Urine Output Monitoring for the Diagnosis of Early-Onset Acute Kidney Injury in Very Preterm Infants

Risk factors for acute kidney injury in very-low birth weight newborns: a systematic review with meta-analysis

This study aims to analyze the main risk factors for acute kidney injury in the subgroup of very-low birth weight newborns, using the diagnosing criteria of the Kidney Disease Improving Global Outcomes (KDIGO) or the Acute Kidney Injury Network (AKIN). A systematic review of the literature was performed on the EMBASE® and PubMed® platforms. Studies that evaluated the risk factors for developing AKI in VLBW newborns were included. For the meta-analysis, we only included the risk factors that were associated with AKI in the univariate analysis of at least two studies. After an initial screening, abstract readings, and full-text readings, 10 articles were included in the systematic review and 9 in the meta-analysis. The incidence of AKI varied from 11.6 to 55.8%. All the studies have performed multivariate analysis, and the risk factors that appeared most were PDA and hemodynamic instability (use of inotropes or hypotension), sepsis, and invasive mechanical ventilation. After the meta-analysis, only cesarian delivery did not show an increased risk of AKI, all the other variables remained as important risk factors. Moreover, in our meta-analysis, we found a pooled increased risk of death in newborns with AKI almost 7 times.  Conclusion: AKI in VLBW has several risk factors and must be seen as a multifactorial disease. The most common risk factors were PDA, hemodynamic instability, sepsis, and invasive mechanical ventilation. What is known: • Acute kidney injury is associated with worst outcomes in all ages. It´s prevention can help diminish mortality. What is new: • A synthesis of the main risk factors associated with AKI in very low birth weight newborns.

Urine Output and Acute Kidney Injury in Neonates/Younger Children: A Prospective Study of Cardiac Surgery Patients with Indwelling Urinary Catheters

Introduction:

Pediatric acute kidney injury (AKI) is associated with significant morbidity and mortality, yet a precise definition, especially concerning urine output (UO) thresholds, remains unproven. We evaluate UO thresholds for AKI in neonates and children aged 1-24 months with indwelling urinary catheters undergoing cardiac surgery.

Methodology:

A six-year prospective cohort study (2018-2023) after cardiac surgery was conducted at a reference center in Brazil. All patients had indwelling urinary catheters up to 48 hours after surgery and at least two serum creatinine (sCr) measurements, including one before surgery. The main objective of this study was to determine the optimal UO thresholds for AKI definition and staging in neonates and younger children compared with the currently used criteria—neonatal and adult Kidney Disease Improving Global Outcomes (KDIGO) definitions. The outcome was a composite of severe AKI (stage 3 AKI diagnosed by the sCr criterion only), kidney replacement therapy, or hospital mortality.

Results:

The study included 1,024 patients: 253 in the neonatal group and 772 in the younger children group. In both groups, the lowest UO at 24 hours as a continuous variable had good discriminatory capacity for the composite outcome (AUC-ROC 0.75 [95% CI 0.70–0.81] and 0.74 [95% CI 0.68–0.79]). In neonates, the best thresholds were 3.0, 2.0 and 1.0 mL/kg/hour, and in younger children, the thresholds were 1.8, 1.0 and 0.5 mL/kg/hour. These values were used for modified AKI staging for each age group. In neonates, this modified criterion was associated with the best discriminatory capacity (AUC-ROC 0.74 [0.67-0.80] vs. 0.68 [0.61-0.75], P<0.05) and net reclassification improvement (NRI) in comparison with the neonatal KDIGO criteria. In younger children, the modified criteria had good discriminatory capacity but were comparable to the adult KDIGO criteria, and the NRI was near zero.

Conclusion:

Using indwelling catheters for UO measurements, our study reinforced that the current KDIGO criteria may require adjustments to better serve the neonate population. Additionally, using the UO criteria, we validated the adult KDIGO criteria in children aged 1-24 months.

