Acute kidney injury: controversies revisited

Acute Kidney Injury: Medical Causes and Pathogenesis

Acute kidney injury (AKI) is a common clinical syndrome characterized by a sudden decline in or loss of kidney function. AKI is not only associated with substantial morbidity and mortality but also with increased risk of chronic kidney disease (CKD). AKI is classically defined and staged based on serum creatinine concentration and urine output rates. The etiology of AKI is conceptually classified into three general categories: prerenal, intrarenal, and postrenal. Although this classification may be useful for establishing a differential diagnosis, AKI has mostly multifactorial, and pathophysiologic features that can be divided into different categories. Acute tubular necrosis, caused by either ischemia or nephrotoxicity, is common in the setting of AKI. The timely and accurate identification of AKI and a better understanding of the pathophysiological mechanisms that cause kidney dysfunction are essential. In this review, we consider various medical causes of AKI and summarize the most recent updates in the pathogenesis of AKI.

Advances in the study of subclinical AKI biomarkers

Acute kidney injury (AKI) is a prevalent and serious illness in all clinical departments, with a high morbidity and death rate, particularly in intensive care units, where prevention and treatment are crucial. As a result, active prevention, early detection, and timely intervention for acute kidney injury are critical. The current diagnostic criteria for acute kidney injury are an increase in serum creatinine concentration and/or a decrease in urine output, although creatinine and urine output merely reflect changes in kidney function, and AKI suggests injury or damage, but not necessarily dysfunction. The human kidney plays a crucial functional reserve role, and dysfunction is only visible when more than half of the renal mass is impaired. Tubular damage markers can be used to detect AKI before filtration function is lost, and new biomarkers have shown a new subset of AKI patients known as “subclinical AKI.” Furthermore, creatinine and urine volume are only marginally effective for detecting subclinical AKI. As a result, the search for new biomarkers not only identifies deterioration of renal function but also allows for the early detection of structural kidney damage. Several biomarkers have been identified and validated. This study discusses some of the most promising novel biomarkers of AKI, including CysC, NGAL, KIM-1, lL-18, L-FABP, IGFBP7, TIMP-2, Clusterin, and Penkid. We examine their performance in the diagnosis of subclinical AKI, limitations, and future clinical practice directions.

Risk Factors Associated with 30-day Mortality in Patients with Postoperative Acute Kidney Injury Who Underwent Continuous Renal Replacement Therapy in the Intensive Care Unit

Purpose: To evaluate the risk factors associated with 30-day mortality in patients with postoperative acute kidney injury who underwent continuous renal replacement therapy (CRRT).Methods: Retrospective analysis of the medical charts of patients with postoperative acute kidney injury who underwent CRRT in the intensive care unit between April 2012 and May 2019 was conducted.Results: There were 71 patients whose average age was 64.8 years, and average Acute Physiology and Chronic Health Evaluation 2 score was 26.2. There were 37 patients who had non-trauma emergency surgery, 16 who required trauma surgery, and 18 who had elective major surgery. In most patients, CRRT was started based on Stage 3 Acute Kidney Injury Network criteria, and the mean creatinine level at the time of CRRT initiation (3.62 mg/dL). The median period from surgery to CRRT was 3 days, and the median CRRT application was 4 days. Forty-seven patients died within 30 days of receiving CRRT. Age, elective major surgery, creatinine level on initiation of CRRT, use of norepinephrine upon the initiation of CRRT, and average daily fluid balance/body weight for 3 days following the initiation of CRRT were associated with increasing 30-day mortality in univariate analysis. In multivariate analysis, age, major elective surgery, and norepinephrine use upon initiation of CRRT were identified as independent risk factors for 30-day mortality.Conclusion: Surgical patients who underwent CRRT postoperatively had a poor prognosis. The risk of death in elderly patients who have undergone major elective surgery, or are receiving norepinephrine upon initiation of CRRT should be considered.

