Uncomplicated acute renal failure and hospital resource utilization: a retrospective multicenter analysis

Differences in the incidence, characteristics, and outcomes of patients with acute kidney injury in the medical and surgical intensive care units

BACKGROUND

Though acute kidney injury (AKI) is a prevalent complication in critically ill patients, knowledge on the epidemiological differences and clinical characteristics of patients with AKI admitted to medical and surgical intensive care units (ICUs) remains limited.

METHODS

Electronic medical records of patients in ICUs in Pusan National University Hospital and Pusan National University Hospital Yangsan, from January 2011 to December 2020, were retrospectively analyzed. Different characteristics of AKI between patients were analyzed. The contribution of AKI to the in-hospital mortality rate was assessed using a Cox proportional hazards model.

RESULTS

A total of 7,150 patients were included in this study. AKI was more frequent in medical (48.7%) than in surgical patients (19.7%), with the severity of AKI higher in medical patients. In surgical patients, hospital-acquired AKI was more frequent (51.0% vs. 49.0%), whereas community-acquired AKI was more common in medical patients (58.5% vs. 41.5%). 16.9% and 5.9% of medical and surgical patients died in the hospital, respectively. AKI affected patient groups to different degrees. In surgical patients, AKI patients had 4.778 folds higher risk of mortality (95% confidence interval [CI], 3.577-6.382; p < 0.001) than non-AKI patients; whereas in medical AKI patients, it was 1.239 (95% CI, 1.051-1.461; p = 0.01).

CONCLUSION

While the prevalence of AKI itself is higher in medical patients, the impact of AKI on mortality was stronger in surgical patients compared to medical patients. This suggests that more attention is needed for perioperative patients to prevent and manage AKI.

The Risk of Kidney Injury in Patients With Sickle Cell Disease Treated With Ketorolac for Acute Pain

Ketorolac, a nonsteroidal anti-inflammatory drug, is used in combination with opioids to manage vaso-occlusive episodes (VOEs). The relationship between ketorolac use and kidney injury in pediatric patients with sickle cell disease (SCD) remains incompletely understood. We hypothesize that ketorolac is associated with acute kidney injury (AKI) in patients with SCD presenting with pain. All nonsurgical hospitalizations for VOEs treated with ketorolac between January 2014 and December 2022 were included. We used optimal matching methodology to identify control admissions (2:1 ratio) and used nonparametric tests to compare ketorolac administration between cases and controls. A total of 1319 encounters/253 patients were included in this study. AKI was noted in 1.1% of encounters and 5.5% of patients. Cases had significantly higher initial BUN than controls (9.0 vs. 6.0 mg/dL, P =0.012). In cases versus controls, there was significantly lower serum sodium (136.0 vs. 138.0 mmol/L, P =0.021). There was no association between ketorolac dose and development of AKI among children with SCD. Higher BUN and lower sodium in cases suggest that patients with AKI were more volume depleted on admission than controls. This highlights the need for strict assessment of fluid status upon admission for VOE.

Machine learning algorithms to predict colistin-induced nephrotoxicity from electronic health records in patients with multidrug-resistant Gram-negative infection

OBJECTIVES

Colistin-induced nephrotoxicity prolongs hospitalisation and increases mortality. The study aimed to construct machine learning models to predict colistin-induced nephrotoxicity in patients with multidrug-resistant Gram-negative infection.

METHODS

Patients receiving colistin from three hospitals in the Clinical Research Database were included. Data were divided into a derivation cohort (2011-2017) and a temporal validation cohort (2018-2020). Fifteen machine learning models were established by categorical boosting, light gradient boosting machine and random forest. Classifier performances were compared by the sensitivity, F1 score, Matthews correlation coefficient (MCC), area under the receiver operating characteristic (AUROC) curve, and area under the precision-recall curve (AUPRC). SHapley Additive exPlanations plots were drawn to understand feature importance and interactions.

RESULTS

The study included 1392 patients, with 360 (36.4%) and 165 (40.9%) experiencing nephrotoxicity in the derivation and temporal validation cohorts, respectively. The categorical boosting with oversampling achieved the highest performance with a sensitivity of 0.860, an F1 score of 0.740, an MCC of 0.533, an AUROC curve of 0.823, and an AUPRC of 0.737. The feature importance demonstrated that the days of colistin use, cumulative dose, daily dose, latest C-reactive protein, and baseline haemoglobin were the most important risk factors, especially for vulnerable patients. A cutoff colistin dose of 4.0 mg/kg body weight/d was identified for patients at higher risk of nephrotoxicity.

CONCLUSIONS

Machine learning techniques can be an early identification tool to predict colistin-induced nephrotoxicity. The observed interactions suggest a modification in dose adjustment guidelines. Future geographic and prospective validation studies are warranted to strengthen the real-world applicability.

The effects of timing onset and progression of AKI on the clinical outcomes in AKI patients with sepsis: a prospective multicenter cohort study

BACKGROUND

Limited studies are available concerning on the earlier identification of AKI with sepsis. The aim of the study was to identify the risk factors of AKI early which depended on the timing onset and progression of AKI and investigate the effects of timing onset and progression of AKI on clinical outcomes.

METHODS

Patients who developed sepsis during their first 48-h admission to ICU were included. The primary outcome was major adverse kidney events (MAKE) consisted of all-cause mortality, RRT-dependence, or an inability to recover to 1.5 times of the baseline creatinine value up to 30 days. We determined MAKE and in-hospital mortality by multivariable logistic regression and explored the risk factors of early persistent-AKI. C statistics were used to evaluate model fit.

RESULTS

58.7% sepsis patients developed AKI. According to the timing onset and progression of AKI, Early transient-AKI, early persistent-AKI, late transient-AKI, late persistent-AKI were identified. Clinical outcomes were quite different among subgroups. Early persistent-AKI had 3.0-fold (OR 3.04, 95% CI 1.61 - 4.62) risk of MAKE and 2.6-fold (OR 2.60, 95%CI 1.72 - 3.76) risk of in-hospital mortality increased compared with the late transients-AKI. Older age, underweight, obese, faster heart rate, lower MAP, platelet, hematocrit, pH and energy intake during the first 24 h on ICU admission could well predict the early persistent-AKI in patients with sepsis.

CONCLUSION

Four AKI subphenotypes were identified based on the timing onset and progression of AKI. Early persistent-AKI showed higher risk of major adverse kidney events and in-hospital mortality.

TRIAL REGISTRATION

This study was registered in the Chinese Clinical Trials Registry (www.chictr.org/cn) under registration number ChiCTR-ECH-13003934.