Advocating for the inclusion of kidney health outcomes in neonatal research: best practice recommendations by the Neonatal Kidney Collaborative

Acute kidney injury (AKI) occurs in nearly 30% of sick neonates. Chronic kidney disease (CKD) can be detected in certain populations of sick neonates as early as 2 years. AKI is often part of a multisystem syndrome that negatively impacts developing organs resulting in short- and long-term pulmonary, neurodevelopmental, and cardiovascular morbidities. It is critical to incorporate kidney-related data into neonatal clinical trials in a uniform manner to better understand how neonatal AKI or CKD could affect an outcome of interest. Here, we provide expert opinion recommendations and rationales to support the inclusion of short- and long-term neonatal kidney outcomes using a tiered approach based on study design: (1) observational studies (prospective or retrospective) limited to data available within a center's standard practice, (2) observational studies involving prospective data collection where prespecified kidney outcomes are included in the design, (3) interventional studies with non-nephrotoxic agents, and (4) interventional studies with known nephrotoxic agents. We also provide recommendations for biospecimen collection to facilitate ancillary kidney specific research initiatives. This approach balances the costs of AKI and CKD ascertainment with knowledge gained. We advocate that kidney outcomes be included routinely in neonatal clinical study design. Consistent incorporation of kidney outcomes across studies will increase our knowledge of neonatal morbidity.

Initial lactate levels linked to oliguria in term neonates with perinatal asphyxia

BACKGROUND

Oliguria is a sign of impaired kidney function and has been shown to be an early predictor of adverse prognoses in patients with acute kidney injury. The relationship between urine output (UOP) and early lactate levels in neonates with perinatal asphyxia (PA) has not been extensively explored. This study aimed to investigate the link between oliguria during the first 24 h of life and early lactate levels in neonates with PA.

METHODS

The medical records of 293 term neonates with asphyxia from 9216 hospitalized newborns were retrospectively analyzed, including 127 cases designated as the oliguria group and 166 cases as controls. Peripheral arterial blood gas after PA and UOP within 24 h after birth were analyzed. Logistic regression analyses and receiver operating characteristic curve analysis were conducted.

RESULTS

Oliguria occurred in 43.34% of neonates with PA. The median UOP of the oliguria and control groups were 0.65 and 1.46 mL/kg/h, respectively. Elevated lactate levels after PA are an independent risk factor for oliguria in the following 24 h (p = 0.01; OR: 1.19; 95%CI: 1.04-1.35) and show a moderate discriminatory power for oliguria (AUC = 0.62). Using a cut off value of 8.15 mmol/L, the positive and negative predictive values and the specificity were 59.34%, 63.86%, and 78.30%, respectively.

CONCLUSION

Neonates with elevated lactate levels after PA face a risk of oliguria in the following 24 h. Based on early elevated lactate levels after resuscitation, especially ≥ 8.15 mmol/L, meticulously monitoring UOP will allow this vulnerable population to receive early, tailored fluid management and medical intervention.

Low incidence of acute kidney injury in VLBW infants with restrictive use of mechanical ventilation

BACKGROUND

We assessed the incidence of and risk factors for acute kidney injury (AKI) in very low birthweight infants (VLBW) in a center with a specific neonatal management protocol focusing on avoidance of early mechanical ventilation (MV).

METHODS

This retrospective single center analysis includes 128 infants born in 2020 with a gestational age ≥ 22 weeks who were screened for AKI using the nKDIGO criteria.

RESULTS

AKI was identified in 25/128 patients (19.5%) with eight of them (6.3%) presenting with severe AKI. Low gestational age, birthweight and 10-minute Apgar score as well as high CRIB-1 score were all associated with incidence of AKI. Forty-five percent of the infants with MV developed AKI vs. 8.9% of those without MV (p < 0.001). Early onset of MV and administration of more than 3 dosages of NSAIDs for patent duct were identified as independent risk factors for AKI in a logistic regression analysis.

CONCLUSIONS

We report a substantially lower frequency of AKI in VLBW infants as compared to previous studies, along with a very low rate of MV. A neonatal protocol focusing on avoidance of MV within the first days of life may be a key factor to decrease the risk of AKI in immature infants.

