Long-term outcomes of acute kidney injury

Drug-Related Problems and Recommendations Made during Home Medicines Reviews for Sick Day Medication Management in Australia

Backgrounds and Objectives: Using certain medications during an intercurrent illness can increase the risk of drug related problems (DRP) occurring such as acute kidney injury (AKI). Medications that increase this risk include sulfonylureas, angiotensin converting enzyme inhibitors, diuretics, metformin, angiotensin receptor blockers, non-steroidal anti-inflammatories drugs, and sodium glucose co-transporter 2 inhibitors (SADMANS). Sick day medication guidance (SDMG) recommends withholding SADMANS medications during an intercurrent illness where adequate fluid intake cannot be maintained. But uptake of these recommendations is poor, and it is not known whether Australian pharmacists currently provide these recommendations during home medicine reviews (HMR) as per SDMG. We aimed to gain an understanding of the characteristics of DRP identified by pharmacists during HMR, especially those relating to SADMANS medications. Materials and Methods: We conducted a retrospective audit of 201 randomly selected HMR reports, conducted by accredited pharmacists from 2020 to 2022, that were analysed in 2023. All DRP and recommendations were categorised using a modified DOCUMENT system. Results: Overall, over 98% of participants experienced a DRP and a total of 710 DRP were found, where participants experienced an average of 4.0 ± 2.0 DRP each. Non-SADMANS medications accounted for 83.1% of all DRPs, with nervous system medications contributing the most. Common problems seen in non-SADMANS medications were related to toxicity, over/underdosing and undertreating. Diuretics contributed most to DRP in SADMANS medications. Problems with SADMANS were mainly related to toxicity and contraindications. No pharmacists provided SDMG despite 71.1% of participants using at least one SADMANS medication. Conclusions: We conclude that DRP remain prevalent in community pharmacy settings. Sick day recommendations were not provided in the HMRs included in our study, possibly due to lack of pharmacist knowledge and awareness. To ensure best practice, more research should be conducted to determine pharmacists' knowledge of and barriers to provision of sick day recommendations.

Impact of the first 24 h of continuous kidney replacement therapy on hemodynamics, ventilation, and analgo-sedation in critically ill children

BACKGROUND

In a group of children admitted to the paediatric intensive care unit (PICU) receiving continuous kidney replacement therapy (CKRT), we aim to evaluate the data about their hemodynamic, ventilation and analgo-sedation profile in the first 24 h of treatment and possible associations with mortality.

METHODS

Retrospective cohort study of children admitted to the PICU of the University Hospital of Padova undergoing CKRT between January 2011 and March 2021. Data was collected at baseline (T0), after 1 h (T1) and 24 h (T24) of CKRT treatment. The differences in outcome measures were compared between these time points, and between survivors and non-survivors.

RESULTS

Sixty-nine patients received CKRT, of whom 38 (55%) died during the PICU stay. Overall, the vasoactive inotropic score and the adrenaline dose increased at T1 compared to T0 (p = 0.012 and p = 0.022, respectively). Compared to T0, at T24 patients showed an improvement in the following ventilatory parameters: Oxygenation Index (p = 0.005), Oxygenation Saturation Index (p = 0.013) PaO2/FiO2 ratio (p = 0.005), SpO2/FiO2 ratio (p = 0.002) and Mean Airway Pressure (p = 0.016). These improvements remained significant in survivors (p = 0.01, p = 0.027, p = 0.01 and p = 0.015, respectively) but not in non-survivors. No changes in analgo-sedative drugs have been described.

CONCLUSIONS

CKRT showed a significant impact on hemodynamics and ventilation in the first 24 h of treatment. We observed a significant rise in the inotropic/vasoactive support required after 1 h of treatment in the overall population, and an improvement in the ventilation parameters at 24 h only in survivors.

Impact of Acute Kidney Injury After Transcatheter Aortic Valve Replacement: A Nationwide Study

BACKGROUND

In patients undergoing transcatheter aortic valve replacement (TAVR), the impact of acute kidney injury (AKI) on the prognosis and especially on future kidney function has been sparsely examined, and data from large cohorts are warranted.

METHODS AND RESULTS

With Danish nationwide registries, we identified all patients undergoing TAVR from 2014 to 2021 with no previous dialysis treatment. According to 2 plasma creatinine samples, we identified those suffering a postprocedural AKI within 21 days after TAVR. With 1 year of follow-up, we compared the associated rates of dialysis treatment and death between patients with and without an AKI using multivariable Cox analysis. Finally, according to the lowest recorded creatinine sample, we assessed the kidney function among AKI survivors between 90 and 180 days after the index date. We identified 4091 TAVRs: 193 (4.7%) with AKI (55.4% men; median age, 82 years) and 3898 (95.3%) without AKI (57.0% men; median age, 81 years). Compared with those without AKI, patients with AKI showed increased associated 1-year rates of dialysis treatment (hazard ratio [HR], 7.20 [95% CI, 4.10-12.66]) and death (HR, 2.39 [95% CI, 1.59-3.58]). After 6 months, 74% of AKI survivors had complete kidney recovery, 14.7% had incomplete kidney recovery, 6.3% failed to recover, and 5.1% were on dialysis treatment.

CONCLUSIONS

We identified that AKI after TAVR was associated with an increased rate of future dialysis treatment and all-cause death. Among survivors, 74% had complete kidney recovery within 6 months.

Kidney and lung crosstalk during critical illness: large-scale cohort study

BACKGROUND

The relationship between the lung and kidney investigated in animal and clinical models has demonstrated substantial crosstalk. We aimed to evaluate the association between single vs. concurrent AKI and ARDS and its impact on patient outcomes. Secondly, we aimed to assess whether the order of appearance of these pathologies affected patient outcomes in patients with both diseases.

METHODS

This single-center retrospective cohort study included adult patients admitted to the ICU from January 1, 2007 through May 1, 2018 (n = 76,988). Baseline characteristics and outcomes were compared among patients without ARDS or AKI and those with one or both ARDS and AKI. We also assessed outcomes across the order of appearance of these diseases among patients with both AKI and ARDS.

RESULTS

We enrolled 76,988 unique patients in the final analysis: 47,043 patients with neither AKI nor ARDS, 491 patients with ARDS alone, 27,928 patients with AKI alone, and 1,526 patients with both ARDS and AKI. Patients with both ARDS and AKI had higher ICU (21.2%) and hospital (28.4%) mortality compared to patients with ARDS alone (9.0% ICU mortality, 14.0% hospital mortality) or AKI alone (4.4% ICU mortality, 8.4% hospital mortality) (p < 0.001). These findings remained unchanged after adjusting for illness severity and comorbidities. Of the 1136 patients with both AKI and ARDS, 136 (12%) developed AKI first, 303 (27%) ARDS first, and 697 (61%) had simultaneous diseases. Patients who developed ARDS after AKI had significantly increased ICU (29.4%) and hospital (36.8%) mortality compared to patients who developed AKI after ARDS (13.9% ICU mortality, 21.5% hospital mortality) (p < 0.001).

CONCLUSIONS

The combination of AKI and ARDS leads to worse outcomes, including longer hospital and ICU lengths of stay, higher mortality, longer kidney replacement therapy, and longer ventilation requirements than in patients with AKI or ARDS alone. Among patients with both diagnoses, those who developed ARDS after AKI had the highest mortality.

Identification of Pre-Renal and Intrinsic Acute Kidney Injury by Anamnestic and Biochemical Criteria: Distinct Association with Urinary Injury Biomarkers

Acute kidney injury (AKI) is a syndrome of sudden renal excretory dysfunction with severe health consequences. AKI etiology influences prognosis, with pre-renal showing a more favorable evolution than intrinsic AKI. Because the international diagnostic criteria (i.e., based on plasma creatinine) provide no etiological distinction, anamnestic and additional biochemical criteria complement AKI diagnosis. Traditional, etiology-defining biochemical parameters, including the fractional excretion of sodium, the urinary-to-plasma creatinine ratio and the renal failure index are individually limited by confounding factors such as diuretics. To minimize distortion, we generated a composite biochemical criterion based on the congruency of at least two of the three biochemical ratios. Patients showing at least two ratios indicative of intrinsic AKI were classified within this category, and those with at least two pre-renal ratios were considered as pre-renal AKI patients. In this study, we demonstrate that the identification of intrinsic AKI by a collection of urinary injury biomarkers reflective of tubular damage, including NGAL and KIM-1, more closely and robustly coincide with the biochemical than with the anamnestic classification. Because there is no gold standard method for the etiological classification of AKI, the mutual reinforcement provided by the biochemical criterion and urinary biomarkers supports an etiological diagnosis based on objective diagnostic parameters.

