Acute Kidney Injury, Fluid Overload, and Renal Replacement Therapy Differ by Underlying Diagnosis in Neonatal Extracorporeal Support and Impact Mortality Disparately

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.

Timing of Kidney Replacement Therapy Initiation and Survival During Pediatric Extracorporeal Membrane Oxygenation: An Extracorporeal Life Support Organization Registry Study

To characterize kidney replacement therapy (KRT) and pediatric extracorporeal membrane oxygenation (ECMO) outcomes and to identify the optimal timing of KRT initiation during ECMO associated with increased survival. Observational retrospective cohort study using the Extracorporeal Life Support Organization Registry database in children (0-18 yo) on ECMO from January 1, 2016, to December 31, 2020. Of the 14,318 ECMO runs analyzed, 26% of patients received KRT during ECMO. Patients requiring KRT before ECMO had increased mortality to ECMO decannulation (29% vs. 17%, OR 1.97, P < 0.001) and to hospital discharge (58% vs. 39%, OR 2.16, P < 0.001). Patients requiring KRT during ECMO had an increased mortality to ECMO decannulation (25% vs. 15%, OR 1.85, P < 0.001) and to hospital discharge (56% vs. 34%, OR 2.47, P < 0.001). Multivariable logistic regression demonstrated that the need for KRT during ECMO was an independent predictor for mortality to ECMO decannulation (OR 1.49, P < 0.001) and to hospital discharge (OR 2.02, P < 0.001). Patients initiated on KRT between 24 and 72 hours after cannulation were more likely to survive to ECMO decannulation and showed a trend towards survival to hospital discharge as compared to those initiated before 24 hours and after 72 hours.

An update on the role of fluid overload in the prediction of outcome in acute kidney injury

Over the past two decades, our understanding of the impact of acute kidney injury, disorders of fluid balance, and their interplay have increased significantly. In recent years, the epidemiology and impact of fluid balance, including the pathologic state of fluid overload on outcomes has been studied extensively across multiple pediatric and neonatal populations. A detailed understating of fluid balance has become increasingly important as it is recognized as a target for intervention to continue to work to improve outcomes in these populations. In this review, we provide an update on the epidemiology and outcomes associated with fluid balance disorders and the development of fluid overload in children with acute kidney injury (AKI). This will include a detailed review of consensus definitions of fluid balance, fluid overload, and the methodologies to define them, impact of fluid balance on the diagnosis of AKI and the concept of fluid corrected serum creatinine. This review will also provide detailed descriptions of future directions and the changing paradigms around fluid balance and AKI in critical care nephrology, including the incorporation of the sequential utilization of risk stratification, novel biomarkers, and functional kidney tests (furosemide stress test) into research and ultimately clinical care. Finally, the review will conclude with novel methods currently under study to assess fluid balance and distribution (point of care ultrasound and bioimpedance).

Neonatal Extracorporeal Membrane Oxygenation: Associations between Continuous Renal Replacement Therapy, Thrombocytopenia, and Outcomes

INTRODUCTION

The incidence of thrombocytopenia in neonates receiving extracorporeal membrane oxygenation (ECMO) with and without concurrent continuous renal replacement therapy (CRRT) and associated complications have not been well described. The primary aims of the current study were to (1) characterize thrombocytopenia in neonates receiving ECMO (including those treated concurrently with CRRT) and (2) evaluate risk factors (including CRRT utilization) associated with severe thrombocytopenia. In a planned exploratory secondary aim, we explored the association of severe thrombocytopenia with outcomes in neonates receiving ECMO.

METHODS

We conducted a retrospective single-center chart review of neonates who received ECMO 07/01/14-03/01/20 and evaluated associations between CRRT, severe thrombocytopenia (platelet count <50,000/mm3), and outcomes (ECMO duration, length of stay, and survival).

