Furosemide stress test as a predictive marker of acute kidney injury progression or renal replacement therapy: a systemic review and meta-analysis

Predictive enrichment for the need of renal replacement in sepsis-associated acute kidney injury: combination of furosemide stress test and urinary biomarkers TIMP-2 and IGFBP-7

BACKGROUND

In sepsis, initial resuscitation with fluids is followed by efforts to achieve a negative fluid balance. However, patients with sepsis-associated acute kidney injury (SA-AKI) often need diuretic or renal replacement therapy (RRT). The dilemma is to predict whether early RRT might be advantageous or diuretics will suffice. Both the Furosemide Stress Test (FST) and measurements of the urinary biomarkers TIMP-2*IGFBP-7, if applied solely, do not provide sufficient guidance. We tested the hypothesis that a combination of two tests, i.e., an upstream FST combined with downstream measurements of urinary TIMP-2*IGFBP-7 concentrations improves the accuracy in predicting RRT necessity.

METHODS

In this prospective, multicenter study 100 patients with sepsis (diagnosed < 48h), AKI stage ≥ 2, and an indication for negative fluid balance were included between 02/2020 and 12/2022. All patients received a standardized FST and urinary biomarkers TIMP-2*IGFBP-7 were serially measured immediately before and up to 12 h after the FST. The primary outcome was the RRT requirement within 7 days after inclusion.

RESULTS

32% (n = 32/99) of SA-AKI patients eventually required RRT within 7 days. With the FST, urine TIMP-2*IGFBP-7 decreased within 2 h from 3.26 ng2/mL2/1000 (IQR: 1.38-5.53) to 2.36 ng2/mL2/1000 (IQR: 1.61-4.87) in RRT and 1.68 ng2/mL2/1000 (IQR: 0.56-2.94) to 0.27 ng2/mL2/1000 (IQR: 0.12-0.89) and non-RRT patients, respectively. While TIMP-2*IGFBP-7 concentrations remained low for up to 12 h in non-RRT patients, we noted a rebound in RRT patients after 6 h. TIMP-2*IGFBP-7 before FST (accuracy 0.66; 95%-CI 0.55-0.78) and the FST itself (accuracy 0.74; 95%-CI: 0.64-0.82) yielded moderate test accuracies in predicting RRT requirement. In contrast, a two-step approach, utilizing FST as an upstream screening tool followed by TIMP-2*IGFBP-7 quantification after 2 h improved predictive accuracy (0.83; 95%-CI 0.74-0.90, p = 0.03) compared to the FST alone, resulting in a positive predictive value of 0.86 (95%-CI 0.64-0.97), and a specificity of 0.96 (95%-CI 0.88-0.99).

CONCLUSIONS

The combined application of an upstream FST followed by urinary TIMP-2*IGFBP-7 measurements supports highly specific identification of SA-AKI patients requiring RRT. Upcoming interventional trials should elucidate if this high-risk SA-AKI subgroup, identified by our predictive enrichment approach, benefits from an early RRT initiation.

When to start renal replacement therapy in acute kidney injury: What are we waiting for?

Acute kidney injury remains a serious condition with a high mortality risk. In the absence of any new drugs, renal replacement therapy (RRT) is the most important treatment option. Randomized controlled trials have concluded that in critically ill patients without an emergency indication for RRT, a watchful waiting strategy is safe; however, further delays in RRT did not seem to confer any benefit, rather was associated with potential harm. During this process, balancing the risks of complications due to an unnecessary intervention with the risk of not correcting a potentially life-threatening complication remains a challenge. Dynamic renal function assessment, especially dynamic assessment of renal demand-capacity matching, combined with renal biomarkers such as neutrophil gelatinase-associated lipocalin and furosemide stress test, is helpful to identify which patients and when the patients may benefit from RRT.

AKI-Pro score for predicting progression to severe acute kidney injury or death in patients with early acute kidney injury after cardiac surgery

BACKGROUND

No reliable clinical tools exist to predict acute kidney injury (AKI) progression. We aim to explore a scoring system for predicting the composite outcome of progression to severe AKI or death within seven days among early AKI patients after cardiac surgery.

