comparable slopes. Sildenafil-exposed infants (n = 5) showed lower renal rSO₂ than placebo-exposed infants (n = 6) during several time intervals on day one and two. At 69-72 h, however, the sildenafil group showed higher renal rSO₂ than the placebo group. Initially, diastolic blood pressure was higher and heart rate lower in the sildenafil than the placebo group, which changed during day two. Conclusions: Although limited by sample size, our data suggest that prenatal sildenafil alters renal but not cerebral oxygenation in FGR neonates during the first 72 post-natal hours. The observed changes in renal oxygenation could reflect a vasoconstrictive rebound from sildenafil. Similar changes observed in accompanying vital parameters support this hypothesis.

Associated factors for acute kidney injury in preterm infants

ABSTRACT Objective: to analyze the prevalence and factors associated with acute kidney injury in preterm newborns. Method: a cross-sectional study based on records data of preterm newborns hospitalized in two neonatal units in northwest Paraná State in 2015. For data analysis, the logistic regression model was used by the stepwise forward method and Fisher’s Exact Test. Results: 132 preterm newborns, with a prevalence of 7.5% of acute kidney injury, were hospitalized. Majority of males, extremely preterm and very low birth weight. Associated factors were the use of non-nephrotoxic antibiotics and the presence of mechanical pulmonary ventilation, increasing the chance of developing acute kidney damage by 2.98 and 1.33/day, respectively. Hospitalization days constituted a protection factor. Conclusion: this study was able to identify the prevalence, and outline the variables associated with acute kidney injury in preterm newborns in a particular care situation.

Fatty-Acid Binding Protein 4 (FABP4) as a Potential Preclinical Biomarker of Drug-Induced Kidney Injury

Identification of improved translatable biomarkers of nephrotoxicity is an unmet safety biomarker need. Fatty-acid-binding protein 4 (FABP4) was previously found to be associated with clinical renal dysfunction and was proposed as a biomarker of glomerular damage. The aim of this study was to evaluate FABP4 as a potential preclinical biomarker of drug-induced kidney injury (DIKI). Han-Wistar rats were dosed with cisplatin [2.5 mg/kg, single, intraperitoneally (i.p.)], puromycin (10 mg/kg, daily, i.p.) or N-phenylanthranylic acid [NPAA, 500 mg/kg, daily, per os (p.o.)] over a 28-day period to induce proximal tubule, glomerular or collecting duct injury, respectively. An increase in urinary FABP4 levels was observed on days 1 and 3 after NPAA treatment and on days 14, 21, and 28 after puromycin treatment, whereas cisplatin treatment had no effect. No significant changes were reported for plasma levels of FABP4 after any treatment. Interestingly, immunohistochemical analysis showed a marked decrease in FABP4 expression in the loop of Henle on day 7 after NPAA treatment and a complete loss of FABP4 expression on day 14 after puromycin treatment. The magnitude of increase in FABP4 urinary levels in response to NPAA and puromycin was higher than for established preclinical biomarkers serum creatinine, clusterin, or cystatin C. Our results suggest that FABP4 has the potential for preclinical application as a biomarker of DIKI.

Urinary Nephrin as a Biomarker of Glomerular Maturation and Injury Is Associated with Acute Kidney Injury and Mortality in Critically Ill Neonates

BACKGROUND

Nephrin is a key component of the slit diaphragm of the glomerular podocyte, and increased urinary nephrin level may reflect glomerular injury.

OBJECTIVES

To determine whether urinary nephrin is a useful biomarker of glomerular maturation and injury and whether it is associated with acute kidney injury (AKI) and neonatal intensive care unit (NICU) mortality in critically ill neonates.

METHODS

Urinary samples were serially collected in 234 neonates during NICU stay for measurements of nephrin, cystatin C (CysC), and albumin. AKI diagnosis was based on neonatal Kidney Disease: Improving Global Outcome (KDIGO) criteria.