Resident macrophage subpopulations occupy distinct microenvironments in the kidney

The kidney contains a population of resident macrophages from birth that expands as it grows and forms a contiguous network throughout the tissue. Kidney-resident macrophages (KRMs) are important in homeostasis and the response to acute kidney injury. While the kidney contains many microenvironments, it is unknown whether KRMs are a heterogeneous population differentiated by function and location. We combined single-cell RNA-Seq (scRNA-Seq), spatial transcriptomics, flow cytometry, and immunofluorescence imaging to localize, characterize, and validate KRM populations during quiescence and following 19 minutes of bilateral ischemic kidney injury. scRNA-Seq and spatial transcriptomics revealed 7 distinct KRM subpopulations, which are organized into zones corresponding to regions of the nephron. Each subpopulation was identifiable by a unique transcriptomic signature, suggesting distinct functions. Specific protein markers were identified for 2 clusters, allowing analysis by flow cytometry or immunofluorescence imaging. Following injury, the original localization of each subpopulation was lost, either from changing locations or transcriptomic signatures. The original spatial distribution of KRMs was not fully restored for at least 28 days after injury. The change in KRM localization confirmed a long-hypothesized dysregulation of the local immune system following acute injury and may explain the increased risk for chronic kidney disease.

Diagnosis of Cardiac Surgery-Associated Acute Kidney Injury: State of the Art and Perspectives

Diagnosis of cardiac surgery-associated acute kidney injury (CSA-AKI), a syndrome of sudden renal dysfunction occurring in the immediate post-operative period, is still sub-optimal. Standard CSA-AKI diagnosis is performed according to the international criteria for AKI diagnosis, afflicted with insufficient sensitivity, specificity, and prognostic capacity. In this article, we describe the limitations of current diagnostic procedures and of the so-called injury biomarkers and analyze new strategies under development for a conceptually enhanced diagnosis of CSA-AKI. Specifically, early pathophysiological diagnosis and patient stratification based on the underlying mechanisms of disease are presented as ongoing developments. This new approach should be underpinned by process-specific biomarkers including, but not limited to, glomerular filtration rate (GFR) to other functions of renal excretion causing GFR-independent hydro-electrolytic and acid-based disorders. In addition, biomarker-based strategies for the assessment of AKI evolution and prognosis are also discussed. Finally, special focus is devoted to the novel concept of pre-emptive diagnosis of acquired risk of AKI, a premorbid condition of renal frailty providing interesting prophylactic opportunities to prevent disease through diagnosis-guided personalized patient handling. Indeed, a new strategy of risk assessment complementing the traditional scores based on the computing of risk factors is advanced. The new strategy pinpoints the assessment of the status of the primary mechanisms of renal function regulation on which the impact of risk factors converges, namely renal hemodynamics and tubular competence, to generate a composite and personalized estimation of individual risk.

Nephrotoxin Exposure in the 3 Years following Hospital Discharge Predicts Development or Worsening of Chronic Kidney Disease among Acute Kidney Injury Survivors

INTRODUCTION

Survivors of acute kidney injury (AKI) are at high risk of progression to chronic kidney disease (CKD), for which drugs may be a modifiable risk factor.

METHODS

We conducted a population-based cohort study of Olmsted County, MN residents who developed AKI while hospitalized between January 1, 2006, and December 31, 2014, using Rochester Epidemiology Project data. Adults with a hospitalization complicated by AKI who survived at least 90 days after AKI development were included. Medical records were queried for prescription of potentially nephrotoxic medications over the 3 years after discharge. The primary outcome was de novo or progressive CKD defined by either a new diagnosis code for CKD or ≥30% decline in estimated glomerular filtration rate from baseline. The composite of CKD, AKI readmission, or death was also evaluated.

RESULTS

Among 2,461 AKI survivors, 2,140 (87%) received a potentially nephrotoxic medication during the 3 years following discharge. When nephrotoxic medication use was analyzed in a time-dependent fashion, those actively prescribed at least one of these drugs experienced a significantly higher risk of de novo or progressive CKD (HR 1.38: 95% CI: 1.24, 1.54). Similarly, active potentially nephrotoxic medication use predicted a greater risk of the composite endpoint of CKD, AKI readmission, or death within 3 years of discharge (HR 1.41: 95% CI: 1.28, 1.56).

CONCLUSION

In this population-based cohort study, AKI survivors actively prescribed one or more potentially nephrotoxic medications were at significantly greater risk for de novo or progressive CKD. An opportunity exists to reassess nephrotoxin appropriateness following an AKI episode to improve patient outcomes.

Vitamin C Deficiency Causes Cell Type-Specific Epigenetic Reprogramming and Acute Tubular Necrosis in a Mouse Model

BACKGROUND

Vitamin C deficiency is found in patients with variable kidney diseases. However, the role of vitamin C as an epigenetic regulator in renal homeostasis and pathogenesis remains largely unknown.

METHODS

We showed that vitamin C deficiency leads to acute tubular necrosis (ATN) using a vitamin C-deficient mouse model (Gulo knock-out). DNA/RNA epigenetic modifications and injured S3 proximal tubule cells were identified in the vitamin C-deficient kidneys using whole-genome bisulfite sequencing, methylated RNA immunoprecipitation sequencing, and single-cell RNA sequencing.

RESULTS

Integrated evidence suggested that epigenetic modifications affected the proximal tubule cells and fenestrated endothelial cells, leading to tubule injury and hypoxia through transcriptional regulation. Strikingly, loss of DNA hydroxymethylation and DNA hypermethylation in vitamin C-deficient kidneys preceded the histologic sign of tubule necrosis, indicating the causality of vitamin C-induced epigenetic modification in ATN. Consistently, prophylactic supplementation of an oxidation-resistant vitamin C derivative, ascorbyl phosphate magnesium, promoted DNA demethylation and prevented the progression of cisplatin-induced ATN.

CONCLUSIONS

Vitamin C played a critical role in renal homeostasis and pathogenesis in a mouse model, suggesting vitamin supplementation may be an approach to lower the risk of kidney injury.

Fasting during Ramadan and acute kidney injury (AKI): a retrospective, propensity matched cohort study

Background

During the month of Ramadan, Muslims abstain from daytime consumption of fluids and foods, although some high-risk individuals are exempt. Because fasting's effects on the risk of acute kidney injury (AKI) have not been established, this study assesses the relationship between fasting and risk of AKI and identifies patients at high risk.

Methods

A single-center, retrospective, propensity-score matched, cohort study was conducted with data collected from adult patients admitted to the emergency room during Ramadan and the following month over two consecutive years (2016 and 2017). AKI was diagnosed based on the 2012 definition from the Kidney Disease: Improving Global Outcomes clinical practice guideline. Multivariable logistic regression analyses were used to examine the correlation and measure the effect of fasting on the incidence of AKI, and assess the effect of different variables on the incidence of AKI between the matching cohorts.

Results

A total of 1199 patients were included; after matching, each cohort had 499 patients. In the fasting cohort, the incidence of AKI and the risk of developing AKI were significantly lower (adjusted odds ratio (AOR) 0.65;95% confidence interval (CI) 0.44–0.98). The most indicative risk factors for AKI were hypertension (AOR 2.17; 95% CI 1.48–3.18), history of AKI (AOR 5.05; 95% CI 3.46–7.39), and liver cirrhosis (AOR 3.01; 95% CI 1.04–8.70). Patients with these factors or most other comorbidities in the fasting cohort had a lower risk of AKI as compared with their nonfasting counterparts.

Conclusion

The data show a strong reduction in the risk of developing AKI as a benefit of fasting, particularly in patients with comorbid conditions. Therefore, most patients with comorbid conditions are not harmed from fasting during Ramadan. However, larger prospective studies are needed to investigate the benefit of fasting in reducing the risk of developing AKI.

Kidney-Targeted Redox Scavenger Therapy Prevents Cisplatin-Induced Acute Kidney Injury

Cisplatin-induced acute kidney injury (CI-AKI) is a significant co-morbidity of chemotherapeutic regimens. While this condition is associated with substantially lower survival and increased economic burden, there is no pharmacological agent to effectively treat CI-AKI. The disease is hallmarked by acute tubular necrosis of the proximal tubular epithelial cells primarily due to increased oxidative stress. We investigated a drug delivery strategy to improve the pharmacokinetics of an approved therapy that does not normally demonstrate appreciable efficacy in CI-AKI, as a preventive intervention. In prior work, we developed a kidney-selective mesoscale nanoparticle (MNP) that targets the renal proximal tubular epithelium. Here, we found that the nanoparticles target the kidneys in a mouse model of CI-AKI with significant damage. We evaluated MNPs loaded with the reactive oxygen species scavenger edaravone, currently used to treat stroke and ALS. We found a marked and significant therapeutic benefit with edaravone-loaded MNPs, including improved renal function, which we demonstrated was likely due to a decrease in tubular epithelial cell damage and death imparted by the specific delivery of edaravone. The results suggest that renal-selective edaravone delivery holds potential for the prevention of acute kidney injury among patients undergoing cisplatin-based chemotherapy.

