The intensive care medicine agenda on acute kidney injury

Multifunctional Nanosystem Based on Ultrasmall Carbon Dots for the Treatment of Acute Kidney Injury

Acute kidney injury (AKI) is a critical medical condition characterized by high morbidity and mortality rates. The pathogenesis of AKI potentially involves bursts of reactive oxygen species (ROS) bursts and elevated levels of inflammatory mediators. Developing nanoparticles (NPs) that downregulate ROS and inflammatory mediators is a promising approach to treat AKI. However, such NPs would be affected by the glomerular filtration barrier (GFB). Typically, NPs are too large to penetrate the glomerular system and reach the renal tubules─the primary site of AKI injury. Herein, we report the development of ultrasmall carbon dots-gallic acid (CDs-GA) NPs (∼5 nm). These NPs exhibited outstanding biocompatibility and were shown not only to efficiently eliminate ROS and alleviate oxidative stress but also to suppress the activation of the NF-κB signaling pathway, leading to a reduction in the release of inflammatory factors. Importantly, CDs-GA NPs were shown to be able to rapidly accumulate rapidly in the renal tissues without the need for intricate targeting strategies. In vivo studies demonstrated that CDs-GA NPs significantly reduced the incidence of cisplatin (CDDP)-induced AKI in mice, surpassing the efficacy of the small molecular drug, N-acetylcysteine. This research provides an innovative strategy for the treatment of AKI.

How a positive fluid balance develops in acute kidney injury: A binational, observational study

PURPOSE

A positive fluid balance (FB) is associated with harm in intensive care unit (ICU) patients with acute kidney injury (AKI). We aimed to understand how a positive balance develops in such patients.

METHODS

Multinational, retrospective cohort study of critically ill patients with AKI not requiring renal replacement therapy.

RESULTS

AKI occurred at a median of two days after admission in 7894 (17.3%) patients. Cumulative FB became progressively positive, peaking on day three despite only 848 (10.7%) patients receiving fluid resuscitation in the ICU. In those three days, persistent crystalloid use (median:60.0 mL/h; IQR 28.9-89.2), nutritional intake (median:18.2 mL/h; IQR 0.0-45.9) and limited urine output (UO) (median:70.8 mL/h; IQR 49.0-96.7) contributed to a positive FB. Although UO increased each day, it failed to match input, with only 797 (10.1%) patients receiving diuretics in ICU. After adjustment, a positive FB four days after AKI diagnosis was associated with an increased risk of hospital mortality (OR 1.12;95% confidence intervals 1.05-1.19;p-value <0.001).

CONCLUSION

Among ICU patients with AKI, cumulative FB increased after diagnosis and was associated with an increased risk of mortality. Continued crystalloid administration, increased nutritional intake, limited UO, and minimal use of diuretics all contributed to positive FB.

KEY POINTS

Question How does a positive fluid balance develop in critically ill patients with acute kidney injury? Findings Cumulative FB increased after AKI diagnosis and was secondary to persistent crystalloid fluid administration, increasing nutritional fluid intake, and insufficient urine output. Despite the absence of resuscitation fluid and an increasing cumulative FB, there was persistently low diuretics use, ongoing crystalloid use, and a progressive escalation of nutritional fluid therapy. Meaning Current management results in fluid accumulation after diagnosis of AKI, as a result of ongoing crystalloid administration, increasing nutritional fluid, limited urine output and minimal diuretic use.

Acute and long-term renal effects after iodine contrast media-enhanced computerised tomography in the critically ill-a retrospective bi-centre cohort study

OBJECTIVES

To determine if current clinical use of iodine contrast media (ICM) for computerised tomography (CT) increases the risk of acute kidney injury (AKI) and long-term decline in renal function in patients treated in intensive care.

METHODS

A retrospective bi-centre cohort study was performed with critically ill subjects undergoing either ICM-enhanced or unenhanced CT. AKI was defined and staged based on the Kidney Disease Improve Global Outcome AKI criteria, using both creatinine and urine output criteria. Follow-up plasma creatinine was recorded three to six months after CT to assess any long-term effects of ICM on renal function.

RESULTS

In total, 611 patients were included in the final analysis, median age was 65.0 years (48.0-73.0, quartile 1-quartile 3 (IQR)) and 62.5% were male. Renal replacement therapy was used post-CT in 12.9% and 180-day mortality was 31.2%. Plasma creatinine level on day of CT was 100.0 µmol/L (66.0-166.5, IQR) for non-ICM group and 77.0 µmol/L (59.0-109.0, IQR) for the ICM group. The adjusted odds ratio for developing AKI if the patient received ICM was 1.03 (95% confidence interval 0.64-1.66, p = 0.90). No significant association between ICM and increase in plasma creatinine at long-term follow-up was found, with an adjusted effect size of 2.92 (95% confidence interval - 6.52-12.36, p = 0.543).

CONCLUSIONS

The results of this study do not indicate an increased risk of AKI or long-term decline in renal function when ICM is used for enhanced CT in patients treated at intensive care units.

CLINICAL RELEVANCE STATEMENT

Patients treated in intensive care units had no increased risk of acute kidney injury or persistent decline in renal function after contrast-enhanced CT. This information underlines the need for a proper risk-reward assessment before denying patients a contrast-enhanced CT.

KEY POINTS

• Iodine contrast media is considered a risk factor for the development of acute kidney injury. • Patients receiving iodine contrast media did not have an increased incidence of acute kidney injury or persistent decline in renal function. • A more clearly defined risk of iodine contrast media helps guide clinical decisions whether to perform contrast-enhanced CTs or not.

Urinary cell cycle biomarkers for the prediction of renal non-recovery in patients with septic acute kidney injury: a prospective study

BACKGROUND

Poor prognosis has been associated with the absence of renal recovery after acute kidney injury (AKI). This study aimed to investigate whether urinary biomarkers at 0 and 24 h could be used independently or in conjunction with a clinical model to predict renal non-recovery in septic AKI.

METHODS

A prospective observational study was conducted to measure the urinary levels of insulin-like growth factor-binding protein 7 (IGFBP7) and tissue inhibitor of metalloproteinase-2 (TIMP-2) at the time of AKI diagnosis (0 h) and 24 h later. Renal non-recovery within 7 days was defined as the outcome. The predictive value of urinary biomarkers for renal non-recovery in septic AKI was assessed using the area under the curve (AUC).

RESULTS

A total of 198 individuals with septic AKI were included in the final analysis. Among them, 38.9% (n = 77) did not experience renal recovery within 7 days. The combination of urinary IGFBP7 and TIMP-2 at the initial time point demonstrated prognostic value for non-recovery of renal function, with an AUC of 0.782. When [TIMP-2]*[IGFBP7] was measured at 0 h, the clinical prognostic model, incorporating AKI stage 2-3 and the non-renal sequential organ failure assessment score, showed an improved AUC of 0.822 (with a sensitivity of 88.3% and specificity of 59.5%).

CONCLUSIONS

The combination of urinary [TIMP-2]*[IGFBP7] at 0 h exhibited moderate predictive ability for renal non-recovery in cases of septic AKI. However, there is potential to enhance the prognostic capabilities of the [TIMP-2]*[IGFBP7]-clinical prediction model.

Assessing GFR With Proenkephalin

Introduction

In clinical practice, kidney (dys)function is monitored through creatinine-based estimations of glomerular filtration rate (eGFR: Modification of Diet in Renal Disease [MDRD], Chronic Kidney Disease Epidemiology Collaboration [CKD-EPI]). Creatinine is recognized as a late and insensitive biomarker of glomerular filtration rate (GFR). The novel biomarker proenkephalin (PENK) may overcome these limitations, but no PENK-based equation for eGFR is currently available. Therefore, we developed and validated a PENK-based equation to assess GFR.

Methods

In this international multicenter study in 1354 stable and critically ill patients, GFR was measured (mGFR) through iohexol or iothalamate clearance. A generalized linear model with sigmoidal nonlinear transfer function was used for equation development in the block-randomized development set. Covariates were selected in a data-driven fashion. The novel equation was assessed for bias, precision (mean ± SD), and accuracy (eGFR percentage within ±30% of mGFR, P30) in the validation set and compared with MDRD and CKD-EPI.

Results

Median mGFR was 61 [44-81] ml/min per 1.73 m2. In order of importance, PENK, creatinine, and age were included, and sex or race did not improve performance. The PENK-based equation mean ± SD bias of the mGFR was 0.5 ± 15 ml/min per 1.73 m2, significantly less compared with MDRD (8 ± 17, P < 0.001) and 2009 CKD-EPI (5 ± 17, P < 0.001), not reaching statistical significance compared with 2021 CKD-EPI (1.3 ± 16, P = 0.06). The P30 accuracy of the PENK-based equation was 83%, significantly higher compared with MDRD (68%, P < 0.001) and 2009 CKD-EPI (76%, P < 0.001), similar to 2021 CKD-EPI (80%, P = 0.13).

Conclusion

Overall, the PENK-based equation to assess eGFR performed better than most creatinine-based equations without using sex or race.

