Acute changes in fluid status affect the incidence, associative clinical outcomes, and urine biomarker performance in premature infants with acute kidney injury

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.

Acute Kidney Injury Defined by Fluid-Corrected Creatinine in Premature Neonates: A Secondary Analysis of the PENUT Randomized Clinical Trial

Importance

Acute kidney injury (AKI) and disordered fluid balance are common in premature neonates; a positive fluid balance dilutes serum creatinine, and a negative fluid balance concentrates serum creatinine, both of which complicate AKI diagnosis. Correcting serum creatinine for fluid balance may improve diagnosis and increase diagnostic accuracy for AKI.

Objective

To determine whether correcting serum creatinine for fluid balance would identify additional neonates with AKI and alter the association of AKI with short-term and long-term outcomes.

Design, Setting, and Participants

This study was a post hoc cohort analysis of the Preterm Erythropoietin Neuroprotection Trial (PENUT), a phase 3, randomized clinical trial of erythropoietin, conducted at 19 academic centers and 30 neonatal intensive care units in the US from December 2013 to September 2016. Participants included extremely premature neonates born at less than 28 weeks of gestation. Data analysis was conducted in December 2022.

Exposure

Diagnosis of fluid-corrected AKI during the first 14 postnatal days, calculated using fluid-corrected serum creatinine (defined as serum creatinine multiplied by fluid balance [calculated as percentage change from birth weight] divided by total body water [estimated 80% of birth weight]).

Main Outcomes and Measures

The primary outcome was invasive mechanical ventilation on postnatal day 14. Secondary outcomes included death, hospital length of stay, and severe bronchopulmonary dysplasia (BPD). Categorical variables were analyzed by proportional differences with the χ2 test or Fisher exact test. The t test and Wilcoxon rank sums test were used to compare continuous and ordinal variables, respectively. Odds ratios (ORs) and 95% CIs for the association of exposure with outcomes of interest were estimated using unconditional logistic regression models.

Results

A total of 923 premature neonates (479 boys [51.9%]; median [IQR] birth weight, 801 [668-940] g) were included, of whom 215 (23.3%) received a diagnosis of AKI using uncorrected serum creatinine. After fluid balance correction, 13 neonates with AKI were reclassified as not having fluid-corrected AKI, and 111 neonates previously without AKI were reclassified as having fluid-corrected AKI (ie, unveiled AKI). Therefore, fluid-corrected AKI was diagnosed in 313 neonates (33.9%). Neonates with unveiled AKI were similar in clinical characteristics to those with AKI whose diagnoses were made with uncorrected serum creatinine. Compared with those without AKI, neonates with unveiled AKI were more likely to require ventilation (81 neonates [75.0%] vs 254 neonates [44.3%] and have longer hospital stays (median [IQR], 102 [84-124] days vs 90 [71-110] days). In multivariable analysis, a diagnosis of fluid-corrected AKI was associated with increased odds of adverse clinical outcomes, including ventilation (adjusted OR, 2.23; 95% CI, 1.56-3.18) and severe BPD (adjusted OR, 2.05; 95% CI, 1.15-3.64).

Conclusions and Relevance

In this post hoc cohort study of premature neonates, fluid correction increased the number of premature neonates with a diagnosis of AKI and was associated with increased odds of adverse clinical outcomes, including ventilation and BPD. Failing to correct serum creatinine for fluid balance underestimates the prevalence and impact of AKI in premature neonates. Future studies should consider correcting AKI for fluid balance.

Trial Registration

ClinicalTrials.gov Identifier: NCT01378273.