RESULTS

Of the neonates, 26 developed AKI and 24 died during NICU stay. The independent contributors to the initial urinary nephrin level obtained on the first 24 h admitted to NICU were gestational age (p = 0.004) and initial urinary CysC level (p < 0.001). Both initial (p = 0.037) and peak (p = 0.039) urinary nephrin were significantly associated with AKI, even after controlling for significant covariates, and had an area under the receiver-operating characteristic curve (AUC) of 0.71 and 0.70, respectively, for predicting AKI. At the optimal cutoff value of 0.375 μg/mg urinary creatinine, the initial urinary nephrin displayed sensitivity of 61.5% and specificity of 76.9% for predicting AKI. The AUCs for initial and peak urinary nephrin to predict NICU mortality were 0.81 and 0.83, respectively.

CONCLUSIONS

Urinary nephrin, which may decrease with increasing glomerular maturity, is significantly associated with increased risk for AKI and NICU mortality even after adjustment for potential confounders. A higher level of urinary nephrin may be independently predictive of AKI and NICU mortality in critically ill neonates.

Safety of Rectal Administration of Acetaminophen in Neonates

BACKGROUND

On the basis of pharmacokinetic modelling, high-dose acetaminophen by rectal administration has been recommended for neonates needing antipyretic or analgesic therapy, but the safety and efficacy of this approach have not been established in vivo.

OBJECTIVES

The primary objective was to assess the safety of rectal acetaminophen administration for neonates, as indicated by changes in the results of hepatic and renal function tests. The secondary objective was to assess the efficacy of rectal acetaminophen administration in terms of the Premature Infant Pain Profile-Revised (PIPP-R) score.

METHODS

This single-centre retrospective chart analysis was conducted in the neonatal intensive care unit at a quaternary care children's hospital. Neonates who received all prescribed doses of acetaminophen by continu - ous rectal administration for 24 h or more, from January 1, 2011, to December 31, 2012, were included. For the primary objective, hepatotoxicity was assessed in terms of changes in liver enzyme levels, and nephrotoxicity was assessed in terms of changes from baseline serum creatinine values.

RESULTS

Twenty-five patients, who received a total of 27 courses of acetaminophen by rectal administration, met the inclusion criteria. Median gestational age at initiation of acetaminophen was 37.0 weeks (interquartile range 35.0-39.8 weeks). Values of alanine aminotransferase remained within normal limits during acetaminophen therapy for all but 3 patients, for whom the changes were attributable to confounding factors. Renal function remained unchanged. The secondary outcome of efficacy (based on PIPP-R score) could not be evaluated because of concurrent use of opioids for most patients.

CONCLUSIONS

Continuous rectal administration of acetaminophen over a short period (< 48 h) appeared to be well tolerated. The conclusions that can be drawn from these results are limited because of small sample size, the prescribing of doses lower than those recommended by the hospital's formulary, and limited blood sampling. Further studies are required.

Subclinical acute kidney injury is associated with adverse outcomes in critically ill neonates and children

Background

Research on acute kidney injury (AKI) has focused on identifying early biomarkers. However, whether AKI could be diagnosed in the absence of the classic signs of clinical AKI and whether the condition of subclinical AKI, identified by damage or functional biomarkers in the absence of oliguria or increased serum creatinine (sCr) levels, is clinically significant remains to be elucidated in critically ill children. The aims of the study were to investigate the associations between urinary cystatin C (uCysC) levels and AKI and mortality and to determine whether uCysC-positive subclinical AKI is associated with adverse outcomes in critically ill neonates and children.

Methods

In this prospective cohort study, uCysC levels were serially measured during the first week after intensive care unit (ICU) admission in a heterogeneous group of patients (n = 510) presenting to a tertiary neonatal and pediatric ICU. The diagnosis of neonatal AKI that developed during the first week after admission was based on neonatal KDIGO criteria or sCr >1.5 mg/dL, and pediatric AKI was based on Kidney Disease: Improving Global Outcomes (KDIGO) criteria. The term “uCysC(−)” or “uCysC(+)”, indicating the absence or presence of tubular injury, was defined by the optimal peak uCysC cutoff value for predicting ICU mortality.