External validation of the Madrid Acute Kidney Injury Prediction Score

Background

The Madrid Acute Kidney Injury Prediction Score (MAKIPS) is a recently described tool capable of performing automatic calculations of the risk of hospital-acquired acute kidney injury (HA-AKI) using data from from electronic clinical records that could be easily implemented in clinical practice. However, to date, it has not been externally validated. The aim of our study was to perform an external validation of the MAKIPS in a hospital with different characteristics and variable case mix.

Methods

This external validation cohort study of the MAKIPS was conducted in patients admitted to a single tertiary hospital between April 2018 and September 2019. Performance was assessed by discrimination using the area under the receiver operating characteristics curve and calibration plots.

Results

A total of 5.3% of the external validation cohort had HA-AKI. When compared with the MAKIPS cohort, the validation cohort showed a higher percentage of men as well as a higher prevalence of diabetes, hypertension, cardiovascular disease, cerebrovascular disease, anaemia, congestive heart failure, chronic pulmonary disease, connective tissue diseases and renal disease, whereas the prevalence of peptic ulcer disease, liver disease, malignancy, metastatic solid tumours and acquired immune deficiency syndrome was significantly lower. In the validation cohort, the MAKIPS showed an area under the curve of 0.798 (95% confidence interval 0.788–0.809). Calibration plots showed that there was a tendency for the MAKIPS to overestimate the risk of HA-AKI at probability rates ˂0.19 and to underestimate at probability rates between 0.22 and 0.67.

Conclusions

The MAKIPS can be a useful tool, using data that are easily obtainable from electronic records, to predict the risk of HA-AKI in hospitals with different case mix characteristics.

Peritoneal dialysis: Status report in South and South East Asia

BACKGROUND

Peritoneal dialysis (PD) as a modality of kidney replacement therapy (KRT) is largely underutilized globally. We analyzed PD utilization, impact of economic status, projected growth and impact of state policy(s) on PD growth in South Asia and Southeast Asia (SA&SEA) region.

METHODS

The National Nephrology Societies of the region responded to a questionnaire on KRT practices. The responses were based on the latest registry data, acceptable community-based studies and societal perceptions. The representative countries were divided into high income and higher-middle income (HI & HMI) and low income and lower-middle income (LI & LMI) groups.

RESULTS

Data provided by 15 countries showed almost similar percentage of GDP as health expenditure (4%-7%). But there was a significant difference in per capita income (HI & HMI -US$ 28 129 vs. LI & LMI - US$ 1710.2) between the groups. Even after having no significant difference in monthly cost of haemodialysis (HD) and PD in LI & LMI countries, they have poorer PD utilization as compared to HI & HMI countries (3.4% vs. 10.1%); the reason being lack of formal training/incentives and time constraints for the nephrologist while lack of reimbursement and poor general awareness of modalities has been a snag for the patients. The region expects ≥10% PD growth in the near future. Hong Kong and Thailand with 'PD first' policy have the highest PD utilization.

CONCLUSION

Important deterrents to PD underutilization were lack of PD centric policies, lackadaisical patient/physician's attitude, lack of structured patient awareness programs, formal training programs and affordability.

Development and Validation of a Model to Predict Severe Hospital-Acquired Acute Kidney Injury in Non-Critically Ill Patients

BACKGROUND

The current models developed to predict hospital-acquired AKI (HA-AKI) in non-critically ill fail to identify the patients at risk of severe HA-AKI stage 3.

OBJECTIVE

To develop and externally validate a model to predict the individual probability of developing HA-AKI stage 3 through the integration of electronic health databases.

METHODS

Study set: 165,893 non-critically ill hospitalized patients. Using stepwise logistic regression analyses, including demography, chronic comorbidities, and exposure to risk factors prior to AKI detection, we developed a multivariate model to predict HA-AKI stage 3. This model was then externally validated in 43,569 non-critical patients admitted to the validation center.