Neonatal fluid overload-ignorance is no longer bliss

Excessive accumulation of fluid may result in interstitial edema and multiorgan dysfunction. Over the past few decades, the detrimental impact of fluid overload has been further defined in adult and pediatric populations. Growing evidence highlights the importance of monitoring, preventing, managing, and treating fluid overload appropriately. Translating this knowledge to neonates is difficult as they have different disease pathophysiologies, and because neonatal physiology changes rapidly postnatally in many of the organ systems (i.e., skin, kidneys, and cardiovascular, pulmonary, and gastrointestinal). Thus, evaluations of the optimal targets for fluid balance need to consider the disease state as well as the gestational and postmenstrual age of the infant. Integration of what is known about neonatal fluid overload with individual alterations in physiology is imperative in clinical management. This comprehensive review will address what is known about the epidemiology and pathophysiology of neonatal fluid overload and highlight the known knowledge gaps. Finally, we provide clinical recommendations for monitoring, prevention, and treatment of fluid overload.

Association of early dysnatremia with mortality in the neonatal intensive care unit: results from the AWAKEN study

OBJECTIVE

To determine the association of dysnatremia in the first postnatal week and risk of acute kidney injury (AKI) and mortality.

STUDY DESIGN

A secondary analysis of 1979 neonates in the AWAKEN cohort evaluated the association of dysnatremia with (1) AKI in the first postnatal week and (2) mortality, utilizing time-varying Cox proportional hazard models.

RESULT

Dysnatremia developed in 50.2% of the cohort and was not associated with AKI. Mortality was associated with hyponatremia (HR 2.15, 95% CI 1.07-4.31), hypernatremia (HR 4.23, 95% CI 2.07-8.65), and combined hypo/hypernatremia (HR 6.39, 95% CI 2.01-14.01). In stratified models by AKI-status, hypernatremia and hypo/hypernatremia increased risk of mortality in neonates without AKI.

CONCLUSION

Dysnatremia within the first postnatal week was associated with increased risk of mortality. Hypernatremia and combined hypo/hypernatremia remained significantly associated with mortality in neonates without AKI. This may reflect fluid strategies kidney injury independent of creatinine and urine-output defined AKI, and/or systemic inflammation.

Neutrophil Gelatinase-Associated Lipocalin (NGAL) in kidney injury- A systematic review

BACKGROUND

Neutrophil Gelatinase Associated Lipocalin (NGAL) is a secretory protein of neutrophils that can be found both in plasma and urine. Previous works have demonstrated a valuable marker for the early detection of acute kidney injury. In this systematic review, we aimed to assess whether NGAL could be helpful in the diagnosis and prognosis of systemic diseases with kidney involvement.

METHODS

MEDLINE, PubMed, and EMBASE databases were searched for NGAL, described as a human biomarker for diseases (total: 1690). Specifically, included studies describing the use of NGAL for determining kidney injury outcomes and other conditions associated with kidney dysfunction, including cardiovascular diseases, cardiac surgery, and critically ill systemic disorders.

RESULTS

A total of 24 validated studies were included in the systemic review after applying the exclusion criteria. In all these studies, NGAL appeared to have a predictive value irrespective of age, from newborn to 78 years. The results indicate that NGAL levels can accurately predict the outcome and severity of acute kidney injury occur in several disease processes, including contrast-induced AKI during cardiac surgery, kidney transplant rejection, chronic heart failure, and systemic inflammation in critically ill patients, even though the significance of NGAL is highly variable across studies. Very high plasma NGAL levels were observed in the patients before the acute rejection of the kidney, indicating the prognostic potential of the NGAL. Specifically, the assays conducted before 72 hrs provided a significant predictive value.

CONCLUSION

Urinary and serum NGAL appears to be an independent predictor of not only kidney complications but also cardiovascular and liver-related diseases. The kidney is also involved in pathogenesis.

The Use of Renal Biomarkers in Pediatric Cardiac Patients With Acute Kidney Injury

Acute kidney injury (AKI) is a common and serious condition that occurs in approximately 30% to 50% of pediatric patients that undergo cardiac surgery. Currently used parameters to measure kidney function (serum creatinine and urine output) are often unreliable and delay the prediction of AKI, despite their adoption into clinical guidelines. Emerging evidence suggests that biomarkers such as neutrophil gelatinase-associated lipocalin, cystatin C, interleukin-18, kidney injury molecule 1, and liver-type fatty acid– binding protein may be useful in the identification and location of pediatric renal injury. Ontogeny-related changes in tubular function and nephrogenesis result in reference values that differ based on age and sex. In addition, changes in endogenous concentrations may result from factors such as cardiopulmonary bypass. The use of urine samples to measure renal biomarkers offers a significant advantage compared with routine blood sampling, especially in the neonatal patient population. Future research is warranted to determine age-dependent changes in AKI biomarkers and the relationship with pharmacokinetic clearance of commonly used medications in the postoperative cardiac patient.