Incidence, Risk Factors, and Outcomes Associated With Recurrent Neonatal Acute Kidney Injury in the AWAKEN Study

Importance

The incidence and associated outcomes of recurrent acute kidney injury (rAKI) in neonates remain largely unknown.

Objective

To determine the incidence, risk factors, and clinical outcomes associated with rAKI in critically ill neonates.

Design, Setting, and Participants

This cohort study was a secondary analysis of the multicenter, international Assessment of Worldwide Acute Kidney Injury Epidemiology in Neonates retrospective study. Comparisons were made among neonates with no AKI, a single AKI episode (sAKI), and rAKI. All neonates younger than 14 days who were admitted between January 1 and March 31, 2014, to 24 participating level II to IV neonatal intensive care units and received intravenous fluids for at least 48 hours were considered for inclusion. Neonates with congenital heart disease requiring surgery within the first week of life, lethal chromosomal anomalies, death within 48 hours of admission, or severe congenital kidney abnormalities were excluded. Data were analyzed from May 23, 2022, to December 8, 2023.

Exposure

Recurrent AKI using the neonatal Kidney Disease: Improving Global Outcomes criteria. Determination of each rAKI required a complete return to the baseline serum creatinine level that defined the prior AKI episode.

Main Outcomes and Measures

Incidence and risk factors of rAKI and associations of rAKI with length of stay (LOS; ie, birth to hospital discharge) and mortality.

Results

The study cohort (n = 2162) included 1233 male neonates (57.0%). Gestational age distribution was less than 29 weeks for 276 neonates (12.8%), 29 to less than 36 weeks for 958 (44.3%), and 36 weeks or older for 928 (42.9%). Of 605 neonates with AKI, 133 (22.0%) developed rAKI with risk factors including younger gestational age, lower birthweight, and higher stage of initial AKI. Infants with rAKI experienced longer median LOS (no AKI, 17 [IQR, 8-34] days; sAKI, 18 [IQR, 9-45] days; rAKI, 60 [IQR, 25-109] days; P < .001). Time-varying Cox proportional hazards regression models suggest rAKI is independently associated with a lower hazard of discharge (adjusted hazard ratio, 0.7 [95% CI, 0.6-0.9]; P = .01) when compared with sAKI, but mortality did not differ between groups (adjusted hazard ratio, 1.4 [95% CI, 0.6-3.0]; P = .44).

Conclusions and Relevance

In this cohort study, neonatal rAKI was independently associated with longer LOS when compared with sAKI, suggesting that rAKI in neonates may be an important clinical distinction warranting further study and careful monitoring after an initial AKI episode.

Early recognition and prevention of acute kidney injury in hospitalised children

Acute kidney injury is common in hospitalised children and is associated with poor patient outcomes. Once acute kidney injury occurs, effective therapies to improve patient outcomes or kidney recovery are scarce. Early identification of children at risk of acute kidney injury or at an early injury stage is essential to prevent progression and mitigate complications. Paediatric acute kidney injury is under-recognised by clinicians, which is a barrier to optimisation of inpatient care and follow-up. Acute kidney injury definitions rely on functional biomarkers (ie, serum creatinine and urine output) that are inadequate, since they do not account for biological variability, analytical issues, or physiological responses to volume depletion. Improved predictive tools and diagnostic biomarkers of kidney injury are needed for earlier detection. Novel strategies, including biomarker-guided care algorithms, machine-learning methods, and electronic alerts tied to clinical decision support tools, could improve paediatric acute kidney injury care. Clinical prediction models should be studied in different paediatric populations and acute kidney injury phenotypes. Research is needed to develop and test prevention strategies for acute kidney injury in hospitalised children, including care bundles and therapeutics.