METHODS

In this study, we used two independent cohorts, and patients who experienced mild/moderate AKI within 48 h after cardiac surgery were enrolled. Eventually, 3188 patients from the MIMIC-IV database were used as the derivation cohort, while 499 patients from the Zhongshan cohort were used as external validation. The primary outcome was defined by the composite outcome of progression to severe AKI or death within seven days after enrollment. The variables identified by LASSO regression analysis were entered into logistic regression models and were used to construct the risk score.

RESULTS

The composite outcome accounted for 3.7% (n = 119) and 7.6% (n = 38) of the derivation and validation cohorts, respectively. Six predictors were assembled into a risk score (AKI-Pro score), including female, baseline eGFR, aortic surgery, modified furosemide responsiveness index (mFRI), SOFA, and AKI stage. And we stratified the risk score into four groups: low, moderate, high, and very high risk. The risk score displayed satisfied predictive discrimination and calibration in the derivation and validation cohort. The AKI-Pro score discriminated the composite outcome better than CRATE score, Cleveland score, AKICS score, Simplified renal index, and SRI risk score (all P < 0.05).

CONCLUSIONS

The AKI-Pro score is a new clinical tool that could assist clinicians to identify early AKI patients at high risk for AKI progression or death.

Evaluation of renal tubular function by multiparametric functional MRI in early diabetes

Purpose To evaluate the tubular function in an alloxan-induced type 1 diabetes mellitus (DM) rabbit model measured by renal oxygenation (R2*), oxygen extraction fraction (OEF), and renal blood flow (RBF) using blood oxygenation level dependent, asymmetric spin echo, and arterial spin labeling MRI. Methods Twenty-six rabbits were randomized into the 3-day DM group (n = 13) and the 7-day DM group (n = 13). We performed pairs of multiparametric MRIs (before and after furosemide injection) at baseline and 3/7 days post-DM, and scored pathological kidney injury. We performed statistical analyses using non-parametric, chi-square, and Spearman correlation tests. Results At baseline, medullary R2* significantly decreased by 24.97% and 16.74% in the outer and inner stripes of the outer medulla (OS and IS, p = 0.006 and 0.003, respectively) after furosemide administration. While the corresponding OEF decreased by 15.91% for OS and 16.67% for IS (both p = 0.003), and no significant change in medullary RBF was observed (p > 0.05). In the 3-day DM group, the decrease of medullary R2* and OEF post-furosemide became unremarkable, suggesting tubular dysfunction. We noticed similar changes in the 7-day DM group. Correlation analysis showed pathological tubular injury score significantly correlated with medullary ∆R2* (post-furosemide - pre-furosemide difference, r = 0.82 for OS and 0.82 for IS) and ∆OEF (r = 0.82 for OS and 0.82 for IS) (p < 0.001, respectively). Conclusion: The combination of medullary OEF and R2* in response to furosemide could detect renal tubular dysfunction in early DM.

Furosemide stress test to predict acute kidney injury progression in critically ill children

BACKGROUND

Furosemide stress test (FST) is a novel functional biomarker for predicting severe acute kidney injury (AKI); however, pediatric studies are limited.

METHODS

Children 3 months to 18 years of age admitted to the intensive care unit (ICU) of a tertiary care hospital from Nov 2019 to July 2021 were screened and those who developed AKI stage 1 or 2 within 7 days of admission underwent FST (intravenous furosemide 1 mg/kg). Urine output was measured hourly for the next 6 h; a value > 2 ml/kg within the first 2 h was deemed furosemide responsive. Other biomarkers like plasma neutrophil gelatinase-associated lipocalin (NGAL) and proenkephalin (PENK) were also evaluated.

RESULTS

Of the 480 admitted patients, 51 developed AKI stage 1 or 2 within 7 days of admission and underwent FST. Nine of these patients were furosemide non-responsive. Thirteen (25.5%) patients (eight of nine from FST non-responsive group) developed stage 3 AKI within 7 days of FST, nine (17.6%) of whom (seven from non-responsive group) required kidney support therapy (KST). FST emerged as a good biomarker for predicting stage 3 AKI and need for KST with area-under-the-curve (AUC) being 0.93 ± 0.05 (95% CI 0.84-1.0) and 0.96 ± 0.03 (95% CI 0.9-1.0), respectively. FST outperformed NGAL and PENK in predicting AKI stage 3 and KST; however, the combination did not improve the diagnostic accuracy.