Renal Oxygenation Measured by Near-Infrared Spectroscopy in Neonates

BACKGROUND

Acute kidney injury (AKI) affects approximately 30% of infants admitted to the neonatal intensive care unit (NICU), and increases mortality risk by 50%. Current diagnostic criteria (serum creatinine rise with oliguria) cannot detect early-onset AKI, as up to 50% of nephron damage may occur by the time these abnormalities present. Once AKI is established, clinical management is often ineffective; therefore, prevention is key. Near-infrared spectroscopy (NIRS) offers a feasible, noninvasive approach to continuously monitor renal oxygenation trends over time, serving as a surrogate marker for renal perfusion.

PURPOSE

To provide an overview of NIRS principles for measuring renal oxygenation, and to describe current evidence of how this technology is being used among infants admitted to the NICU relative to the prediction and identification of AKI.

METHODS

A comprehensive search of PubMed and CINHAL focused on renal NIRS studies in NICU preterm and term infants was conducted.

RESULTS

Findings from 34 studies were included. In term infants, reduced renal oxygenation correlated to invasive SvO2 monitoring, predicted survivability and AKI. In preterm infants, reduced renal oxygenation was associated with AKI in one study, yet contrasting findings were reported in those with patent ductus arteriosus, including those who received prostaglandin inhibitors. Normative data in all infants were sparse.

IMPLICATIONS FOR PRACTICE

Renal NIRS may offer a noninvasive measurement of kidney hypoperfusion that may precede conventional diagnostic measures.

IMPLICATIONS FOR RESEARCH

Normative data are lacking, the threshold for renal ischemia is not defined, and consensus guiding clinical treatment based on NIRS data is nonexistent.

Patterns of Urinary Neutrophil Gelatinase-Associated Lipocalin and Acute Kidney Injury in Neonates Receiving Cardiopulmonary Bypass

Elevated urinary neutrophil gelatinase-associated lipocalin (uNGAL) predicts acute kidney injury (AKI) in children following cardiopulmonary bypass (CPB) during cardiac surgery, but little is known about uNGAL’s predictive ability in neonates in this setting. We sought to determine the relationship between AKI and post-CPB uNGAL in neonates in the first 72 post-operative hours. Methods: Urine samples for uNGAL analysis were collected at preoperative baseline and serially post-operatively from 76 neonates undergoing CPB. Mixed-effects regression models and logistic models assessed associations between uNGAL and AKI (controlling for sex, gestational age, CPB time, surgical complexity, and age at surgery). Receiver-operator curves were applied to define optimal uNGAL cut-off values for AKI diagnosis. Results: Between 0 and 4 h post-operatively, uNGAL values did not differ between neonates with and without AKI. After 4 h until 16 h post-operatively, significant time-wise separation occurred between uNGAL values of neonates with AKI and those without AKI. Odds ratios at each time point significantly exceeded unity, peaking at 10 h post-operatively (3.48 (1.58, 8.71)). Between 4 and 16 h post-operatively, uNGAL discriminated AKI from no-AKI, with a sensitivity of 0.63 (0.49, 0.75) and a specificity of 0.68 (0.62, 0.74) at a cut-off value of 100 ng/mL. Conclusion: After 4 h until 16 h post-operatively, elevated uNGAL is associated with AKI in neonates receiving CPB during cardiac surgery; however, this relationship is more complex than in older children.