RESULTS

The incidence of HA-AKI stage 3 in the study set was 0.6%. Among chronic comorbidities, the highest odds ratios were conferred by ischemic heart disease, ischemic cerebrovascular disease, chronic congestive heart failure, chronic obstructive pulmonary disease, chronic kidney disease and liver disease. Among acute complications, the highest odd ratios were associated with acute respiratory failure, major surgery and exposure to nephrotoxic drugs. The model showed an AUC of 0.906 (95% CI 0.904 to 0.908), a sensitivity of 89.1 (95% CI 87.0-91.0) and a specificity of 80.5 (95% CI 80.2-80.7) to predict HA-AKI stage 3, but tended to overestimate the risk at low-risk categories with an adequate goodness-of-fit for all risk categories (Chi2: 16.4, p: 0.034). In the validation set, incidence of HA-AKI stage 3 was 0.62%. The model showed an AUC of 0.861 (95% CI 0.859-0.863), a sensitivity of 83.0 (95% CI 80.5-85.3) and a specificity of 76.5 (95% CI 76.2-76.8) to predict HA-AKI stage 3 with an adequate goodness of fit for all risk categories (Chi2: 15.42, p: 0.052).

CONCLUSIONS

Our study provides a model that can be used in clinical practice to obtain an accurate dynamic assessment of the individual risk of HA-AKI stage 3 along the hospital stay period in non-critically ill patients.

Co-orchestration of acute kidney injury and non-kidney organ failures in critically ill patients with cirrhosis

BACKGROUND & AIMS

Little is known on the course of acute kidney injury (AKI) and its relation to non-kidney organ failures and mortality in critically ill patients with cirrhosis (CICs).

METHODS

We conducted a large prospective, single-centre, observational study in which CICs were followed up daily, during the first 7 days of intensive care, collecting prespecified criteria for AKI, extrarenal extrahepatic organ failures (ERH-OFs) and systemic inflammatory response syndrome (SIRS).

RESULTS

A total of 291 patients admitted to ICU were enrolled; 231 (79.4%) had at least one ERH-OFs, 168 (58%) had AKI at presentation, and 145 (49.8%) died by 28 days. At day seven relative to baseline, 151 (51.8%) patients had progressive or persistent AKI, while the rest remained free of AKI or had AKI improvement. The 28-day mortality rate was higher among patients with progressive/persistent AKI (74.2% vs 23.5%; P < .001) or maximum stage 3 of AKI in the first week. Two-level mixed logistic regression modelling identified independent baseline risk factors for progressive/persistent AKI, including 3 to 4 SIRS criteria, infections due to multidrug-resistant bacteria (MDR), elevated serum bilirubin, and number of ERH-OFs. Follow-up risk factors included increases in bilirubin and chloride levels, and new development of 2 or 3 ERH-OFs.

CONCLUSIONS

Our results show that among CICs admitted to the ICU, the stage and course of AKI in the first week determines outcomes. Strategies combating MDR infections, multiorgan failure, liver failure and intense systemic inflammation could prevent AKI progression or persistence in CICs.

Association between Urinary Potassium Excretion and Acute Kidney Injury in Critically Ill Patients

Introduction

Acute kidney injury (AKI) is defined in terms of serum creatinine (SrCrt) and urine output (UO). AKI occurs in 25% of critically ill patients, which increases the risk of morbidity and mortality. Early diagnosis of AKI is challenging, as utility of biomarkers is limited. This study is the first of its kind to estimate urinary potassium (UrK) excretion and its association with AKI in an Indian intensive care unit (ICU).

Aims and objectives

To study the association between UrK excretion and its ability to predict AKI in ICU patients.

Material and methods

During this prospective observational study, the patient's urinary indices and renal function tests were measured on day 1 of the ICU admission. UrK excretion and creatinine clearance (CrCl) were calculated from a 2-hour morning urine sample. Association between 2-hour UrK excretion and calculated CrCl and their ability to predict AKI in the subsequent 7 days was evaluated by Kidney Disease Improving Global Outcome (KDIGO)-AKI grading.

Results

Hundred patients admitted to ICU with a mean age of 53.59 ± 15.8 years were studied. The mean UrK excretion of 4.39 ± 2.52 was correlated linearly with CrCl and has a better prediction to AKI with the area under the receiver-operating characteristic curve value of 0.809 (CI 0.719-0.899), with a significant p-value (p <0.05). UrK excretion value of 3.49 on day 1 of ICU admission had 87% sensitivity and 74% specificity in predicting AKI. Thirty-one (31%) developed AKI, of which seven (22.58%) required renal replacement therapy (RRT), with 19% of all-cause mortality.