Results

The initial and peak uCysC levels were significantly associated with AKI and mortality, and had an area under the receiver operating characteristic curve of 0.76 and 0.81, respectively, for predicting mortality. At the optimal cutoff value of 1260 ng/mg uCr, the peak uCysC displayed sensitivity of 79.2% and specificity of 72.3% for predicting mortality. Among all patients, 130 (25.5%) developed uCysC(+)/AKI(−) status during the first week after admission. The adjusted odds ratio for patients with uCysC(+)/AKI(−) status in association with an increased risk of mortality compared with that for patients with uCysC(−)/AKI(−) was 9.34 (P < 0.001). Patients with uCysC(+)/AKI(−) spent 2.8 times as long in the ICU as those with uCysC(−)/AKI(−) (P < 0.001).

Conclusions

Both initial and peak uCysC levels are associated with AKI and mortality and are independently predictive of mortality in critically ill neonates and children. Subclinical AKI may occur without detectable loss of kidney function, and uCysC-positive subclinical AKI is associated with worse clinical outcomes in this population.

Electronic supplementary material

The online version of this article (10.1186/s13054-018-2193-8) contains supplementary material, which is available to authorized users.

Comparison of urine neutrophil gelatinase-associated lipocalin and interleukin-18 in prediction of acute kidney injury in adults

BACKGROUND

Neutrophil gelatinase-associated lipocalin (NGAL) and interleukin-18 (IL-18) were considered as the most promising biomarkers in prediction of acute kidney injury (AKI), but the priority of them remains unclear.

METHODS

Databases of PubMed, Elsevier, Cochrane library, and Web of science were searched until August 23, 2017 for studies investigated the diagnostic value of urine NGAL (uNGAL) and urine IL-18 (uIL-18) for AKI in adults. Statistical analysis and investigation of heterogeneity source were using RevMan5.3, MetaDiSc1.40, and Stata14.0.

RESULTS

A total of 7 studies were included involving 2315 patients from 7 countries in this article, of whom 443 (19.1%) developed AKI. The present meta-analysis demonstrated that uNGAL was more valuable compare with uIL-18 with effect size of 1.09 (95% CI 1.03-1.15, P = .004) in specificity, but not in sensitivity with effect size of 1.12 (95% CI 0.98-1.29, P = .104). Subgroup analysis presented that research design may be a foundation affecting the diagnostic accuracy of uNGAL and uIL-18 for AKI. No substantial publication bias was found.

CONCLUSIONS

uNGAL is more specific for prediction of AKI in adults as compared with uIL-18.

Incidence, risk factors, and outcome of neonatal acute kidney injury: a prospective cohort study

BACKGROUND

Acute kidney injury (AKI) is common in neonates admitted to the neonatal intensive care unit (NICU). AKI is associated with increased morbidity and mortality and a greater long-term risk of chronic kidney disease.

OBJECTIVES

To study the incidence and outcome of neonatal AKI in a single Saudi Arabian center, level 2\3 NICU.

METHODS

This single-center prospective cohort study included all infants who received level II or III NICU care during 2015 (January to December). We excluded infants who survived less than 48 h after admission, had evidence of congenital renal anomalies, or had insufficient data. AKI was defined according to the Kidney Disease: Improving Global Outcomes (KDIGO) criteria. Both AKI and non-AKI neonates were prospectively followed up until NICU discharge. Outcomes studied included mortality and length of NICU stay. The results of adjusted risk analyses were expressed as relative risk (RR) with 95% confidence interval (95% CI).

RESULTS

The incidence of AKI (modified neonatal KDIGO stages) was 56% (120/214 patients). Compared with neonates without AKI, those with AKI had a lower birth weight (2202 ± 816 vs. 1570 ± 776 g; p < 0.001) and a lower gestational age (35 ± 3 vs. 32 ± 4 weeks; p < 0.001). After adjustment for potential confounders, only gestational age (RR, 4.8; 95% CI, 3-9) and perinatal depression (RR, 10; 95% CI, 2-46) were significantly associated with an increased risk of AKI. For infants with gestational age < 32 weeks, only the Clinical Risk Index for Babies (CRIB II) score was associated with an increased risk of AKI (RR, 1.9; 95% CI, 1-3). After adjustment for gestational age, AKI was significantly associated with mortality (RR, 5.4; 95% CI, 2-14), but not with the length of hospital stay (LOS) (p = 0.133). However, the AKI group had a significantly longer LOS (mean difference: 14 days; 95% CI, 5.5-23 days), and 33 patients (27.5%) with AKI were discharged with abnormally high serum creatinine levels (> 65 μmol/L).