Circular RNAs in Acute Kidney Injury: Roles in Pathophysiology and Implications for Clinical Management

Acute kidney injury (AKI) is a common clinical condition, results in patient morbidity and mortality, and incurs considerable health care costs. Sepsis, ischaemia-reperfusion injury (IRI) and drug nephrotoxicity are the leading causes. Mounting evidence suggests that perturbations in circular RNAs (circRNAs) are observed in AKI of various aetiologies, and have pathogenic significance. Aberrant circRNA expressions can cause altered intracellular signalling, exaggerated oxidative stress, increased cellular apoptosis, excess inflammation, and tissue injury in AKI due to sepsis or IRI. While circRNAs are dysregulated in drug-induced AKI, their roles in pathogenesis are less well-characterised. CircRNAs also show potential for clinical application in diagnosis, prognostication, monitoring, and treatment. Prospective observational studies are needed to investigate the role of circRNAs in the clinical management of AKI, with special focus on the safety of therapeutic interventions targeting circRNAs and the avoidance of untoward off-target effects.

Associations of Chinese diagnosis-related group systems with inpatient expenditures for older people with hip fracture

Background

Hip fracture is frequent in older people and represents a major public health issue worldwide. The increasing incidence of hip fracture and the associated hospitalization costs place a significant economic burden on older patients and their families. On January 1, 2018, the Chinese diagnosis-related group (C-DRG) payment system, which aims to reduce financial barriers, was implemented in Sanming City, southern China. This study aimed to evaluate the associations of C-DRG system with inpatient expenditures for older people with hip fracture.

Methods

An uncontrolled before-and-after study employed data of all the patients with hip fracture aged 60 years or older from all the public hospitals enrolled in the Sanming Basic Health Insurance Scheme from January 1, 2016 to December 31, 2018. The ‘pre C-DRG sample’ included patients from January 1, 2016 to December 31, 2017. The ‘post C-DRG sample’ included patients from January 1, 2018 to December 31, 2018. A propensity score matching analysis was used to adjust the difference in baseline characteristic parameters between the pre and post samples. Data were analyzed using generalized linear models adjusted for the demographic, clinical, and institutional factors. Robust tests were performed by accounting for time trend, the fixed effects of the year and hospitals, and clustering effect within hospitals.

Results

After propensity score matching, we obtained two homogeneous groups of 1123 patients each, and the characteristic variables of the two matched groups were similar. We found that C-DRG reform was associated with a 19.51% decrease in out-of-pocket (OOP) payments (p < 0.001) and a 99.93% decrease in OOP payments as a share of total inpatient expenditure (p < 0.001); whereas total inpatient expenditure was not significantly associated with the C-DRG reform. All the sensitivity analyses did not change the results significantly.

Conclusion

The implementation of C-DRG payment system reduced both the absolute amount of OOP payments and OOP payments as a share of total inpatient expenditure for older patients with hip fracture, without affecting total inpatient expenditure. These results may provide significant insights for policymakers in reducing the financial burden on older patients with hip fracture in other countries.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12877-022-02865-3.

Elevated Levels of Urinary Biomarkers TIMP-2 and IGFBP-7 Predict Acute Kidney Injury in Neonates after Congenital Heart Surgery

Objectives  This article investigated the utility of urine biomarkers tissue inhibitor of metalloproteinase-2 (TIMP-2) and insulin-like growth factor binding protein-7 (IGFBP-7) in identifying acute kidney injury (AKI) in neonates after congenital heart surgery (CHS). TIMP-2 and IGFBP-7 are cell cycle arrest proteins detected in urine during periods of kidney stress/injury. Methods  We conducted a single-center, prospective study between September 2017 and May 2019 with neonates undergoing CHS requiring cardiopulmonary bypass (CPB). Urine samples were analyzed using NephroCheck prior to surgery and 6, 12, 24, and 96 hours post-CPB. All patients were evaluated using the Acute Kidney Injury Network (AKIN) criteria. Wilcoxon rank sum tests were used to compare the medians of the [TIMP-2*IGFBP-7] values in the AKIN negative and positive groups at each time point. Receiver operating characteristic curves were used to measure how well the [TIMP-2*IGFBP-7] values predict AKIN status. Results  Thirty-six patients were included. No patients met the AKIN criteria for AKI preoperatively. Postoperatively, 19 patients (53%) met the AKIN criteria for AKI diagnosis: 13 (36%) stage 1, 5 (14%) stage 2, and 1 (3%) stage 3. None required renal replacement therapy. At the 24-hour time points, patients who met the AKIN criteria for AKI had a statistically significantly higher [TIMP-2*IGFBP7] values than the patients without AKI (1.1 vs. 0.27 [ng/mL] ² /1,000) at 24 hours (adj- p  = 0.0019). Conclusion  AKI is a serious complication associated with adverse outcomes in patients undergoing cardiac surgery. [TIMP-2*IGFBP-7] urinary level 24 hours after CPB is a good predictor of AKI in this population.

Under-recognition of Acute Kidney Injury after Cardiac Surgery in the ICU Impedes Early Detection and Prevention

BACKGROUND

Acute kidney injury (AKI) is associated with high morbidity and mortality; therefore, prevention is important. The aim of this study was to systematically assess AKI incidence after cardiac surgery as documented in clinical routine compared to the real incidence because AKI may be under-recognized in clinical practice. Further, its postoperative management was compared to Kidney Disease: Improving Global Outcomes (KDIGO) recommendations because recognition and adequate treatment represent the fundamental cornerstone in the prevention and management of AKI.

METHODS

This retrospective single-center study included n = 100 patients who underwent cardiac surgery with cardiopulmonary bypass. The coded incidence of postoperative AKI during intensive care unit stay after surgery was compared to the real AKI incidence. Furthermore, conformity of postoperative parameters with KDIGO recommendations for AKI prevention and management was reviewed.

RESULTS

We found a considerable discrepancy between coded and real incidence, and conformity with KDIGO recommendations was found to be relatively low. The coded incidence was significantly lower (n = 12 vs. n = 52, p < 0.05), representing a coding rate of 23.1%. Regarding postoperative management, 90% of all patients had at least 1 episode with mean arterial pressure <65 mm Hg within the first 72 h. Furthermore, regarding other preventive parameters (avoiding hyperglycemia, stopping angiotensin-converting enzyme inhibitors/angiotensin receptor blockers, avoiding contrast media, and nephrotoxic drugs), only 10 patients (20.8%) in the non-AKI group and in 5 (9.6%) subjects in the AKI group had none of all the above potential AKI-promoting factors.

CONCLUSIONS

AKI recognition in everyday clinical routine seems to be low, especially in lower AKI stages, and the current postoperative management still offers potential for optimization. Possibly, higher AKI awareness and stricter postoperative management could already achieve significant effects in prevention and treatment of AKI.

Economic Implications of Chinese Diagnosis-Related Group-Based Payment Systems for Critically Ill Patients in ICUs

OBJECTIVES

To evaluate the economic implications of payments based on Chinese diagnosis-related groups for critically ill patients in ICUs in terms of total hospital expenditure, out-of-pocket payments, and length of stay.