Conclusion

Diagnosis of AKI with traditional methods is not promising. UrK excretion correlates well with CrCl, which can be considered as the simplest accessible marker for predicting AKI in ICUs.

How to cite this article

Kumar NS, Kumar GN, Misra KC, Rao M, Chitithoti S, Prakash SY. Association between Urinary Potassium Excretion and Acute Kidney Injury in Critically Ill Patients. Indian J Crit Care Med 2021;25(7):768-772.

Urinary Biochemistry in the Diagnosis of Acute Kidney Injury

Acute kidney injury (AKI) is a common complication, impacting short- and long-term patient outcomes. Although the application of the classification systems for AKI has improved diagnosis, early clinical recognition of AKI is still challenging, as increments in serum creatinine may be late and low urine output is not always present. The role of urinary biochemistry has remained unclear, especially in critically ill patients. Differentiating between a transient and persistent acute kidney injury is of great need in clinical practice, and despite studies questioning their application in clinical practice, biochemistry indices continue to be used while we wait for a novel early injury biomarker. An ideal marker would provide more detailed information about the type, intensity, and location of the injury. In this review, we will discuss factors affecting the fractional excretion of sodium (FeNa) and fractional excretion of urea (FeU). We believe that the frequent assessment of urinary biochemistry and microscopy can be useful in evaluating the likelihood of AKI reversibility. The availability of early injury biomarkers could help guide clinical interventions.

Lipocalin 2 enhances mesenchymal stem cell-based cell therapy in acute kidney injury rat model

Acute kidney injury (AKI) is one of the most common health-threatening diseases in the world. There is still no effective medical treatment for AKI. Recently, Mesenchymal stem cell (MSC)-based therapy has been proposed for treatment of AKI. However, the microenvironment of damaged kidney tissue is not favorable for survival of MSCs which would be used for therapeutic intervention. In this study, we genetically manipulated MSCs to up-regulate lipocalin-2 (Lcn2) and investigated whether the engineered MSCs (MSC-Lcn2) could improve cisplatin-induced AKI in a rat model. Our results revealed that up-regulation of Lcn2 in MSCs efficiently enhanced renal function. MSC Lcn2 up-regulates expression of HGF, IGF, FGF and VEGF growth factors. In addition, they reduced molecular biomarkers of kidney injury such as KIM-1 and Cystatin C, while increased the markers of proximal tubular epithelium such as AQP-1 and CK18 following cisplatin-induced AKI. Overall, here we over-expressed Lcn2, a well-known cytoprotective factor against acute ischemic renal injury, in MSCs. This not only potentiated beneficial roles of MSCs for cell therapy purposes but also suggested a new modality for treatment of AKI.

The potential use of biomarkers in predicting contrast-induced acute kidney injury

Contrast-induced acute kidney injury (CI-AKI) is a problem associated with the use of iodinated contrast media, causing kidney dysfunction in patients with preexisting renal failure. It accounts for 12% of all hospital-acquired kidney failure and increases the length of hospitalization, a situation that is worsening with increasing numbers of patients with comorbidities, including those requiring cardiovascular interventional procedures. So far, its diagnosis has relied upon the rise in creatinine levels, which is a late marker of kidney damage and is believed to be inadequate. Therefore, there is an urgent need for biomarkers that can detect CI-AKI sooner and more reliably. In recent years, many new biomarkers have been characterized for AKI, and these are discussed particularly with their use in known CI-AKI models and studies and include neutrophil gelatinase-associated lipocalin, cystatin C (Cys-C), kidney injury molecule-1, interleukin-18, N-acetyl-β-d-glucosaminidase, and L-type fatty acid-binding protein (L-FABP). The potential of miRNA and metabolomic technology is also mentioned. Early detection of CI-AKI may lead to early intervention and therefore improve patient outcome, and in future any one or a combination of several of these markers together with development in technology for their analysis may prove effective in this respect.