CONCLUSION

AKI occurred in more than half of all NICU admissions, was associated with an increased risk of mortality, and had a higher incidence among smaller and sicker infants. Therefore, close monitoring of renal function during hospitalization and after discharge is warranted in such infants.

Serum cystatin C as an early predictor of acute kidney injury in preterm neonates with respiratory distress syndrome

Preterm neonates with respiratory distress syndrome (RDS) are at increased risk of acute kidney injury (AKI). Our study aimed at determining whether serum cystatin C (sCysC) on day 3 of life (D3) can early predict AKI in preterm neonates with RDS. This prospective study was conducted on 75 preterm neonates; 50 with RDS and 25 without RDS. On D3, sCysC, serum creatinine (sCr) and blood urea nitrogen (BUN) were measured and estimated glomerular filtration rate (eGFR) was calculated. sCr and BUN levels were measured again on days 5 and 7. Neonates were evaluated for development of AKI during first week of life according to the modified pediatric RIFLE (pRIFLE) criteria. Thirteen neonates with RDS developed AKI (26%).There was no significant difference between RDS and control groups with respect to sCysC. RDS neonates with AKI had significantly higher sCysC than those without AKI (1.62 ± 0.12 versus 1.16 ± 0.09 mg/l; p < .001). RDS grade III-IV neonates had significantly higher sCysC than RDS grade I-II. There was a significant positive correlation between D3 sCysC and (D5 and D7 sCr and BUN). Receiver operating characteristic (ROC) curve showed that D3 sCysC can predict AKI in preterm neonates with RDS at a cutoff point of >1.3 mg/l with sensitivity of 92.30% and specificity of 96%. We conclude that neonates with RDS are at increased risk of AKI. sCysC on day 3 of life can predict AKI earlier than Cr and eGFR.

[Monitoring of kidney injury in preterm infants]

Acute kidney injury (AKI) is a common complication in the neonatal intensive care unit that causes a high mortality of preterm infants and various chronic kidney diseases in adulthood. Preterm infants have immature development of the kidneys at birth. The kidneys continue to develop within a specific time window after birth. However, due to various factors during pregnancy and after birth, preterm infants tend to develop AKI. At present, serum creatinine and urine volume are used for the assessment of kidney injury, and their early sensitivity and specificity have attracted increasing attention. In recent years, various new biomarkers have been identified for early recognition of AKI. This article reviews the features, risk factors, renal function assessment, and prevention/treatment of AKI of preterm infants, in order to provide a reference for improving early diagnosis and treatment of AKI in preterm infants and long-term quality of life.

Cell-Free Plasma Hemoglobin and Male Gender Are Risk Factors for Acute Kidney Injury in Low Risk Children Undergoing Cardiopulmonary Bypass

OBJECTIVES

To determine the relationship between the production of cell-free plasma hemoglobin and acute kidney injury in infants and children undergoing cardiopulmonary bypass for cardiac surgery.

DESIGN

Prospective observational study.

SETTING

Twelve-bed cardiac ICU in a university-affiliated children's hospital.

