Establishing a continuum of acute kidney injury - tracing AKI using data source linkage and long-term follow-up: Workgroup Statements from the 15th ADQI Consensus Conference

Acute Kidney Injury: Gaps and Opportunities for Knowledge and Growth

Acute kidney injury (AKI) occurs frequently in hospitalized patients, regardless of age or prior medical history. Increasing awareness of the epidemiologic problem of AKI has directly led to increased study of global recognition, diagnostic tools, both reactive and proactive management, and analysis of long-term sequelae. Many gaps remain, however, and in this article we highlight opportunities to add significantly to the increasing bodies of evidence surrounding AKI. Practical considerations related to initiation, prescription, anticoagulation, and monitoring are discussed. In addition, the importance of AKI follow-up evaluation, particularly for those surviving the receipt of renal replacement therapy, is highlighted as a push for global equity in the realm of critical care nephrology is broached. Addressing these gaps presents an opportunity to impact patient care directly and improve patient outcomes.

Risk of de novo proteinuria following hospitalization with acute kidney injury

BACKGROUND

Acute Kidney Injury (AKI) incidence has continued to rise and is recognized as a major risk factor for kidney disease progression and cardiovascular complications. Early recognition of factors associated with post-AKI complications is fundamental to stratifying patients that could benefit from closer follow-up and management after an episode of AKI. Recent studies have shown that proteinuria is a prevalent sequela after AKI and a strong predictor of complications post-AKI. This study aims to evaluate the frequency and timing of the development of de-novo proteinuria after an AKI episode in patients with known kidney function and no prior history of proteinuria.

METHODS

We retrospectively analyzed data from adult AKI patients with pre- and post-kidney function information between Jan 2014 and March 2019. The presence of proteinuria determined before and after index AKI encounter was based on ICD-10 code and/or urine dipstick and UPCR during the follow-up period.

RESULTS

Of 9697 admissions with AKI diagnoses between Jan 2014 and March 2019, 2120 eligible patients with at least one assessment of Scr and proteinuria before AKI index admission were included in the analysis. The median age was 64 (IQR 54-75) years, and 57% were male. 58% (n-1712) patients had stage 1 AKI, 19% (n = 567) stage 2 AKI, and 22% (n = 650) developed stage 3 AKI. De novo proteinúria was found in 62% (n = 472) of patients and was already present by 90 days post-AKI in 59% (209/354). After adjusting for age and comorbidities, severe AKI (stage 2/3 AKI) and diabetes, were independently associated with increased risk for De novo proteinuria.

CONCLUSION

Severe AKI is an independent risk factor for subsequent de novo proteinuria post-hospitalization. Further prospective studies are needed to determine whether strategies to detect AKI patients at risk of proteinuria and early therapeutics to modify proteinuria can delay the progression of kidney disease.

Real-world Health Data and Precision for the Diagnosis of Acute Kidney Injury, Acute-on-Chronic Kidney Disease, and Chronic Kidney Disease: Observational Study

Background

The criteria for the diagnosis of kidney disease outlined in the Kidney Disease: Improving Global Outcomes guidelines are based on a patient’s current, historical, and baseline data. The diagnosis of acute kidney injury, chronic kidney disease, and acute-on-chronic kidney disease requires previous measurements of creatinine, back-calculation, and the interpretation of several laboratory values over a certain period. Diagnoses may be hindered by unclear definitions of the individual creatinine baseline and rough ranges of normal values that are set without adjusting for age, ethnicity, comorbidities, and treatment. The classification of correct diagnoses and sufficient staging improves coding, data quality, reimbursement, the choice of therapeutic approach, and a patient’s outcome.

Objective

In this study, we aim to apply a data-driven approach to assign diagnoses of acute, chronic, and acute-on-chronic kidney diseases with the help of a complex rule engine.

Methods

Real-time and retrospective data from the hospital’s clinical data warehouse of inpatient and outpatient cases treated between 2014 and 2019 were used. Delta serum creatinine, baseline values, and admission and discharge data were analyzed. A Kidney Disease: Improving Global Outcomes–based SQL algorithm applied specific diagnosis-based International Classification of Diseases (ICD) codes to inpatient stays. Text mining on discharge documentation was also conducted to measure the effects on diagnosis.

Results

We show that this approach yielded an increased number of diagnoses (4491 cases in 2014 vs 11,124 cases of ICD-coded kidney disease and injury in 2019) and higher precision in documentation and coding. The percentage of unspecific ICD N19-coded diagnoses of N19 codes generated dropped from 19.71% (1544/7833) in 2016 to 4.38% (416/9501) in 2019. The percentage of specific ICD N18-coded diagnoses of N19 codes generated increased from 50.1% (3924/7833) in 2016 to 62.04% (5894/9501) in 2019.