Comparative incidence of acute kidney injury in patients on vancomycin therapy in combination with cefepime, piperacillin-tazobactam or meropenem

Recent studies have shown that the incidence of nephrotoxicity increases when vancomycin is combined with a beta-lactam antibiotic. The objective of this study was to compare the incidence of acute kidney injury (AKI) in adult patients who received vancomycin with either piperacillin-tazobactam (VPT), cefepime (VC), or meropenem (VM). This was a single center retrospective chart review. Patients were included if they were 18 years or older, received 48 hours of combination therapy and antibiotics were started within 24 hours of each other. Exclusion criteria were receiving more than one combination of antibiotics, serum creatinine > 1.2 mg/dL, AKI at the time of inclusion, or any form of renal replacement therapy. Two hundred patients met inclusion criteria. A total of 27 (13%) patients experienced AKI. The incidence of AKI was 21.6%, 9%, and 7.4% in the VPT, VC and VM groups, respectively. A patient who received VPT was 5 times more likely to develop AKI when compared to a patient who received VC (adjusted OR 5.09 95% CI (1.51-17.08), p = 0.008) and 7 times more likely to develop AKI when compared to VM (adjusted OR 7.03 95% CI (1.97-28.08), p = 0.002). This study found a statistically significant difference in the incidence of AKI in patient receiving VPT when compared to VC or VM. This finding supports the need for careful monitoring of renal function in patients receiving VPT therapy and routine evaluation for de-escalation of antimicrobial therapy.

The Consequences of Aging On the Response to Injury and Critical Illness

Changing demographic trends have led to an increase in the overall geriatric trauma patient volume. Furthermore, the intersection of aging and injury can be problematic because geriatric patients have multiple comorbidities, geriatric-specific syndromes, and reduced physiological reserve. Despite mounting evidence that frail geriatric patients have inferior outcomes following trauma, very few studies have examined the effect of aging on the biological response to injury. In the present article, we review the current literature and explore the pathophysiological rationale underlying observed data, available evidence, and future directions on this topic.

Risk and consequences of dehydration following colorectal cancer resection with diverting ileostomy. A systematic review and meta-analysis

AIM

This systematic review aims to assess dehydration prevalence and dehydration-related morbidity from diverting ileostomy compared to resections without ileostomy formation in adults undergoing colorectal resection for cancer.

METHOD

MEDLINE, Embase, CENTRAL and ClinicalTrials.gov were searched for studies of any design that reported dehydration, renal function and dehydration-related morbidity in adult colorectal cancer patients with diverting ileostomy (last search 12 August 2020). Bias was assessed using the Cochrane Collaboration's tool for assessing risk of bias in randomized trials and the Risk of Bias in Non-randomized Studies of Interventions tool.

RESULTS

Of 1927 screened papers, 22 studies were included (21 cohort studies and one randomized trial) with a total of 19 485 patients (12 209 with ileostomy). The prevalence of dehydration was 9.00% (95% CI 5.31-13.45, P < 0.001). The relative risk of dehydration following diverting ileostomy was 3.37 (95% CI 2.30-4.95, P < 0.001). Three studies assessing long-term trends in renal function demonstrated progressive renal impairment persisting beyond the initial insult. Consequences identified included unplanned readmission, delay or non-commencement of adjuvant chemotherapy, and development of chronic kidney disease.

DISCUSSION

Significant dehydration is common following diverting ileostomy; it is linked to acute kidney injury and has a long-term impact on renal function. This study suggests that ileostomy confers significant morbidity particularly related to dehydration and renal impairment.

Novel roles of the renal angiotensin-converting enzyme

The observation that all components of the renin angiotensin system (RAS) are expressed in the kidney and the fact that intratubular angiotensin (Ang) II levels greatly exceed the plasma concentration suggest that the synthesis of renal Ang II occurs independently of the circulating RAS. One of the main components of this so-called intrarenal RAS is angiotensin-converting enzyme (ACE). Although the role of ACE in renal disease is demonstrated by the therapeutic effectiveness of ACE inhibitors in treating several conditions, the exact contribution of intrarenal versus systemic ACE in renal disease remains unknown. Using genetically modified mouse models, our group demonstrated that renal ACE plays a key role in the development of several forms of hypertension. Specifically, although ACE is expressed in different cell types within the kidney, its expression in renal proximal tubular cells is essential for the development of high blood pressure. Besides hypertension, ACE is involved in several other renal diseases such as diabetic kidney disease, or acute kidney injury even when blood pressure is normal. In addition, studies suggest that ACE might mediate at least part of its effect through mechanisms that are independent of the Ang I conversion into Ang II and involve other substrates such as N-acetyl-seryl-aspartyl-lysyl-proline (AcSDKP), Ang-(1-7), and bradykinin, among others. In this review, we summarize the recent advances in understanding the contribution of intrarenal ACE to different pathological conditions and provide insight into the many roles of ACE besides the well-known synthesis of Ang II.

The Role of CXCL12 in Kidney Diseases: A Friend or Foe?

Background

Chemokines are a family of proteins mainly mediating the homing and migration of various cells. The CXC chemokine CXCL12 is a member of low-weight-molecular chemokines. In the kidney, CXCL12 is pivotal for renal development and exerts a modulatory effect in kidney diseases under different etiologic settings by binding with CXC chemokine receptor 4 (CXCR4) or CXC chemokine receptor 7 (CXCR7). Besides, CXCL12 also exerts homeostasis influence in diverse physical conditions and various pathological situations. Thus, we conclude the complicated relationship between CXCL12 and kidney diseases in this review.

Summary

In renal development, CXCL12 contributes a lot to nephrogenesis and the formation of renal vasculature via correlating with CXCR4. CXCL12 also plays an essential role in renal recovery from acute kidney injury. However, the CXCL12/CXCR4 axis plays a dual regulatory role in the initiation and development of diabetic kidney disease as well as chronic allogeneic nephropathy after kidney transplantation through dialectical consideration. Additionally, the CXCL12/CXCR4 link is considered as a new risk factor for lupus nephritis and renal cell carcinoma.

Key Messages

Plenty of studies have presented the influence of CXCL12 and the relation with corresponding receptors in diverse biological and pathological statuses. Simultaneously, some drugs and antagonists targeting CXCL12/CXCR4 axis effectively treat various kidney diseases. However, more researches are needed to explore thorough influence and mechanisms, providing more cues for clinical treatments.

Enhancing Military Burn- and Trauma-Related Acute Kidney Injury Prediction Through an Automated Machine Learning Platform and Point-of-Care Testing

CONTEXT.—

Delayed recognition of acute kidney injury (AKI) results in poor outcomes in military and civilian burn-trauma care. Poor predictive ability of urine output (UOP) and creatinine contribute to the delayed recognition of AKI.

OBJECTIVE.—

To determine the impact of point-of-care (POC) AKI biomarker enhanced by machine learning (ML) algorithms in burn-injured and trauma patients.

DESIGN.—

We conducted a 2-phased study to develop and validate a novel POC device for measuring neutrophil gelatinase-associated lipocalin (NGAL) and creatinine from blood samples. In phase I, 40 remnant plasma samples were used to evaluate the analytic performance of the POC device. Next, phase II enrolled 125 adults with either burns that were 20% or greater of total body surface area or nonburn trauma with suspicion of AKI for clinical validation. We applied an automated ML approach to develop models predicting AKI, using a combination of NGAL, creatinine, and/or UOP as features.

RESULTS.—

Point-of-care NGAL (mean [SD] bias: 9.8 [38.5] ng/mL, P = .10) and creatinine results (mean [SD] bias: 0.28 [0.30] mg/dL, P = .18) were comparable to the reference method. NGAL was an independent predictor of AKI (odds ratio, 1.6; 95% CI, 0.08-5.20; P = .01). The optimal ML model achieved an accuracy, sensitivity, and specificity of 96%, 92.3%, and 97.7%, respectively, with NGAL, creatinine, and UOP as features. Area under the receiver operator curve was 0.96.

CONCLUSIONS.—

Point-of-care NGAL testing is feasible and produces results comparable to reference methods. Machine learning enhanced the predictive performance of AKI biomarkers including NGAL and was superior to the current techniques.

Acute Kidney Injury following Cardiopulmonary Bypass: A Challenging Picture

Recent studies have recognized several risk factors for cardiopulmonary bypass- (CPB-) associated acute kidney injury (AKI). However, the lack of early biomarkers for AKI prevents practitioners from intervening in a timely manner. We reviewed the literature with the aim of improving our understanding of the risk factors for CPB-associated AKI, which may increase our ability to prevent or improve this condition. Some novel early biomarkers for AKI have been introduced. In particular, a combinational use of these biomarkers would be helpful to improve clinical outcomes. Furthermore, we discuss several interventions that are aimed at managing CPB-associated AKI, may increase the effect of renal replacement therapy (RRT), and may contribute to preventing CPB-associated AKI. Collectively, the conclusions of this paper are limited by the availability of clinical trial evidence and conflicting definitions of AKI. A guideline is urgently needed for CPB-associated AKI.