PATIENTS

Children were prospectively enrolled during their preoperative outpatient appointment with the following criteria: greater than 1 month to less than 18 years old, procedures requiring cardiopulmonary bypass, no preexisting renal dysfunction.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Plasma and urine were collected at baseline (in a subset), the beginning and end of cardiopulmonary bypass, and 2 hours and 24 hours after cardiopulmonary bypass in 60 subjects. Levels of plasma hemoglobin increased during cardiopulmonary bypass and were associated (p < 0.01) with cardiopulmonary bypass duration (R = 0.22), depletion of haptoglobin at end and 24 hours after cardiopulmonary bypass (R = 0.12 and 0.15, respectively), lactate dehydrogenase levels at end cardiopulmonary bypass (R = 0.27), and change in creatinine (R = 0.12). Forty-three percent of patients developed acute kidney injury. There was an association between plasma hemoglobin level and change in creatinine that varied by age (overall [R = 0.12; p < 0.01]; in age > 2 yr [R = 0.22; p < 0.01]; and in < 2 yr [R = 0.03; p = 0.42]). Change in plasma hemoglobin and male gender were found to be risk factors for acute kidney injury (odds ratio, 1.02 and 3.78, respectively; p < 0.05).

CONCLUSIONS

Generation of plasma hemoglobin during cardiopulmonary bypass and male gender are associated with subsequent renal dysfunction in low-risk pediatric patients, especially in those older than 2 years. Further studies are needed to determine whether specific subgroups of pediatric patients undergoing cardiopulmonary bypass would benefit from potential treatments for hemolysis and plasma hemoglobin-associated renal dysfunction.

Biomarkers for Diagnosis and Prognosis of AKI in Children: One Size Does Not Fit All

Pediatric AKI has become a significant health concern due to its rising incidence and association with adverse outcomes. Because of the limitations of serum creatinine, ongoing research has evaluated multiple novel biomarkers for the early detection of AKI. Identifying biomarkers that precede changes in serum creatinine is vital, because these biomarkers provide opportunities to improve outcomes through early diagnosis and timely disease management. In this review, we discuss salient findings on 16 candidate biomarkers and their association with AKI. We explore the differences in biomarker distribution by age and discuss why adult biomarker research findings cannot be directly extrapolated to children. With future research, more consideration needs to be given to how the maturing kidney affects biomarker levels and how we interpret biomarker performance in children. A comprehensive approach using age-specific biomarker reference ranges is required to develop pediatric biomarkers and improve outcomes for children with kidney disease.

Increased urinary neutrophil gelatinase-associated lipocalin in very-low-birth-weight infants with oliguria and normal serum creatinine

BACKGROUND

In infants, oliguria is defined as a urine output of <1.5 mL/kg/h. The aim of our study was to assess the impact of oliguria on urinary neutrophil gelatinase-associated lipocalin (NGAL) and serum cystatin C (CysC) levels in very-low-birth-weight infants (VLBWIs) with a normal serum creatinine (Cr) level.

METHODS

Fifty-seven VLBWIs were enrolled in the study. Urinary NGAL, serum CysC and Cr levels and urinary NGAL/Cr ratios were measured. Infants with Apgar scores of >5 at 5 min and/or a serum Cr level of >1.5 mg/dL or those treated for patent ductus arteriosus were excluded. In case of antibiotic treatment, blood and urine samples were collected at ≥48 h after discontinuation of antibiotic treatment.

RESULTS

There was a significant difference in gestational age between infants with oliguric episodes during hospitalization and those without, but not in birth weight, perinatal or postnatal factors. Gestational age was negatively correlated with urinary NGAL and serum CysC levels and urinary NGAL/Cr ratio (p < 0.05), whereas postnatal age was negatively correlated with serum Cr level and urinary NGAL/Cr ratio (p < 0.05). Of the 117 urine and blood samples collected, 25 (21.4%) were obtained from neonates with oliguric episodes. After adjusting for gestational age and postnatal age, comparison of samples collected in infants with and without oliguric episodes revealed significant differences in the mean level of urinary NGAL and in the urinary NGAL/Cr ratio, but not in mean serum CysC or serum Cr levels. The urinary NGAL level [area under the curve (AUC) 0.886, 95% confidence interval (CI) 0.814-0.937] and urinary NGAL/Cr ratio (AUC 0.853, 95% CI 0.775-0.911) showed significantly greater discrimination for oliguria than serum CysC (AUC 0.610, 95% CI: 0.515-0.699) or serum Cr (AUC 0.747, 95%CI 0.659-0.823) levels.