RESULTS

Fifty-two neonates received ECMO; 35 (67%) received concurrent CRRT. Severe thrombocytopenia occurred in 27 (52%) neonates overall and in 21 (60%) neonates who received concurrent CRRT. Underlying diagnosis, ECMO mode, care unit, and moderate/severe hemolysis differed between those who did and did not receive CRRT. CRRT receivers experienced shorter hospital stays than CRRT non-receivers, but ECMO duration, length of intensive care unit (ICU) stay, and survival did not differ between groups. CRRT receipt was associated with severe thrombocytopenia. Exploratory classification and regression tree (CART) analysis suggests CRRT use, birthweight, and ICU location are all predictors of interest for severe thrombocytopenia.

CONCLUSIONS

In our cohort, CRRT use during ECMO was associated with severe thrombocytopenia, and patients who received ECMO with CRRT experienced shorter hospital stays than those who did not receive CRRT. Exploratory CART analysis suggests CRRT use, birthweight, and ICU location are all predictors for severe thrombocytopenia and warrant further investigations in larger studies.

Recurrent neonatal acute kidney injury: incidence, predictors, and outcomes in the neonatal intensive care unit

OBJECTIVE

Determine recurrent neonatal acute kidney injury (rAKI) incidence, risk factors, and associated outcomes.

STUDY DESIGN

Single-center retrospective cohort of neonates admitted to the NICU 1/1/20-6/30/21. Comparisons were made between those with no AKI, single AKI episode (sAKI), and rAKI. Multivariable linear and logistic regression models were used to assess associations between rAKI and length of mechanical ventilation (LMV), length of hospitalization stay (LOS), mortality, and hypertension (HTN) at discharge.

RESULTS

The incidence of AKI in the cohort of 869 infants was 19%: 705 (81%) no AKI, 100 (12%) sAKI, 64 (7%) rAKI. Both sAKI and rAKI were independently associated with longer LMV and LOS. sAKI was independently associated with almost 4x higher odds of mortality than rAKI.

CONCLUSION

In this single center cohort of neonates, sAKI independently predicts mortality, however rAKI is independently associated with increased LMV and LOS suggesting rAKI is clinically important and warrants further study.

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.

Managing the kidney - The role of continuous renal replacement therapy in neonatal and pediatric ECMO

Extracorporeal membrane oxygenation (ECMO) represents a lifesaving therapy utilized in in the most critically ill neonates and children with reversible cardiopulmonary failure. As a result of the severity of their critical illness these patients are among the highest risk populations for developing acute kidney injury (AKI) and disorders of fluid balance including the pathologic state of fluid overload (FO). In multiple studies AKI has been shown to occur commonly in 60-80% children treated with ECMO and is associated with adverse outcomes. In early studies evaluating ECMO in neonatal respiratory populations, the importance of fluid balance and the development of FO was recognized as an important contributor to adverse outcomes. Multiple single center studies and multicenter work have confirmed that FO occurs commonly across ECMO populations and is consistently associated with adverse outcomes. As a result of the high rates of AKI and the high rates of FO, continuous renal replacement therapy (CRRT) is increasingly utilized in neonatal and pediatric ECMO. In this state-of-the-art review, we cover the definitions, pathophysiology, incidence, and impact of AKI and FO in neonates and children supported with ECMO and summarize and appraise the evidence regarding the use of CRRT concurrently with ECMO. This review will cover the appropriate timing of this initiation, the options for providing CRRT with ECMO, overview of CRRT prescription, and the long-term implications of kidney support therapy in this population.

Synergistic association of fluid overload and acute kidney injury on outcomes in pediatric cardiac ECMO: a retrospective analysis of the KIDMO database

BACKGROUND

Acute kidney injury (AKI) and fluid overload (FO) are associated with poor outcomes in children receiving extracorporeal membrane oxygenation (ECMO). Our objective is to evaluate the impact of AKI and FO on pediatric patients receiving ECMO for cardiac pathology.

METHODS

We performed a secondary analysis of the six-center Kidney Interventions During Extracorporeal Membrane Oxygenation (KIDMO) database, including only children who underwent ECMO for cardiac pathology. AKI was defined using Kidney Disease: Improving Global Outcomes (KDIGO) creatinine criteria. FO was defined as < 10% (FO-) vs. ≥ 10% (FO +) and was evaluated at ECMO initiation, peak during ECMO, and ECMO discontinuation. Primary outcomes were mortality and length of stay (LOS).