DESIGN

A pre-post comparison of patient cohorts admitted to ICUs 1 year before and 1 year after Chinese diagnosis-related group reform was undertaken. Demographic characteristics, clinical data, and medical expenditures were collated from a health insurance database.

SETTING

Twenty-two public hospitals in Sanming, Southern China.

PATIENTS

All patients admitted to ICUs from January 1, 2017, to December 31, 2018.

INTERVENTION

The implementation of Chinese diagnosis-related group-based payments on January 1, 2018.

MEASUREMENTS AND MAIN RESULTS

Economic variables (total expenditures, out-of-pocket payments, and length of stay) were calculated for each patient from the day of hospital admission to the day of hospital discharge. Adjusted mean out-of-pocket payment estimates were 29.46% (p < 0.001) lower following reform. Adjusted mean out-of-pocket payments fell by 41.32% for patients in neonatal ICU, whereas there were no significant decreases in out-of-pocket payments for patients in PICU and adult ICU. Furthermore, adjusted mean out-of-pocket payments decreased by 55.74% in secondary hospitals, but there was no significant change in tertiary hospitals after Chinese diagnosis-related group reform. No significant changes were found in total expenditures and length of stay.

CONCLUSIONS

Chinese diagnosis-related group policy provided an opportunity for critically ill patients in ICUs to achieve at least short-term financial benefits in reducing out-of-pocket payments, without affecting the total expenditures and length of stay. Chinese diagnosis-related group-based payment significantly relieved financial burdens for patients with lower illness severities, such as patients in neonatal ICU. The results of this study can offer significant insights for policymakers in reducing the financial burden on critically ill patients, both in China and in other countries with similar systems.

Prevalence, Length of Stay, and Hospitalization of Acute Kidney Injury in Patients With and Without Sjogren's Syndrome

Background:

Literature on the outcome of acute kidney injury (AKI) in Sjogren’s syndrome (SJS) is quite scanty. Acute kidney injury has emerged as a significant cause of morbidity and mortality in patients with autoimmune diseases such as systemic lupus erythematosus.

Objective:

To examine the outcome of AKI with and without SJS. To achieve this, we examined the prevalence, mortality, outcomes, length of stay (LOS), and hospital charges in patients with AKI with SJS compared with patients without SJS from a National Inpatient Sample (NIS) database in the period 2010 to 2013.

Design:

A retrospective cohort study using NIS.

Setting:

United States.

Sample:

Cohort of 97 055 weighted patient discharges with AKI from the NIS.

Measurements:

Not applicable.

Methods:

Data were retrieved from the NIS for adult patients admitted with a principal diagnosis of AKI between 2010 and 2013, using the respective International Classification of Diseases, Ninth Revision (ICD-9) codes. The study population divided into 2 groups, with and without Sjogren’s disease. Multivariate and linear regression analysis conducted to adjust for covariates. We omitted patients with systemic sclerosis and rheumatoid arthritis from the analysis to avoid any discrepancy as they were not meant to be a primary outcome in our study.

Results:

The study population represented 97 055 weighted patient discharges with AKI. Analysis revealed AKI patients with Sjogren’s compared with patients without Sjogren’s had statistically significant lower hyperkalemia rates (adjusted odds ratio: 0.65, confidence interval: 0.46-0.92; P = .017. There was no statistically significant difference in mortality, LOS, hospital charges, and other outcomes.

Limitations:

Study is not up to date as data are from ICD-9 which are testing data from 2010 to 2013, and data were obtained through SJS codes, which have their limitations. Also, limitations included lack of data on metabolic acidosis, hypokalemia, and not including all causes of AKI.

Conclusions:

At present, our study is unique as it has examined prevalence, mortality, and outcomes of Sjogren’s in patients with AKI. Patients with Sjogren’s had significantly lower hyperkalemia during the hospitalization. Further research is needed to identify the underlying protective mechanisms associated with Sjogren’s that resulted in lower hyperkalemia.

Trial registration:

Not applicable.

Acute kidney injury is associated with higher mortality and healthcare costs in hospitalized patients with cirrhosis

INTRODUCTION AND OBJECTIVES

AKI is known to be associated with increased risk of mortality, however limited information is available on how AKI impacts healthcare costs and resource utilization in hospitalized patients with cirrhosis. Previous studies have had variable definitions of AKI, resulting in inconsistent reporting of the true impact of AKI in patients with cirrhosis.

METHODS

Data from the Nationwide Inpatient Sample (NIS) which contains data from 44 states and 4378 hospitals, accounting for over 7 million discharges were analyzed. The inclusion data were all discharges in the 2012 NIS dataset with a discharge diagnosis of cirrhosis.

RESULTS

A total of 32,605 patients were included in the analysis, incidence of AKI was 12.12% in patients with cirrhosis. Crude mortality was much higher for patients with cirrhosis and AKI (14.9% vs. 1.8%, OR 9.42, p<0.001) than for patients without AKI. In addition, mean LOS was longer (8.5 vs. 4.3 days, p<0.001) and median total hospital charges were higher for patients with AKI ($43,939 vs. $22,270, p<0.001). In multivariate logistic regression, controlling for covariates and mortality risk score, sepsis, ascites and SBP were predictors of AKI.

CONCLUSIONS

AKI is relatively common in hospitalized patients with cirrhosis. Presence of AKI results in significantly higher inpatient mortality as well as LOS and resource utilization. Median hospitalization cost was twice as high in AKI patients. Early identification of patients at high risk for AKI should be implemented to reduce mortality and contain costs. Prognosis could be enhanced by utilizing biomarkers which could rapidly detect AKI.

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

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

A systematic review and meta-analysis of acute kidney injury in the intensive care units of developed and developing countries

Objectives

Although the majority of the global population lives in developing countries, most of the epidemiological data related to intensive care unit (ICU) acute kidney injury (AKI) comes from developed countries. This systematic review aims to ascertain the methodology of studies on ICU AKI patients in developing and developed countries, to determine whether epidemiological comparisons between these two settings are possible, and to present a summary estimate of AKI incidence.

Methods

A systematic review of published studies reporting AKI in intensive care units (2005–2015) identified in PubMed, LILACS, and IBECs databases was conducted. We compared developed and developing countries by evaluating study methodology, AKI reference serum creatinine definitions, population characteristics, AKI incidence and mortality. AKI incidence was calculated with a random-effects model.

Results

Ninety-two studies were included, one of which reported data from both country categories: 60 from developed countries (1,057,332 patients) and 33 from developing countries (34,539 patients). In 78% of the studies, AKI was defined by the RIFLE, AKIN or KDIGO criteria. Oliguria had 11 different definitions and reference creatinine 23 different values. For the meta-analysis, 38 studies from developed and 18 from developing countries were selected, with similar AKI incidence: 39.3% and 35.1%, respectively. The need for dialysis, length of ICU stay and mortality were higher in developing countries.