CONCLUSIONS

Urinary NGAL level and urinary NGAL/Cr ratio were more sensitive markers for the presence of oliguria in VLBWIs with normal serum Cr levels than serum CysC level.

Optimising the use of medicines to reduce acute kidney injury in children and babies

The majority of medications in children are administered in an unlicensed or off-label manner. Paediatricians are obliged to prescribe using the limited evidence available. The 2007 EU regulation on the use of paediatric drugs means pharmaceutical companies are now obliged to (and receive incentives for) contributing to paediatric drug data and carrying out paediatric clinical trials. This is important, as the efficacy and adverse effect profiles of medicines vary across childhood. Additionally, there are significant age-related changes in the pharmacodynamic and pharmacokinetic activity of many drugs. This may be related to physiological (differential expressions of cytochrome P450 enzymes or variable glomerular filtration rates at different ages for example) and psychological (increasing autonomy and risk perception in teenage years) changes. Increasing numbers of children are surviving life-threatening childhood conditions due to medical advances. This means there is an increasing population who are at risk of the consequences of the long-term, early exposure to nephrotoxic agents. The kidney is an organ that is particularly vulnerable to damage as a consequence of drugs. Drug-induced acute kidney injury (AKI) episodes in children and babies are principally due to non-steroidal anti-inflammatory drugs, antibiotics or chemotherapeutic agents. The renal tubules are vulnerable to injury because of their concentrating ability and high-energy hypoxic environment. This review focuses on drug-induced AKI and the methods to minimise its effect, including general management plus the role of child-specific pharmacokinetic data, the use of pharmacogenomics and early detection of AKI using urinary biomarkers and electronic triggers.

Neonatal acute kidney injury - Severity and recovery prediction and the role of serum and urinary biomarkers

Neonatal acute kidney injury is common, in part due to incomplete renal maturation and also due to frequent exposure to risk factors for acute kidney injury such as perinatal asphyxia, extracorporeal-membrane-oxygenation, cardiac surgery, sepsis, prematurity and nephrotoxicity. However the current method by which acute kidney injury is diagnosed is sub-optimal and not universally accepted which impairs the accurate estimation of the true incidence of neonatal acute kidney injury. Serum Cystatin-C, urinary NGAL, KIM-1 and IL-18 are promising neonatal acute kidney injury biomarkers however the diagnosis of acute kidney injury remains serum creatinine/urine output-based in many studies. Emerging biomarkers which require further study in the neonatal population include netrin-1 and EGF. Increased awareness amongst clinicians of nephrotoxic medications being a modifiable risk factor for the development of neonatal acute kidney injury is imperative. The burden of chronic kidney failure following neonatal acute kidney injury is unclear and requires further study.

Non-dialytic management of acute kidney injury in newborns

Treating acute kidney injury (AKI) in newborns is often challenging due to the functional immaturity of the neonatal kidney. Because of this physiological limitation, renal replacement therapy (RRT) in this particular patient population is difficult to execute and may lead to unwanted complications. Although fluid overload and electrolyte abnormalities, as seen in neonatal AKI, are indications for RRT initiation, there is limited evidence that RRT initiated in the first year of life improves long-term outcome. The underlying cause of AKI in a newborn patient should determine the treatment strategies to restore appropriate renal function. However, our understanding of this common clinical condition remains limited, as no standardized, evidence-based definition of neonatal AKI currently exists. Non-dialytic management of AKI in these patients may restore appropriate renal function to these patients without exposure to complications often encountered with RRT.

Health term-born girls had higher levels of urine neutrophil gelatinase-associated lipocalin than boys during the first postnatal days

Neutrophil gelatinase-associated lipocalin (NGAL) is one of the most extensively examined biological markers for early prediction of acute kidney injury, but there is a lack of data on normal NGAL values in healthy term-born infants. This encouraged us to established serum and urine levels using samples collected from 38 girls and 50 boys, born at a median age of 39 weeks, during the first 48 hours after birth.

CONCLUSION

Our findings showed that urine NGAL, but not serum levels, were significantly higher in girls than in boys.