Acute peritoneal dialysis in a Jehovah's Witness post laparotomy

A 56-year-old man who was a Jehovah's Witness with an advanced directive against autologous procedures developed acute kidney injury needing renal replacement therapy while he was intubated and ventilated on the intensive care unit. He was being treated for hyperosmolar hyperglycaemic state. He also had a healing laparotomy wound, having undergone a splenectomy less than a month ago following a road traffic accident. His hyperkalaemia and metabolic acidosis were refractory to medical treatment. As he became oligoanuric, decision was taken to carry out acute peritoneal dialysis (PD) by inserting a Tenckhoff catheter in his abdomen using peritoneoscopic technique. The patient was started on automated PD without any complications. His urine output gradually improved, and his renal function eventually recovered. On discharge from hospital, his renal function was within normal range, and he had no abdominal complications from the acute PD.

Outcomes After Post-Traumatic AKI Requiring RRT in United States Military Service Members

BACKGROUND AND OBJECTIVES

Mortality and CKD risk have not been described in military casualties with post-traumatic AKI requiring RRT suffered in the Iraq and Afghanistan wars.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

This is a retrospective case series of post-traumatic AKI requiring RRT in 51 military health care beneficiaries (October 7, 2001-December 1, 2013), evacuated to the National Capital Region, documenting in-hospital mortality and subsequent CKD. Participants were identified using electronic medical and procedure records.

RESULTS

Age at injury was 26±6 years; of the participants, 50 were men, 16% were black, 67% were white, and 88% of injuries were caused by blast or projectiles. Presumed AKI cause was acute tubular necrosis in 98%, with rhabdomyolysis in 72%. Sixty-day all-cause mortality was 22% (95% confidence interval [95% CI], 12% to 35%), significantly less than the 50% predicted historical mortality (P<0.001). The VA/NIH Acute Renal Failure Trial Network AKI integer score predicted 60-day mortality risk was 33% (range, 6%-96%) (n=49). Of these, nine died (mortality, 18%; 95% CI, 10% to 32%), with predicted risks significantly miscalibrated (P<0.001). The area under the receiver operator characteristic curve for the AKI integer score was 0.72 (95% CI, 0.56 to 0.88), not significantly different than the AKI integer score model cohort (P=0.27). Of the 40 survivors, one had ESRD caused by cortical necrosis. Of the remaining 39, median time to last follow-up serum creatinine was 1158 days (range, 99-3316 days), serum creatinine was 0.85±0.24 mg/dl, and eGFR was 118±23 ml/min per 1.73 m(2). No eGFR was <60 ml/min per 1.73 m(2), but it may be overestimated because of large/medium amputations in 54%. Twenty-five percent (n=36) had proteinuria; one was diagnosed with CKD stage 2.

CONCLUSIONS

Despite severe injuries, participants had better in-hospital survival than predicted historically and by AKI integer score. No patient who recovered renal function had an eGFR<60 ml/min per 1.73 m(2) at last follow-up, but 23% had proteinuria, suggesting CKD burden.

A review of acute and chronic peritoneal dialysis in developing countries

Various modalities of renal replacement therapy (RRT) are available for the management of acute kidney injury (AKI) and end-stage renal disease (ESRD). While developed countries mainly use hemodialysis as a form of RRT, peritoneal dialysis (PD) has been increasingly utilized in developing countries. Chronic PD offers various benefits including lower cost, home-based therapy, single access, less requirement of highly trained personnel and major infrastructure, higher number of patients under a single nephrologist with probably improved quality of life and freedom of activities. PD has been found to be lifesaving in the management of AKI in patients in developing countries where facilities for other forms of RRT are not readily available. The International Society of Peritoneal Dialysis has published guidelines regarding the use of PD in AKI, which has helped in ensuring uniformity. PD has also been successfully used in certain special situations of AKI due to snake bite, malaria, febrile illness, following cardiac surgery and in poisoning. Hemodialysis is the most common form of RRT used in ESRD worldwide, but some countries have begun to adopt a 'PD first' policy to reduce healthcare costs of RRT and ensure that it reaches the underserved population.