CONCLUSIONS

Furosemide stress test is a simple, inexpensive, and robust biomarker for predicting stage 3 AKI and KST need in critically ill children. Further research is required to identify the best FST cut-off in children.

Furosemide Responsiveness Predicts Acute Kidney Injury Progression After Cardiac Surgery

BACKGROUND

As patients with acute kidney injury (AKI) progress to a higher stage, the risk for poor outcomes dramatically rises. Early identification of patients at high risk for AKI progression remains a major challenge. This study aimed to evaluate the value of furosemide responsiveness (FR) for predicting AKI progression in patients with initial mild and moderate AKI after cardiac surgery.

METHODS

We performed 2 separate exploratory analyses. The Zhongshan cohort was a single-center, prospective, observational cohort, whereas the Beth Israel Deaconess Medical Center cohort was a single-center, retrospective cohort. We calculated 2 FR parameters for each patient, namely the FR index and modified FR index, defined as 2-hour urine output divided by furosemide dose (FR index, mL/mg/2 h) and by furosemide dose and body weight (modified FR index, mL/[mg·kg]/2 h), respectively. The primary outcome was AKI progression within 7 days.

RESULTS

AKI progression occurred in 80 (16.0%) and 359 (11.3%) patients in the Zhongshan and Beth Israel Deaconess Medical Center cohorts, respectively. All FR parameters (considered continuously or in quartiles) were inversely associated with risk of AKI progression in both cohorts (all adjusted P < .01). The addition of FR parameters significantly improved prediction for AKI progression based on baseline clinical models involving C-index, net reclassification improvement, and integrated discrimination improvement index in both cohorts (all P < .01).

CONCLUSIONS

FR parameters were inversely associated with risk of AKI progression in patients with mild and moderate AKI after cardiac surgery. The addition of FR parameters significantly improved prediction for AKI progression based on baseline clinical models.

Urine Quantification Following Furosemide for Severe Acute Kidney Injury Prediction in Critically Ill Children

A standardized, quantified assessment of furosemide responsiveness predicts acute kidney injury (AKI) in children after cardiac surgery and AKI progression in critically ill adults. The purpose of this study was to determine if response to furosemide is predictive of severe AKI in critically ill children outside of cardiac surgery. We performed a multicenter retrospective study of critically ill children. Quantification of furosemide response was based on urine flow rate (normalized for weight) measurement 0 to 6 hours after the dose. The primary outcome was presence of creatinine defined severe AKI (Kidney Disease Improving Global Outcomes stage 2 or greater) within 7 days of furosemide administration. Secondary outcomes included mortality, duration of mechanical ventilation and length of stay. A total of 110 patients were analyzed. Severe AKI occurred in 20% ( n  = 22). Both 2- and 6-hour urine flow rate were significantly lower in those with severe AKI compared with no AKI ( p  = 0.002 and p  < 0.001). Cutoffs for 2- and 6-hour urine flow rate for prediction of severe AKI were <4 and <3 mL/kg/hour, respectively. The adjusted odds of developing severe AKI for 2-hour urine flow rate of <4 mL/kg/hour was 4.3 (95% confidence interval [CI]: 1.33-14.15; p  = 0.02). The adjusted odds of developing severe AKI for 6-hour urine flow rate of <3 mL/kg/hour was 6.19 (95% CI: 1.85-20.70; p  = 0.003). Urine flow rate in response to furosemide is predictive of severe AKI in critically ill children. A prospective assessment of urine flow rate in response to furosemide for predicting subsequent severe AKI is warranted.

Update on persistent acute kidney injury in critical illnesses

Acute kidney injury (AKI) affects about half of patients admitted to the intensive care unit (ICU), and worsens their short- and long-term outcomes. Apparently self-limiting AKI episodes initiate a progression toward chronic kidney disease (CKD) through cellular and molecular mechanisms that are yet to be explained. In particular, persistent AKI, defined in 2016 by the Acute Dialysis Quality Initiative as an AKI which lasts more than 48 h from its onset, has been correlated with higher morbidity and mortality, and with a higher progression to acute kidney disease (AKD) and CKD than transient AKI (i.e. AKI with a reversal within 48 h). This classification has been also used in the setting of solid organ transplantation, demonstrating similar outcomes. Due to its incidence and poor prognosis and because prompt interventions seem to change its course, persistent AKI should be recognized early and followed-up also after its recovery. However, while AKI and CKD are well-described syndromes, persistent AKI and AKD are relatively new entities. The purpose of this review is to highlight the key phases of persistent AKI in ICU patients in terms of both clinical and mechanistic features in order to offer to clinicians and researchers an updated basis from which to start improving patients' care and direct future research.