Conclusions

Our data-driven method supports the process and reliability of diagnosis and staging and improves the quality of documentation and data. Measuring patient outcomes will be the next step in this project.

A Review on the Application and Limitations of Administrative Health Care Data for the Study of Acute Kidney Injury Epidemiology and Outcomes in Children

Administrative health care databases contain valuable patient information generated by health care encounters. These "big data" repositories have been increasingly used in epidemiological health research internationally in recent years as they are easily accessible and cost-efficient and cover large populations for long periods. Despite these beneficial characteristics, it is also important to consider the limitations that administrative health research presents, such as issues related to data incompleteness and the limited sensitivity of the variables. These barriers potentially lead to unwanted biases and pose threats to the validity of the research being conducted. In this review, we discuss the effectiveness of health administrative data in understanding the epidemiology of and outcomes after acute kidney injury (AKI) among adults and children. In addition, we describe various validation studies of AKI diagnostic or procedural codes among adults and children. These studies reveal challenges of AKI research using administrative data and the lack of this type of research in children and other subpopulations. Additional pediatric-specific validation studies of administrative health data are needed to promote higher volume and increased validity of this type of research in pediatric AKI, to elucidate the large-scale epidemiology and patient and health systems impacts of AKI in children, and to devise and monitor programs to improve clinical outcomes and process of care.

For Whom the Bell Tolls: Acute Kidney Injury and Electronic Alerts for the Pediatric Nephrologist

With the advent of the electronic medical record, automated alerts have allowed for improved recognition of patients with acute kidney injury (AKI). Pediatric patients have the opportunity to benefit from such alerts, as those with a diagnosis of AKI are at risk of developing long-term consequences including reduced renal function and hypertension. Despite extensive studies on the implementation of electronic alerts, their overall impact on clinical outcomes have been unclear. Understanding the results of these studies have helped define best practices in developing electronic alerts with the aim of improving their impact on patient care. As electronic alerts for AKI are applied to pediatric patients, identifying their strengths and limitations will allow for continued improvement in its use and efficacy.

Post-contrast acute kidney injury in a hospitalized population: short-, mid-, and long-term outcome and risk factors for adverse events

Objectives

To investigate the prognosis including major adverse kidney events within 30 days (MAKE30) and 90-day and 1-year adverse outcome in hospitalized patients with post-contrast acute kidney injury (PC-AKI) to identify high-risk factors.

Methods

This retrospective observational study included 288 PC-AKI patients selected from 277,898 patients admitted to hospitals from January 2015 to December 2015. PC-AKI was defined according to the 2018 guideline of European Society of Urogenital Radiology. Multivariable Cox regression and logistic regression analyses were used to analyze main outcome and risk factors.

Results

PC-AKI patients with AKI stage ≥ 2 had much higher incidence of MAKE30 than those with AKI stage 1 (RR = 7.027, 95% CI 4.918–10.039). Persistent renal dysfunction, heart failure, central nervous system failure, baseline eGFR < 60 mL/min/1.73 m², oliguria or anuria, blood urea nitrogen ≥ 7.14 mmol/L, respiratory failure, and shock were independent risk factors of 90-day or 1-year adverse prognosis (p < 0.05). Compared with transient renal dysfunction, PC-AKI patients with persistent renal dysfunction had a higher all-cause mortality rate (RR = 3.768, 95% CI 1.612–8.810; RR = 4.106, 95% CI 1.765–9.551) as well as combined endpoints of death, chronic kidney disease, or end-stage renal disease (OR = 3.685, 95% CI 1.628–8.340; OR = 5.209, 95% CI 1.730–15.681) within 90 days or 1 year.

Conclusions

PC-AKI is not always a transient, benign creatininopathy, but can result in adverse outcome. AKI stage is independently correlated to MAKE30 and persistent renal dysfunction may exaggerate the risk of long-term adverse events.

Key Points

• PC-AKI can result in adverse outcome such as persistent renal dysfunction, dialysis, chronic kidney disease (CKD), end-stage renal disease (ESRD), or death.

• AKI stage is independently correlated to MAKE30.

• Persistent renal dysfunction may exaggerate the risk of long-term adverse events.

Electronic supplementary material

The online version of this article (10.1007/s00330-020-06690-3) contains supplementary material, which is available to authorized users.