The predictive value of [TIMP-2]*[IGFBP7] in adverse outcomes for acute kidney injury: a systematic review and meta-analysis

MATERIALS AND METHODS

Relevant articles published up to 17 June 2023 were retrieved from five databases (Cochrane Library/Embase/PubMed/SinoMed/Web of Science). The pre-established inclusion and exclusion criteria determined the selection of publications. Pooled sensitivity (SEN), specificity (SPE), diagnostic odds ratio, likelihood ratio, and summary receiver operating characteristic curve were employed to assess the predictive value. The presence or potential sources of heterogeneity were investigated via subgroup and SEN analyses.

RESULTS

Ten published and eligible studies (1559 cases) were included in the evaluation for the capability of [TIMP-2]*[IGFBP7] to predict the poor prognosis of AKI through the random effect model. Pooled SEN, SPE, diagnostic odds ratio, and positive and negative likelihood ratios were 0.82 (95% CI: 0.77-0.86, I2 = 53.4%), 0.64 (95% CI: 0.61-0.67, I2 = 88.3%), 14.06 (95% CI: 7.31-27.05, I2 = 55.0%), 2.859 (95% CI: 2.15-3.77, I2 = 80.7%), and 0.28 (95% CI: 0.20-0.40, I2 = 35.0%), respectively. The estimated area under the curve was 0.8864 (standard error: 0.0306), and the Q* was 0.7970 (standard error: 0.0299). The endpoints and cutoff values were the main causes of heterogeneity.

CONCLUSIONS

[TIMP-2]*[IGFBP7] is possible in predicting poor prognosis of AKI, but it is better to be applied along with other indicators or clinical risk factors.

Knockdown of ELF4 aggravates renal injury in ischemia/reperfusion mice through promotion of pyroptosis, inflammation, oxidative stress, and endoplasmic reticulum stress

BACKGROUND

Renal ischemia/reperfusion (I/R) injury is a major cause of acute kidney injury (AKI). Dysfunction of E74-like ETS transcription factor 4 (ELF4) leads to inflammation. This research intended to look into the function and mechanisms of ELF4 in I/R and oxygen-glucose deprivation/reperfusion (OGD/R) model.

RESULTS

In I/R and OGD/R model, ELF4 expression was downregulated. ELF4 knockout aggravated I/R-induced kidney injury, oxidative stress (OS), endoplasmic reticulum stress (ERS), apoptosis, inflammation, and pyroptosis in mice. In HK-2 cells treated with OGD/R, suppression of ELF4 expression inhibited cell proliferation and promoted cell apoptosis, OS, ERS, inflammation, and pyroptosis. Moreover, ELF4 overexpression led to the opposite results.

CONCLUSION

ELF4 deficiency aggravated I/R induced AKI, which was involved in apoptosis, OS, ERS, inflammation, and pyroptosis. Targeting ELF4 may be a promising new therapeutic strategy for preventing inflammation after IR-AKI.

Cardiovascular Magnetic Resonance in Survivors of Critical Illness: Cardiac Abnormalities Are Associated With Acute Kidney Injury

Background The objective of this study was to investigate cardiac abnormalities in intensive care unit (ICU) survivors of critical illness and to determine whether temporary acute kidney injury (AKI) is associated with more pronounced findings on cardiovascular magnetic resonance. Methods and Results There were 2175 patients treated in the ICU (from 2015 until 2021) due to critical illness who were screened for study eligibility. Post-ICU patients without known cardiac disease were prospectively recruited from March 2021 to May 2022. Participants underwent cardiovascular magnetic resonance including assessment of cardiac function, myocardial edema, late gadolinium enhancement, and mapping including extracellular volume fraction. Student t test, Mann-Whitney U test, and χ2 tests were used. There were 48 ICU survivors (46±15 years of age, 28 men, 29 with AKI and continuous kidney replacement therapy, and 19 without AKI) and 20 healthy controls who were included. ICU survivors had elevated markers of myocardial fibrosis (T1: 995±31 ms versus 957±21 ms, P<0.001; extracellular volume fraction: 24.9±2.5% versus 22.8±1.2%, P<0.001; late gadolinium enhancement: 1% [0%-3%] versus 0% [0%-0%], P<0.001), more frequent focal late gadolinium enhancement lesions (21% versus 0%, P=0.03), and an impaired left ventricular function (eg, ejection fraction: 57±6% versus 60±5%, P=0.03; systolic longitudinal strain: 20.3±3.7% versus 23.1±3.5%, P=0.004) compared with healthy controls. ICU survivors with AKI had higher myocardial T1 (1002±33 ms versus 983±21 ms; P=0.046) and extracellular volume fraction values (25.6±2.6% versus 23.9±1.9%; P=0.02) compared with participants without AKI. Conclusions ICU survivors of critical illness without previously diagnosed cardiac disease had distinct abnormalities on cardiovascular magnetic resonance including signs of myocardial fibrosis and systolic dysfunction. Findings were more abnormal in participants who experienced AKI with necessity of continuous kidney replacement therapy during their ICU stay. Registration URL: https://www.clinicaltrials.gov; Unique identifier: NCT05034588.

Long-term outcomes after severe acute kidney injury in critically ill patients: the SALTO study

BACKGROUND

The extent of the consequences of an episode of severe acute kidney injury (AKI) on long-term outcome of critically ill patients remain debated. We conducted a prospective follow-up of patients included in a large multicenter clinical trial of renal replacement therapy (RRT) initiation strategy during severe AKI (the Artificial Kidney Initiation in Kidney Injury, AKIKI) to investigate long-term survival, renal outcome and health related quality of life (HRQOL). We also assessed the influence of RRT initiation strategy on these outcomes.

RESULTS

Follow-up of patients extended from 60 days to a median of 3.35 years [interquartile range (IQR), 1.89 to 4.09] after the end of initial study. Of the 619 patients included in the AKIKI trial, 316 survived after 60 days. The overall survival rate at 3 years from inclusion was 39.4% (95% CI 35.4 to 43.4). A total of 46 patients (on the 175 with available data on long-term kidney function) experienced worsening of renal function (WRF) at the time of follow-up [overall incidence of 26%, cumulative incidence at 4 years: 20.6% (CI 95% 13.0 to 28.3)]. Fifteen patients required chronic dialysis (5% of patients who survived after day 90). Among the 226 long-term survivors, 80 (35%) answered the EQ-5D questionnaire. The median index value reported was 0.67 (IQR 0.40 to 1.00) indicating a noticeable alteration of quality of life. Initiation strategy for RRT had no effect on any long-term outcome.

CONCLUSION

Severe AKI in critically ill patients was associated with a high proportion of death within the first 2 months but less so during long-term follow-up. A quarter of long-term survivors experienced a WRF and suffered from a noticeable impairment of quality of life. Renal replacement therapy initiation strategy was not associated with mortality outcome.

Diagnosing acute kidney injury ahead of time in critically ill septic patients using kinetic estimated glomerular filtration rate

INTRODUCTION

Accurate and actionable diagnosis of Acute Kidney Injury (AKI) ahead of time is important to prevent or mitigate renal insufficiency. The purpose of this study was to evaluate the performance of Kinetic estimated Glomerular Filtration Rate (KeGFR) in timely predicting AKI in critically ill septic patients.

METHODS

We conducted a retrospective analysis on septic ICU patients who developed AKI in AmsterdamUMCdb, the first freely available European ICU database. The reference standard for AKI was the Kidney Disease: Improving Global Outcomes (KDIGO) classification based on serum creatinine and urine output (UO). Prediction of AKI was based on stages defined by KeGFR and UO. Classifications were compared by length of ICU stay (LOS), need for renal replacement therapy and 28-day mortality. Predictive performance and time between prediction and diagnosis were calculated.

RESULTS

Of 2492 patients in the cohort, 1560 (62.0%) were diagnosed with AKI by KDIGO and 1706 (68.5%) by KeGFR criteria. Disease stages had agreement of kappa = 0.77, with KeGFR sensitivity 93.2%, specificity 73.0% and accuracy 85.7%. Median time to recognition of AKI Stage 1 was 13.2 h faster for KeGFR, and 7.5 h and 5.0 h for Stages 2 and 3. Outcomes revealed a slight difference in LOS and 28-day mortality for Stage 1.

CONCLUSIONS

Predictive performance of KeGFR combined with UO criteria for diagnosing AKI is excellent. Compared to KDIGO, deterioration of renal function was identified earlier, most prominently for lower stages of AKI. This may shift the actionable window for preventing and mitigating renal insufficiency.

Renal scintigraphy to predict persistent renal failure after acute kidney injury: an observational study

INTRODUCTION

Renal scintigraphy (RS) is occasionally performed to assess the risk of persistent renal failure (PRF) in patients with acute kidney disease (AKD). However, its diagnostic performance has never been assessed.

METHODS

We identified all patients with AKD for whom RS was performed in our institution between 2010 and 2017. PRF was defined as persistently low (< 33% of baseline) estimated glomerular filtration rates (eGFR), 1 year after RS. Nuclear medicine specialists reviewed RS data and rated, for each patient, the likelihood of PRF ("PRF score"). We evaluated the performance to predict PRF (area under the ROC curve (AUC)) of RS-derived parameters such as renal accumulation index, accumulation slope, and new parameters derived from serial kidney activity counts. We tested the ability of those parameters to improve a clinical model including hypertension, diabetes, AKI severity and baseline eGFR. Finally, we conducted sensitivity analyses using alternate PRF definitions.