Long-Term Mortality Related to Acute Kidney Injury Following Intracerebral Hemorrhage: A 10-Year (2010-2019) Retrospective Study

OBJECTIVES

Acute kidney injury (AKI) following intracerebral hemorrhage (ICH) is an intractable medical complication and an independent predictor of short-term mortality. However, the correlation between AKI and long-term mortality has not been fully investigated. The aim of the present study was to determine the relationship between AKI following ICH and long-term mortality in a 10-year (2010-2019) retrospective cohort.

MATERIALS AND METHODS

A total of 1449 ICH patients were screened and enrolled at the Department of Neurosurgery, Southwest Hospital, Third Military Medical University (Army Medical University) from January 2010 to December 2016. The endpoint for follow-up was May 31, 2019. The estimated all-cause mortality was determined using Cox proportional hazard regression models.

RESULTS

Among 1449 ICH patients, 136 (9.4%) suffered from AKI, and the duration of follow-up was a median of 5.1 years (IQR 3.2-7.2). The results indicated that the risk factors for AKI without preexisting chronic kidney disease (CKD) in the multivariable analysis were age (p = 0.002), nephrotoxic antibiotics (p = 0.000), diabetes mellitus (p = 0.005), sepsis (p = 0.000), antiplatelet therapy (p = 0.002), infratentorial hemorrhage (p = 0.000) and ICH volume (p = 0.003). Age (p = 0.008), ACEIs/ARBs (p = 0.010), nephrotoxic antibiotics (p = 0.014), coronary artery disease (p = 0.009), diabetes mellitus (p = 0.014), hypertension (p = 0.000) and anticoagulant therapy (p = 0.000) were independent predictors of AKI with preexisting CKD. Meanwhile, the data demonstrated that the estimated all-cause mortality was significantly higher in ICH patients with AKI without preexisting CKD (HR 4.208, 95% CI 2.946-6.011; p = 0.000) and in ICH patients with AKI with preexisting CKD (HR 2.470, 95% CI 1.747-3.492; p = 0.000) than in those without AKI.

CONCLUSIONS

AKI is a long-term independent predictor of mortality in ICH patients. Thus, renal function needs to be routinely determined in ICH patients during clinical practice.

Restoration of afferent arteriolar autoregulatory behavior in ischemia-reperfusion injury in rat kidneys

Renal autoregulation is critical in maintaining stable renal blood flow (RBF) and glomerular filtration rate (GFR). Renal ischemia-reperfusion (IR)-induced kidney injury is characterized by reduced RBF and GFR. The mechanisms contributing to renal microvascular dysfunction in IR have not been fully determined. We hypothesized that increased reactive oxygen species (ROS) contributed to impaired renal autoregulatory capability in IR rats. Afferent arteriolar autoregulatory behavior was assessed using the blood-perfused juxtamedullary nephron preparation. IR was induced by 60 min of bilateral renal artery occlusion followed by 24 h of reperfusion. Afferent arterioles from sham rats exhibited normal autoregulatory behavior. Stepwise increases in perfusion pressure caused pressure-dependent vasoconstriction to 65 ± 3% of baseline diameter (13.2 ± 0.4 μm) at 170 mmHg. In contrast, pressure-mediated vasoconstriction was markedly attenuated in IR rats. Baseline diameter averaged 11.7 ± 0.5 µm and remained between 90% and 101% of baseline over 65-170 mmHg, indicating impaired autoregulatory function. Acute antioxidant administration (tempol or apocynin) to IR kidneys for 20 min increased baseline diameter and improved autoregulatory capability, such that the pressure-diameter profiles were indistinguishable from those of sham kidneys. Furthermore, the addition of polyethylene glycol superoxide dismutase or polyethylene glycol-catalase to the perfusate blood also restored afferent arteriolar autoregulatory responsiveness in IR rats, indicating the involvement of superoxide and/or hydrogen peroxide. IR elevated mRNA expression of NADPH oxidase subunits and monocyte chemoattractant protein-1 in renal tissue homogenates, and this was prevented by tempol pretreatment. These results suggest that ROS accumulation, likely involving superoxide and/or hydrogen peroxide, impairs renal autoregulation in IR rats in a reversible fashion.NEW & NOTEWORTHY Renal ischemia-reperfusion (IR) leads to renal microvascular dysfunction manifested by impaired afferent arteriolar autoregulatory efficiency. Acute administration of scavengers of reactive oxygen species, polyethylene glycol-superoxide dismutase, or polyethylene glycol-catalase following renal IR restored afferent arteriolar autoregulatory capability in IR rats, indicating that renal IR led to reversible impairment of afferent arteriolar autoregulatory capability. Intervention with antioxidant treatment following IR may improve outcomes in patients by preserving renovascular autoregulatory function and potentially preventing the progression to chronic kidney disease after acute kidney injury.

Risk Factor Analysis of Acute Kidney Injury After Microwave Ablation of Hepatocellular Carcinoma: A Retrospective Study

Objectives: Acute kidney injury (AKI) is a recently observed side effect in patients after microwave ablation (MWA) of hepatocellular carcinoma (HCC) and is associated with negative outcomes. The aim of this study is to explore the risk factors of affecting the occurrence of AKI (stages 1b, 2, and 3), because they have a higher mortality rate than patients with AKI (stage 1a) and without AKI.

Materials and methods: In this retrospective study, a total of 1,214 patients with HCC who were treated with MWA under ultrasound (US) guidance in our department between January 2005 and November 2017 were enrolled. We evaluated the influence of 20 risk factors. Univariate and multivariate analysis were used for statistical analysis. The possible risk factors of AKI after MWA for HCC were summarized.

Results: AKI, AKI (stage 1a), and AKI (stages 1b, 2, and 3) after MWA were found in 34, 15, and 19 patients (2.80, 1.24, and 1.57%), respectively. Among 34 patients with AKI, 10 cases with AKI (stage 1a) and 6 cases with AKI (stages 1b, 2, and 3) recovered before their discharge without any treatment for AKI and 9 cases with AKI (stages 1b, 2, and 3) with further treatment. Four cases who had chronic renal failure before MWA of liver accepted renal dialysis. By univariate analysis, the number of antenna insertions (P = 0.027, OR = 3.3), MWA time ≥20 min (P = 0.029, OR = 4.3), creatinine (Cr)-pre above the upper limit of the reference value (P < 0.001, OR = 35.5), albumin (Alb)-pre (P = 0.030, OR = 0.9), and red blood cell (RBC)-pre (P < 0.001, OR = 0.3) were significant risk factors. By multivariate analysis, Cr-pre ≥ 110 μmol/L (P < 0.001, OR = 31.4) and MWA time ≥20 min (P = 0.043 OR = 9.9) were the independent risk factors.

Conclusion: AKI (stages 1b, 2, and 3) is a relatively serious complication after MWA for HCC, which is related to MWA time and Cr-pre. It requires attention by clinicians. So it is of great necessity to assess the Cr-pre level and reduce the MWA time to <20 min to minimize the risk of AKI after MWA for HCC.

Combined use of GM2AP and TCP1-eta urinary levels predicts recovery from intrinsic acute kidney injury

Deficient recovery from acute kidney injury (AKI) has immediate and long-term health, clinical and economic consequences. Pre-emptive recovery estimation may improve nephrology referral, optimize decision making, enrollment in trials, and provide key information for subsequent clinical handling and follow-up. For this purpose, new biomarkers are needed that predict outcome during the AKI episode. We hypothesized that damage pattern-specific biomarkers are expected to more closely associate to outcome within distinct subpopulations (i.e. those affected by specific pathological processes determining a specific outcome), as biomarker pleiotropy (i.e. associated to phenomena unrelated to AKI) introduced by unselected, heterogeneous populations may blur statistics. A panel of urinary biomarkers was measured in patients with AKI and their capacity to associate to normal or abnormal recovery was studied in the whole cohort or after sub-classification by AKI etiology, namely pre-renal and intrinsic AKI. A combination of urinary GM2AP and TCP1-eta best associates with recovery from AKI, specifically within the sub-population of renal AKI patients. This two-step strategy generates a multidimensional space in which patients with specific characteristics (i.e. renal AKI patients with good or bad prognosis) can be identified based on a collection of biomarkers working serially, applying pathophysiology-driven criteria to estimate AKI recovery, to facilitate pre-emptive and personalized handling.

Microenvironment derived from metanephros transplantation inhibits the progression of acute kidney injury in glycerol-induced rat models

Background

Embryonic metanephros is the mammalian renal anlagen, which is considered as a potential source for the regeneration of functional whole kidneys. Some studies reported that metanephros implanted into unilateral nephrectomized animals can develop into kidney tissue. However, kidneys are nephrotoxic in renal failure patients, and whether metanephros can grow in nephrotoxic has not been reported. This study aims to investigate the growth of metanephros in acute nephrotoxic environment and analyze the therapeutic effect of metanephros microenvironment on acute kidney injury (AKI).