Tubular and Glomerular Biomarkers of Acute Kidney Injury in Newborns

BACKGROUND

Acute Kidney Injury (AKI) is a sudden decrease in kidney function. In the early period, the highest percentage of AKI occurs among newborns hospitalized in the neonatal intensive care units, especially premature neonates. The prognosis of AKI depends on the type and severity of the cause of an injury, the accuracy and the time of diagnosis and treatment. The concentration of serum creatinine is still the main diagnostic test, although it changes in the course of AKI later than glomerular filtration rate GFR. In addition, the reliability of the determination of creatinine level is limited because it depends on many factors. New studies have presented other, more useful laboratory markers of renal function that can be measured in serum and/or in urine.

OBJECTIVE

The aim of the work was to present the latest data about tubular and glomerular biomarkers of acute kidney injury in newborns.

METHODS

We undertook a structured search of bibliographic databases for peer-reviewed research literature by using focused review topics. According to the conceptual framework, the main idea of research literature has been summarized and presented in this study.

RESULTS

The concentrations of some novel biomarkers are higher in serum and/or urine of term and preterm newborns with AKI, especially in the course of perinatal asphyxia.

CONCLUSION

In this systematic review of the literature, we have highlighted the usefulness of biomarkers in predicting tubular and/or glomerular injury in newborns. However, novel biomarkers need to prove their clinical applicability, accuracy, and cost-effectiveness prior to their implementation in clinical practice.

Continuous Renal Replacement Therapy in Preterm Infants

PURPOSE

Despite the increasing use of continuous renal replacement therapy (CRRT) in the neonatal intensive care unit (NICU), few studies have investigated its use in preterm infants. This study evaluated the prognosis of preterm infants after CRRT and identified risk factors of mortality after CRRT.

MATERIALS AND METHODS

A retrospective review was performed in 33 preterm infants who underwent CRRT at the NICU of Samsung Medical Center between 2008 and 2017. Data of the demographic characteristics, predisposing morbidity, cardiopulmonary function, and CRRT were collected and compared between surviving and non-surviving preterm infants treated with CRRT. Univariable and multivariable analyses were performed to identify factors affecting mortality.

RESULTS

Compared with the survivors, the non-survivors showed younger gestational age (29.3 vs. 33.6 weeks), lower birth weight (1359 vs. 2174 g), and lower Apgar scores at 1 minute (4.4 vs. 6.6) and 5 minutes (6.5 vs. 8.6). At the initiation of CRRT, the non-survivors showed a higher incidence of inotropic use (93% vs. 40%, p=0.017) and fluid overload (16.8% vs. 4.0%, p=0.031). Multivariable analysis revealed that fluid overload >10% at CRRT initiation was the primary determinant of mortality after CRRT in premature infants, with an adjusted odds ratio of 14.6 and a 95% confidence interval of 1.10-211.29.

CONCLUSION

Our data suggest that the degree of immaturity, cardiopulmonary instability, and fluid overload affect the prognosis of preterm infants after CRRT. Preventing fluid overload and earlier initiation of CRRT may improve treatment outcomes.

Optimizing the AKI definition during first postnatal week using Assessment of Worldwide Acute Kidney Injury Epidemiology in Neonates (AWAKEN) cohort

BACKGROUND

Neonates with serum creatinine (SCr) rise ≥0.3 mg/dL and/or ≥50% SCr rise are more likely to die, even when controlling for confounders. These thresholds have not been tested in newborns. We hypothesized that different gestational age (GA) groups require different SCr thresholds.

METHODS

Neonates in Assessment of Worldwide Acute Kidney Epidemiology in Neonates (AWAKEN) with ≥1 SCr on postnatal days 1-2 and ≥1 SCr on postnatal days 3-8 were assessed. We compared the mortality predictability of SCr absolute (≥0.3 mg/dL) vs percent (≥50%) rise. Next, we determine usefulness of combining absolute with percent rise. Finally, we determined the optimal absolute, percent, and maximum SCr thresholds that provide the highest mortality area under curve (AUC) and specificity for different GA groups.

RESULTS

The ≥0.3 mg/dL rise outperformed ≥50% SCr rise. Addition of percent rise did not improve mortality predictability. The optimal SCr thresholds to predict AUC and specificity were ≥0.3 and ≥0.6 mg/dL for ≤29 weeks GA, and ≥0.1 and ≥0.3 mg/dL for >29 week GA. The maximum SCr value provides great specificity.