RESULTS

Among 97 patients included, 57 (59%) fulfilled the criteria for PRF. The PRF score was able to predict PRF with an AUC of 0.63. Similarly, the accumulation index and accumulation slope respective AUCs were 0.64 and 0.63. None of these parameters were able to improve the performance of the clinical model. Among new parameters, the 3rd/2nd minute activity ratio and 3rd/2nd minute activity slope had fair diagnostic performance (AUC 0.72 and 0.74, respectively) and improved the performance of the clinical model. Results were confirmed in sensitivity analyses.

CONCLUSION

Conventional renal scintigraphy can identify patients at high risk of PRF with a high specificity but a low sensitivity. New parameters, with comparable diagnostic abilities can be obtained within three minutes of injection.

Monitoring kidney size to interpret MRI-based assessment of renal oxygenation in acute pathophysiological scenarios

AIM

Tissue hypoxia is an early key feature of acute kidney injury. Assessment of renal oxygenation using magnetic resonance imaging (MRI) markers T₂ and T₂ * enables insights into renal pathophysiology. This assessment can be confounded by changes in the blood and tubular volume fractions, occurring upon pathological insults. These changes are mirrored by changes in kidney size (KS). Here, we used dynamic MRI to monitor KS for physiological interpretation of T₂ * and T₂ changes in acute pathophysiological scenarios.

METHODS

KS was determined from T₂ *, T₂ mapping in rats. Six interventions that acutely alter renal tissue oxygenation were performed directly within the scanner, including interventions that change the blood and/or tubular volume. A biophysical model was used to estimate changes in O₂ saturation of hemoglobin from changes in T₂ * and KS.

RESULTS

Upon aortic occlusion KS decreased; this correlated with a decrease in T₂ *, T₂ . Upon renal vein occlusion KS increased; this negatively correlated with a decrease in T₂ *, T₂ . Upon simultaneous occlusion of both vessels KS remained unchanged; there was no correlation with decreased T₂ *, T₂ . Hypoxemia induced mild reductions in KS and T₂ *, T₂ . Administration of an X-ray contrast medium induced sustained KS increase, with an initial increase in T₂ *, T₂ followed by a decrease. Furosemide caused T₂ *, T₂ elevation and a minor increase in KS. Model calculations yielded physiologically plausible calibration ratios for T₂ *.

CONCLUSION

Monitoring KS allows physiological interpretation of acute renal oxygenation changes obtained by T₂ *, T₂ . KS monitoring should accompany MRI-oximetry, for new insights into renal pathophysiology and swift translation into human studies.

The Versatile Role of miR-21 in Renal Homeostasis and Diseases

MicroRNAs (miRNAs) are small, non-coding RNA species that control gene expression and confer robustness to biological processes. Over the last two decades, their important roles during kidney development, homeostasis and the treatment of diseases have been established, in particular during the onset and progression of various forms of acute and chronic renal disorders. In recent years, miR-21, one of the best-characterized miRNAs to date, has received much attention in renal physiology in particular given its high degree of conservation and expression in kidneys, as well as its potent pathogenic role in various debilitating renal diseases. This review summarizes the current knowledge on miR-21’s involvement in both renal homeostasis and diseases, in particular its double-edged-sword role in acute versus chronic kidney injuries. Finally, we also discuss the potential of miR-21 as a biomarker and therapeutic target in renal diseases.

Renal replacement therapy for acute kidney injury in burn patients, an international survey and a qualitative review of current controversies

BACKGROUND OF THE STUDY

Acute kidney injury (AKI) is a common complication in critically ill burn patients and is associated with a number of serious adverse outcomes. The clinical decision-making process related to the management of AKI in burn patients is complex and has not been sufficiently standardized. The main aim of this study was to explore the diagnostic approach and clinician's attitudes toward the management of AKI and RRT in burn patients around the world.

METHODS

The questionnaire was widely distributed among the members of International Society for Burn Injury (ISBI), who were invited to complete the survey. Data collection and report was compliant with the the Checklist for Reporting Results of Internet E-Surveys (CHERRIES) Web-survey guidelines. The survey form with multiple-choice questions was divided into 3 parts: a. physician and institutional demographics, b. AKI diagnostic information, c. technical aspects of RRT.

RESULTS

A total of 44 respondents worldwide submitted valuable data in the 2-month period. Of all respondents, 43.2% were from Europe, 30% from North America, 7% from South-East Asia 2.3% from Africa and 18.2% from other regions. 93.1% of participants declare that they use specific definitions to detect AKI, while 11.4% declare the use of renal ultrasonography for AKI diagnosis. CRRT appeared to be the most preferred option by 43.2% of participants, followed by intermittent hemodialysis (25%), and prolonged intermittent RRT (6.8%). The expertise to deliver a modality and the availability of resources were considered important factors when selecting the optimal RRT modality by 20.5% and 29.6% of respondents. The use of specific serum biomarkers for AKI diagnosis are stated by 16% of respondents; 25% of specialists refer to the use of biomarkers of AKI as a criterium for discontinuing the RRT. Femoral vena and right jugular vena were the most frequently used location for RRT temporary catheter placement, 54.6% of respondents declared using ultrasound guidance for catheter placement.

CONCLUSIONS

The majority of burn specialists use specific consensus classifications to detect acute kidney injury. Continuous renal replacement therapy appeared to be the most preferred option, while the expertise to deliver a particular modality and resources availability play a significant role in modality selection. The use of ultrasound and specific biomarkers for AKI evaluation is infrequent in routine clinical practice.

Internal and external validation of machine learning-assisted prediction models for mechanical ventilation-associated severe acute kidney injury

BACKGROUND

Currently, very few preventive or therapeutic strategies are used for mechanical ventilation (MV)-associated severe acute kidney injury (AKI).

OBJECTIVES

We developed clinical prediction models to detect the onset of severe AKI in the first week of intensive care unit (ICU) stay during the initiation of MV.

METHODS

A large ICU database Medical Information Mart for Intensive Care IV (MIMIC-IV) was analysed retrospectively. Data were collected from the clinical information recorded at the time of ICU admission and during the initial 12 h of MV. Using univariate and multivariate analyses, the predictors were selected successively. For model development, two machine learning algorithms were compared. The primary goal was to predict the development of AKI stage 2 or 3 (AKI-23) and AKI stage 3 (AKI-3) in the first week of patients' ICU stay after initial 12 h of MV. The developed models were externally validated using another multicentre ICU database (eICU Collaborative Research Database, eICU) and evaluated in various patient subpopulations.

RESULTS

Models were developed using data from the development cohort (MIMIC-IV: 2008-2016; n = 3986); the random forest algorithm outperformed the logistic regression algorithm. In the internal (MIMIC-IV: 2017-2019; n = 1210) and external (eICU; n = 1494) validation cohorts, the incidences of AKI-23 were 154 (12.7%) and 119 (8.0%), respectively, with areas under the receiver operator characteristic curve of 0.78 (95% confidence interval [CI]: 0.74-0.82) and 0.80 (95% CI: 0.76-0.84); the incidences of AKI-3 were 81 (6.7%) and 67 (4.5%), with areas under the receiver operator characteristic curve of 0.81 (95% CI: 0.76-0.87) and 0.80 (95% CI: 0.73-0.86), respectively.

CONCLUSIONS

Models driven by machine learning and based on routine clinical data may facilitate the early prediction of MV-associated severe AKI. The validated models can be found at: https://apoet.shinyapps.io/mv_aki_2021_v2/.

Small, short-term, point-of-care creatinine changes as predictors of acute kidney injury in critically ill patients

PURPOSE

To assess short-term creatinine changes as predictors of acute kidney injury (AKI) when used alone and in combination with AKI risk factors.

METHODS

In this prospective cohort study, we identified all creatinine measurements from frequent point-of-care arterial blood gas measurements from ICU admission until AKI. We evaluated the predictive value of small changes between these creatinine measurements for AKI development, alone and with AKI risk factors.

RESULTS

Of 377 patients with 3235 creatinine measurements, generating 15,075 creatinine change episodes, 215 (57%) patients developed AKI, and 68 (18%) developed stage 2 or 3 AKI. In isolation, a creatinine increase over 4.1-7.3 h had a 0.65 area under the curve for predicting stage 2 or 3 AKI within 3-37.7 h. Combining creatinine increases of ≥1 μmol/L/h (≥0.0113 mg/dL/h) over 4-5.8 h with three AKI risk factors (cardiac surgery, use of vasopressors, chronic liver disease) had 83% sensitivity, 79% specificity and 0.87 area under the curve for stage 2 or 3 AKI occurring 8.7-25.6 h later.

CONCLUSION

In combination with key risk factors, frequent point-of-care creatinine assessment on arterial blood gases to detect small, short-term creatinine changes provides a robust, novel, low-cost, and rapid method for predicting AKI in critically ill patients.