Case report: Resolution of oligo-anuric acute kidney injury with furosemide administration in a cat following lily toxicity

Objective

To describe the successful outcome of a case of oligo-anuric acute kidney injury in a cat secondary to lily ingestion.

Case summary

A 12-week-old intact male domestic short-hair cat weighing 1.64 kg (3.6 lb) presented with a 12-h duration of vomiting and lethargy after exposure to lilies of the genera Lilium species 24 h prior to presentation. Severe azotemia (Creatinine 5.8 mg/dL, BUN > 100 mg/dL) and hyperkalemia (9.36 mmol/L) were noted on the day of presentation. Treatment of hyperkalemia was instituted with calcium gluconate, lactated ringers solution, dextrose, regular short-acting insulin, albuterol, and sodium bicarbonate, Oliguria to anuria was highly suspected based on a lack of urine production 21 h after hospitalization with intravenous fluid administration and a static bladder size. The cat was administered 4 mg/kg of furosemide, and urinated at 6 h following administration and continued to produce over 6 ml/kg/h of urine in the next 24 h. Two days following furosemide administration, the cat's hyperkalemia and azotemia resolved. The cat was discharged after 4 days of hospitalization, and a recheck revealed no persistent azotemia or hyperkalemia.

Unique information

Anuric acute kidney injury secondary to lily toxicity is associated with a poor prognosis, and the only treatment modality previously described is hemodialysis. The cat in this report was successfully managed with medical intervention and furosemide administration, with complete resolution of the acute kidney injury.

Lack of furosemide responsiveness predict severe acute kidney injury after liver transplantation

Acute kidney injury (AKI) remains to be a common but severe complication after liver transplantation (LT). However, there are still few clinically validated biomarkers. A total of 214 patients who underwent routine furosemide (1-2 mg/kg) after LT were retrospectively included. The urine output during the first 6 h was recorded to evaluate the predictive value of AKI stage 3 and renal replacement therapy (RRT). 105 (49.07%) patients developed AKI, including 21 (9.81%) progression to AKI stage 3 and 10 (4.67%) requiring RRT. The urine output decreased with the increasing severity of AKI. The urine output of AKI stage 3 did not significantly increase after the use of furosemide. The area under the receiver operator characteristic (ROC) curves for the total urine output in the first hour to predict progression to AKI stage 3 was 0.94 (p < 0.001). The ideal cutoff for predicting AKI progression during the first hour was a urine volume of less than 200 ml with a sensitivity of 90.48% and specificity of 86.53%. The area under the ROC curves for the total urine output in the six hours to predict progression to RRT was 0.944 (p < 0.001). The ideal cutoff was a urine volume of less than 500 ml with a sensitivity of 90% and specificity of 90.91%. Severe AKI after liver transplantation seriously affects the outcome of patients. Lack of furosemide responsiveness quickly and accurately predict AKI stage 3, and patients requiring RRT after the operation.

Management of Acute Kidney Injury in Critically Ill Children

Acute kidney injury (AKI) is common in critically ill patients, affecting almost one in four critically ill children and one in three neonates. Higher stages of AKI portend worse outcomes. Identifying AKI timely and instituting appropriate measures to prevent and manage severe AKI is important, since it is independently associated with mortality. Methods to predict severe AKI should be applied to all critically ill patients. Assessment of volume status to prevent the development of fluid overload is useful to prevent adverse outcomes. Patients with metabolic or clinical complications of AKI need prompt kidney replacement therapy (KRT). Various modes of KRT are available, and the choice of modality depends most on the technical competence of the center, patient size, and hemodynamic stability. Given the significant risk of chronic kidney disease, patients with AKI require long-term follow-up. It is important to focus on improving awareness about AKI, incorporate AKI prevention as a quality initiative, and improve detection, prevention, and management of AKI with the aim of reducing acute and long-term morbidity and mortality.