Acute Kidney Injury in the Critically Ill Patient: A Current Review of the Literature

PURPOSE

A comprehensive review of the literature to provide a focused and thorough update on the issue of acute kidney injury (AKI) in the surgical patient.

METHODS

A PubMed and Medline search was performed and keywords included AKI, renal failure, critically ill, and renal replacement therapy (RRT).

PRINCIPAL FINDINGS

A common clinical problem encountered in critically ill patients is AKI. The recent consensus definitions for the diagnosis and classification of AKI (ie, Risk, Injury, Failure, Loss of kidney function, and End-stage kidney disease/Acute Kidney Injury Network) have enabled us to standardize the severity of AKI and facilitate strategies for prevention. These strategies as well as treatment modalities of AKI are discussed. We provide a concise overview of the issue of renal failure. We describe strategies for prevention including types of fluids used for resuscitation, timing of initiation of RRT, and different treatment modalities currently available for clinical practice.

CONCLUSIONS

Acute kidney injury is a common problem in the critically ill patient and is associated with worse clinical outcomes. A standardized definition and staging system has led to improved diagnosis and understanding of the pathophysiology of AKI. There are many trials leading to improved prevention and management of the disease.

Acute kidney injury in acute liver failure: a review

Acute liver failure is a rare and often devastating condition consequent on massive liver cell necrosis that frequently affects young, previously healthy individuals resulting in altered cognitive function, coagulopathy and peripheral vasodilation. These patients frequently develop concurrent acute kidney injury (AKI). This abrupt and sustained decline in renal function, through a number of pathogenic mechanisms such as renal hypoperfusion, direct drug-induced nephrotoxicity or sepsis/systemic inflammatory response contributes to increased morbidity and is strongly associated with a worse prognosis. Improved understanding of the pathophysiology AKI in the context of acute liver failure may be beneficial in a number of areas; the development of new and sensitive biomarkers of renal dysfunction, refining prognosis and organ allocation, and ultimately leading to the development of novel treatment strategies, these issues are discussed in more detail in this expert review.

Earlier-start versus usual-start dialysis in patients with community-acquired acute kidney injury: a randomized controlled trial

BACKGROUND

Optimum timing of the initiation of dialysis therapy in acute kidney injury is not clear.

STUDY DESIGN

Prospective, open label, 2-arm, randomized, controlled trial.

SETTING & PARTICIPANTS

208 adults with acute kidney injury with progressively worsening azotemia at the artificial kidney dialysis unit of a tertiary-care referral center in western India.

INTERVENTION

Earlier-start dialysis was initiated when serum urea nitrogen and/or creatinine levels increased to 70 and 7 mg/dL, respectively, whereas the usual-start dialysis patients (control group) received dialysis when clinically indicated as judged by treating nephrologists.

OUTCOMES

Primary outcome was in-hospital mortality and dialysis dependence at 3 months. Secondary outcome in patients receiving dialysis was time to recovery of kidney function, computed from time of enrollment to the last dialysis session.

RESULTS

Of 585 screened patients, 102 were assigned to earlier-start dialysis, and 106 to usual-start dialysis. Baseline characteristics were similar between randomized groups. 93 (91.1%) and 88 (83.1%) participants received dialysis in the intervention and control groups, respectively. Mean serum urea nitrogen and serum creatinine levels at dialysis therapy initiation were 71.7 ± 21.7 (SD) and 7.4 ± 5.3 mg/dL, respectively, in the intervention group versus 100.9 ± 32.6 and 10.41 ± 3.3 mg/dL in the control group. Data on primary outcome were available for all patients. In-hospital mortality was 20.5% and 12.2% in the intervention and control groups, respectively (relative risk, 1.67; 95% CI, 0.88-3.17; P = 0.2). 4.9% and 4.7% of patients in the intervention and control groups, respectively, were dialysis dependent at 3 months (relative risk, 1.04; 95% CI, 0.29-3.7; P = 0.9).

LIMITATIONS

Study was not double blind, event rate (ie, mortality) was less than predicted, wide CIs preclude definitive findings.

CONCLUSIONS

Our data do not support the earlier initiation of dialysis therapy in community-acquired acute kidney injury.