RESULTS

Data from 191 patients were included. Non-survivors (56%) were more likely to be FO + than survivors at peak ECMO fluid status and ECMO discontinuation. There was a significant interaction between AKI and FO. In the presence of AKI, the adjusted odds of mortality for FO + was 4.79 times greater than FO- (95% CI: 1.52-15.12, p = 0.01). In the presence of FO + , the adjusted odds of mortality for AKI + was 2.7 times higher than AKI- [95%CI: 1.10-6.60; p = 0.03]. Peak FO + was associated with a 55% adjusted relative increase in LOS [95%CI: 1.07-2.26, p = 0.02].

CONCLUSIONS

The association of peak FO + with mortality is present only in the presence of AKI + . Similarly, AKI + is associated with mortality only in the presence of peak FO + . FO + was associated with LOS. Studies targeting fluid management have the potential to improve LOS and mortality outcomes. A higher resolution version of the Graphical abstract is available as Supplementary information.

Effect of a standardized fluid management algorithm on acute kidney injury and mortality in pediatric patients on extracorporeal support

Acute kidney injury (AKI), fluid overload (FO), and mortality are common in pediatric patients supported by extracorporeal membrane oxygenation (ECMO). The aim of this study is to evaluate if using a fluid management algorithm reduced AKI and mortality in children supported by ECMO. We performed a retrospective study of pediatric patients aged birth to 25 years requiring ECMO at a quaternary level children's hospital from 2007 to 2019 In October 2017, a fluid management algorithm was implemented for protocolized fluid removal after deriving a daily fluid goal using a combination of diuretics and ultrafiltration. Daily algorithm compliance was defined as ≥ 12 h on the algorithm each day. The primary and secondary outcomes were AKI and mortality, respectively, and were assessed in the entire cohort and the sub-analysis of children from the era in which the algorithm was implemented. Two hundred and ninety-nine (median age 5.3 months; IQR: 0.2, 62.3; 45% male) children required ECMO (venoarterial in 85%). The fluid algorithm was applied in 74 patients. The overall AKI rate during ECMO was 38% (26% severe-stage 2/3). Both AKI incidence and mortality were significantly lower in patients managed on the algorithm (p = 0.02 and p = 0.05). After adjusting for confounders, utilization of the algorithm was associated with lower odds of AKI (aOR: 0.40, 95%CI: 0.21, 0.76; p = 0.005) but was not associated with a reduction in mortality. In the sub-analysis, algorithm compliance of 80-100% was associated with a 54% reduction in mortality (ref: < 60% compliant; aOR:0.46, 95%CI:0.22-1.00; p = 0.05).  Conclusion: Among the entire cohort, the use of a fluid management algorithm reduced the odds of AKI. Better compliance on the algorithm was associated with lower mortality. Multicenter studies that implement systematic fluid removal may represent an opportunity for improving ECMO-related outcomes. What is Known: • Acute kidney injury and fluid overload are associated with morbidity and mortality in children supported by extracorporeal membrane oxygenation. What is New: • A systematic and protocolized approach to fluid removal in children supported by extracorporeal membrane oxygenation reduces acute kidney injury incidence. • Greater adherence to a protocolized fluid removal algorithm is associated with a reduction in mortality.

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.

Kidney support for babies: building a comprehensive and integrated neonatal kidney support therapy program