Acute Kidney Injury and Renal Replacement Therapy: A Review and Update for the Perioperative Physician

Post-operative acute kidney injury is a devastating complication with significant morbidity and mortality associated with it. The perioperative anesthesiologist is in a unique position to potentially mitigate the risk of postoperative AKI, however, understanding the pathophysiology, risk factors and preventative strategies is paramount. There are also certain clinical scenarios, where renal replacement therapy may be indicated intraoperatively including severe electrolyte abnormalities, metabolic acidosis and massive volume overload. A multidisciplinary approach including the nephrologist, critical care physician, surgeon and anesthesiologist is necessary to determine the optimal management of these critically ill patients.

Relationship Between Mean Arterial Pressure and Furosemide Stress Test Success Rates: A Retrospective Cohort Study

BACKGROUND

The furosemide stress test (FST) is a safe and easy assessment of renal tubular function. Other factors, such as mean arterial pressure (MAP), which may influence the success rates of the FST, have not been well defined.

OBJECTIVE

To evaluate the relationship between MAP and success rates of the FST in critically ill patients.

METHODS

Retrospective, single-center, institutional review board (IRB)-approved cohort study. Critically ill adult patients given at least one dose of intravenous (IV) furosemide (≥1-1.5 mg/kg) were included. Primary outcome was whether a MAP ≥ 75 mm Hg would equate to a higher FST success rate. Secondary outcome was the success rates of patient on one or more vasopressors.

RESULTS

Of 225 patients, 88 (39.1%) had a successful FST. In patients with a MAP ≥ 75 mm Hg, 60 out of 104 (57.7%) had a successful FST compared to 28 out of 121 (23.1%) of patients who had a MAP < 75 mm Hg (odds ratio [OR], 4.53, 95% CI, 2.55-8.74, P < 0.001). Patients on vasopressors at the time of the furosemide dose had lower rates of success compared to those not on vasoactive agents (30.4% versus 68.2%, p = 0.026). Limitations of this study include its retrospective design and reliance on documented urine output.

CONCLUSION AND RELEVANCE

Patients with a MAP ≥ 75 mm Hg were significantly more likely to have a successful FST compared to those with a MAP < 75 mm Hg. This represents the first report of factors that may influence FST success rates.

Neonatal fluid overload-ignorance is no longer bliss

Excessive accumulation of fluid may result in interstitial edema and multiorgan dysfunction. Over the past few decades, the detrimental impact of fluid overload has been further defined in adult and pediatric populations. Growing evidence highlights the importance of monitoring, preventing, managing, and treating fluid overload appropriately. Translating this knowledge to neonates is difficult as they have different disease pathophysiologies, and because neonatal physiology changes rapidly postnatally in many of the organ systems (i.e., skin, kidneys, and cardiovascular, pulmonary, and gastrointestinal). Thus, evaluations of the optimal targets for fluid balance need to consider the disease state as well as the gestational and postmenstrual age of the infant. Integration of what is known about neonatal fluid overload with individual alterations in physiology is imperative in clinical management. This comprehensive review will address what is known about the epidemiology and pathophysiology of neonatal fluid overload and highlight the known knowledge gaps. Finally, we provide clinical recommendations for monitoring, prevention, and treatment of fluid overload.

External validation of a deep-learning model to predict severe acute kidney injury based on urine output changes in critically ill patients

OBJECTIVES

The purpose of this study was to externally validate algorithms (previously developed and trained in two United States populations) aimed at early detection of severe oliguric AKI (stage 2/3 KDIGO) in intensive care units patients.

METHODS

The independent cohort was composed of 10'596 patients from the university hospital ICU of Amsterdam (the "AmsterdamUMC database") admitted to their intensive care units. In this cohort, we analysed the accuracy of algorithms based on logistic regression and deep learning methods. The accuracy of investigated algorithms had previously been tested with electronic intensive care unit (eICU) and MIMIC-III patients.