Mesenchymal Stem Cells-Derived Exosomes Ameliorate Ischemia/Reperfusion Induced Acute Kidney Injury in a Porcine Model

Exosomes are membrane-enclosed vesicles secreted by cells, containing a variety of biologically active ingredients including proteins, nucleic acids and lipids. In this study, we investigated the therapeutic effects of the exosomes and underlying mechanisms in a miniature pig model of ischemia/reperfusion-induced acute kidney injury (I/R-AKI). The exosomes were extracted from cultured human umbilical cord derived mesenchymal stem cells (hUC-MSCs) and infused into a miniature pig model of I/R AKI. Our results showed that 120 min of unilateral ischemia followed by reperfusion and contralateral nephrectomy resulted in renal dysfunction, severe kidney damage, apoptosis and necroptosis. Intravenous infusion of one dose of exosomes collected from about 4 × 108 hUC-MSCs significantly improved renal function and reduced apoptosis and necroptosis. Administration of hUC-MSC exosomes also reduced the expression of some pro-inflammatory cytokines/chemokines, decreased infiltration of macrophages to the injured kidneys and suppressed the phosphorylation of nuclear factor-κB and signal transducer and activator of transcription 3, two transcriptional factors related to inflammatory regulation. Moreover, hUC-MSC exosomes could promote proliferation of renal tubular cells, angiogenesis and upregulation of Klotho and Bone Morphogenetic Protein 7, two renoprotective molecules and vascular endothelial growth factor A and its receptor. Collectively, our results suggest that injection of hUC-MSC exosomes could ameliorate I/R-AKI and accelerate renal tubular cell repair and regeneration, and that hUC-MSC exosomes may be used as a potential biological therapy for Acute kidney injury patients.

Downregulation of IRF2 Alleviates Sepsis-Related Acute Kidney Injury in vitro and in vivo

Objective

We investigated the roles and mechanisms of IRF2 in sepsis-related acute kidney injury (S-AKI) in a lipopolysaccharide (LPS)-induced HK-2 cell line and caecal ligation and puncture (CLP)-induced IRF2^−/− mouse model.

Methods

Quantitative real-time polymerase chain reaction assay was used to detect IRF2 in the serum of S-AKI patients and LPS-induced HK-2 cells. Cell proliferation, death, and apoptosis were analysed by CCK-8, lactate dehydrogenase release, and flow cytometry assays, respectively. The levels of interleukin (IL)-1β, IL-18, IL-6, tumour necrosis factor (TNF)-α, non-canonical inflammasomes, including caspase-4 and gasdermin-D (GSDMD), and canonical inflammasomes, such as caspase-1, NLR family pyrin domain containing 3 (NLRP3), and apoptosis-associated speck-like protein (ASC) in S-AKI cells or animal models were analysed by enzyme-linked immunosorbent assay or Western blotting.

Results

IRF2 was upregulated in the serum of S-AKI patients and LPS-induced HK-2 cells. IRF2 downregulation promoted cell proliferation and inhibited cell death and apoptosis, respectively. IRF2 inhibition reduced the levels of IL-1β, IL-18, IL-6, and TNF-α in S-AKI cells and animal models. IRF2 knockdown inhibited LPS-treated HK-2 cell pyroptosis by decreasing the expression of caspase-4 and GSDMD, instead of affecting caspase-1, NLRP3, and ASC. An elevated survival rate and alleviated pathological features and scores were observed in the CLP-induced IRF2^−/− animal models. IRF2 deficiency also suppressed inflammation and pyroptosis by inhibiting non-canonical inflammasomes as indicated by the decreased expression of caspase-11 and GSDMD.

Conclusion

Our findings suggest that IRF2 downregulation protects against S-AKI in vitro and in vivo.

[Epidemiology and Causes of Acute Renal Failure and Transition to Chronic Kidney Disease]

Acute kidney injury (AKI) refers to an acute functional deterioration of the kidneys, which leads to retention of urinary substances, dysregulation of the electrolyte and acid-base balance, and disturbance of fluids. Although didactically helpful, the oversimplified AKI classification of prerenal/renal/postrenal is currently considered obsolete. Indeed, the boundaries blur quite quickly, particularly between prerenal and renal causes. Based on the AKI pathophysiology, it can be etiologically divided into decreased renal perfusion, postrenal obstruction and kidney specific injury or unspecific injury. AKI is a common event in hospitalized patients and associates strongly with mortality and chronic kidney disease (CKD). Today it is accepted that AKI and CKD are rather an individually variable continuum, than 2 distinct entities. If AKI has not regressed after 7 days, it is referred to as acute kidney disease (AKD). Persisting AKD for > 90 days is classified as CKD. The transition from AKD to CKD is the result of an incomplete and maladaptive repair process. Although follow-up of post-AKI patients is essential, optimal concepts still need to be developed.

Acute Kidney Injury: Biomarker-Guided Diagnosis and Management

Acute kidney injury (AKI) is a common clinical syndrome that is characterized by abnormal renal function and structure. The Kidney Disease: Improving Global Outcomes (KDIGO) Controversies Conference in 2019 reviewed the stages of AKI and the definitions of AKI-related terminologies, and discussed the advances in the last decade. Along with serum creatinine level and urine output, more accurate novel biomarkers for predicting AKI are being applied for the early detection of renal dysfunction. A literature search was conducted in PubMed, Scopus, Medline, and ClinicalTrials.gov using the terms AKI and biomarker, combined with diagnosis, management, or prognosis. Because of the large volume of data (160 articles) published between 2005 and 2022, representative literature was chosen. A number of studies have demonstrated that new biomarkers are more sensitive in detecting AKI in certain populations than serum creatinine and urine output according to the recommendations from the Acute Disease Quality Initiative Consensus Conference. To be specific, there is a persistently unresolved need for earlier detection of patients with AKI before AKI progresses to a need for renal replacement therapy. Biomarker-guided management may help to identify a high-risk group of patients in progression to severe AKI, and decide the initiation time to renal replacement therapy and optimal follow-up period. However, limitations such as biased data to certain studied populations and absence of cutoff values need to be solved for worldwide clinical use of biomarkers in the future. Here, we provide a comprehensive review of biomarker-based AKI diagnosis and management and highlight recent developments.

Cell cycle arrest biomarkers for predicting renal recovery from acute kidney injury: a prospective validation study

Background

Acute kidney injury (AKI) is a common disease in the intensive care unit (ICU). AKI patients with nonrecovery of renal function have a markedly increased risk of death compared with patients with recovery. The current study aimed to explore and validate the utility of urinary cell cycle arrest biomarkers for predicting nonrecovery in patients who developed AKI after ICU admission.

Methods

We prospectively and consecutively enrolled 379 critically ill patients who developed AKI after admission to the ICU, which were divided into a derivation cohort (194 AKI patients) and a validation cohort (185 AKI patients). The biomarkers of urinary tissue inhibitor of metalloproteinase-2 (TIMP-2) and insulin-like growth factor-binding protein 7 (IGFBP7) were detected at inclusion immediately after AKI diagnosis (day 0) and 24 h later (day 1). The optimal cut-off values of these biomarkers for predicting nonrecovery were estimated in the derivation cohort, and their predictive accuracy was assessed in the validation cohort. The primary endpoint was nonrecovery from AKI (within 7 days).

Results

Of 379 patients, 159 (41.9%) patients failed to recover from AKI onset, with 79 in the derivation cohort and 80 in the validation cohort. Urinary [TIMP-2]*[IGFBP7] on day 0 showed a better prediction ability for nonrecovery than TIMP-2 and IGFBP7 alone, with an area under the reciever operating characteristic curve (AUC) of 0.751 [95% confidence interval (CI) 0.701–0.852, p < 0.001] and an optimal cut-off value of 1.05 ((ng/mL)²/1000). When [TIMP-2]*[IGFBP7] was combined with the clinical factors of AKI diagnosed by the urine output (UO) criteria, AKI stage 2–3 and nonrenal SOFA score for predicting nonrecovery, the AUC was significantly improved to 0.852 (95% CI 0.750–0.891, p < 0.001), which achieved a sensitivity and specificity of 88.8% (72.9, 98.7) and 92.6% (80.8, 100.0), respectively. However, urine [TIMP-2]*[IGFBP7], TIMP-2 alone, and IGFBP7 alone on day 1 performed poorly for predicting AKI recovery.

Conclusion

Urinary [TIMP-2]*[IGFBP7] on day 0 showed a fair performance for predicting nonrecovery from AKI. The predictive accuracy can be improved when urinary [TIMP-2]*[IGFBP7] is combined with the clinical factors of AKI diagnosed by the UO criteria, AKI stage 2–3 and nonrenal SOFA score.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13613-022-00989-8.

Development and Validation of a Prediction Model for Acute Kidney Injury Among Patients With Acute Decompensated Heart Failure

Background: Acute kidney injury is an adverse event that carries significant morbidity among patients with acute decompensated heart failure (ADHF). We planned to develop a parsimonious model that is simple enough to use in clinical practice to predict the risk of acute kidney injury (AKI) occurrence. Methods: Six hundred and fifty patients with ADHF were enrolled in this study. Data for each patient were collected from medical records. We took three different approaches of variable selection to derive four multivariable logistic regression model. We selected six candidate predictors that led to a relatively stable outcome in different models to derive the final prediction model. The prediction model was verified through the use of the C-Statistics and calibration curve. Results: Acute kidney injury occurred in 42.8% of the patients. Advanced age, diabetes, previous renal dysfunction, high baseline creatinine, high B-type natriuretic peptide, and hypoalbuminemia were the strongest predictors for AKI. The prediction model showed moderate discrimination C-Statistics: 0.766 (95% CI, 0.729-0.803) and good identical calibration. Conclusion: In this study, we developed a prediction model and nomogram to estimate the risk of AKI among patients with ADHF. It may help clinical physicians detect AKI and manage it promptly.