Kidney support therapy (KST), previously referred to as Renal Replacement Therapy, is utilized to treat children and adults with severe acute kidney injury (AKI), fluid overload, inborn errors of metabolism, and kidney failure. Several forms of KST are available including peritoneal dialysis (PD), intermittent hemodialysis (iHD), and continuous kidney support therapy (CKST). Traditionally, extracorporeal KST (CKST and iHD) in neonates has had unique challenges related to small patient size, lack of neonatal-specific devices, and risk of hemodynamic instability due to large extracorporeal circuit volume relative to patient total blood volume. Thus, PD has been the most commonly used modality in infants, followed by CKST and iHD. In recent years, CKST machines designed for small children and novel filters with smaller extracorporeal circuit volumes have emerged and are being used in many centers to provide neonatal KST for toxin removal and to achieve fluid and electrolyte homeostasis, increasing the options available for this unique and vulnerable group. These new treatment options create a dramatic paradigm shift with recalibration of the benefit: risk equation. Renewed focus on the infrastructure required to deliver neonatal KST safely and effectively is essential, especially in programs/units that do not traditionally provide KST to neonates. Building and implementing a neonatal KST program requires an expert multidisciplinary team with strong institutional support. In this review, we first describe the available neonatal KST modalities including newer neonatal and infant-specific platforms. Then, we describe the steps needed to develop and sustain a neonatal KST team, including recommendations for provider and nursing staff training. Finally, we describe how quality improvement initiatives can be integrated into programs.

Acute Kidney Injury and Fluid Overload in Pediatric Extracorporeal Cardio-Pulmonary Resuscitation: A Multicenter Retrospective Cohort Study

Acute kidney injury (AKI) and fluid overload (FO) are common complications of extracorporeal membrane oxygenation (ECMO). The purpose of this study was to characterize AKI and FO in children receiving extracorporeal cardiopulmonary resuscitation (eCPR). We performed a multicenter retrospective study of children who received eCPR. AKI was assessed during ECMO and FO defined as <10% [FO-] vs. ≥10% [FO+] evaluated at ECMO initiation and discontinuation. A composite exposure, defined by a four-group discrete phenotypic classification [FO-/AKI-, FO-/AKI+, FO+/AKI-, FO+/AKI+] was also evaluated. Primary outcome was mortality and hospital length of stay (LOS) among survivors. 131 patients (median age 29 days (IQR:9, 242 days); 51% men and 82% with underlying cardiac disease) were included. 45.8% survived hospital discharge. FO+ at ECMO discontinuation, but not AKI was associated with mortality [aOR=2.3; 95% CI: 1.07-4.91]. LOS for FO+ patients was twice as long as FO- patients, irrespective of AKI status [(FO+/AKI+ (60 days; IQR: 49-83) vs. FO-/AKI+ (30 days, IQR: 19-48 days); P = 0.01]. FO+ at ECMO initiation and discontinuation was associated with an adjusted 66% and 50% longer length of stay respectively. Prospective studies that target timing and strategy of fluid management, including its removal in children receiving ECPR are greatly needed.

Neonatal Acute Kidney Injury

Acute kidney injury (AKI) is a common occurrence in the neonatal intensive care unit (NICU). In recent years, our knowledge of the incidence and impact of neonatal AKI on outcomes has expanded exponentially. Neonatal AKI has been shown to be associated with adverse outcomes including increased length of mechanical ventilation, prolonged length of stay, and rise in mortality. There has also been increasing work suggesting that neonates with AKI are at higher risk of chronic kidney disease (CKD). In the past, AKI had been defined multiple ways. The utilization of the neonatal modified Kidney Disease: Improving Global Outcomes (KDIGO) criteria as the standard definition for neonatal AKI in research and clinical care has driven the advances in our understanding of neonatal AKI over the last 10 years. This definition has allowed researchers and clinicians to better understand the incidence, risk factors, and outcomes associated with neonatal AKI across populations through a multitude of single-center studies and the seminal, multicenter Assessment of Worldwide Acute Kidney Injury Epidemiology in Neonates (AWAKEN) study. As the impacts of neonatal AKI have become clear, a shift in efforts toward identifying those at highest risk, protocolizing AKI surveillance, improving prevention and diagnosis, and expanding kidney support therapy (KST) for neonates has occurred. These efforts also include improving risk stratification (identifying high risk populations, including those with nephrotoxic medication exposure) and diagnostics (novel biomarkers and diagnostic tools). Recent work has also shown that the targeted use of methylxanthines may prevent AKI in a variety of high-risk populations. One of the most exciting developments in neonatal AKI is the advancement in technology to provide KST to neonates with severe AKI. In this comprehensive review we will provide an overview of recent work and advances in the field of neonatal AKI. This will include a detailed review of (1) the definition of neonatal AKI, (2) the epidemiology, risk factors, and outcomes associated with neonatal AKI, (3) improvements in risk stratification and diagnostics, (4) mitigation and treatment, (5) advancements in the provision of KST to neonates, and (6) the incidence and risk of subsequent CKD.