Urinary Neutrophil Gelatinase-Associated Lipocalin Levels in Neonates

BACKGROUND

Acute kidney injury (AKI) is common in preterm infants and is associated with high mortality and morbidity. New biomarkers for the early detection of AKI have been identified. Specifically, urinary neutrophil gelatinase-associated lipocalin (uNGAL) is a new and powerful biomarker for AKI and sepsis. Our study evaluated the reference range of uNGAL in healthy neonates in Taiwan.

METHODS

This study examined 24 preterm and 38 term infants without clinical complications. Urine samples were collected and the uNGAL values were measured at postnatal age (PNA) 3 days, 7 days, 14 days, and 21 days in the preterm infants and at PNA 3 days in the term infants. The uNGAL values were tested using enzyme-linked immunosorbent assay.

RESULTS

The median uNGAL values in the preterm infants at PNA 3 days, 7 days, 14 days, and 21 days were 41.52 ng/mL, 35.82 ng/mL, 43.79 ng/mL, and 30.85 ng/mL, respectively. The median value at PNA 3 days in the term infants was 88.1 ng/mL. No significant differences associated with gestational age, birth body weight, or PNA were observed among the preterm infants. However, the uNGAL values in the female term infants were higher than those in the male term infants (p = 0.003).

CONCLUSION

This study presents preliminary data on uNGAL levels in neonates in Taiwan. A large-scale study investigating the correlations between uNGAL and with gestational age, birth body weight, sex, and PNA is recommended.

Urinary Protein Creatinine Ratio in Normal Zero to Three-Day-Old Indian Neonates

INTRODUCTION

Early neonates (1-7-day-old) may develop acute kidney injury or acute renal failure due to functional (pre-renal, may be caused by decreased renal perfusion), intrinsic (renal, may be caused by acute insult), or obstructive (due to anatomic urinary tract obstruction) causes. Urinary protein estimation is important for diagnosis, follow-up and prognosis of disease. The Protein Creatinine Ratio (PCR) has been successfully used to establish proteinuria in different types of patients.

AIM

This study was undertaken to establish normal PCR range in neonates, to rule out abnormal protein excretion in sick neonates.

MATERIALS AND METHODS

A total of 37 normal early neonates of age 0-3 days were enrolled for this study. Random spot urine samples were collected in paediatric urine bags for protein and creatinine estimation.

RESULTS

The urinary PCR varied between 0.1-0.8. The range of PCR values obtained was greater in 0-1 day old infants, compared to infants older than one day. Changes in PCR values were due to variations in the creatinine excretion.

CONCLUSION

Urinary PCR values ≤ 0.8 indicate normal protein excretion. However, reference intervals of PCR should be established for narrow age groups in case of early neonates, e.g. 0-6h, 6-12h, 12-24h, 24-72h old babies.

Assessment of glomerular filtration rate in the neonate: is creatinine the best tool?

PURPOSE OF REVIEW

This article answers the question of whether creatinine is the best biomarker for monitoring neonatal glomerular filtration rate (GFR) in view of recent advances in measuring neonatal renal function.

RECENT FINDINGS

We rely largely on serum creatinine for the estimation of GFR in the newborn, even though creatinine is freely exchanged through the placenta. During the first few days of life, the serum creatinine reflects maternal renal function or the maternal creatinine. Back filtration of creatinine in preterm newborns is also a serious limitation. This review summarizes current knowledge on the prenatal and postnatal handling of creatinine as well as that of other, more novel biomarkers of GFR, such as cystatin C (CysC) and β-trace protein (BTP). Only small amounts of CysC cross the placenta, whereas BTP does not cross the placenta at all. However, BTP measurements are not widely available. Recent studies on renal volumetry are also discussed.

SUMMARY

Currently, CysC may be the most suitable marker of neonatal renal function, but its availability is still limited, it is more costly, and the best method of reporting acute kidney injury and neonatal estimated GFR remains to be established.