RESULTS

The deep learning model had an area under the ROC curve (AUC) of 0,907 (± 0,007SE) with a sensitivity and specificity of 80% and 89%, respectively, for identifying oliguric AKI episodes. Logistic regression models had an AUC of 0,877 (± 0,005SE) with a sensitivity and specificity of 80% and 81%, respectively. These results were comparable to those obtained in the two US populations upon which the algorithms were previously developed and trained.

CONCLUSION

External validation on the European sample confirmed the accuracy of the algorithms, previously investigated in the US population. The models show high accuracy in both the European and the American databases even though the two cohorts differ in a range of demographic and clinical characteristics, further underlining the validity and the generalizability of the two analytical approaches.

Accuracy of clinicians' ability to predict the need for renal replacement therapy: a prospective multicenter study

PURPOSE

Identifying patients who will receive renal replacement therapy (RRT) during intensive care unit (ICU) stay is a major challenge for intensivists. The objective of this study was to evaluate the performance of physicians in predicting the need for RRT at ICU admission and at acute kidney injury (AKI) diagnosis.

METHODS

Prospective, multicenter study including all adult patients hospitalized in 16 ICUs in October 2020. Physician prediction was estimated at ICU admission and at AKI diagnosis, according to a visual Likert scale. Discrimination, risk stratification and benefit of physician estimation were assessed. Mixed logistic regression models of variables associated with risk of receiving RRT, with and without physician estimation, were compared.

RESULTS

Six hundred and forty-nine patients were included, 270 (41.6%) developed AKI and 77 (11.8%) received RRT. At ICU admission and at AKI diagnosis, a model including physician prediction, the experience of the physician, SOFA score, serum creatinine and diuresis to determine need for RRT performed better than a model without physician estimation with an area under the ROC curve of 0.90 [95% CI 0.86-0.94, p < 0.008 (at ICU admission)] and 0.89 [95% CI 0.83-0.93, p = 0.0014 (at AKI diagnosis)]. In multivariate analysis, physician prediction was strongly associated with the need for RRT, independently of creatinine levels, diuresis, SOFA score and the experience of the doctor who made the prediction.

CONCLUSION

As physicians are able to stratify patients at high risk of RRT, physician judgement should be taken into account when designing new randomized studies focusing on RRT initiation during AKI.

ISCCM Guidelines on Acute Kidney Injury and Renal Replacement Therapy

Acute kidney injury (AKI) is a complex syndrome with a high incidence and considerable morbidity in critically ill patients. Renal replacement therapy (RRT) remains the mainstay of treatment for AKI. There are at present multiple disparities in uniform definition, diagnosis, and prevention of AKI and timing of initiation, mode, optimal dose, and discontinuation of RRT that need to be addressed. The Indian Society of Critical Care Medicine (ISCCM) AKI and RRT guidelines aim to address the clinical issues pertaining to AKI and practices to be followed for RRT, which will aid the clinicians in their day-to-day management of ICU patients with AKI.

How to cite this article

Mishra RC, Sodhi K, Prakash KC, Tyagi N, Chanchalani G, Annigeri RA, et al. ISCCM Guidelines on Acute Kidney Injury and Renal Replacement Therapy. Indian J Crit Care Med 2022;26(S2):S13-S42.

Delivering optimal renal replacement therapy to critically ill patients with acute kidney injury

Critical illness is often complicated by acute kidney injury (AKI). In patients with severe AKI, renal replacement therapy (RRT) is deployed to address metabolic dysfunction and volume excess until kidney function recovers. This review is intended to provide a comprehensive update on key aspects of RRT prescription and delivery to critically ill patients. Recently completed trials have enhanced the evidence base regarding several RRT practices, most notably the timing of RRT initiation and anticoagulation for continuous therapies. Better evidence is still needed to clarify several aspects of care including optimal targets for ultrafiltration and effective strategies for RRT weaning and discontinuation.

Perioperative acute kidney injury: impact and recent update

PURPOSE OF REVIEW

Acute kidney injury (AKI) is common in hospitalized patients and is a major risk factor for increased length of stay, morbidity, and mortality in postoperative patients. There are multiple barriers to reducing perioperative AKI - the etiology is multi-factorial and the diagnosis is fraught with issues. We review the recent literature on perioperative AKI and some considerations for anesthesiologists that examine the far-reaching effects of AKI on multiple organ systems.