Acute kidney injury in infants with congenital diaphragmatic hernia

OBJECTIVES

To assess the incidence of acute kidney injury (AKI) in infants with congenital diaphragmatic hernia (CDH), including those who had fetoscopic endoluminal tracheal occlusion (FETO), and the effect of AKI on mortality and length of stay.

STUDY DESIGN

Ten-year retrospective review of infants admitted with CDH to a tertiary perinatal centre.

RESULT

Ninety-four infants with median gestational age of 38⁺¹ weeks were included. Fifty-nine (62.8%) infants had AKI. Compared to infants without AKI, infants with AKI, had a similar incidence of mortality (p = 0.989). In survivors, AKI was not independently associated with a longer adjusted median length of stay [23 versus 15 days (p = 0.194)]. FETO was associated with an increased risk of AKI (p = 0.005), but neither the mortality nor length of stay of FETO infants who had AKI was increased.

CONCLUSION

AKI was present in the majority of infants with CDH and most common in those who had undergone FETO.

Epidemiology of Acute Kidney Injury After Neonatal Cardiac Surgery: A Report From the Multicenter Neonatal and Pediatric Heart and Renal Outcomes Network

OBJECTIVES

Cardiac surgery-associated acute kidney injury occurs commonly following congenital heart surgery and is associated with adverse outcomes. This study represents the first multicenter study of neonatal cardiac surgery-associated acute kidney injury. We aimed to describe the epidemiology, including perioperative predictors and associated outcomes of this important complication.

DESIGN

This Neonatal and Pediatric Heart and Renal Outcomes Network study is a multicenter, retrospective cohort study of consecutive neonates less than 30 days. Neonatal modification of The Kidney Disease Improving Global Outcomes criteria was used. Associations between cardiac surgery-associated acute kidney injury stage and outcomes (mortality, length of stay, and duration of mechanical ventilation) were assessed through multivariable regression.

SETTING

Twenty-two hospitals participating in Pediatric Cardiac Critical Care Consortium.

PATIENTS

Twenty-two-thousand forty neonates who underwent major cardiac surgery from September 2015 to January 2018.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Cardiac surgery-associated acute kidney injury occurred in 1,207 patients (53.8%); 983 of 1,657 in cardiopulmonary bypass patients (59.3%) and 224 of 583 in noncardiopulmonary bypass patients (38.4%). Seven-hundred two (31.3%) had maximum stage 1, 302 (13.5%) stage 2, 203 (9.1%) stage 3; prevalence of cardiac surgery-associated acute kidney injury peaked on postoperative day 1. Cardiac surgery-associated acute kidney injury rates varied greatly (27-86%) across institutions. Preoperative enteral feeding (odds ratio = 0.68; 0.52-0.9) and open sternum (odds ratio = 0.76; 0.61-0.96) were associated with less cardiac surgery-associated acute kidney injury; cardiopulmonary bypass was associated with increased cardiac surgery-associated acute kidney injury (odds ratio = 1.53; 1.01-2.32). Duration of cardiopulmonary bypass was not associated with cardiac surgery-associated acute kidney injury in the cardiopulmonary bypass cohort. Stage 3 cardiac surgery-associated acute kidney injury was independently associated with hospital mortality (odds ratio = 2.44; 1.3-4.61). No cardiac surgery-associated acute kidney injury stage was associated with duration of mechanical ventilation or length of stay.

CONCLUSIONS

Cardiac surgery-associated acute kidney injury occurs frequently after neonatal cardiac surgery in both cardiopulmonary bypass and noncardiopulmonary bypass patients. Rates vary significantly across hospitals. Only stage 3 cardiac surgery-associated acute kidney injury is associated with mortality. Cardiac surgery-associated acute kidney injury was not associated with any other outcomes. Kidney Disease Improving Global Outcomes criteria may not precisely define a clinically meaningful renal injury phenotype in this population.