The updated national research agenda 2021-2026 for prehospital emergency medical services in the Netherlands: a Delphi study

Background

In 2015, a national research agenda was established for Dutch prehospital EMS to underpin the evidence base of care delivery and inform policymakers and funders. The continuously increasing demand for ambulance care and the reorientation towards the role of EMS in recent years may have changed research priorities. Therefore, this study aimed to update the Dutch national EMS research agenda.

Methods

A three-round online Delphi survey was used to explore and discuss different viewpoints and to reach consensus on research priorities (i.e., themes and special interest groups, e.g. patient types who require specific research attention). A multidisciplinary expert panel (n = 62) was recruited in the field of prehospital EMS and delegates of relevant professional organizations and stakeholders participated. In round one, fifty-nine research themes and six special interest groups (derived from several resources) were rated on importance on a 5-point scale by the panel members. In round two, the panel selected their priority themes and special interest groups (yes/no), and those with a positive difference score were further assessed in round three. In this final round, appropriateness of the remaining themes and agreement within the panel was taken into account, following the RAND/UCLA appropriateness method, which resulted in the final list of research priorities.

Results

The survey response per round varied between 94 and 100 percent. In round one, a reduction from 59 to 25 themes and the selection of three special interest groups was realized. Round two resulted in the prioritization of six themes and one special interest group ('Vulnerable elderly'). Round three showed an adequate level of agreement regarding all six themes: 'Registration and (digital) exchange of patient data in the chain of emergency care'; 'Mobile care consultation/Non conveyance'; 'Care coordination'; 'Cooperation with professional partners within the care domain'; 'Care differentiation' and 'Triage and urgency classification'.

Conclusions

The updated Dutch national EMS research agenda builds further on the previous version and introduces new EMS research priorities that correspond with the future challenges prehospital EMS care is faced with. This agenda will guide researchers, policymakers and funding bodies in prioritizing future research projects.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13049-021-00971-6.

Discharge Documentation and Follow-Up of Critically Ill Patients With Acute Kidney Injury Treated With Kidney Replacement Therapy: A Retrospective Cohort Study

Leading organisations recommend follow-up of acute kidney injury (AKI) survivors, as these patients are at risk of long-term complications and increased mortality. Information transfer between specialties and from tertiary to primary care is essential to ensure timely and appropriate follow-up. Our aim was to examine the association between completeness of discharge documentation and subsequent follow-up of AKI survivors who received kidney replacement therapy (KRT) in the Intensive Care Unit (ICU). We retrospectively analysed the data of 433 patients who had KRT for AKI during ICU admission in a tertiary care centre in the UK between June 2017 and May 2018 and identified patients who were discharged from hospital alive. Patients with pre-existing end-stage kidney disease and patients who were transferred from hospitals outside the catchment area were excluded. The primary objective was to assess the completeness of discharge documentation from critical care and hospital; secondary objectives were to determine cardiovascular medications reconciliation after AKI, and to investigate kidney care and outcomes at 1 year. The development of AKI and the need for KRT were mentioned in 85 and 82% of critical care discharge letters, respectively. Monitoring of kidney function post-discharge was recommended in 51.6% of critical care and 36.3% of hospital discharge summaries. Among 35 patients who were prescribed renin-angiotensin-aldosterone system inhibitors before hospitalisation, 15 (42.9%) were not re-started before discharge from hospital. At 3 months, creatinine and urine protein were measured in 88.2 and 11.8% of survivors, respectively. The prevalence of chronic kidney disease stage III or worse increased from 27.2% pre-hospitalisation to 54.9% at 1 year (p < 0.001). Our data demonstrate that discharge summaries of patients with AKI who received KRT lacked essential information. Furthermore, even in patients with appropriate documentation, renal follow-up was poor suggesting the need for more education and streamlined care pathways.

Reliable kidney size determination by magnetic resonance imaging in pathophysiological settings

AIM

Kidney diseases constitute a major health challenge, which requires noninvasive imaging to complement conventional approaches to diagnosis and monitoring. Several renal pathologies are associated with changes in kidney size, offering an opportunity for magnetic resonance imaging (MRI) biomarkers of disease. This work uses dynamic MRI and an automated bean-shaped model (ABSM) for longitudinal quantification of pathophysiologically relevant changes in kidney size.

METHODS

A geometry-based ABSM was developed for kidney size measurements in rats using parametric MRI (T₂ , T₂ * mapping). The ABSM approach was applied to longitudinal renal size quantification using occlusion of the (a) suprarenal aorta or (b) the renal vein, (c) increase in renal pelvis and intratubular pressure and (d) injection of an X-ray contrast medium into the thoracic aorta to induce pathophysiologically relevant changes in kidney size.

RESULTS

The ABSM yielded renal size measurements with accuracy and precision equivalent to the manual segmentation, with >70-fold time savings. The automated method could detect a ~7% reduction (aortic occlusion) and a ~5%, a ~2% and a ~6% increase in kidney size (venous occlusion, pelvis and intratubular pressure increase and injection of X-ray contrast medium, respectively). These measurements were not affected by reduced image quality following administration of ferumoxytol.

CONCLUSION

Dynamic MRI in conjunction with renal segmentation using an ABSM supports longitudinal quantification of changes in kidney size in pathophysiologically relevant experimental setups mimicking realistic clinical scenarios. This can potentially be instrumental for developing MRI-based diagnostic tools for various kidney disorders and for gaining new insight into mechanisms of renal pathophysiology.

Acute kidney injury detection using refined and physiological-feature augmented urine output

Acute kidney injury (AKI) is common in the intensive care unit, where it is associated with increased mortality. AKI is often defined using creatinine and urine output criteria. The creatinine-based definition is more reliable but less expedient, whereas the urine output based definition is rapid but less reliable. Our goal is to examine the urine output criterion and augment it with physiological features for better agreement with creatinine-based definitions of AKI. The objectives are threefold: (1) to characterize the baseline agreement of urine output and creatinine definitions of AKI; (2) to refine the urine output criteria to identify the thresholds that best agree with the creatinine-based definition; and (3) to build generalized estimating equation (GEE) and generalized linear mixed-effects (GLME) models with static and time-varying features to improve the accuracy of a near-real-time marker for AKI. We performed a retrospective observational study using data from two independent critical care databases, MIMIC-III and eICU, for critically ill patients who developed AKI in intensive care units. We found that the conventional urine output criterion (6 hr, 0.5 ml/kg/h) has specificity and sensitivity of 0.49 and 0.54 for MIMIC-III database; and specificity and sensitivity of 0.38 and 0.56 for eICU. Secondly, urine output thresholds of 12 hours and 0.6 ml/kg/h have specificity and sensitivity of 0.58 and 0.48 for MIMIC-III; and urine output thresholds of 10 hours and 0.6 ml/kg/h have specificity and sensitivity of 0.49 and 0.48 for eICU. Thirdly, the GEE model of four hours duration augmented with static and time-varying features can achieve a specificity and sensitivity of 0.66 and 0.61 for MIMIC-III; and specificity and sensitivity of 0.66 and 0.64 for eICU. The GLME model of four hours duration augmented with static and time-varying features can achieve a specificity and sensitivity of 0.71 and 0.55 for MIMIC-III; and specificity and sensitivity of 0.66 and 0.60 for eICU. The GEE model has greater performance than the GLME model, however, the GLME model is more reflective of the variables as fixed effects or random effects. The significant improvement in performance, relative to current definitions, when augmenting with patient features, suggest the need of incorporating these features when detecting disease onset and modeling at window-level rather than patient-level.

Unexpected Outcomes of Renal Function after Radical Nephrectomy: Histology Relevance along with Clinical Aspects

Acute kidney injury (AKI) and chronic kidney disease (CKD) are common events after radical nephrectomy (RN). In this study we aimed to predict AKI and CKD after RN relying on specific histological aspects. We collected data from a cohort of 144 patients who underwent radical nephrectomy. A histopathological review of the healthy part of the removed kidney was performed using an established chronicity score (CS). Logistic regression analyses were performed to predict AKI after RN, while linear regression analysis was adopted for estimated glomerular filtration rate (eGFR) variation at 1 year. The outcomes of the study were to determine variables correlated with AKI onset, and with eGFR decay at 1 year. The proportion of AKI was 64%. Logistic analyses showed that baseline eGFR independently predicted AKI (odds ratio 1.04, 95%CI 1.02:1.06). Moreover, AKI (Beta −16, 95%CI −21:−11), baseline eGFR (Beta −0.42, 95%CI −0.52:−0.33), and the presence of arterial narrowing (Beta 10, 95%CI 4:15) were independently associated with eGFR decline. Our findings showed that AKI onset and eGFR decline were more likely to occur with higher baseline eGFR and lower CS, highlighting that RN in normal renal function patients represents a more traumatic event than its CKD counterpart.