Methods

AKI was induced in 200 g Wistar rats by giving intramuscular injections of 50% glycerol (10 mL/kg) in their hind limbs. 45 rats were divided randomly into three groups (control, glycerin, and metanephros). Metanephros group was transplanted two metanephroi (embryonic day 15) into the renal capsule of AKI rats. Glycerin group was AKI rats without transplantation. Control group was untreated.

Results

Mature glomeruli and tubules were detected in the grafts in metanephros group, which means that metanephroi can grow into tissues with mature kidney structure under acute nephrotoxic. Then, we assessed the renal function of host rats and found that there were fewer tubular necrosis in metanephros group than glycerin group, and the serum creatinine and urea nitrogen were significantly lower in metanephros group than glycerin group.

Conclusion

These results suggested that embryonic metanephroi can grow into tissues with mature kidney structure under acute nephrotoxic, and the graft microenvironment was effective in inhibiting the progression of AKI, which provides a new approach for the treatment of acute renal injury.

Lgr5-positive endothelial progenitor cells occupy a tumor and injury prone niche in the kidney vasa recta

The Wnt pathway co-receptor, Leucine Rich Repeat Containing G Protein-Coupled Receptor 5 (LGR5), labels tumor-prone stem cell populations in certain types of tissue. In this study, we show that ARID1A and PIK3CA mutations in LGR5⁺ cells result in renal angiosarcomas in adult mice. The tumors originate in the renal medulla. We further show that LGR5 labels SOX17⁺/CD31⁺/CD34⁺/CD133⁺/AQP1⁺/CD146⁺ endothelial progenitor cells within the descending vasa recta or straight arterioles of the kidney, which are specialized capillaries that maintain medullary osmotic gradients necessary for water reabsorption and the production of concentrated urine. LGR5⁺ endothelial progenitor cells are tightly associated with contractile pericytes within the descending vasa recta. Long-term in vivo lineage tracing revealed that LGR5⁺ cells give rise to renal medullary vasculature. We further show that LGR5⁺ cells are activated in response to ischemic kidney injury. Our findings uncover a physiologically relevant endothelial progenitor cell population within the kidney vasa recta.

Will cell therapies provide the solution for the shortage of transplantable organs?

PURPOSE OF REVIEW

The potential to regenerate ischemically damaged kidneys while being perfused ex-vivo offers the best near-term solution to increasing kidney allografts for transplantation.

RECENT FINDINGS

There are a number of stem-cell sources including: stromal mesenchymal cells (MSC), induced adult pluripotent stem cells, fetal stem cells from placenta, membranes, amniotic fluid and umbilical cord and hematopoietic cells. MSC are increasingly the stem cell of choice and studies are primarily focused on novel induction immunosuppression to prevent rejection. Stem-cell therapies applied in vivo may be of limited benefit because the nonintegrating cells do not remain in the kidney and are not detectable in the body after several days. MSC therapies for transplantation have demonstrated early safety and feasibility. However, efficacy has not been clearly established. A more feasible application of a stem-cell therapy in transplantation is the administration of MSC to treat damaged renal allografts directly while being perfused ex vivo. Initial feasibility has been established demonstrating MSC-treatment results in statistically significant reduction of inflammatory responses, increased ATP and growth factor synthesis and mitosis.

SUMMARY

The ability to regenerate renal tissue ex-vivo sufficiently to result in immediate function could revolutionize transplantation by solving the chronic organ shortage.

Clinical spectrum of community-acquired acute kidney injury: A prospective study from central India

The aim is to study the epidemiology of acute kidney injury (AKI), since it differs from country to country and varies from center to center within a country. Owing to the absence of a central registry, data on overall epidemiology of AKI are scanty from India. This study was conducted in an urban tertiary care center in central India with the aim to identify the etiology and outcomes as well as the factors associated with in-hospital mortality of community-acquired AKI (CAAKI) patients. A two-year prospective study of all patients with CAAKI admitted to the Nephrology Department from January 2014 to December 2015 was performed. Of the 9800 admitted patients, 286 patients (2.9%), with a mean age of 48 ± 17.1 years, were diagnosed to have CAAKI as per our specified criteria. The most common cause of CAAKI was medical (77.27%), followed by obstetrical (13.98%) and surgical (9%) causes. Among the medical causes, hypoperfusion (57.4%) was the most common, followed by sepsis (26.69%), glomerulonephritis (8.14%), and drugs (7%). Nephrolithiasis was the most common surgical cause. Puerperal sepsis (52.5%), preeclampsia (20%), hemorrhage (17.5%), and thrombotic microangiopathy (10%) were the obstetric causes of CAAKI. The overall in-hospital mortality among patients with CAAKI was 20% and 8% of patients became dialysis dependent. Sepsis had the highest in-hospital mortality (44%). The epidemiological characteristics of CAAKI are changing rapidly. There has been an increase in the overall incidence of AKI with changing etiology in recent years. In contrast to developed nations, CAAKI is more common in developing countries. It often affects younger individuals. For early diagnosis of kidney injury and reducing the risk of poor outcome, patients should be referred to nephrologists early in the course of disease.

CYP2J2-produced epoxyeicosatrienoic acids attenuate ischemia/reperfusion-induced acute kidney injury by activating the SIRT1-FoxO3a pathway

Cytochrome P450 (CYP) epoxygenases can metabolize arachidonic acids to epoxyeicosatrienoic acids (EETs), which play a protective role in the renal system, but their involvement in ischemia/reperfusion (I/R)-induced acute kidney injury remains unknown. Here, using a rat model, we demonstrated that forced CYP2J2 expression attenuated I/R-induced renal dysfunction and protected histological integrity. We showed that CYP2J2 significantly decreased I/R-induced upregulation of blood urea nitrogen and serum creatinine and enhanced autophagy during I/R treatment. In addition, we determined the protective effect of CYP2J2 against I/R-caused apoptosis. We demonstrated that CYP2J2 overexpression attenuated the downregulation of SIRT1 and FoxO3a by I/R-induced injury. Moreover, exogenous 11,12-EET addition obviously promoted I/R-induced autophagic flux and suppressed I/R-induced apoptosis through SIRT1-FoxO3a signaling activation. Our data indicate that CYP2J2-produced EETs improve I/R-caused kidney injury by activating the SIRT1-FoxO3a signaling pathway, which protects from renal I/R injury.

Biomarkers of renal recovery after acute kidney injury

Novel biomarkers can be suitable for early acute kidney injury diagnosis and the prediction of the need for dialysis. It remains unclear whether such biomarkers may also play a role in the prediction of recovery after established acute kidney injury or in aiding the decision of when to stop renal support therapy. PubMed, Web of Science and Google Scholar were searched for studies that reported on the epidemiology of renal recovery after acute kidney injury, the risk factors of recovery versus non-recovery after acute kidney injury, and potential biomarkers of acute kidney injury recovery. The reference lists of these articles and relevant review articles were also reviewed. Final references were selected for inclusion in the review based on their relevance. New biomarkers exhibited a potential role in the early diagnosis of acute kidney injury recovery. Urine HGF, IGFBP-7, TIMP-2 and NGAL may improve our ability to predict the odds and timing of recovery and eventually renal support withdrawal. Acute kidney injury recovery requires more study, and its definition needs to be standardized to allow for better and more powerful research on biomarkers because some of them show potential for the prediction of acute kidney injury recovery.

Extracorporeal Stromal Cell Therapy for Subjects With Dialysis-Dependent Acute Kidney Injury

Introduction

The pathophysiology of acute kidney injury (AKI) involves damage to renal epithelial cells, podocytes, and vascular beds that manifests into a deranged, self-perpetuating immune response and peripheral organ dysfunction. Such an injury pattern requires a multifaceted therapeutic to alter the wound healing response systemically. Mesenchymal stromal cells (MSCs) are a unique source of secreted factors that can modulate an inflammatory response to acute organ injury and enhance the repair of injured tissue at the parenchymal and endothelial levels. This phase Ib/IIa clinical trial evaluates SBI-101, a combination product that administers MSCs extracorporeally to overcome pharmacokinetic barriers of MSC transplantation. SBI-101 contains allogeneic human MSCs inoculated into a hollow-fiber hemofilter for the treatment of patients with severe AKI who are receiving continuous renal replacement therapy (CRRT). SBI-101 therapy is designed to reprogram the molecular and cellular components of blood in patients with severe organ injury.

Methods

This study is a prospective, multicenter, randomized, double-blind, sham-controlled, study of subjects with a clinical diagnosis of AKI who are receiving CRRT. Up to 32 subjects may be enrolled to provide 24 evaluable subjects (as a per protocol population). Subjects will receive CRRT in tandem with a sham control (0 MSCs), or the low- (250 × 10⁶ MSCs) or high-dose (750 × 10⁶ MSCs) SBI-101 therapeutic.

