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

Recognition patterns of acute kidney injury in hospitalized patients

Background

Acute kidney injury (AKI) during hospitalization is associated with increased complications and mortality. Despite efforts to standardize AKI management, its recognition in clinical practice is limited.

Methods

To assess and characterize different patterns of AKI diagnosis, we collected clinical data, serum creatinine (sCr) levels, comorbidities and outcomes from adult patients using the Hospital Discharge Form (HDF). AKI diagnosis was based on administrative data and according to Kidney Disease: Improving Global Outcomes (KDIGO) criteria by evaluating sCr variations during hospitalization. Additionally, patients were categorized based on the timing of AKI onset.

Results

Among 56 820 patients, 42 900 (75.5%) had no AKI, 1893 (3.3%) had AKI diagnosed by sCr changes and coded in the HDF (full-AKI), 2529 (4.4%) had AKI reported on the HDF but not meeting sCr-based criteria (HDF-AKI) and 9498 (16.7%) had undetected AKI diagnosed by sCr changes but not coded in the HDF (KDIGO-AKI). Overall, AKI incidence was 24.5%, with a 68% undetection rate. Patients with KDIGO-AKI were younger and had a higher proportion of females, lower comorbidity burden, milder AKI stages, more frequent admissions to surgical wards and lower mortality compared with full-AKI patients. All AKI groups had worse outcomes than those without AKI, and AKI, even if undetected, was independently associated with mortality risk. Patients with AKI at admission had different profiles and better outcomes than those developing AKI later.

Conclusions

AKI recognition in hospitalized patients is highly heterogeneous, with a significant prevalence of undetection. This variability may be affected by patients' characteristics, AKI-related factors, diagnostic approaches and in-hospital patient management. AKI remains a major risk factor, emphasizing the importance of ensuring proper diagnosis for all patients.

Doppler-based evaluation of intrarenal venous flow as a new tool to predict acute kidney injury: A systematic review and meta-analysis

Congestion is a common complication in the critical care setting, these patients are at increased risk of developing acute kidney injury (AKI). Congestive nephropathy (CN) has recently been described as a mechanism of worsening renal function, and evaluation of renal venous flow by pulsed Doppler (PD) is a useful tool to assess the presence of renal vein congestion. We comprehensively explore the ability of the PD in the evaluation of the intrarenal venous flow (IRVF) to predict the development of AKI in critically ill patients. We searched Pubmed-MEDLINE, Scopus, Embase, and Cochrane Library of Systematic Reviews (to 31th December 2021). We evaluated the association between Doppler-based Intrarenal venous flow demodulation and AKI. CN was defined as the presence of a pulsatile pattern (biphasic or monophasic) in the PD. A total of 4 articles (660 patients) were included in our systematic review, three of these in the metanalysis (413 patients): one study was excluded because its data were inadequate for pooling. Two studies originated in Europe and the other two in the United States. AKI occurrence ranged between 34 and 68%. Patients who developed AKI had a significant difference in PD pattern (continuous vs. pulsatile) in the IRVF (RR=0.46; 95% CI 0.28-0.76). Nevertheless, a large heterogeneity was observed among the studies (I2=68.7%; p=0.04). Albeit preliminary, these findings suggest that the presence of a pulsatile pattern in the PD of the IRVF may be involved in the development of AKI in the critically ill patient. The effect of alterations in the IRVF and renal function warrant further investigation.

Nomenclature of Extracorporeal Blood Purification Therapies for Acute Indications: The Nomenclature Standardization Conference

The development of new extracorporeal blood purification (EBP) techniques has led to increased application in clinical practice but also inconsistencies in nomenclature and misunderstanding. In November 2022, an international consensus conference was held to establish consensus on the terminology of EBP therapies. It was agreed to define EBP therapies as techniques that use an extracorporeal circuit to remove and/or modulate circulating substances to achieve physiological homeostasis, including support of the function of specific organs and/or detoxification. Specific acute EBP techniques include renal replacement therapy, isolated ultrafiltration, hemoadsorption, and plasma therapies, all of which can be applied in isolation and combination. This paper summarizes the proposed nomenclature of EBP therapies and serves as a framework for clinical practice and future research.

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.

Metabolomics in Acute Kidney Injury: The Clinical Perspective

BACKGROUND

Acute kidney injury (AKI) affects increasing numbers of hospitalized patients worldwide. The diagnosis of AKI is made too late in most individuals since it is still based on dynamic changes in serum creatinine. In recent years, new AKI biomarkers have been identified; however, none of these can reliably replace serum creatinine yet. Metabolomic profiling (metabolomics) allows the concomitant detection and quantification of large numbers of metabolites from biological specimens. The current article aims to summarize clinical studies on metabolomics in AKI diagnosis and risk prediction.

METHODS

The following databases were searched for references: PubMed, Web of Science, Cochrane Library, and Scopus, and the period lasted from 1940 until 2022. The following terms were utilized: 'AKI' OR 'Acute Kidney Injury' OR 'Acute Renal Failure' AND 'metabolomics' OR 'metabolic profiling' OR 'omics' AND 'risk' OR 'death' OR 'survival' OR 'dialysis' OR 'KRT' OR 'kidney replacement therapy' OR 'RRT' OR 'renal replacement therapy' OR 'recovery of kidney function' OR 'renal recovery' OR 'kidney recovery' OR 'outcome'. Studies on AKI risk prediction were only selected if metabolomic profiling allowed differentiation between subjects that fulfilled a risk category (death or KRT or recovery of kidney function) and those who did not. Experimental (animal-based) studies were not included.

RESULTS

In total, eight studies were identified. Six studies were related to the diagnosis of AKI; two studies were performed on metabolic analysis in AKI risk (death) prediction. Metabolomics studies in AKI already helped to identify new biomarkers for AKI diagnosis. The data on metabolomics for AKI risk prediction (death, KRT, recovery of kidney function), however, are very limited.

CONCLUSIONS

Both the heterogenous etiology and the high degree of pathogenetic complexity of AKI most likely require integrated approaches such as metabolomics and/or additional types of '-omics' studies to improve clinical outcomes in AKI.