Conclusion

Although patient characteristics and AKI incidence were similar in developed and developing countries, main outcomes were worse in developing country studies. There are significant caveats when comparing AKI epidemiology in developed and developing countries, including lack of standardization of reference serum creatinine, oliguria and the timeframe for AKI assessment. Larger, prospective, multicenter studies from developing countries are urgently needed to capture AKI data from the overall population without ICU access.

Polymyxin B and colistin-the economic burden of nephrotoxicity against multidrug resistant bacteria

BACKGROUND

Polymyxin B and colistin are nephrotoxic drugs used in the treatment of carbapenem-resistant Enterobacteriaceae. The aim of this study is to evaluate the burden of costs due to polymyxin associated AKI and propose a simulated break-even price for new therapies.

METHODS

The pharmacoeconomic model is based on two large cross-sectional studies of polymyxin nephrotoxicity. Total direct costs in patients with and without renal failure were compared. The direct cost of each hemodialysis section (USD82.94) and daily hospital charges (USD934.85) were based on the values used in a major public hospital in the city where the clinical study was performed. The break-even price of new drugs was simulated considering eventual new drugs as effective as polymyxins, but less nephrotoxic in different percentages. Outcomes of patients after hospital discharge were not evaluated.

RESULTS

Total direct cost of the group of patients who survived without AKI was significantly lower than total direct cost of the groups either with AKI or the group who died without AKI. There was a tendency of even higher costs in those who died with AKI and dialysis. Direct cost of hemodialysis was not as important as the longer hospitalization after sepsis. Considering daily cost of polymyxin is USD60, drugs with 50% less AKI could be considered cost-beneficial if the daily cost is lower than USD160.

CONCLUSIONS

AKI in patients with carbapenem-resistant Enterobacteriaceae treated with polymyxin increases both length of stay in hospital and total costs.

A Prospective Micro-costing Pilot Study of the Health Economic Costs of Acute Kidney Injury

Introduction

Acute kidney injury (AKI) prevalence in the UK is estimated to be approximately 20% of all emergency admissions. Complications of AKI have a huge impact on health care costs. Most studies that have researched the economic costs of AKI have used macro-level costing using national tariffs and applying this to hospital episode statistics.

Methods

The Acute Kidney Outreach to Reduce Deterioration and Death (AKORDD) study was a pilot study that tested the provision of early specialist advice to improve outcomes for patients with AKI. As part of this prospective study, we undertook a health economics substudy that involved micro-costing to help more accurately define the total cost per patient.

Results

We found that the total cost of providing an AKI alert system and an outreach service (intervention group) was lower than current practice (control group) for patients with AKI. Overall, an episode of AKI that required inpatient care costs approximately £5000 over 12 months, which is somewhat higher than previous UK estimates. Although it was feasible to collect the required complex dataset needed to conduct a health economics analysis of an outreach service, significant amounts of time and resources needed to be dedicated to this endeavor.

Conclusion

We showed that it is possible to demonstrate a clearer, more detailed picture of the prolonged economic costs of AKI for a health care system, as part of a substudy of a larger trial. A larger scale, randomized controlled trial of AKI outreach is needed, with a prospective full economic evaluation conducted alongside the trial.

The Economic Consequences of Acute Kidney Injury

Acute kidney injury (AKI) is an increasingly common condition associated with poor health outcomes. Combined with its rising incidence, AKI has emerged as a major public health concern with high human and financial costs. In England, the estimated inpatient costs related to AKI consume 1% of the National Health Service budget. In the United States, AKI is associated with an increase in hospitalization costs that range from $5.4 to $24.0 billion. The most expensive patients are those with AKI of sufficient severity to require dialysis, where cost increases relative to patients without AKI range from $11,016 to $42,077 per hospitalization. Even with these high costs, significant hospital-level variation still exists in the cost of AKI care. In this article, we review the economic consequences of AKI for both the general and critically ill AKI population. Our primary objective is to shed light on an opportunity for hospitals and policymakers to develop new care processes for patients with AKI that have the potential to yield substantial cost savings. By exposing the high rates of death and disability experienced by affected patients and the immense financial burden attributable to AKI, we also hope to motivate scientists and entrepreneurs to pursue a variety of innovative therapeutic strategies to combat AKI in the near term.

Does NGAL reduce costs? A cost analysis of urine NGAL (uNGAL) & serum creatinine (sCr) for acute kidney injury (AKI) diagnosis

Introduction

Urine neutrophil gelatinase-associated lipocalin (uNGAL) is a sensitive and specific diagnostic test for acute kidney injury (AKI) in the Emergency Department (ED), but its economic impact has not been investigated. We hypothesized that uNGAL used in combination with serum creatinine (sCr) would reduce costs in the management of AKI in patients presenting to the ED in comparison to using sCr alone.

Materials and methods

A cost simulation model was developed for clinical algorithms to diagnose AKI based on sCr alone vs. uNGAL plus sCr (uNGAL+sCr). A cost minimization analysis was performed to determine total expected costs for patients with AKI. uNGAL test characteristics were validated with eight-hundred forty-nine patients with sCr ≥1.5 from a completed study of 1635 patients recruited from EDs at two U.S. hospitals from 2007–8. Biomarker test, AKI work-up, and diagnostic imaging costs were incorporated.

Results

For a hypothetical cohort of 10,000 patients, the model predicted that the expected costs were $900 per patient (pp) in the sCr arm and $950 in the uNGAL+sCr arm. uNGAL+sCr resulted in 1,578 fewer patients with delayed diagnosis and treatment than sCr alone (2,013 vs. 436 pts) at center 1 and 1,973 fewer patients with delayed diagnosis and treatment than sCr alone at center 2 (2,227 vs. 254 patients). Although initial evaluation costs at each center were $50 pp higher in with uNGAL+sCr, total costs declined by $408 pp at Center 1 and by $522 pp at Center 2 due to expected reduced delays in diagnosis and treatment. Sensitivity analyses confirmed savings with uNGAL + sCr for a range of cost inputs.

Discussion

Using uNGAL with sCr as a clinical diagnostic test for AKI may improve patient management and reduce expected costs. Any cost savings would likely result from avoiding delays in diagnosis and treatment and from avoidance of unnecessary testing in patients given a false positive AKI diagnosis by use of sCr alone.