Results

The study will measure dose-dependent safety, renal efficacy, and exploratory biomarkers to characterize the pharmacokinetics and pharmacodynamics of SBI-101 in treated subjects.

Conclusion

This first-in-human clinical trial will evaluate the safety and tolerability of SBI-101 in patients with AKI who require CRRT.

Nephrogenic acute respiratory distress syndrome: A narrative review on pathophysiology and treatment

The kidneys have a close functional relationship with other organs especially the lungs. This connection makes the kidney and the lungs as the most organs involved in the multi-organ failure syndrome. The combination of acute lung injury (ALI) and renal failure results a great clinical significance of 80% mortality rate. Acute kidney injury (AKI) leads to an increase in circulating cytokines, chemokines, activated innate immune cells and diffuse of these agents to other organs such as the lungs. These factors initiate pathological cascade that ultimately leads to ALI and acute respiratory distress syndrome (ARDS). We comprehensively searched the English medical literature focusing on AKI, ALI, organs cross talk, renal failure, multi organ failure and ARDS using the databases of PubMed, Embase, Scopus and directory of open access journals. In this narrative review, we summarized the pathophysiology and treatment of respiratory distress syndrome following AKI. This review promotes knowledge of the link between kidney and lung with mechanisms, diagnostic biomarkers, and treatment involved ARDS induced by AKI.

Protective effect of vascular endothelial growth factor against cardiopulmonary bypass-associated acute kidney injury in beagles

The present study aimed to examine the hypothesis that vascular endothelial growth factor (VEGF) has a protective effect against cardiopulmonary bypass (CPB)-associated acute kidney injury (AKI). Eighteen male beagles were randomly allocated to three groups (n=6 per group): Sham group, animals received sternotomy without going through CPB; CPB group, animals received CPB only; VEGF group, animals received CPB and VEGF. VEGF infusion was completed 1 h prior to the initiation of CPB. Renal microcirculation perfusion, serum creatinine (SCr) and blood urea nitrogen (BUN), histopathological injury score and apoptotic index were determined. Hypoxia inducible factor-1α, VEGF, phosphorylated (p)-Akt serine/threonine kinase (Akt), p-endothelial nitric oxide synthase (eNOS), cleaved caspase-3, B-cell lymphoma 2 (Bcl-2) and cluster of differentiation (CD)95 expression levels were assessed by western blot analysis, Enzyme-linked immunosorbent assay quantitative assays were used to evaluate tumor necrosis factor (TNF)-α, interleukin (IL)-6, superoxide dismutase and malondialdehyde levels. Renal microcirculation perfusion of the VEGF group was higher than that of the CPB group (P<0.05) and lower than that of the sham surgery group (P<0.05). SCr and BUN were significantly elevated after CPB in the CPB and VEGF groups, with significantly lower levels in group VEGF than group CPB. Renal pathology scores and apoptotic indices were significantly lower in the VEGF group than the CPB group. Levels of TNF-α, IL-6 in the VEGF group were significantly lower than in the CPB group. Levels of VEGF, p-Akt, p-eNOS and Bcl-2 expression in the VEGF group increased significantly in comparison with group CPB. Cleaved caspase-3 in the VEGF group was significantly lower than in the group CPB. CPB-associated reduction of renal microcirculation perfusion may predispose to AKI. VEGF appears to provide a protective effect on the kidneys through improvement in renal microperfusion.

Urine metabolomics insight into acute kidney injury point to oxidative stress disruptions in energy generation and H2S availability

Acute kidney injury (AKI) is one of the main complications in acute care medicine and a risk factor for chronic kidney disease (CKD). AKI incidence has increased; however, its diagnosis has limitations and physiopathological mechanisms are underexplored. We investigated urine samples, aiming to identify major metabolite changes during human AKI evolution. Metabolic signatures found were further explored for a potential link to severity of injury. Twenty-four control subjects and 38 hospitalized patients with AKI were recruited and urine samples were collected at the time of diagnosis, during follow-up and at discharge. Nuclear magnetic resonance (NMR) was used in a first discovery phase for identifying potential metabolic differences. Target metabolites of interest were confirmed by liquid chromatography-mass spectrometry (LC-MS/MS) in an independent group. Underlying metabolic defects were further explored by kidney transcriptomics of murine toxic AKI. Urinary 2-hydroxybutyric acid, pantothenic acid, and hippuric acid were significantly downregulated and urinary N-acetylneuraminic acid, phosphoethanolamine, and serine were upregulated during AKI. Hippuric acid, phosphoethanolamine, and serine showed further downregulation/upregulation depending on the metabolite in acute tubular necrosis (ATN) AKI compared to prerenal AKI. Kidney transcriptomics disclosed decreased expression of cystathionase, cystathionine-β-synthase, and ethanolamine-phosphate cytidylyltransferase, and increased N-acetylneuraminate synthase as the potentially underlying cause of changes in urinary metabolites. A urinary metabolite panel identified AKI patients and provided insight into intrarenal events. A urine fingerprint made up of six metabolites may be related to pathophysiological changes in oxidative stress, energy generation, and H₂S availability associated with AKI.

KEY MESSAGES

The urinary metabolome reflects AKI evolution and severity of injury. Kidney transcriptomics revealed enzymatic expression changes. Enzymatic expression changes may be the potentially underlying cause of changes in urine metabolites. Identified metabolite changes link oxidative stress, energy generation, and H₂S availability to AKI.

Evaluation of autologous bone marrow-derived mesenchymal stem cells on renal regeneration after experimentally induced acute kidney injury in dogs

OBJECTIVE

To evaluate the usefulness of autologous bone marrow-derived mesenchymal stem cell (BM-MSC) therapy for the treatment of dogs with experimentally induced acute kidney injury.

ANIMALS

6 healthy dogs.

PROCEDURES

After induction of kidney injury (day 0) with cisplatin (5 mg/kg, IV), dogs immediately received saline (0.9% NaCl) solution (10 mL; n = 3) or BM-MSCs (1 × 10(6) cells/kg in 10 mL of saline solution; 3) IV. A CBC, serum biochemical analysis, and urinalysis were performed for each dog before administration of cisplatin and on days 1 through 4. Glomerular filtration rate was determined for all dogs on days -7 and 2; BM-MSC tracking by MRI was performed on BM-MSC-treated dogs on days -14 and 4. After sample collection and BM-MSC tracking on day 4, all dogs were euthanized; kidney tissue samples underwent histologic evaluation, immunohistochemical analysis, and cytokine profiling via reverse transcriptase PCR assays.

RESULTS

Kidney tissue from both groups had mononuclear inflammatory cell infiltration, tubular necrosis, dilated tubules, and glomerular damage. However, there was less fibrotic change and increased proliferation of renal tubular epithelial cells in the BM-MSC-treated dogs, compared with findings for the control dogs. Expressions of tumor necrosis factor-α and transforming growth factor-β were lower in the BM-MSC-treated group, compared with findings for the control group. Laboratory data revealed no improvement in the renal function in BM-MSC-treated dogs.

CONCLUSIONS AND CLINICAL RELEVANCE

Results of this study suggested that autologous BM-MSCs may accelerate renal regeneration after experimentally induced acute kidney injury in dogs.

Cellular Therapies in Trauma and Critical Care Medicine: Forging New Frontiers

Trauma is a leading cause of death in both military and civilian populations worldwide. Although medical advances have improved the overall morbidity and mortality often associated with trauma, additional research and innovative advancements in therapeutic interventions are needed to optimize patient outcomes. Cell-based therapies present a novel opportunity to improve trauma and critical care at both the acute and chronic phases that often follow injury. Although this field is still in its infancy, animal and human studies suggest that stem cells may hold great promise for the treatment of brain and spinal cord injuries, organ injuries, and extremity injuries such as those caused by orthopedic trauma, burns, and critical limb ischemia. However, barriers in the translation of cell therapies that include regulatory obstacles, challenges in manufacturing and clinical trial design, and a lack of funding are critical areas in need of development. In 2015, the Department of Defense Combat Casualty Care Research Program held a joint military–civilian meeting as part of its effort to inform the research community about this field and allow for effective planning and programmatic decisions regarding research and development. The objective of this article is to provide a “state of the science” review regarding cellular therapies in trauma and critical care, and to provide a foundation from which the potential of this emerging field can be harnessed to mitigate outcomes in critically ill trauma patients.