Proenkephalin Compared to Conventional Methods to Assess Kidney Function in Critically Ill Sepsis Patients

BACKGROUND

The assessment of renal function in clinical practice remains challenging. Using creatinine to assess the glomerular filtration rate (GFR) is notoriously inaccurate, and determination of the true GFR, e.g., using inulin or iohexol, is laborious and not feasible in daily practice. Proenkephalin (PENK) is a novel candidate biomarker for kidney function that is filtrated in the glomerulus, has shown to represent steady-state GFR in patients with different severities of renal insufficiency. In this pilot study in non-steady-state critically ill patients, we compared plasma PENK concentrations with creatinine-based GFR assessments and validated both against the "true GFR" measured using a gold standard method: iohexol plasma clearance.

METHODS

Twenty-three critically ill patients with septic shock were included. Kidney function was determined using the Modification of Diet in Renal Disease formula (eGFRMDRD), Endogenous Creatinine Clearance (GFRECC), and iohexol plasma clearance (GFRiohexol) during a 6-h window. Plasma PENK concentrations were measured using the penKid immunoassay.

RESULTS

The eGFRMDRD and GFRECC correlated with the GFRiohexol (R = 0.82, P < 0.0001 and R = 0.82, P < 0.0001 respectively); however, bias and variability were considerable: the eGFRMDRD overestimated the true GFR with 31 ± 35% (95% limits of agreement: -37% to 100%) and the GFRECC with 37 ± 49% (95% limits of agreement: -59% to 133%). Plasma PENK concentrations showed a very strong inverse correlation with the GFRiohexol (R = 0.90, P < 0.0001) which tended to be better compared with the correlation of eGFRMDRD (P = 0.06) and GFRECC (P = 0.08) with the GFRiohexol.

CONCLUSIONS

In this pilot study in non-steady-state critically ill sepsis patients, GFR appears to be more accurately reflected by plasma PENK concentrations compared to conventional creatinine-based methods. Therefore, PENK holds promise as an accurate and feasible biomarker to determine kidney function during non-steady-state conditions in the critically ill.

Continuous diffusion spectrum computation for diffusion-weighted magnetic resonance imaging of the kidney tubule system

Background

The use of rigid multi-exponential models (with a priori predefined numbers of components) is common practice for diffusion-weighted MRI (DWI) analysis of the kidney. This approach may not accurately reflect renal microstructure, as the data are forced to conform to the a priori assumptions of simplified models. This work examines the feasibility of less constrained, data-driven non-negative least squares (NNLS) continuum modelling for DWI of the kidney tubule system in simulations that include emulations of pathophysiological conditions.

Methods

Non-linear least squares (LS) fitting was used as reference for the simulations. For performance assessment, a threshold of 5% or 10% for the mean absolute percentage error (MAPE) of NNLS and LS results was used. As ground truth, a tri-exponential model using defined volume fractions and diffusion coefficients for each renal compartment (tubule system: D_tubules , f_tubules ; renal tissue: D_tissue , f_tissue ; renal blood: D_blood , f_blood ;) was applied. The impact of: (I) signal-to-noise ratio (SNR) =40-1,000, (II) number of b-values (n=10-50), (III) diffusion weighting (b-range_small =0-800 up to b-range_large =0-2,180 s/mm²), and (IV) fixation of the diffusion coefficients D_tissue and D_blood was examined. NNLS was evaluated for baseline and pathophysiological conditions, namely increased tubular volume fraction (ITV) and renal fibrosis (10%: grade I, mild) and 30% (grade II, moderate).

Results

NNLS showed the same high degree of reliability as the non-linear LS. MAPE of the tubular volume fraction (f_tubules ) decreased with increasing SNR. Increasing the number of b-values was beneficial for f_tubules precision. Using the b-range_large led to a decrease in MAPE _ftubules compared to b-range_small. The use of a medium b-value range of b=0-1,380 s/mm² improved f_tubules precision, and further b_max increases beyond this range yielded diminishing improvements. Fixing D_blood and D_tissue significantly reduced MAPE _ftubules and provided near perfect distinction between baseline and ITV conditions. Without constraining the number of renal compartments in advance, NNLS was able to detect the (fourth) fibrotic compartment, to differentiate it from the other three diffusion components, and to distinguish between 10% vs. 30% fibrosis.

Conclusions

This work demonstrates the feasibility of NNLS modelling for DWI of the kidney tubule system and shows its potential for examining diffusion compartments associated with renal pathophysiology including ITV fraction and different degrees of fibrosis.

Application of nanotechnology in acute kidney injury: From diagnosis to therapeutic implications

Acute kidney injury (AKI), a major health issue concerning ~50% of patients treated in intensive care units, generally leads to severe renal damage associated with high mortality rate. The application of nanotechnology for the management of AKI has profound potential of further development, providing innovative strategies for predicting the early onset and progression of renal disease and improving the treatment efficacy of the life-threating AKI. This review has comprehensively summarized the nanomedicines in the application of AKI diagnosis and emphatically discussed the unique potential of various nanotechnology-based drug delivery systems (e.g., polymeric nanoparticles, organic nanoparticles, inorganic nanoparticles, lipid-based nanoparticles, hydrogels etc.) in the treatment of AKI, allowing for improved therapeutic index by enhancing both efficacy and safety concurrently. These approaches may mechanically mitigate oxidative stress, inflammation, and mitochondrial and other organellar damage, etc. In addition, the combination of nanotechnology with stem cells-based therapy or gene therapy has been explored for reducing renal tissues damage and promoting kidney repair or recovery from AKI. The review provides insights into the synthesis, advantages, and limitations of innovative nanomedicine application in the early detection and effective treatment of AKI.

Restrictive fluid management versus usual care in acute kidney injury (REVERSE-AKI): a pilot randomized controlled feasibility trial

Purpose

We compared a restrictive fluid management strategy to usual care among critically ill patients with acute kidney injury (AKI) who had received initial fluid resuscitation.

Methods

This multicenter feasibility trial randomized 100 AKI patients 1:1 in seven ICUs in Europe and Australia. Restrictive fluid management included targeting negative or neutral daily fluid balance by minimizing fluid input and/or enhancing urine output with diuretics administered at the discretion of the clinician. Fluid boluses were administered as clinically indicated. The primary endpoint was cumulative fluid balance 72 h from randomization.

Results

Mean (SD) cumulative fluid balance at 72 h from randomization was − 1080 mL (2003 mL) in the restrictive fluid management arm and 61 mL (3131 mL) in the usual care arm, mean difference (95% CI) − 1148 mL (− 2200 to − 96) mL, P = 0.033. Median [IQR] duration of AKI was 2 [1–3] and 3 [2–7] days, respectively (median difference − 1.0 [− 3.0 to 0.0], P = 0.071). Altogether, 6 out of 46 (13%) patients in the restrictive fluid management arm and 15 out of 50 (30%) in the usual care arm received renal replacement therapy (RR 0.42; 95% CI 0.16–0.91), P = 0.043. Cumulative fluid balance at 24 h and 7 days was lower in the restrictive fluid management arm. The dose of diuretics was not different between the groups. Adverse events occurred more frequently in the usual care arm.

Conclusions

In critically ill patients with AKI, a restrictive fluid management regimen resulted in lower cumulative fluid balance and less adverse events compared to usual care. Larger trials of this intervention are justified.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00134-021-06401-6.

Effect of Prolonged-Release Pirfenidone on Renal Function in Septic Acute Kidney Injury Patients: A Double-Blind Placebo-Controlled Clinical Trial

Background

There is no treatment for septic acute kidney injury (sAKI). The anti-inflammatory activity of prolonged-release pirfenidone (PR-PFD) could be beneficial in this clinical setting.

Methods

This study was a double-blind randomized clinical trial in sAKI patients with nephrology consultation at the Civil Hospital of Guadalajara, in addition to the usual treatment of AKI associated with sepsis; patients were randomized to receive either PR-PFD at 1,200 mg/day (group A) or 600 mg/day (group B) or a matched placebo for 7 consecutive days. The primary objective was the decrease in serum creatinine (sCr) and increase in urinary volume (UV); the secondary objectives were changes in serum electrolytes, acid-base status, and mortality.

Results

Between August 2016 and August 2017, 88 patients were randomized. The mean age was 54 (17 ± SD) years, and 47% were male. The main site of infection was the lung (39.8%), septic shock was present in 39.1% of the cases, and the mean SOFA score was 8.8 points. 28 patients received PFD 1,200 mg, 30 patients received PFD 600 mg, and 30 patients received placebo. During the study, sCr did not differ among the groups. The reversion rate of sCr, UV, and mortality was not different among the groups (p=0.70, p=0.47, and p=0.38, respectively). Mild adverse events were not different among the groups.

Conclusion

PR-PFD did not improve the clinical course of sAKI and seemed to be safe in terms of adverse events. This trial is registered with NCT02530359.

Optimal timing of initiating CRRT in patients with acute kidney injury after liver transplantation

Background

Acute kidney injury (AKI) is a frequent complication after liver transplantation (LT), and is associated with high mortality. Continuous renal replacement therapy (CRRT) is an important treatment for AKI, but the optimal time for initiation is still controversial. The purpose of this study was to investigate the prognostic effect of initial CRRT treatment time.