The Kidney in Critical Cardiac Disease: Proceedings From the 10th International Conference of the Pediatric Cardiac Intensive Care Society

The field of cardiac intensive care continues to advance in tandem with congenital heart surgery. The focus of intensive care unit care has now shifted to that of morbidity reduction and eventual elimination. Acute kidney injury (AKI) after cardiac surgery is associated with adverse outcomes, including prolonged intensive care and hospital stays, diminished quality of life, and increased long-term mortality. Acute kidney injury occurs frequently, complicating the care of both postoperative patients and those with heart failure. Patients who become fluid overloaded and/or require dialysis are at high risk of mortality, but even minor degrees of AKI portend a significant increase in mortality and morbidity. Clinicians continue to seek methods of early diagnosis and risk stratification of AKI to prevent its adverse sequelae. Previous conventional wisdom that survivors of AKI fully recover renal function without subsequent consequences may be flawed.

Acute Kidney Injury and Cardiorenal Syndromes in Pediatric Cardiac Intensive Care

OBJECTIVES

The objectives of this review are to discuss the definition, diagnosis, and pathophysiology of acute kidney injury and its impact on immediate, short-, and long-term outcomes. In addition, the spectrum of cardiorenal syndromes will be reviewed including the pathophysiology on this interaction and its impact on outcomes.

DATA SOURCE

MEDLINE and PubMed.

CONCLUSION

The field of cardiac intensive care continues to advance in tandem with congenital heart surgery. As mortality has become a rare occurrence, the focus of cardiac intensive care has shifted to that of morbidity reduction. Acute kidney injury adversely impact outcomes of patients following surgery for congenital heart disease as well as in those with heart failure (cardiorenal syndrome). Patients who become fluid overloaded and/or require dialysis are at a higher risk of mortality, but even minor degrees of acute kidney injury portend a significant increase in mortality and morbidity. Clinicians continue to seek methods of early diagnosis and risk stratification of acute kidney injury to prevent its adverse sequelae.

Relative and absolute changes in urinary neutrophil gelatinase-associated lipocalin and correlation with small increases in serum creatinine levels after coronary angiography: an observational study

INTRODUCTION/AIMS

The Acute Kidney Injury Network classification is based on small increases in serum creatinine (sCr) for stage 1. This study investigated whether changes in the urinary concentration of neutrophil gelatinase-associated lipocalin (uNGAL) could predict small increases in sCr in patients undergoing coronary angiography.

METHODS

The uNGAL was measured before contrast infusion and 2 and 4 h afterwards. Patients were divided into 2 subgroups: G1 (n = 103), where sCr increased by <0.3 mg/dl, and G2 (n = 22), where sCr increased by ≥0.3 mg/dl 48 h after the angiography. To determine the sensitivity and specificity for the absolute and relative variations of uNGAL, a receiver operating characteristic curve analysis was performed.

RESULTS

In G2, the uNGAL concentration increased over baseline values (15.9 vs. 9.2 ng/dl; p < 0.05), and it was also 2-fold higher in G2 versus G1 (15.9 vs. 8.0 ng/dl; p < 0.001). The uNGAL remains an independent predictor of the small increases in sCr, and, for an increase of 50% over baseline levels, it showed 60% sensitivity and 81% specificity.

CONCLUSION

Changes in uNGAL concentration 2 h after the infusion of contrast media showed marginal sensitivity to predict small increases in sCr.

Risk factors for acute kidney injury in older adults with critical illness: a retrospective cohort study

BACKGROUND

Risk for acute kidney injury (AKI) in older adults has not been evaluated systematically. We sought to delineate the determinants of risk for AKI in older compared with younger adults.

STUDY DESIGN

Retrospective analysis of patients hospitalized in July 2000 to September 2008.

SETTING & PARTICIPANTS

We identified all adult patients admitted to an intensive care unit (n=45,655) in a large tertiary-care university hospital system. We excluded patients receiving dialysis or a kidney transplant prior to hospital admission and patients with baseline creatinine levels ≥ 4mg/dL, liver transplantation, indeterminate AKI status, or unknown age, leaving 39,938 patients.

PREDICTOR

We collected data for multiple susceptibilities and exposures, including age, sex, race, body mass, comorbid conditions, severity of illness, baseline kidney function, sepsis, and shock.

OUTCOMES

We defined AKI according to KDIGO (Kidney Disease: Improving Global Outcomes) criteria. We examined susceptibilities and exposures across age strata for impact on the development of AKI.

MEASUREMENTS

We calculated area under the receiver operating characteristic curve (AUC) for prediction of AKI across age groups.

RESULTS

25,230 (63.2%) patients were 55 years or older. Overall, 25,120 (62.9%) patients developed AKI (69.2% aged ≥55 years). Examples of risk factors for AKI in the oldest age category (≥75 years) were drugs (vancomycin, aminoglycosides, and nonsteroidal anti-inflammatories), history of hypertension (OR, 1.13; 95% CI, 1.02-1.25), and sepsis (OR, 2.12; 95% CI, 1.68-2.67). Fewer variables remained predictive of AKI as age increased and the model for older patients was less predictive (P<0.001). For the age categories 18 to 54, 55 to 64, 65 to 74, and 75 years or older, AUCs were 0.744 (95% CI, 0.735-0.752), 0.714 (95% CI, 0.702-0.726), 0.706 (95% CI, 0.693-0.718), and 0.673 (95% CI, 0.661-0.685), respectively.

LIMITATIONS

Analysis may not apply to non-intensive care unit patients.

CONCLUSIONS

The likelihood of developing AKI increases with age; however, the same variables are less predictive for AKI as age increases. Efforts to quantify risk for AKI may be more difficult in older adults.

Drug-induced nephrotoxicity: clinical impact and preclinical in vitro models

The kidney is a major target for drug-induced toxicity. Drug-induced nephrotoxicity remains a major problem in the clinical setting, where the use of nephrotoxic drugs is often unavoidable. This leads frequently to acute kidney injury, and current problems are discussed. One strategy to avoid such problems would be the development of drugs with decreased nephrotoxic potential. However, the prediction of nephrotoxicity during preclinical drug development is difficult and nephrotoxicity is typically detected only late. Also, the nephrotoxic potential of newly approved drugs is often underestimated. Regulatory approved or validated in vitro models for the prediction of nephrotoxicity are currently not available. Here, we will review current approaches on the development of such models. This includes a discussion of three-dimensional and microfluidic models and recently developed stem cell based approaches. Most in vitro models have been tested with a limited number of compounds and are of unclear predictivity. However, some studies have tested larger numbers of compounds and the predictivity of the respective in vitro model had been determined. The results showed that high predictivity can be obtained by using primary or stem cell derived human renal cells in combination with appropriate end points.