RECENT FINDINGS

This review will discuss recent literature that addresses the epidemiology, use of novel biomarkers in risk stratification, and therapeutic modalities for AKI in burn, pediatrics, sepsis, trauma, cardiac, and liver disease, contrast-induced AKI, as well as the evidence assessing goal-directed fluid therapy.

SUMMARY

Recent studies address the use of risk stratification models and biomarkers, more sensitive than creatinine, in the preoperative identification of patients at risk for AKI. Although exciting, these scores and models need validation. There is a need for research assessing whether early AKI detection improves outcomes. Enhanced recovery after surgery utilizing goal-directed fluid therapy has not been shown to make an appreciable difference in the incidence of AKI. Reducing perioperative AKI requires a multi-pronged and possibly disease-specific approach.

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.

Machine learning model for predicting acute kidney injury progression in critically ill patients

Background

Acute kidney injury (AKI) is a serve and harmful syndrome in the intensive care unit. Comparing to the patients with AKI stage 1/2, the patients with AKI stage 3 have higher in-hospital mortality and risk of progression to chronic kidney disease. The purpose of this study is to develop a prediction model that predict whether patients with AKI stage 1/2 will progress to AKI stage 3.

Methods

Patients with AKI stage 1/2, when they were first diagnosed with AKI in the Medical Information Mart for Intensive Care, were included. We used the Logistic regression and machine learning extreme gradient boosting (XGBoost) to build two models which can predict patients who will progress to AKI stage 3. Established models were evaluated by cross-validation, receiver operating characteristic curve, and precision–recall curves.

Results

We included 25,711 patients, of whom 2130 (8.3%) progressed to AKI stage 3. Creatinine, multiple organ failure syndromes were the most important in AKI progression prediction. The XGBoost model has a better performance than the Logistic regression model on predicting AKI stage 3 progression. Thus, we build a software based on our data which can predict AKI progression in real time.

Conclusions

The XGboost model can better identify patients with AKI progression than Logistic regression model. Machine learning techniques may improve predictive modeling in medical research.

The use of diagnostic tools for pediatric AKI: applying the current evidence to the bedside

Given the known deleterious consequences of acute kidney injury (AKI), exciting recent research efforts have focused on developing strategies for the earlier recognition of AKI in the pediatric population. Recognizing the limitations of serum creatinine, investigators have focused on the study of novel biomarkers and practical bedside tools for identifying patients at risk for AKI prior to a rise in serum creatinine. In PubMed, there are presently over 30 original research papers exploring the use of pediatric AKI risk prediction tools in just the last 2 years. The following review highlights the most recent advances in the literature regarding opportunities to refine our ability to detect AKI early. Importantly, this review discusses how prediction tools including novel urine and serum biomarkers, practical risk stratification tests, renal functional reserve, and electronic medical record alerts may ultimately be applied to routine clinical practice.

Neutrophil-to-lymphocyte ratio is a marker for acute kidney injury progression and mortality in critically ill populations: a population-based, multi-institutional study

Backgrounds

Neutrophil-to-lymphocyte ratio (NLR), a surrogate marker of systemic response to physiological stress, is used for prognosis prediction in many diseases. However, the usefulness of this marker for predicting acute kidney injury (AKI) progression is unclear.

Methods

This retrospective study was based on the Chang Gung Research Database. Patients admitted to the intensive care unit with a diagnosis of stage 1 or 2 AKI were identified. The primary outcome was a composite of progression to stage 3 AKI, requirement of renal replacement therapy, or 14-day in-hospital mortality. The association between NLR and the primary outcome was examined using a logistic regression model and multivariable analysis. The nonlinearity and cutoff points of this relationship were determined using a restricted cubic spline model.

Results

A total of 10,441 patients were enrolled. NLR level at the time of stage 1–2 AKI diagnosis was a marker of adverse outcomes. After adjustment for confounders, NLR was independently associated with the composite outcome of AKI progression, renal replacement therapy, or mortality. The restricted cubic spline model revealed a J-shaped curve, with the lowest odds ratio for an NLR between 7 and 38. Subgroup analysis revealed linear and J-shaped relationships between NLR and the primary outcome in patients admitted to the intensive care unit for medical reasons and for cardiovascular surgery, respectively.