Acute kidney injury

Acute kidney injury (AKI) is defined by a rapid increase in serum creatinine, decrease in urine output, or both. AKI occurs in approximately 10-15% of patients admitted to hospital, while its incidence in intensive care has been reported in more than 50% of patients. Kidney dysfunction or damage can occur over a longer period or follow AKI in a continuum with acute and chronic kidney disease. Biomarkers of kidney injury or stress are new tools for risk assessment and could possibly guide therapy. AKI is not a single disease but rather a loose collection of syndromes as diverse as sepsis, cardiorenal syndrome, and urinary tract obstruction. The approach to a patient with AKI depends on the clinical context and can also vary by resource availability. Although the effectiveness of several widely applied treatments is still controversial, evidence for several interventions, especially when used together, has increased over the past decade.

A multidisciplinary consensus on dehydration: definitions, diagnostic methods and clinical implications

Background: Dehydration appears prevalent, costly and associated with adverse outcomes. We sought to generate consensus on such key issues and elucidate need for further scientific enquiry. Materials and methods: A modified Delphi process combined expert opinion and evidence appraisal. Twelve relevant experts addressed dehydration's definition, objective markers and impact on physiology and outcome. Results: Fifteen consensus statements and seven research recommendations were generated. Key findings, evidenced in detail, were that there is no universally accepted definition for dehydration; hydration assessment is complex and requires combining physiological and laboratory variables; "dehydration" and "hypovolaemia" are incorrectly used interchangeably; abnormal hydration status includes relative and/or absolute abnormalities in body water and serum/plasma osmolality (pOsm); raised pOsm usually indicates dehydration; direct measurement of pOsm is the gold standard for determining dehydration; pOsm >300 and ≤280 mOsm/kg classifies a person as hyper or hypo-osmolar; outside extremes, signs of adult dehydration are subtle and unreliable; dehydration is common in hospitals and care homes and associated with poorer outcomes. Discussion: Dehydration poses risk to public health. Dehydration is under-recognized and poorly managed in hospital and community-based care. Further research is required to improve assessment and management of dehydration and the authors have made recommendations to focus academic endeavours. Key messages Dehydration assessment is a major clinical challenge due to a complex, varying pathophysiology, non-specific clinical presentations and the lack of international consensus on definition and diagnosis. Plasma osmolality represents a valuable, objective surrogate marker of hypertonic dehydration which is underutilized in clinical practice. Dehydration is prevalent within the healthcare setting and in the community, and appears associated with increased morbidity and mortality.

Kidney Disease Awareness and Knowledge among Survivors ofAcute Kidney Injury

BACKGROUND

Acute kidney injury (AKI) survivors are at risk for chronic kidney disease, recurrent AKI, and cardiovascular disease. The transition from hospital to ambulatory care is an opportunity to reduce these sequelae by launching self-care plans through effective patient education. How well AKI survivors are informationally prepared to apply kidney-specific self-care is unknown. The purpose of this study was to identify awareness and disease-specific knowledge among AKI survivors.

METHODS

We performed a cross-sectional survey of AKI-related awareness and knowledge in 137 patients with Kidney Disease Improving Global Outcomes Stage II or III AKI near the time of hospital discharge. Patients were asked (1) "Did you experience AKI while in the hospital?" and (2) "Do you have a problem with your kidney health?" Objective knowledge of AKI was evaluated with a 15-item adapted version of the validated Kidney Knowledge Survey that included topics such as common causes, risk factors, and how AKI is diagnosed.

RESULTS

Median age was 54 (interquartile range 43-63) and 81% were white. Eighty percent of patients were unaware that they had experienced AKI and 53% were both unaware they had experienced AKI or had a "problem with their kidneys." Multivariable logistic regression identified being male and lack of nephrology consult as predictors of unawareness with ORs of 3.92 (95% CI 1.48-10.33) and 5.10 (95% CI 1.98-13.13), respectively. Less than 50% recognized nonsteroidal anti-inflammatory drugs, contrast, or phosphate-based cathartics as risk factors for AKI. Two-thirds of patients did not agree that they knew a lot about AKI and more than 80% desired more information.

CONCLUSIONS

Most patients with moderate to severe AKI are unaware of their condition, lack understanding of risk factors for recurrent AKI, and desire more information. Patient-centered communication to optimize awareness, understanding, and care will require coordinated educational strategies throughout the continuum of AKI care.