Detecting Neonatal AKI by Serum Cystatin C

SIGNIFICANCE STATEMENT

Serum creatinine is not a sensitive biomarker for neonatal AKI because it is confounded by maternal creatinine level, gestational age, and neonatal muscle mass. In this multicenter cohort study of 52,333 hospitalized Chinese neonates, the authors proposed serum cystatin C-related criteria (CyNA) for neonatal AKI. They found that cystatin C (Cys-C) is a robust and sensitive biomarker for identifying AKI in neonates who are at an elevated risk of in-hospital mortality and that CyNA detects 6.5 times as many cases as the modified Kidney Disease Improving Global Outcomes creatinine criteria. They also show that AKI can be detected using a single test of Cys-C. These findings suggest that CyNA shows promise as a powerful and easily applicable tool for detecting AKI in neonates.

BACKGROUND

Serum creatinine is not a sensitive biomarker for AKI in neonates. A better biomarker-based criterion for neonatal AKI is needed.

METHODS

In this large multicenter cohort study, we estimated the upper normal limit (UNL) and reference change value (RCV) of serum cystatin C (Cys-C) in neonates and proposed cystatin C-based criteria (CyNA) for detecting neonatal AKI using these values as the cutoffs. We assessed the association of CyNA-detected AKI with the risk of in-hospital death and compared CyNA performance versus performance of modified Kidney Disease Improving Global Outcomes (KDIGO) creatinine criteria.

RESULTS

In this study of 52,333 hospitalized neonates in China, Cys-C level did not vary with gestational age and birth weight and remained relatively stable during the neonatal period. CyNA criteria define AKI by a serum Cys-C of ≥2.2 mg/L (UNL) or an increase in Cys-C of ≥25% (RCV) during the neonatal period. Among 45,839 neonates with measurements of both Cys-C and creatinine, 4513 (9.8%) had AKI detected by CyNA only, 373 (0.8%) by KDIGO only, and 381 (0.8%) by both criteria. Compared with neonates without AKI by both criteria, neonates with AKI detected by CyNA alone had an increased risk of in-hospital mortality (hazard ratio [HR], 2.86; 95% confidence interval [95% CI], 2.02 to 4.04). Neonates with AKI detected by both criteria had an even higher risk of in-hospital mortality (HR, 4.86; 95% CI, 2.84 to 8.29).

CONCLUSIONS

Serum Cys-C is a robust and sensitive biomarker for detecting neonatal AKI. Compared with modified KDIGO creatinine criteria, CyNA is 6.5 times more sensitive in identifying neonates at elevated risk of in-hospital mortality.

Early urine output monitoring in very preterm infants to predict in-hospital neonatal outcomes: a bicentric retrospective cohort study

OBJECTIVE

To evaluate whether urine output (UO), rarely assessed in the literature, is associated with relevant neonatal outcomes in very preterm infants, and which UO threshold may be the most clinically relevant.

DESIGN

Retrospective cohort study.

SETTING

Two Level IV neonatal intensive care units.

PATIENTS

Very preterm infants born between 24^0/7 and 29^6/7 weeks of gestation documented with eight UO measurements per day between postnatal day 1 and day 7.

MAIN OUTCOME MEASURES

Composite outcome defined as death before discharge, or moderate to severe bronchopulmonary dysplasia, or severe brain lesions. The association between this outcome and UO was studied using several UO thresholds.

RESULTS

Among 532 infants studied, UO <1.0 mL/kg/hour for at least 24 consecutive hours was measured in 55/532 (10%) infants and the primary outcome was recorded in 25 patients. The association between a UO threshold <1.0 mL/kg/hour and the primary outcome was found marginally significant (crude OR 1.80, 95% CI 1.02 to 3.16, p=0.04). The primary outcome was recorded in 112/242 (46%) patients with a UO <2.0 mL/kg/hour and only 64/290 (22%) patients with a UO ≥2.0 mL/kg/hour (p<0.001). This UO threshold was found significantly associated with the primary outcome (crude OR 3.1, 95% CI 2.1 to 4.7, p<0.001), an association confirmed using a multivariate logistic regression model including baseline covariates (adjusted OR 3.7, 95% CI 2.2 to 6.4, p<0.001).

CONCLUSION

A UO <2 mL/kg/hour over 24 hours between postnatal day 1 and day 7 strongly predicts neonatal mortality or severe morbidities in very preterm infants.