Performance and limitations of administrative data in the identification of AKI

BACKGROUND AND OBJECTIVES

Billing codes are frequently used to identify AKI events in epidemiologic research. The goals of this study were to validate billing code-identified AKI against the current AKI consensus definition and to ascertain whether sensitivity and specificity vary by patient characteristic or over time.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

The study population included 10,056 Atherosclerosis Risk in Communities study participants hospitalized between 1996 and 2008. Billing code-identified AKI was compared with the 2012 Kidney Disease Improving Global Outcomes (KDIGO) creatinine-based criteria (AKIcr) and an approximation of the 2012 KDIGO creatinine- and urine output-based criteria (AKIcr_uop) in a subset with available outpatient data. Sensitivity and specificity of billing code-identified AKI were evaluated over time and according to patient age, race, sex, diabetes status, and CKD status in 546 charts selected for review, with estimates adjusted for sampling technique.

RESULTS

A total of 34,179 hospitalizations were identified; 1353 had a billing code for AKI. The sensitivity of billing code-identified AKI was 17.2% (95% confidence interval [95% CI], 13.2% to 21.2%) compared with AKIcr (n=1970 hospitalizations) and 11.7% (95% CI, 8.8% to 14.5%) compared with AKIcr_uop (n=1839 hospitalizations). Specificity was >98% in both cases. Sensitivity was significantly higher in the more recent time period (2002-2008) and among participants aged 65 years and older. Billing code-identified AKI captured a more severe spectrum of disease than did AKIcr and AKIcr_uop, with a larger proportion of patients with stage 3 AKI (34.9%, 19.7%, and 11.5%, respectively) and higher in-hospital mortality (41.2%, 18.7%, and 12.8%, respectively).

CONCLUSIONS

The use of billing codes to identify AKI has low sensitivity compared with the current KDIGO consensus definition, especially when the urine output criterion is included, and results in the identification of a more severe phenotype. Epidemiologic studies using billing codes may benefit from a high specificity, but the variation in sensitivity may result in bias, particularly when trends over time are the outcome of interest.

Acute kidney injury-epidemiology, outcomes and economics

Acute kidney injury (AKI) is a widespread problem of epidemic status. Compelling evidence indicates that the incidence of AKI is rapidly increasing, particularly among hospitalized patients with acute illness and those undergoing major surgery. This increase might be partially attributable to greater recognition of AKI, improved ascertainment in administrative data and greater sensitivity of consensus diagnostic and classification schemes. Other causes could be an ageing population, increasing incidences of cardiovascular disease, diabetes mellitus and chronic kidney disease (CKD), and an expanding characterization of modifiable risk factors, such as sepsis, administration of contrast media and exposure to nephrotoxins. The sequelae of AKI are severe and characterized by increased risk of short-term and long-term mortality, incident CKD and accelerated progression to end-stage renal disease. AKI-associated mortality is decreasing, but remains unacceptably high. Moreover, the absolute number of patients dying as a result of AKI is increasing as the incidence of the disorder increases, and few proven effective preventative or therapeutic interventions exist. Survivors of AKI, particularly those who remain on renal replacement therapy, often have reduced quality of life and consume substantially greater health-care resources than the general population as a result of longer hospitalizations, unplanned intensive care unit admissions and rehospitalizations.

Acute kidney injury: an increasing global concern

Despite an increasing incidence of acute kidney injury in both high-income and low-income countries and growing insight into the causes and mechanisms of disease, few preventive and therapeutic options exist. Even small acute changes in kidney function can result in short-term and long-term complications, including chronic kidney disease, end-stage renal disease, and death. Presence of more than one comorbidity results in high severity of illness scores in all medical settings. Development or progression of chronic kidney disease after one or more episode of acute kidney injury could have striking socioeconomic and public health outcomes for all countries. Concerted international action encompassing many medical disciplines is needed to aid early recognition and management of acute kidney injury.

Mitochondrial Homeostasis in Acute Organ Failure

The kidneys compose approximately 0.5% of the body mass but consume about 10% of the oxygen in cellular respiration. This discordance is due to the high energy demands on the kidney for reabsorption of filtered blood components and makes the kidney sensitive to mitochondrial stress, the primary source of cellular ATP. Regardless of the etiology, acute kidney injury (AKI) almost always involves aspects of mitochondrial dysfunction. Recent evidence from experimental models suggests that preserving mitochondrial function or promoting mitochondrial repair rescues renal function during AKI. In this review we discuss the effect of AKI on disruption of mitochondrial homeostasis, and how the dynamic processes of mitochondrial biogenesis, fission/fusion, and mitophagy influence renal injury and recovery.

The accuracy of diagnostic coding for acute kidney injury in England - a single centre study

BACKGROUND

Acute kidney injury (AKI) is an independent risk factor for mortality and is responsible for a significant burden of healthcare expenditure, so accurate measurement of its incidence is important. Administrative coding data has been used for assessing AKI incidence, and shows an increasing proportion of hospital bed days attributable to AKI. However, the accuracy of coding for AKI and changes in coding over time have not been studied in England.

METHODS

We studied a random sample of admissions from 2005 and 2010 where ICD-10 code N17 (acute renal failure) was recorded in the administrative coding data at one acute NHS Foundation Trust in England. Using the medical notes and computerised records we examined the demographic and clinical details of these admissions.

RESULTS

Against a 6.3% (95% CI 4.8-7.9%) increase in all non-elective admissions, we found a 64% increase in acute renal failure admissions (95% CI 41%-92%, p < 0.001) in 2010 compared to 2005. Median age was 78 years (IQR 72-87), 11-25% had a relevant pre-admission co-morbidity and 64% (55-73%) were taking drugs known to be associated with AKI. Over both years, 95% (91-99%) of cases examined met the Kidney Disease: Improving Global Outcomes criteria for AKI.

CONCLUSIONS

Patients with hospital admissions where AKI has been coded are elderly with multiple co-morbidities. Our results demonstrate a high positive predictive value of coding data for a clinical diagnosis of AKI, with no suggestion of marked changes in coding of AKI between 2005 and 2010.

Relationship between vancomycin trough concentrations and nephrotoxicity: a prospective multicenter trial

Several single-center studies have suggested that higher doses of vancomycin, aimed at producing trough concentrations of >15 mg/liter, are associated with increased risk of nephrotoxicity. We prospectively assessed the relative incidence of nephrotoxicity in relation to trough concentration in patients with documented methicillin-resistant Staphylococcus aureus (MRSA) infections at seven hospitals throughout South Carolina. Adult patients receiving vancomycin for at least 72 h with at least one vancomycin trough concentration determined under steady-state conditions were prospectively studied. The relationship between vancomycin trough concentrations of >15 mg/ml and the occurrence of nephrotoxicity was assessed using univariate and multivariate analyses, controlling for age, gender, race, dose, length of therapy, use of other nephrotoxins (including contrast media), intensive care unit (ICU) residence, episodes of hypotension, and comorbidities. Nephrotoxicity was defined as an increase in serum creatinine of 0.5 mg/dl or a ≥ 50% increase from the baseline for two consecutive measurements. MICs of vancomycin for the MRSA isolates were also determined. A total of 288 patients were studied between February 2008 and June 2010, with approximately one-half having initial trough concentrations of ≥ 15 mg/ml. Nephrotoxicity was observed for 42 patients (29.6%) with trough concentrations >15 mg/ml and for 13 (8.9%) with trough concentrations of ≤ 15 mg/ml. Multivariate analysis revealed vancomycin trough concentrations of >15 mg/ml and race (black) as risk factors for nephrotoxicity in this population. Vancomycin trough concentrations of >15 mg/ml appear to be associated with a 3-fold increased risk of nephrotoxicity.