Role of renin-angiotensin system in acute kidney injury-chronic kidney disease transition

Acute kidney injury (AKI) can increase the risk of developing incident chronic kidney disease (CKD). The severity, frequency and duration of AKI are crucial predictors of poor renal outcome. A repair process after AKI can be adaptive and kidney recovers completely after a mild injury. However, severe injury will lead to a maladaptive repair, which frequently progresses to nephron loss, vascular rarefaction, chronic inflammation and fibrosis. Although different mechanisms underlying AKI-CKD transition have been extensively discussed, no definite intervention has been proved effective to block or to retard the transition until recently. In CKD, renin-angiotensin system (RAS) inhibitor has been proved effective to slow down disease progression. Furthermore, RAS needs to be highlighted again in AKI-CKD transition because recent animal studies have shown the activation of intra-renal RAS after AKI, and RAS blockade can reduce the ensuing CKD and mortality. In patients with the complete renal recovery after AKI, administration of RAS inhibitor is associated with reduced risk of subsequent CKD as well. In this article, we will demonstrate the role of RAS in AKI-CKD transition comprehensively. We will then emphasize the promising effect of RAS inhibitor on CKD prevention in patients recovering from AKI based on evidence from the bench to clinical research. All of these discussions will contribute to the establishment of reliable monitoring and therapeutic strategies for patients with functional recovery from AKI who can be most easily ignored.

Big Data and Pediatric Acute Kidney Injury: The Promise of Electronic Health Record Systems

Over the last decade, our understanding of acute kidney injury (AKI) has evolved considerably. The development of a consensus definition standardized the approach to identifying and investigating AKI in children. As a result, pediatric AKI epidemiology has been refined and the consequences of renal injury are better established. Similarly, "big data" methodologies experienced a dramatic evolution and maturation, leading the critical care community to explore potential AKI/big data synergies. One such concept with tremendous potential is electronic health record (EHR) enabled informatics. Much of the promise surrounding these approaches is due to the unique position of the EHR which sits at the intersection of data accumulation and care delivery. EHR data is generated simply via the provision of routine clinical care and should be considered "big" from the standpoint of volume, variety, and velocity as a myriad of diverse elements accumulate rapidly in real time, spontaneously generating an immense dataset. This massive dataset interfaces directly with providers which creates tremendous opportunity. AKI can be diagnosed more accurately, AKI-related care can be optimized, and subsequent outcomes can be improved. Although applying big data concepts to the EHR has proven more challenging than originally thought, we have seen much success and continue to explore its potential. In this review article, we will discuss the EHR in the context of big data concepts, describe approaches applied to date, examine the challenges surrounding optimal application, and explore future directions.

Management of post-operative acute kidney injury

Post-operative acute kidney injury (AKI) is a common complication of surgery with significant short- and long-term adverse consequences. The adoption of diagnostic criteria for AKI (RIFLE, AKIN and KDIGO) has facilitated comparison of data reported by different centres, confirming that even mild AKI is associated with excess mortality. It remains unclear whether this is caused by the kidney injury itself or whether AKI is simply a marker of underlying disease severity. There is no trial evidence to support the use of any specific therapeutic intervention in post-operative AKI. Best current treatment is, therefore, preventative by optimizing hydration and avoidance of nephrotoxins, emphasizing the importance of earlier detection and identification of individuals at high risk for AKI. In this review, we examine the latest literature on the management of post-operative AKI in adult patients, specifically the diagnosis and definition of AKI, epidemiology and pathogenesis and risk stratification in cardiac and non-cardiac surgery. We also review the latest evidence on pharmacological and non-pharmacological interventions.

Sequelae of AKI

Large epidemiologic studies in a variety of patient populations reveal increased morbidity and mortality that occur months to years after an episode of acute kidney injury (AKI). Even milder forms of AKI have increased associated morbidity and mortality. Residual confounding may account for these findings, but considering the huge number of individuals afflicted with AKI, the sequelae of AKI may be a very large public health burden. AKI may simply be a marker for increased risk, but there is increasing evidence that it is part of the causal pathway to chronic kidney disease. These studies have upended the traditional view that AKI survivors who returned to baseline, or near baseline renal function, do not suffer additional long-term consequences. Recovery of renal function after AKI, short of independence from renal replacement therapy, is yet to be clearly defined but may be of significant importance in the management of AKI survivors. The association between AKI in patients who undergo cardiac surgery and clinical outcomes is of considerable importance to clinicians, surgeons, and anesthesiologists alike and is a major focus of this review.