CONCLUSION

Unique SCr rise cutoffs for different GA improves outcome prediction. Percent SCr rise does not add value to the neonatal AKI definition.

Association between Furosemide Exposure and Patent Ductus Arteriosus in Hospitalized Infants of Very Low Birth Weight

OBJECTIVE

To evaluate the association between furosemide exposure and patent ductus arteriosus (PDA) in a large, contemporary cohort of hospitalized infants with very low birth weight (VLBW).

STUDY DESIGN

Using the Pediatrix Medical Group Clinical Data Warehouse, we identified all inborn infants of VLBW <37 weeks of gestation discharged from the neonatal intensive care unit after the first postnatal week from 2011 to 2015. We defined PDA as any medical (ibuprofen or indomethacin) or surgical PDA therapy. We collected data up to the day of PDA treatment or postnatal day 18 for infants not diagnosed with PDA. We performed multivariable logistic regression to evaluate the association between PDA and exposure to furosemide.

RESULTS

We included 43 576 infants from 337 neonatal intensive care units, of whom 6675 (15%) underwent PDA treatment. Infants with PDA were more premature and more often exposed to mechanical ventilation and inotropes. Furosemide was prescribed to 4055 (9%) infants. On multivariable regression, exposure to furosemide was associated with decreased odds of PDA treatment (OR 0.72; 95% CI 0.65-0.79). Increasing percentage of days with furosemide exposure was not associated with PDA treatment (OR 1.01; 95% CI 0.97-1.06).

CONCLUSIONS

Furosemide exposure was not associated with increased odds of PDA treatment in hospitalized infants of VLBW. Further studies are needed to characterize the efficacy and safety of furosemide in premature infants.

Urinary Biomarkers to Predict Neonatal Acute Kidney Injury: A Review of the Science

Acute kidney injury (AKI) occurs in approximately 30% of all infants hospitalized in the neonatal intensive care unit. About 40% of very low-birth-weight infants develop AKI, with an estimated mortality rate of 50% to 80%. Very low-birth-weight survivors have twice the risk of developing chronic renal disease later in life compared with their term counterparts. Current diagnostic modalities for AKI include serum creatinine and urine output; however, recent studies suggest that these measures are imprecise, as they may not change until 25% to 50% of renal function is lost. Urinary biomarkers may more accurately identify infants at risk for early AKI development. The purpose of this review is to discuss current research findings related to neonatal AKI risk factors, provide an overview of short- and long-term outcomes, describe innovative diagnostic approaches, and identify future research direction needed to improve prediction and intervention strategies associated with renal impairment.

Renal injury in neonates: use of "omics" for developing precision medicine in neonatology

Preterm birth is associated with increased risks of morbidity and mortality along with increased healthcare costs. Advances in medicine have enhanced survival for preterm infants but the overall incidence of major morbidities has changed very little. Abnormal renal development is an important consequence of premature birth. Acute kidney injury (AKI) in the neonatal period is multifactorial and may increase lifetime risk of chronic kidney disease.Traditional biomarkers in newborns suffer from considerable confounders, limiting their use for early identification of AKI. There is a need to develop novel biomarkers that can identify, in real time, the evolution of renal dysfunction in an early diagnostic, monitoring and prognostic fashion. Use of "omics", particularly metabolomics, may provide valuable information regarding functional pathways underlying AKI and prediction of clinical outcomes.The emerging knowledge generated by the application of "omics" (genomics, proteomics, metabolomics) in neonatology provides new insights that can help to identify markers of early diagnosis, disease progression, and identify new therapeutic targets. Additionally, omics will have major implications in the field of personalized healthcare in the future. Here, we will review the current knowledge of different omics technologies in neonatal-perinatal medicine including biomarker discovery, defining as yet unrecognized biologic therapeutic targets, and linking of omics to relevant standard indices and long-term outcomes.