Methods

We retrospectively reviewed the clinical data of 173 recipients undergoing LT from January 2018 to March 2019. AKI was defined according to Kidney Disease: Improving Global Outcomes (KDIGO) criteria. All patients receiving CRRT were divided into early and late group according to urine output. Prognosis was compared between the two groups.

Results

A total of 48 (27.8%) patients were identified with AKI, 23 (13.3%) of whom received CRRT. According to urine output, 13 (56.5%) patients were in early group and 10 (43.5%) patients in late group. AKI was associated with longer intensive care unit (ICU) and hospital stay, increased post-operative 90-day mortality and the incidence of early allograft dysfunction (EAD). Patients in late CRRT group had a longer ICU stay {median, IQR, 183.5 [92.25–336.75] vs. 139 [94–240] hours, P=0.043} and hospital stay {median, IQR, 38.5 [17.5–62.75] vs. 35 [17–38] days, P=0.019} than patients in early CRRT group, respectively. The rate of severe infection was significantly higher in the late CRRT group than in the early CRRT group (80.0% vs. 30.8%, P=0.026).

Conclusions

AKI was associated with longer length of ICU and hospital stay, poor short-term mortality and functional recovery of transplanted organ. Early initiation of CRRT could reduce the severe infection and length of ICU and hospital stay.

Targeting acute kidney injury in COVID-19

As of 15 August 2020, Coronavirus disease 2019 (COVID-19) has been reported in >21 million people world-wide and is responsible for more than 750,000 deaths. The occurrence of acute kidney injury (AKI) in patients hospitalized with COVID-19 has been reported to be as high as 43%. This is comparable to AKI in other forms of pneumonia requiring hospitalization, as well as in non-infectious conditions like cardiac surgery. The impact of AKI on COVID-19 outcomes is difficult to assess at present but, similar to other forms of sepsis, AKI is strongly associated with hospital mortality. Indeed, mortality is reported to be very low in COVID-19 patients without AKI. Given that AKI contributes to fluid and acid-base imbalances, compromises immune response and may impair resolution of inflammation, it seems likely that AKI contributes to mortality in these patients. The pathophysiologic mechanisms of AKI in COVID-19 are thought to be multifactorial including systemic immune and inflammatory responses induced by viral infection, systemic tissue hypoxia, reduced renal perfusion, endothelial damage and direct epithelial infection with Severe Acute Respiratory Syndrome Coronavirus 2. Mitochondria play a central role in the metabolic deregulation in the adaptive response to the systemic inflammation and are also found to be vital in response to both direct viral damage and tissue reperfusion. These stress conditions are associated with increased glycolysis and reduced fatty acid oxidation. Thus, there is a strong rationale to target AKI for therapy in COVID-19. Furthermore, many approaches that have been developed for other etiologies of AKI such as sepsis, inflammation and ischemia-reperfusion, have relevance in the treatment of COVID-19 AKI and could be rapidly pivoted to this new disease.

Protocol and statistical analysis plan for the REstricted fluid therapy VERsus Standard trEatment in Acute Kidney Injury-REVERSE-AKI randomized controlled pilot trial

Background

Fluid accumulation frequently coexists with acute kidney injury (AKI) and is associated with increased risk for AKI progression and mortality. Among septic shock patients, restricted use of resuscitation fluid has been reported to reduce the risk of worsening of AKI. Restrictive fluid therapy, however, has not been studied in the setting of established AKI. Here, we present the protocol and statistical analysis plan of the REstricted fluid therapy VERsus Standard trEatment in Acute Kidney Injury—the REVERSE‐AKI trial that compares a restrictive fluid therapy regimen to standard therapy in critically ill patients with AKI.

Methods

REVERSE‐AKI is an investigator‐initiated, multinational, open‐label, randomized, controlled, feasibility pilot trial conducted in seven ICUs in five countries. We aim to randomize 100 critically ill patients with AKI to a restrictive fluid treatment regimen vs standard management. In the restrictive fluid therapy regimen, the daily fluid balance target is neutral or negative. The primary outcome is the cumulative fluid balance assessed after 72 hours from randomization. Secondary outcomes include safety, feasibility, duration, and severity of AKI, and outcome at 90 days (mortality and dialysis dependence).

Conclusions

This is the first multinational trial investigating the feasibility and safety of a restrictive fluid therapy regimen in critically ill patients with AKI.

Trial registration

clinical.trials.gov NCT03251131.

Evaluation of Urinary NGAL as a Diagnostic Tool for Acute Kidney Injury in Critically Ill Patients With Infection: An Original Study

Background:

Acute kidney injury (AKI) is a common complication in critical care patients. The presence of AKI is a marker for poor outcomes such as longer hospitalization durations, more hospital readmissions, and especially, higher mortality rates. Sepsis is one of the major causes of AKI within the intensive care unit (ICU) population. Sepsis-related AKI occurs in approximately 20% of patients, reaching more than 50% in patients with septic shock. The diagnosis of AKI depends on urine output and/or serum creatinine measurements. Unfortunately, serum creatinine is a late and unreliable (insensitive and nonspecific) indicator of AKI. However, biomarkers of renal damage have great potential in facilitating early diagnosis of AKI. Several biomarkers, including urinary neutrophil gelatinase-associated lipocalin (uNGAL), have been used in the early detection of AKI.

Objectives:

The aim of this study was to evaluate uNGAL for the diagnosis and prognosis of AKI in critical ill patients with infections.

Design:

Original study (Cohort Prospective Observational).

Setting:

Study in 2 ICUs of different Brazilian hospitals, in the city of Curitiba: Hospital de Clínicas da Universidade Federal do Paraná and Hospital da Polícia Militar do Paraná, from November 12, 2016 to May 15, 2018.

Participants:

Critically ill patients with infections, sepsis, or septic shock were selected. The inclusion criteria were patients older than 18 years with infection. They were followed up for 30 days in the analysis of outcomes. We requested that consent forms be signed by all eligible patients or their caregivers.

Measurements:

The urinary neutrophil gelatinase-associated lipocalin (uNGAL) levels of the patients were measured on 4 consecutive days and was assayed using a chemiluminescent microparticle immunoassay system. The screening time occurred within 72 hours of admission to the ICU. The first urine sample was collected within the first 24 hours of the screening hours. Mortality and AKI were assessed during first 30 days.

Methods:

clinical and laboratory data, including daily uNGAL levels, were assessed. The AKI stage using the KDIGO criteria was evaluated. Sensitivity, specificity, and the area under the curve-receiver operating characteristic (AUC-ROC) values were calculated to determine the optimal uNGAL level for predicting AKI.

Results:

We had 38 patients who completed the study during the screening period. The incidence of AKI was 76.3%. The hospitalization period was longer in the group that developed AKI, with 21 days of median (interquartile range [IQR]: 13.5-25); non-AKI group had a median of 13 days (IQR 7-18; P = .019). We found a direct relationship between uNGAL levels and the progression to AKI. Increased values of the biomarker were associated with the worsening of AKI (P < .05). The cutoff levels of uNGAL that identified patients who would progress to AKI were the following: (d1) >116 ng/mL, (d2) >100 ng/mL, and (d3) 284 ng/mL. The value of the fourth and last measurement was not predictive of patients who would progress to AKI. The median urinary uNGAL was also associated with mortality on Days 1, 3, and 4: d1, P = .039; d3, P = .005; d4, P = .005. The performance of uNGAL in detecting AKI patients (AUC-ROC = 0.881). There were no risk factors other than AKI that could be correlated with increased uNGAL levels on Day 1.

Limitations:

The study was carried out in 2 centers, having used only 1 biomarker, and our small number of patients were limitations.

Conclusion:

the uNGAL had an association in its values with the diagnosis and prognosis of patients with severe infections and AKI. We suggest that studies with a greater number of patients could better establish the cutoff values of uNGAL and/or serum NGAL in the identification of infected patients who are at a high risk of developing AKI.

Risk prediction for severe acute kidney injury by integration of urine output, glomerular filtration, and urinary cell cycle arrest biomarkers

BACKGROUND

Frequent assessment of urine output (UO), serum creatinine (sCr) and urinary cell cycle arrest biomarkers (CCAB) may improve acute kidney injury (AKI) prediction.

OBJECTIVE

To study the performance of UO, short term sCr changes and urinary CCAB to predict severe AKI.

METHODS

We measured 6 hours of UO, 6-hourly sCr changes, and urinary CCABs in all critically ill patients with cardiovascular or respiratory failure or early signs of renal stress between February and October 2018. We studied the association of such measurements, and their combination, with the development of AKI Stage 2 or 3 of the Kidney Disease: Improving Global Outcomes (KDIGO) definition at 12 hours. We evaluated predictive performance with logistic regression, area under the receiver operating characteristic (AUROC) curve, and net reclassification indices. We computed an optimal cut-off value for each biomarker.

RESULTS

We assessed 622 patients and, as per the exclusion criteria, we enrolled 105 critically ill patients. After 12 hours of enrolment, AKI occurred in 32 patients (30%). UO, sCr change over 6 hours and CCABs were significantly associated with severe AKI at 12 hours, with all variables achieving an AUROC > 0.7 after adjustment. Combination of any of the two or three variables achieved an AUROC > 0.7 for subsequent severe AKI at 12 hours. The optimal predictive high specificity cut-off values were ≤ 0.4 mL/kg/h for UO, variation of +15 μmol/L over 6 hours in sCr, and ≥ 1.5 (ng/mL)2/1000 for CCABs.