Human recombinant alkaline phosphatase inhibits ex vivo platelet activation in humans

Sepsis-associated acute kidney injury (AKI) is associated with high morbidity and mortality. Excessive platelet activation contributes to AKI through the formation of microthrombi and amplification of systemic inflammation. Two phase II trials demonstrated that bovine-intestinal alkaline phosphatase (AP) improved renal function in critically ill patients with sepsis-associated AKI. In this study, we characterised the platelet-inhibiting effects of a human recombinant AP. Whole blood and platelet-rich plasma (PRP) of healthy volunteers (n=6) was pre-treated ex vivo with recAP, whereafter platelet reactivity to ADP, collagen-related peptide (CRP-XL) and Pam3CSK4 was determined by flow cytometry. RecAP (40 U/ml) reduced the platelet reactivity to ADP (inhibition with a median of 47 %, interquartile range 43-49 %; p<0.001) and tended to reduce platelet reactivity to CRP-XL (9 %, 2-25 %; p=0.08) in whole blood. The platelet-inhibiting effects of recAP were more pronounced in PRP both for ADP- (64 %, 54-68 %; p=0.002) and CRP-XL-stimulated samples (60 %, 46-71 %; p=0.002). RecAP rapidly converted ADP into adenosine, whereas antagonism of the A2A adenosine receptor partially reversed the platelet inhibitory effects of recAP. Platelets of septic shock patients (n=5) showed a 31% (22-34%; p=0.03) more pronounced reactivity compared to healthy volunteers, and this was completely reversed by recAP treatment. In conclusion, we demonstrate that recAP inhibits ex vivo human platelet activation through dephosphorylation of ADP and formation of adenosine as its turnover product. RecAP is able to reverse the platelet hyperreactivity present in septic shock patients. These effects may contribute to the beneficial effects of recAP as a new therapeutic candidate for sepsis-associated AKI.

Daily urinary creatinine predicts the weaning of renal replacement therapy in ICU acute kidney injury patients

Background

In acute kidney injury (AKI), useless continuation of renal replacement therapy (RRT) may delay renal recovery and impair patient’s outcome. In this study, we aimed to identify predictive parameters that may help to a successful RRT weaning for AKI patients.

Methods

We studied 54 surviving AKI patients in which a weaning of RRT was attempted. On the day of weaning (D₀) and the following 2 days (D₁ and D₂), SAPS II and SOFA scores, 24-h diuresis, 24-h urinary creatinine and urea (UCr and UUr), creatinine and urea generation rates (CrGR and UrGR) and clearances (CrCl and UrCl) were collected. Patients who remained free of RRT 15 days after its discontinuation were considered as successfully weaned.

Results

Twenty-six RRT weaning attempts succeeded (S₊) and 28 failed (S₋). Age, previous renal function, SAPS II and SOFA scores were comparable between groups. At D₀, 24-h diuresis was 2300 versus 1950 ml in S₊ and S_−, respectively, p = 0.05. At D₀, D₁ and D₂, 24-h UUr and UCr levels, UrCl and CrCl, and UUr/UrGR and UCr/CrGR ratios were significantly higher in S₊ group. By multivariate analysis, D₁ 24-h UCr was the most powerful parameter that was associated with RRT weaning success with an area under the ROC curve of 0.86 [0.75–0.97] and an odds ratio of 2.01 [1.27–3.18], p = 0.003.

Conclusions

In ICU AKI, 24-h UCr appeared as an efficient and independent marker of a successful weaning of RRT. A 24-h UCr ≥5.2 mmol was associated with a successful weaning in 84 % of patients.

Acute kidney injury: short-term and long-term effects

Acute kidney injury (AKI) is the most common cause of organ dysfunction in critically ill adults, with a single episode of AKI, regardless of stage, carrying a significant morbidity and mortality risk. Since the consensus on AKI nomenclature has been reached, data reflecting outcomes have become more apparent allowing investigation of both short- and long-term outcomes.Classically the short-term effects of AKI can be thought of as those reflecting an acute deterioration in renal function per se. However, the effects of AKI, especially with regard to distant organ function ("organ cross-talk"), are being elucidated as is the increased susceptibility to other conditions. With regards to the long-term effects, the consideration that outcome is a simple binary endpoint of dialysis or not, or survival or not, is overly simplistic, with the reality being much more complex.Also discussed are currently available treatment strategies to mitigate these adverse effects, as they have the potential to improve patient outcome and provide considerable economic health savings. Moving forward, an agreement for defining renal recovery is warranted if we are to assess and extrapolate the efficacy of novel therapies. Future research should focus on targeted therapies assessed by measure of long-term outcomes.

Effect of granulocyte colony-stimulating factor administration on renal regeneration after experimentally induced acute kidney injury in dogs

OBJECTIVE

To evaluate the effects of granulocyte colony-stimulating factor (GCSF) administration in dogs with experimentally induced acute kidney injury.

ANIMALS

6 healthy dogs.

PROCEDURES

After induction of kidney injury (day 0) with cisplatin (5 mg/kg, IV), the dogs were randomly assigned into 2 groups (n = 3 dogs/group). Then dogs immediately received GCSF (10 μg/kg) or 1 mL of saline (0.9% NaCl) solution (control group) SC; this treatment was repeated once daily for 4 additional days (days 1 through 4). A once-daily CBC (day 0 to 4), serum biochemical analysis (day 0 to 3), and urinalysis (day 0 to 3) were performed for each dog; samples were collected before administration of cisplatin (day 0) and before treatment with GCSF or saline solution (days 1 through 4). After sample collection and treatment on day 4, all dogs were euthanized; kidney tissue samples underwent histologic evaluation, immunohistochemical analyses, and cytokine profiling via reverse transcriptase PCR assay.

RESULTS

In the GCSF-treated group, the histologic evaluation and immunohistochemical analyses of kidney tissue revealed less fibrotic change and greater proliferation of renal tubular epithelial cells, compared with findings in the control group. The mRNA profiles of kidney tissue from the GCSF-treated group indicated lower expression of tumor necrosis factor-α and tumor growth factor-β, compared with findings in the control group; however, concentrations of factors related to renal regeneration were not greater in the GCSF-treated group.

CONCLUSIONS AND CLINICAL RELEVANCE

Results indicated that GCSF treatment can impede renal fibrosis and increase proliferation of renal tubules after experimentally induced acute kidney injury in dogs.

Follow-Up Renal Assessment of Injury Long-Term After Acute Kidney Injury (FRAIL-AKI)

BACKGROUND AND OBJECTIVES

Novel urinary kidney damage biomarkers detect AKI after cardiac surgery using cardiopulmonary bypass (CPB-AKI). Although there is growing focus on whether AKI leads to CKD, no studies have assessed whether novel urinary biomarkers remain elevated long term after CPB-AKI. We assessed whether there was clinical or biomarker evidence of long-term kidney injury in patients with CPB-AKI.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

We performed a cross-sectional evaluation for signs of chronic kidney injury using both traditional measures and novel urinary biomarkers in a population of 372 potentially eligible children (119 AKI positive and 253 AKI negative) who underwent surgery using cardiopulmonary bypass for congenital heart disease at Cincinnati Children's Hospital Medical Center between 2004 and 2007. A total of 51 patients (33 AKI positive and 18 AKI negative) agreed to long-term assessment. We also compared the urinary biomarker levels in these 51 patients with those in healthy controls of similar age.

RESULTS

At long-term follow-up (mean duration±SD, 7±0.98 years), AKI-positive and AKI-negative patients had similarly normal assessments of kidney function by eGFR, proteinuria, and BP measurement. However, AKI-positive patients had higher urine concentrations of IL-18 (48.5 pg/ml versus 20.3 pg/ml [P=0.01] and 20.5 pg/ml [P<0.001]) and liver-type fatty acid-binding protein (L-FABP) (5.9 ng/ml versus 3.9 ng/ml [P=0.001] and 3.2 ng/ml [P<0.001]) than did AKI-negative patients and healthy controls.

CONCLUSIONS

Novel urinary biomarkers remain elevated 7 years after an episode of CPB-AKI in children. However, there is no conventional evidence of CKD in these children. These biomarkers may be a more sensitive marker of chronic kidney injury after CPB-AKI. Future studies are needed to understand the clinical relevance of persistent elevations in IL-18, kidney injury molecule-1, and L-FABP in assessments for potential long-term kidney consequences of CPB-AKI.

Alkaline phosphatase protects against renal inflammation through dephosphorylation of lipopolysaccharide and adenosine triphosphate

BACKGROUND AND PURPOSE

Recently, two phase-II trials demonstrated improved renal function in critically ill patients with sepsis-associated acute kidney injury treated with the enzyme alkaline phosphatase. Here, we elucidated the dual active effect on renal protection of alkaline phosphatase.

EXPERIMENTAL APPROACH

The effect of human recombinant alkaline phosphatase (recAP) on LPS-induced renal injury was studied in Sprague-Dawley rats. Renal function was assessed by transcutaneous measurement of FITC-sinistrin elimination in freely moving, awake rats. The mechanism of action of recAP was further investigated in vitro using conditionally immortalized human proximal tubular epithelial cells (ciPTEC).