Acute kidney injury: not just acute renal failure anymore?

Until recently, no uniform standard existed for diagnosing and classifying acute renal failure. To clarify diagnosis, the Acute Dialysis Quality Initiative group stated its consensus on the need for a clear definition and classification system of renal dysfunction with measurable criteria. Today the term acute kidney injury has replaced the term acute renal failure, with an understanding that such injury is a common clinical problem in critically ill patients and typically is predictive of an increase in morbidity and mortality. A classification system, known as RIFLE (risk of injury, injury, failure, loss of function, and end-stage renal failure), includes specific goals for preventing acute kidney injury: adequate hydration, maintenance of renal perfusion, limiting exposure to nephrotoxins, drug protective strategies, and the use of renal replacement therapies that reduce renal injury.

Acute kidney injury: novel biomarkers and potential utility for patient care in urology

Urologists are integrally involved in the management of acute kidney injury (AKI), which is common after renal surgery or secondary to postrenal (obstructive) etiologies. The measurement of serum creatinine is a suboptimal indicator of AKI because it lags behind acute changes in renal function. Recent advances indicate that serum/urine biomarkers will prove useful for early detection of AKI, analogous to the use of cardiac enzymes for acute myocardial infarction. These serum/urine markers may guide future therapy, facilitate research efforts to reduce the severity of AKI, such as after partial nephrectomy, and allow for more accurate prognostication for patients with AKI.

Renal replacement therapy is an independent risk factor for mortality in critically ill patients with acute kidney injury

INTRODUCTION

Outcome studies in patients with acute kidney injury (AKI) have focused on differences between modalities of renal replacement therapy (RRT). The outcome of conservative treatment, however, has never been compared with RRT.

METHODS

Nine Belgian intensive care units (ICUs) included all adult patients consecutively admitted with serum creatinine >2 mg/dl. Included treatment options were conservative treatment and intermittent or continuous RRT. Disease severity was determined using the Stuivenberg Hospital Acute Renal Failure (SHARF) score. Outcome parameters studied were mortality, hospital length of stay and renal recovery at hospital discharge.

RESULTS

Out of 1,303 included patients, 650 required RRT (58% intermittent, 42% continuous RRT). Overall results showed a higher mortality (43% versus 58%) as well as a longer ICU and hospital stay in RRT patients compared to conservative treatment. Using the SHARF score for adjustment of disease severity, an increased risk of death for RRT compared to conservative treatment of RR = 1.75 (95% CI: 1.4 to 2.3) was found. Additional correction for other severity parameters (Acute Physiology And Chronic Health Evaluation II (APACHE II), Sequential Organ Failure Assessment (SOFA)), age, type of AKI and clinical conditions confirmed the higher mortality in the RRT group.

CONCLUSIONS

The SHARF study showed that the higher mortality expected in AKI patients receiving RRT versus conservative treatment can not only be explained by a higher disease severity in the RRT group, even after multiple corrections. A more critical approach to the need for RRT in AKI patients seems to be warranted.

Review: neutrophil gelatinase-associated lipocalin: a troponin-like biomarker for human acute kidney injury

Acute kidney injury (AKI) is a common and serious condition, the diagnosis of which currently depends on functional markers such as serum creatinine measurements. Unfortunately, creatinine is a delayed and unreliable indicator of AKI. The lack of early biomarkers of structural kidney injury (akin to troponin in acute myocardial injury) has hampered our ability to translate promising experimental therapies to human AKI. Fortunately, understanding the early stress response of the kidney to acute injuries has revealed a number of potential biomarkers. The discovery, translation and validation of neutrophil gelatinase-associated lipocalin (NGAL), possibly the most promising novel AKI biomarker, is reviewed. NGAL is emerging as an excellent stand-alone troponin-like structural biomarker in the plasma and urine for the early diagnosis of AKI, and for the prediction of clinical outcomes such as dialysis requirement and mortality in several common clinical scenarios. The approach of using NGAL as a trigger to initiate and monitor therapies for AKI, and as a safety biomarker when using potentially nephrotoxic agents, is also promising. In addition, it is hoped that the use of sensitive and specific biomarkers such as NGAL as endpoints in clinical trials will result in a reduction in required sample sizes, and hence the cost incurred. Furthermore, predictive biomarkers like NGAL may play a critical role in expediting the drug development process. However, given the complexity of AKI, additional biomarkers (perhaps a panel of plasma and urinary biomarkers) may eventually need to be developed and validated for optimal progress to occur.

Neutrophil gelatinase-associated lipocalin: a promising biomarker for human acute kidney injury

Acute kidney injury (AKI) is a common and serious condition, the diagnosis of which depends on serum creatinine measurements. Unfortunately, creatinine is a delayed and unreliable indicator of AKI. The lack of early biomarkers has crippled our ability to translate promising experimental therapies to human AKI. Fortunately, understanding the early stress response of the kidney to acute injuries has revealed a number of potential biomarkers. The discovery, translation and validation of neutrophil gelatinase-associated lipocalin, arguably the most promising novel AKI biomarker, are reviewed in this article. Neutrophil gelatinase-associated lipocalin is emerging as an excellent standalone troponin-like biomarker in the plasma and urine for the prediction of AKI, monitoring clinical trials in AKI and for the prognosis of AKI in several common clinical scenarios.

Tubular proteinuria in acute kidney injury: a critical evaluation of current status and future promise

The diagnosis and prognosis of acute kidney injury (AKI) by current clinical means is inadequate. Biomarkers of kidney injury that are easily measured and unaffected by physiological variables could revolutionize the management of AKI. Our objective was to systematically review the diagnostic and prognostic utility of urine and serum biomarkers of AKI in humans. We searched MEDLINE, PubMed and EMBASE databases (January 2000–August 2009) for biomarker studies that could be classified into the following categories: (a) confirmation of the diagnosis of established AKI, (b) early prediction of AKI, and (c) prognostication of AKI. We identified 54 manuscripts published since 2000 that met our inclusion and exclusion criteria. Urinary interleukin-18 (IL-18), kidney injury molecule-1 (KIM-1), neutrophil gelatinase-associated lipocalin (NGAL) and N-acetyl- β-d-glucosaminidase (NAG) are potentially useful biomarkers for the diagnosis of established AKI. Urinary NGAL, IL-18, and liver-type fatty acid binding protein, and serum NGAL and cystatin C represent the most promising biomarkers for early prediction of AKI. Urinary cystatin C, α1-microglobulin, NAG and retinol-binding protein may be useful to predict severity and outcomes of AKI. In conclusion, we identified several studies of promising biomarkers for the diagnosis, prediction and prognostication of AKI. However, we note several limitations, including small sample sizes, inadequate gold standard, exclusion of patients with chronic kidney disease, incomplete statistical analyses, utilization of research-based assays and a paucity of studies examining prediction for clinical outcomes. Future studies will need to address these limitations in order for further progress to be made.