CONCLUSION

In this prospective study, an integrative approach using UO, short term sCr change and/or urinary CCABs showed a satisfactory performance for the prediction of severe AKI development at 12 hours.

Trauma-associated acute kidney injury

PURPOSE OF REVIEW

A summary of recent research into the epidemiology, cause, management and outcomes of trauma-associated acute kidney injury (AKI). There is an increasing focus on subtypes of AKI to better target clinical management and future research.

RECENT FINDINGS

AKI associated with trauma occurs in 20-24% of patients admitted to ICU. On the basis of creatinine and/or urine output, AKI occurs in the first few days of traumatic illness. Although various associations have been identified, shock and high-volume blood transfusion are the most consistent risks for development of trauma-associated AKI. Short-term outcomes appear worse for patients with AKI, but extent of longer term kidney function recovery remains unknown. Recent research in the general critical care population is beginning to better inform AKI management; however, currently, preventive and supportive strategies remain the mainstay of AKI management after trauma.

SUMMARY

Well-designed, prospective research is required to better understand the phenotype, pathophysiology and recovery trajectory of trauma-associated AKI. Only then can potentially unique therapeutic targets be developed for this common subtype of AKI.

Burden of acute kidney injury and 90-day mortality in critically ill patients

BACKGROUND

Mortality rates associated with acute kidney injury (AKI) vary among critically ill patients. Outcomes are often not corrected for severity or duration of AKI. Our objective was to analyse whether a new variable, AKI burden, would outperform 1) presence of AKI, 2) highest AKI stage, or 3) AKI duration in predicting 90-day mortality.

METHODS

Kidney Diseases: Improving Global Outcomes (KDIGO) criteria using creatinine, urine output and renal replacement therapy were used to diagnose AKI. AKI burden was defined as AKI stage multiplied with the number of days that each stage was present (maximum five), divided by the maximum possible score yielding a proportion. The AKI burden as a predictor of 90-day mortality was assessed in two independent cohorts (Finnish Acute Kidney Injury, FINNAKI and Simple Intensive Care Studies I, SICS-I) by comparing four multivariate logistic regression models that respectively incorporated either the presence of AKI, the highest AKI stage, the duration of AKI, or the AKI burden.

RESULTS

In the FINNAKI cohort 1096 of 2809 patients (39%) had AKI and 90-day mortality of the cohort was 23%. Median AKI burden was 0.17 (IQR 0.07-0.50), 1.0 being the maximum. The model including AKI burden (area under the receiver operator curve (AUROC) 0.78, 0.76-0.80) outperformed the models using AKI presence (AUROC 0.77, 0.75-0.79, p = 0.026) or AKI severity (AUROC 0.77, 0.75-0.79, p = 0.012), but not AKI duration (AUROC 0.77, 0.75-0.79, p = 0.06). In the SICS-I, 603 of 1075 patients (56%) had AKI and 90-day mortality was 28%. Median AKI burden was 0.19 (IQR 0.08-0.46). The model using AKI burden performed better (AUROC 0.77, 0.74-0.80) than the models using AKI presence (AUROC 0.75, 0.71-0.78, p = 0.001), AKI severity (AUROC 0.76, 0.72-0.79. p = 0.008) or AKI duration (AUROC 0.76, 0.73-0.79, p = 0.009).

CONCLUSION

AKI burden, which appreciates both severity and duration of AKI, was superior to using only presence or the highest stage of AKI in predicting 90-day mortality. Using AKI burden or other more granular methods may be helpful in future epidemiological studies of AKI.

A multi-center cross-sectional study on blood purification among adult patients in intensive care unit in China: a study protocol

Background

Blood purification (BP) is one of the most important rescue measures for patients with critical illness in the intensive care unit (ICU), especially for those with acute kidney injury. The purpose of this nationwide survey was to reveal the real world of current BP practice in different ICUs all over China. This study was designed to be a multi-center cross-sectional study.

Methods

All adult patients (over 18 years of age), who were admitted to ICU and required BP in 35 sub-centers across China were included during 30-day survey period in 2018. Demographic characteristics and clinical data were recorded including the timing of treatment initiation, indications, modality, relative contraindication, establishment of vascular access, selection of filter/membrane, settings, anti-coagulation, executive department, complication, intake, and output.

Discussion

This nationwide survey may contribute to reveal the real world of current BP practice in different ICUs all over China.

Trial registration

Chinese Clinical Trial Registry, ChiCTR-EOC-17013119; http://www.chictr.org.cn/showproj.aspx?proj=22487.

Risk factors and outcomes of acute kidney injury in South African critically ill adults: a prospective cohort study

Background

There is a marked paucity of data concerning AKI in Sub-Saharan Africa, where there is a substantial burden of trauma and HIV.

Methods

Prospective data was collected on all patients admitted to a multi-disciplinary ICU in South Africa during 2017. Development of AKI (before or during ICU admission) was recorded and renal recovery 90 days after ICU discharge was determined.

Results

Of 849 admissions, the mean age was 42.5 years and mean SAPS 3 score was 48.1. Comorbidities included hypertension (30.5%), HIV (32.6%), diabetes (13.3%), CKD (7.8%) and active tuberculosis (6.2%). The most common reason for admission was trauma (26%). AKI developed in 497 (58.5%). Male gender, illness severity, length of stay, vasopressor drugs and sepsis were independently associated with AKI. AKI was associated with a higher in-hospital mortality rate of 31.8% vs 7.23% in those without AKI. Age, active tuberculosis, higher SAPS 3 score, mechanical ventilation, vasopressor support and sepsis were associated with an increased adjusted odds ratio for death. HIV was not independently associated with AKI or hospital mortality. CKD developed in 14 of 110 (12.7%) patients with stage 3 AKI; none were dialysis-dependent.

Conclusions

In this large prospective multidisciplinary ICU cohort of younger patients, AKI was common, often associated with trauma in addition to traditional risk factors and was associated with good functional renal recovery at 90 days in most survivors. Although the HIV prevalence was high and associated with higher mortality, this was related to the severity of illness and not to HIV status per se.

Report of the first AKI Round Table meeting: an initiative of the ESICM AKI Section

PURPOSE

Critical Care Nephrology is an emerging sub-specialty of Critical Care. Despite increasing awareness about the serious impact of acute kidney injury (AKI) and renal replacement therapy (RRT), important knowledge gaps persist. This report represents a summary of a 1-day meeting of the AKI section of the European Society of Intensive Care Medicine (ESICM) identifying priorities for future AKI research.

METHODS

International Members of the AKI section of the ESICM were selected and allocated to one of three subgroups: "AKI diagnosis and evaluation", "Medical management of AKI" and "Renal Replacement Therapy for AKI." Using a modified Delphi methodology, each group identified knowledge gaps and developed potential proposals for future collaborative research.

RESULTS

The following key research projects were developed: Systematic reviews: (a) epidemiology of AKI with stratification by patient cohorts and diagnostic criteria; (b) role of higher blood pressure targets in patients with hypertension admitted to the Intensive Care Unit, and (c) specific clearance characteristics of different modalities of continuous renal replacement therapy (CRRT). Observational studies: (a) epidemiology of critically ill patients according to AKI duration, and (b) current clinical practice of CRRT. Intervention studies:( a) Comparison of different blood pressure targets in critically ill patients with hypertension, and (b) comparison of clearance of solutes with various molecular weights between different CRRT modalities.

CONCLUSION

Consensus was reached on a future research agenda for the AKI section of the ESICM.

The value of kinetic glomerular filtration rate estimation on medication dosing in acute kidney injury

BACKGROUND

In acute kidney injury (AKI), medication dosing based on Cockcroft-Gault creatinine clearance (CrCl) or Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) estimated glomerular filtration rates (eGFR) are not valid when serum creatinine (SCr) is not in steady state. The aim of this study was to determine the impact of a kinetic estimating equation that incorporates fluctuations in SCrs on drug dosing in critically ill patients.

METHODS

We used data from participants enrolled in the NIH Acute Respiratory Distress Syndrome Network Fluid and Catheters Treatment Trial to simulate drug dosing category changes with the application of the kinetic estimating equation developed by Chen. We evaluated whether kinetic estimation of renal function would change medication dosing categories (≥60, 30-59, 15-29, and <15mL/min) compared with the use of CrCl or CKD-EPI eGFR.

RESULTS

The use of kinetic CrCl and CKD-EPI eGFR resulted in a large enough change in estimated renal function to require medication dosing recategorization in 19.3% [95 CI 16.8%-21.9%] and 23.4% [95% CI 20.7%-26.1%] of participants, respectively. As expected, recategorization occurred more frequently in those with AKI. When we examined individual days for those with AKI, dosing discordance was observed in 8.5% of total days using the CG CrCl and 10.2% of total days using the CKD-EPI equation compared with the kinetic counterparts.

CONCLUSION

In a critically ill population, use of kinetic estimates of renal function impacted medication dosing in a substantial proportion of AKI participants. Use of kinetic estimates in clinical practice should lower the incidence of medication toxicity as well as avoid subtherapeutic dosing during renal recovery.