KEY RESULTS

In vivo, LPS administration significantly prolonged FITC-sinistrin half-life and increased fractional urea excretion, which was prevented by recAP co-administration. Moreover, recAP prevented LPS-induced increase in proximal tubule injury marker, kidney injury molecule-1 expression and excretion. In vitro, LPS-induced production of TNF-α, IL-6 and IL-8 was significantly attenuated by recAP. This effect was linked to dephosphorylation, as enzymatically inactive recAP had no effect on LPS-induced cytokine production. RecAP-mediated protection resulted in increased adenosine levels through dephosphorylation of LPS-induced extracellular ADP and ATP. Also, recAP attenuated LPS-induced increased expression of adenosine A2A receptor. However, the A2A receptor antagonist ZM-241385 did not diminish the effects of recAP.

CONCLUSIONS AND IMPLICATIONS

These results indicate that the ability of recAP to reduce renal inflammation may account for the beneficial effect observed in septic acute kidney injury patients, and that dephosphorylation of ATP and LPS are responsible for this protective effect.

Long-Term Risk of Progressive Chronic Kidney Disease in Patients with Severe Acute Kidney Injury Requiring Dialysis after Coronary Artery Bypass Surgery

AIM

Few studies have evaluated patients after cardiac surgery for subsequent chronic kidney disease (CKD) which increases cardiovascular morbidity and mortality. This study aimed to ascertain the long-term renal outcome in adult patients with severe acute kidney injury (AKI) after coronary artery bypass graft (CABG) surgery.

METHODS

This is a single-center retrospective cohort study of consecutive adult patients who received acute dialysis for AKI after CABG between February 8, 2009 and January 30, 2011. Data on pre- and intra-operative factors were retrieved from electronic medical records. The primary endpoint was CKD progression as defined by dialysis dependence or doubling of serum creatinine from the pre-operative level. Secondary endpoints included in-hospital mortality and renal function at 3 months and 1 year.

RESULTS

Fifty-five patients required acute dialysis after CABG. The median age was 67 years (IQR: 61, 75), and 70.9% were male. Median pre-operative serum creatinine was 157 µmol/l (IQR: 122, 203). A total of 19 patients (34.5%) died. The median follow-up time for hospital survivors was 44.2 months (IQR: 25.0, 49.4) after surgery. Among the 36 survivors, 14 patients (38.9%) reached the primary endpoint. Patients with CKD progression had higher pre-operative serum creatinine [median 214 µmol/l (IQR: 159, 399) vs. 155 µmol/l (112, 187), p = 0.015] and lower eGFR [median 20.4 ml/min/1.73 m(2) (IQR: 11.9, 38.2) vs. 39.9 ml/min/1.73 m(2) (25.9, 55.5), p = 0.027] compared to those who did not have CKD progression.

CONCLUSION

Patients with severe AKI after CABG are at high risk of long-term renal dysfunction and should be monitored regularly for deterioration.

Pharmacological and genetic depletion of fibrinogen protects from kidney fibrosis

Fibrinogen (Fg) has been implicated in the pathogenesis of several fibrotic disorders by acting as a profibrotic ligand for a variety of cellular surface receptors and by modulating the provisional fibrin matrix formed after injury. We demonstrated increased renal Fg expression after unilateral ureteral obstruction and folic acid (FA) nephropathy in mice, respectively. Urinary Fg excretion was also increased in FA nephropathy. Using in vitro and in vivo approaches, our results suggested that IL-6 mediates STAT3 activation in kidney fibrosis and that phosphorylated (p)STAT3 binds to Fgα, Fgβ, and Fgγ promoters in the kidney to regulate their transcription. Genetically modified Fg heterozygous mice (∼75% of normal plasma Fg levels) exhibited only 3% kidney interstitial fibrosis and tubular atrophy after FA nephropathy compared with 24% for wild-type mice. Fibrinogenolysis through Ancrod administration after FA reduced interstitial fibrosis more than threefold compared with vehicle-treated control mice. Mechanistically, we show that Fg acts synergistically with transforming growth factor (TGF)-β1 to induce fibroblast proliferation and activates TGF-β1/pSMAD2 signaling. This study offers increased understanding of Fg expression and molecular interactions with TGF-β1 in the progression to kidney fibrosis and, importantly, indicates that fibrinogenolytics like Ancrod present a treatment opportunity for a yet intractable disease.

Avoidance of systemic anticoagulation during intermittent haemodialysis with heparin-grafted polyacrilonitrile membrane and citrate-enriched dialysate: a retrospective cohort study

Background

Since October 2010, the combination of a heparin-grafted polyacrilonitrile (AN69ST) membrane with a 0.80 mmol/L citric acid-containing dialysate is routinely used in our centre for intermittent haemodialysis, without systemic anticoagulation, in critically ill patients with increased bleeding risk. The primary outcome of this retrospective cohort study was to assess the development of circuit clotting during these dialysis procedures. Secondly, we assessed the impact of clotting on treatment duration, the incidence rate of coagulation-induced retransfusion failure and the association of patient and dialysis characteristics with the occurrence of clotting.

Methods

Dialysis and patient data on consecutive intermittent haemodialysis procedures, performed at the Intensive Care Unit of Universitair Ziekenhuis Brussel between October 2010 and March 2012, were retrospectively reviewed. We used descriptive statistics as well as a random effects logit model with patient identity as a panel variable to assess associations.

Results

Of a total of 309 treatments combining a heparin-grafted AN69ST membrane and a 0.8 mmol/L citric acid-enriched dialysate in 94 patients, circuit clotting was reported in 17.5% (95% CI 13.2% to 21.7%; N = 54), and in 19% (95% CI 13.6% to 24.4%; N = 40) of sessions with prescribed treatment time ≥ 4 hours (N = 210). Clotting shortened treatment time in 15.2% (95% CI 11.4% to 19.7%; N = 47) of sessions by a median of 55 (IQR 20 to 80) minutes. Complete clotting of the circuit with inability for retransfusion occurred in 4.2% (95% CI 2.2% to 7.0%; N = 13) of sessions. Circuit coagulation was not associated with APACHE II score, patient age, gender, number of treatments, type of vascular access or ultrafiltration rate.

Conclusion

Intermittent haemodialysis without systemic anticoagulation combining a heparin-grafted AN69ST dialyzer with a citrate-enriched dialysate favourably compares as to clotting complications with the published outcomes of anticoagulation-free intermittent haemodialysis strategies using saline flushes, heparin-coated dialyzer in combination with regular dialysate or regional citrate anticoagulation with calcium supplemented dialysate. The incidence of circuit clotting in our cohort appears to be higher than previously reported for regional citrate anticoagulation with a calcium-free dialysate.

Activation of the miR-17 family and miR-21 during murine kidney ischemia-reperfusion injury

BACKGROUND

Ischemia-reperfusion (I/R) is the main cause of acute kidney injury (AKI) in patients. We investigated renal microRNA (miRNA) expression profiles and the time course of changes in selected miRNA expressions after renal I/R to characterize the miRNA network activated during development and recovery from AKI.

METHODS AND RESULTS

One day after lethal (30 minutes) and sublethal (20 minutes) renal ischemia, AKI was verified by renal histology (tubular necrosis, regeneration), blood urea nitrogen (BUN) level, renal mRNA expression, and plasma concentration of neutrophil gelatinase-associated lipocalin (NGAL) in C57BL/6J mice. On the first day after 30-minute, lethal I/R miR-21, miR-17-5p, and miR-106a were elevated out of the 21 miRNAs successfully profiled on the Luminex multiplex assay. After 20-minute, sublethal I/R, renal miR-17-5p and miR-106a expressions were elevated on the first and second days of reperfusion, while miR-21 expression increased later and lasted longer. Renal miR-17-5p and miR-21 expressions correlated with each other. Renal function returned to normal on the fourth day after sublethal I/R.

CONCLUSIONS

Our results demonstrate that besides miR-21, miR-17-5p, and miR-106a are additionally activated during the maintenance and recovery phases of renal I/R injury. Furthermore, a correlation between renal miR-17-5p and miR-21 expressions warrants further investigation of how they may influence each other and the outcome of renal ischemia-reperfusion injury.

New tides: using zebrafish to study renal regeneration

Over the past several decades, the zebrafish has become one of the major vertebrate model organisms used in biomedical research. In this arena, the zebrafish has emerged as an applicable system for the study of kidney diseases and renal regeneration. The relevance of the zebrafish model for nephrology research has been increasingly appreciated as the understanding of zebrafish kidney structure, ontogeny, and the response to damage has steadily expanded. Recent studies have documented the amazing regenerative characteristics of the zebrafish kidney, which include the ability to replace epithelial populations after acute injury and to grow new renal functional units, termed nephrons. Here we discuss how nephron composition is conserved between zebrafish and mammals, and highlight how recent findings from zebrafish studies utilizing transgenic technologies and chemical genetics can complement traditional murine approaches in the effort to dissect how the kidney responds to acute damage and identify therapeutics that enhance human renal regeneration.