Sensitivity and specificity of a single emergency department measurement of urinary neutrophil gelatinase-associated lipocalin for diagnosing acute kidney injury

BACKGROUND

A single serum creatinine measurement cannot distinguish acute kidney injury from chronic kidney disease or prerenal azotemia.

OBJECTIVE

To test the sensitivity and specificity of a single measurement of urinary neutrophil gelatinase-associated lipocalin (NGAL) and other urinary proteins to detect acute kidney injury in a spectrum of patients.

DESIGN

Prospective cohort study.

SETTING

Emergency department of Columbia University Medical Center, New York, New York.

PARTICIPANTS

635 patients admitted to the hospital with acute kidney injury, prerenal azotemia, chronic kidney disease, or normal kidney function.

MEASUREMENTS

Diagnosis of acute kidney injury was based on the RIFLE (risk, injury, failure, loss, and end-stage) criteria and assigned by researchers who were blinded to experimental measurements. Urinary NGAL was measured by immunoblot, N-acetyl-beta-d-glucosaminidase (NAG) by enzyme measurement, alpha1-microglobulin and alpha(1)-acid glycoprotein by immunonephelometry, and serum creatinine by Jaffe kinetic reaction. Experimental measurements were not available to treating physicians.

RESULTS

Patients with acute kidney injury had a significantly elevated mean urinary NGAL level compared with the other kidney function groups (416 microg/g creatinine [SD, 387]; P = 0.001). At a cutoff value of 130 microg/g creatinine, sensitivity and specificity of NGAL for detecting acute injury were 0.900 (95% CI, 0.73 to 0.98) and 0.995 (CI, 0.990 to 1.00), respectively, and positive and negative likelihood ratios were 181.5 (CI, 58.33 to 564.71) and 0.10 (CI, 0.03 to 0.29); these values were superior to those for NAG, alpha1-microglobulin, alpha1-acid glycoprotein, fractional excretion of sodium, and serum creatinine. In multiple logistic regression, urinary NGAL level was highly predictive of clinical outcomes, including nephrology consultation, dialysis, and admission to the intensive care unit (odds ratio, 24.71 [CI, 7.69 to 79.42]).

LIMITATIONS

All patients came from a single center. Few kidney biopsies were performed.

CONCLUSION

A single measurement of urinary NGAL helps to distinguish acute injury from normal function, prerenal azotemia, and chronic kidney disease and predicts poor inpatient outcomes.

Long-term outcomes after acute kidney injury

Acute kidney dysfunction is a common problem in intensive care units. It is not only associated with increased morbidity and mortality but also with increased healthcare costs. Limited healthcare budgets have now raised the issue of how much therapy should be dedicated to these critically ill patients. A precondition for any further discussion on this topic is the question on the long-term outcome and quality of life of these patients. However, only limited data are available in this field. In this review, we will focus on the existing literature, considering not only acute renal failure patients requiring renal replacement therapy but also those patients with mild or moderate impaired renal function. The intention of this review is to show that acute kidney injury is an important but often underestimated disease and a disease that deserves major attention because it is associated with impaired short- and long-term outcome. We will demonstrate that acute kidney injury patients requiring dialysis have a reasonable long-term survival rate and good quality of life. There is no doubt that aggressive intensive care unit treatment is justified in these patients, irrespective of the health costs.

Diagnosis, epidemiology and outcomes of acute kidney injury

Acute kidney injury is an increasingly common and potentially catastrophic complication in hospitalized patients. Early observational studies from the 1980s and 1990s established the general epidemiologic features of acute kidney injury: the incidence, prognostic significance, and predisposing medical and surgical conditions. Recent multicenter observational cohorts and administrative databases have enhanced our understanding of the overall disease burden of acute kidney injury and trends in its epidemiology. An increasing number of clinical studies focusing on specific types of acute kidney injury (e.g., in the setting of intravenous contrast, sepsis, and major surgery) have provided further details into this heterogeneous syndrome. Despite our sophisticated understanding of the epidemiology and pathobiology of acute kidney injury, current prevention strategies are inadequate and current treatment options outside of renal replacement therapy are nonexistent. This failure to innovate may be due in part to a diagnostic approach that has stagnated for decades and continues to rely on markers of glomerular filtration (blood urea nitrogen and creatinine) that are neither sensitive nor specific. There has been increasing interest in the identification and validation of novel biomarkers of acute kidney injury that may permit earlier and more accurate diagnosis. This review summarizes the major epidemiologic studies of acute kidney injury and efforts to modernize the approach to its diagnosis.

Uncomplicated acute renal failure and post-hospital care: a not so uncomplicated illness

BACKGROUND

Although uncomplicated acute renal failure (ARF) is associated with significant hospital resource utilization, its health care requirements following hospital discharge are not well understood. The goal of this study was to characterize the post-hospital care requirements incurred by patients with uncomplicated ARF and to determine its important influencing factors.

METHODS

We obtained hospital case mix data sets for a 2-year period (1999-2000) from the Massachusetts Division of Health Care Finance and Policy. Utilizing DRG and ICD-9-CM codes from 23 Massachusetts hospitals, we identified 2,128 adult patients whose primary reason for hospitalization was uncomplicated ARF. Post-hospital care was defined as the receipt of extended facility care or home health care following hospital discharge.

RESULTS

Nearly 50% of patients hospitalized with uncomplicated ARF required some type of post-hospital care, of whom 27% underwent extended facility care while 22% received home health care. The post-hospital care requirements for uncomplicated ARF were similar to those for serious medical conditions (e.g. heart failure) and exceeded those of many common illnesses (e.g., bronchitis). Advancing age, worsening severity of illness, female gender, and emergency room admission were independently associated with receipt of post-hospital care (p < 0.05). A trend existed between less frequent post-hospital care requirements and hospitalization at academic medical centers compared with non-academic hospitals.

CONCLUSIONS

Uncomplicated ARF is frequently associated with prolonged care following hospitalization. As the health care utilization for ARF becomes better characterized, these post-hospital care resources should not be overlooked.