Conclusions

NLR is an independent marker of AKI progression and in-hospital mortality. Because it is readily available in daily practice, it might be used for risk stratification in the AKI population.

Graphic abstract

Supplementary Information

The online version contains supplementary material available at 10.1007/s40620-021-01162-3.

Acute kidney injury in the critically ill: an updated review on pathophysiology and management

Acute kidney injury (AKI) is now recognized as a heterogeneous syndrome that not only affects acute morbidity and mortality, but also a patient’s long-term prognosis. In this narrative review, an update on various aspects of AKI in critically ill patients will be provided. Focus will be on prediction and early detection of AKI (e.g., the role of biomarkers to identify high-risk patients and the use of machine learning to predict AKI), aspects of pathophysiology and progress in the recognition of different phenotypes of AKI, as well as an update on nephrotoxicity and organ cross-talk. In addition, prevention of AKI (focusing on fluid management, kidney perfusion pressure, and the choice of vasopressor) and supportive treatment of AKI is discussed. Finally, post-AKI risk of long-term sequelae including incident or progression of chronic kidney disease, cardiovascular events and mortality, will be addressed.

Effects of IV Fluids in Dogs and Cats With Kidney Failure

Intravenous fluid therapy has long been the mainstay of treatment of kidney disease, including acute kidney injury and uremic crisis associated with chronic kidney disease. Careful management of fluid dose is critical, as animals with kidney disease may have marked derangements in their ability to regulate fluid homeostasis and acid-base status. Understanding of the physiology of renal fluid handling is necessary, along with repeated attention to parameters of fluid status, electrolytes, and acid-base balance, to achieve optimal hydration status and avoid further damage or decrease in function from dehydration or overhydration.

Risk factors and prognosis assessment for acute kidney injury: The 2020 consensus of the Taiwan AKI Task Force

Risk and prognostic factors for acute kidney injury (AKI) have been published in various studies across various populations. We aimed to explore recent advancements in and provide updated recommendations on AKI risk stratification and information about local AKI risk factors. The Taiwan Acute Kidney Injury Task Force reviewed relevant recently published literature and reached a consensus after group meetings. Systemic review and group discussion were performed. We conducted a meta-analysis according to the PRISMA statement for evaluating the diagnostic performance of the furosemide stress test. Several risk and susceptibility factors were identified through literature review. Contrast-associated AKI prediction models after coronary angiography were one of the most discussed prediction models we found. The basic approach and evaluation of patients with AKI was also discussed. Our meta-analysis found that the furosemide stress test can be used as a prognostic tool for AKI progression and to identify patients with AKI who are at low risk of renal replacement therapy. Factors associated with de novo chronic kidney injury or renal non-recovery after AKI were identified and summarized. Our review provided practical information about early identification of patients at high risk of AKI or disease progression for Taiwan local clinics.

Direct Measurement of Creatinine Clearance over a Short Interval in Intensive Care Settings

Background

The definition of acute kidney injury (AKI), based on serum creatinine and urine output, bears significant limitations in intensive care units (ICUs). Serum creatinine has significant lag-time as it needs to be accumulated and stabilized at a new level whereas urine output is affected by diuresis, antidiuresis, and antinatriuresis. Direct measurement of creatinine clearance (CrCl_direct = urine creatinine × urine flow rate/serum creatinine) over a short interval (3-6 hours) was explored to identify patients with AKI.

Materials and methods

We reanalyzed a previous published dataset. We included 11 patients who had serial daily urine collections over 0 to 3 days of stay in ICU and baseline (day -1) serum creatinine levels.

Result

The ratio of CrCl_direct on day 0 to baseline creatinine clearance predicted the progression of AKI over the subsequent 1 to 3 days of ICU stay [area under receiver operating characteristic curve = 0.933 and 95% confidence interval (CI) = 0.780-1.000].

Discussion

CrCl_direct over a short interval may be an alternative marker of kidney function. Future studies may explore its use to identify patients with AKI who may benefit from early renal replacement therapy.

How to cite this article

Law LSC, Lo EAG, Yeoh SF. Direct Measurement of Creatinine Clearance over a Short Interval in Intensive Care Settings. Indian J Crit Care Med 2021;25(7):800-802.