Drug-induced renal damage in preterm neonates: state of the art and methods for early detection

Only a small fraction of drugs widely used in neonatal intensive care units (NICU) are specifically authorized for this population. Even if unlicensed or off-label use is necessary, it is associated with increased adverse drug reactions, which must be carefully weighed against expected benefits. In particular, renal damage is frequent among preterm babies, and is considered a predisposing factor for the development of chronic kidney disease in adulthood. Apart from specific conditions affecting premature neonates (e.g. respiratory distress syndrome, perinatal asphyxia), drugs play an important role in impairing renal function because of well-known nephrotoxicity and/or interaction with renal developmental factors. From a review of the available studies on drug use in NICU patients, we identified and described the most commonly administered drugs that are correlated to renal damage. Early detection of kidney injury is becoming an essential aspects for clinicians because of the limited number of biomarkers applicable in the neonatal population. Postnatal changes of biochemical processes that influence pharmacokinetic and pharmacodynamic aspects need to be further investigated in order to better understand the mechanisms of drug toxicity in this population. The most promising strategies for dose adjustment and therapeutic schemes are discussed. The purpose of this review was to describe current knowledge on drug use among premature babies and their implication in kidney injury development, as well as to highlight available strategies for early detection of renal damage.

Prediction of urine volume soon after birth using serum cystatin C

BACKGROUND

Urine volume is an important clinical finding particularly during the early neonatal period. Oliguria is not a sign of impaired renal function but also a predictive factor for various complications and prognoses. It has been postulated that serum cystatin C (S-CysC) is a more sensitive biomarker for renal function than serum creatinine (S-Cr) in both adults and children. The objective of the current study was to investigate whether urine volume during 24 h after birth can be predicted using S-CysC.

METHODS

The subjects were 87 infants. The average gestational age was 34.7 ± 2.9 weeks and the average birth weight was 2135 ± 614 g. Blood samples were obtained from either the umbilical cord or the peripheral veins or artery of the newborn at birth. Data regarding the amount of urine volume and fluid intake during the first 24 h of life, maternal S-Cr and S-CysC levels within 48 h before delivery, and neonatal S-Cr and S-CysC levels at birth were collected from the medical records.

RESULTS

A significantly positive correlation was observed between maternal and neonatal S-Cr levels (r = 0.84, p < 0.0001) but not between maternal S-Cr levels and neonatal S-CysC levels (r = -0.069, p = 0.52). A significant negative correlation was seen between neonatal S-CysC levels and urine volume (r = -0.47, p < 0.0001).

CONCLUSION

The present study findings indicate that it may be possible to use S-CysC levels at birth to predict urine volume during the first 24 h of life.

Urinary KIM-1 in children undergoing nephrotoxic antineoplastic treatment: a prospective cohort study

BACKGROUND

Acute kidney injury (AKI) is a significant complication in patients with cancer, and nephrotoxic drugs are among the most common causes of AKI. To date, there is no study evaluating the potential role of renal biomarkers in children receiving nephrotoxic chemotherapy.

METHODS

A prospective study was conducted in children receiving methotrexate (MTX) or platinum-based treatment. Urinary kidney injury molecule-1 (KIM-1) was measured 24 h after the initiation of the chemotherapy infusion, and serum creatinine (sCr) was measured prior to drug infusion and at 24, 48, 72, and 96 h, 1 and 2 weeks, and 3 months post-initiation of treatment.

RESULTS

A total of 64 children were evaluated, of whom 21 (32.8%) developed AKI. The majority had AKI stage 1 (n = 12, 57.1%) and only one developed AKI stage 3. Median values of urinary KIM-1 were higher in patients with AKI than in those without AKI [10.7, interquartile range (IQR) 1.6-17.9 vs. 4.3 (IQR 1.3-6.1) ng/mg creatinine; p < 0.01]. Urinary KIM-1 showed good discrimination for AKI in patients receiving nephrotoxic chemotherapy, with an area under the receiver operator characteristic curve for AKI up to 1 week later of 0.82 (95% confidence interval 0.66-0.95). Even when measured only 24 h after drug infusion, urinary KIM-1 still showed good discrimination to predict persistent renal impairment three months later.

CONCLUSION

Urinary KIM-1 measured 24 h after the start of drug infusion has the potential to detect early AKI in pediatric patients treated with MTX or platinum-class drugs.