Novel insights into acute kidney injury-chronic kidney disease continuum and the role of renin-angiotensin system

Acute kidney injury (AKI) is an independent risk factor for chronic kidney disease (CKD). If injury is mild, a repair process can be adaptive and lead to complete renal recovery. However, severe injury will be accompanied by a maladaptive repair which usually leads to nephron loss, fibrosis, vascular rarefaction, and chronic inflammation. Although various mechanisms underlying AKI-CKD transition have been explored, no intervention has been proved effective to block the transition until very recently. A lack of consensus for monitoring renal function and defining renal recovery after AKI should be the reasons for the slow advance in the discovery of a timely pharmacologic treatment to block AKI-CKD transition. Recently, animal studies have shown the activation of renin-angiotensin system (RAS) after AKI. In patients with complete renal recovery after AKI defined as the decrease of serum creatinine level to within 0.3 mg/dL above the baseline, administration of RAS inhibitor can prevent the ensuing CKD. In this review, we will discuss the renal recovery after AKI and the mechanisms underlying AKI-CKD transition. We will then highlight the promising effect of RAS inhibitor on CKD prevention in patients with complete renal recovery from AKI based on the recent clinical evidence.

Continuous Renal Replacement Therapy: Forty-year Anniversary

In 1977 Peter Kramer performed the first CAVH (continuous arteriovenous hemofiltration) treatment in Gottingen, Germany. CAVH soon became a reliable alternative to hemo- or peritoneal dialysis in critically ill patients. The limitations of CAVH spurred new research and the discovery of new treatments such as CVVH and CVVHD (continuous veno-venous hemofiltration and continuous veno-venous hemodialysis). The alliance with industry led to development of new specialized equipment with improved accuracy and performance in delivering continuous renal replacement therapies (CRRTs). Machines and filters have progressively undergone a series of technological steps, reaching a high level of sophistication. The evolution of technology has continued, leading to the development and clinical application of new membranes, new techniques and new treatment modalities. With the progress of technology, the entire field of critical care nephrology moved forward, expanding the areas of application of extracorporeal therapies to cardiac, liver and pulmonary support. A great deal of research made extracorporeal therapies an interesting option for the treatment of sepsis and intoxication and the additional use of sorbents was explored. With the progress in understanding the pathophysiology of acute kidney injury (AKI), new guidelines were developed, driving indications, modalities of prescription, monitoring techniques and quality assurance programs. Information technology and precision medicine have recently contributed to further evolution of CRRT, with the possibility of collecting data in large databases and evaluating policies and practice patterns. This is likely to ultimately result in improved patient care. CRRTs are 40 years old today, but they are still young and full of potential for further evolution.

Leveraging Big Data and Electronic Health Records to Enhance Novel Approaches to Acute Kidney Injury Research and Care

While acute kidney injury (AKI) has been poorly defined historically, a decade of effort has culminated in a standardized, consensus definition. In parallel, electronic health records (EHRs) have been adopted with greater regularity, clinical informatics approaches have been refined, and the field of EHR-enabled care improvement and research has burgeoned. Although both fields have matured in isolation, uniting the 2 has the capacity to redefine AKI-related care and research. This article describes how the application of a consistent AKI definition to the EHR dataset can accurately and rapidly diagnose and identify AKI events. Furthermore, this electronic, automated diagnostic strategy creates the opportunity to develop predictive approaches, optimize AKI alerts, and trace AKI events across institutions, care platforms, and administrative datasets.

Identification of Major Adverse Kidney Events Within the Electronic Health Record

Acute kidney injury is common among critically ill adults and is associated with increased mortality and morbidity. The Major Adverse Kidney Events by 30 days (MAKE30) composite of death, new renal replacement therapy, or persistent renal dysfunction is recommended as a patient-centered outcome for pragmatic trials involving acute kidney injury. Accurate electronic detection of the MAKE30 endpoint using data within the electronic health record (EHR) could facilitate the use of the EHR in large-scale kidney injury research. In an observational study using prospectively collected data from 200 admissions to a single medical intensive care unit, we tested the performance of electronically-extracted data in identifying the MAKE30 composite compared to the reference standard of two-physician manual chart review. The incidence of MAKE30 on manual-review was 16 %, which included 8.5 % for in-hospital mortality, 3.5 % for new renal replacement therapy, and 8.5 % for persistent renal dysfunction. There was strong agreement between the electronic and manual assessment of MAKE30 (98.5 % agreement [95 % CI 96.5-100.0 %]; kappa 0.95 [95 % CI 0.87-1.00]; P < 0.001), with only three patients misclassified by electronic assessment. Performance of the electronic MAKE30 assessment was similar among patients with and without CKD and with and without a measured serum creatinine in the 12 months prior to hospital admission. In summary, accurately identifying the MAKE30 composite outcome using EHR data collected as a part of routine care appears feasible.