Diagnosis, evaluation, and management of acute kidney injury: a KDIGO summary (Part 1)

Advances in urinary protein biomarkers for urogenital and non-urogenital pathologies

The discovery of protein biomarkers that reflect the biological state of the body is of vital importance to disease management. Urine is an ideal source of biomarkers that provides a non-invasive approach to diagnosis, prognosis and prediction of diseases. Consequently, the study of the human urinary proteome has increased dramatically over the last 10 years, with many studies being published. This review focuses on urinary protein biomarkers that have shown potential, in initial studies, for diseases affecting the urogenital tract, specifically chronic kidney disease and prostate cancer, as well as other non-urogenital pathologies such as breast cancer, diabetes, atherosclerosis and osteoarthritis. PubMed was searched for peer-reviewed literature on the subject, published in the last 10 years. The keywords used were "urine, biomarker, protein, and/or prostate cancer/breast cancer/chronic kidney disease/diabetes/atherosclerosis/osteoarthritis". Original studies on the subject, as well as a small number of reviews, were analysed including the strengths and weaknesses, and we summarized the performance of biomarkers that demonstrated potential. One of the biggest challenges found is that biomarkers are often shared by several pathologies so are not specific to one disease. Therefore, the trend is shifting towards implementing a panel of biomarkers, which may increase specificity. Although there have been many advances in urinary proteomics, these have not resulted in similar advancements in clinical practice due to high costs and the lack of large data sets. In order to translate these potential biomarkers to clinical practice, vigorous validation is needed, with input from industry or large collaborative studies.

Post-operative acute kidney injury in non-suprainguinal vascular surgery patients with a pre-operative history of hypertension

Hypertension is an independent predictor of acute kidney injury (AKI) in non-cardiac surgery patients. There are a few published studies which report AKI following non-suprainguinal vascular procedures, but these studies have not investigated predictors of AKI, including anti-hypertensive medications and other comorbidities, in the hypertensive population alone. We sought to identify independent predictors of post-operative AKI in non-suprainguinal vascular surgery patients with a pre-operative history of hypertension. We performed univariate (chi-squared, or Fisher's exact testing) and multivariate (binary logistic regression) statistical analysis of prospectively collected data from 243 adult hypertensive patients who underwent non-suprainguinal vascular surgery (lower limb amputation or peripheral artery bypass surgery) at a tertiary hospital between 2008 and 2011 in an attempt to identify possible associations between comorbidity, acute pre-operative antihypertensive medication administration, and post-operative AKI (a post-operative increase in serum creatinine of ≥ 25 % above the pre-operative measurement) in these patients. The incidence of post-operative AKI in this study was 5.3 % (95 % Confidence Interval: 3.2-8.9 %). Acute pre-operative β-blocker administration was independently associated with post-operative AKI in non-suprainguinal vascular surgery patients with a pre-operative history of hypertension (Odds Ratio: 3.24; 95 % Confidence Interval: 1.03-10.25). The acute pre-operative administration of β-blockers should be carefully considered in non-suprainguinal vascular surgery patients with a pre-operative history of hypertension, in lieu of an increased risk of potentially poor post-operative renal outcomes.

Adverse cardiac events after orthotopic liver transplantation: a cross-sectional study in 389 consecutive patients

Current American College of Cardiology/American Heart Association guidelines caution that preoperative noninvasive cardiac tests may have poor predictive value for detecting coronary artery disease in liver transplant candidates. The purpose of our study was to evaluate the role of clinical predictor variables for early and late cardiac morbidity and mortality and the predictive values of noninvasive cardiac tests for perioperative cardiac events in a high-risk liver transplant population. In all, 389 adult recipients were retrospectively analyzed for a median follow-up time of 3.4 years (range = 2.3-4.4 years). Overall survival was 83%. During the first year after transplantation, cardiovascular morbidity and mortality rates were 15.2% and 2.8%. In patients who survived the first year, cardiovascular morbidity and mortality rates were 3.9% and 2%, with cardiovascular etiology as the third leading cause of death. Dobutamine stress echocardiography (DSE) and single-photon emission computed tomography had respective sensitivities of 9% and 57%, specificities of 98% and 75%, positive predictive values of 33% and 28%, and negative predictive values of 89% and 91% for predicting early cardiac events. A rate blood pressure product less than 12,000 with DSE was associated with an increased risk for postoperative atrial fibrillation. Correspondence analysis identified a statistical association between nonalcoholic steatohepatitis/cryptogenic cirrhosis and postoperative myocardial ischemia. Logistic regression identified 3 risk factors for postoperative acute coronary syndrome: age, history of coronary artery disease, and pretransplant requirement for vasopressors. Multivariable analysis showed statistical associations of the Model for End-Stage Liver Disease score and the development of acute kidney injury as risk factors for overall cardiac-related mortality. These findings may help in identifying high-risk patients and may lead to the development of better cardiac tests.

Sepsis-induced acute kidney injury by standardized colon ascendens stent peritonitis in rats - a simple, reproducible animal model

Background

Up to 50% of septic patients develop acute kidney injury (AKI). The pathomechanism of septic AKI is poorly understood. Therefore, we established an innovative rodent model to characterize sepsis-induced AKI by standardized colon ascendens stent peritonitis (sCASP). The model has a standardized focus of infection, an intensive care set up with monitoring of haemodynamics and oxygenation resulting in predictable impairment of renal function, AKI parameters as well as histopathology scoring.

Methods

Anaesthetized rats underwent the sCASP procedure, whereas sham animals were sham operated and control animals were just monitored invasively. Haemodynamic variables and blood gases were continuously measured. After 24 h, animals were reanesthetized; cardiac output (CO), inulin and PAH clearances were measured and later on kidneys were harvested; and creatinine, urea, cystatin C and neutrophil gelatinase-associated lipocalin (NGAL) were analysed. Additional sCASP-treated animals were investigated after 3 and 9 days.

Results

All sCASP-treated animals survived, whilst ubiquitous peritonitis and significantly deteriorated clinical and macrohaemodynamic sepsis signs after 24 h (MAP, CO, heart rate) were obvious. Blood analyses showed increased lactate and IL-6 levels as well as leucopenia. Urine output, inulin and PAH clearance were significantly decreased in sCASP compared to sham and control. Additionally, significant increase in cystatin C and NGAL was detected. Standard parameters like serum creatinine and urea were elevated and sCASP-induced sepsis increased significantly in a time-dependent manner. The renal histopathological score of sCASP-treated animals deteriorated after 3 and 9 days.

Conclusions

The presented sCASP method is a standardized, reliable and reproducible method to induce septic AKI. The intensive care set up, continuous macrohaemodynamic and gas exchange monitoring, low mortality rate as well as the opportunity of detailed analyses of kidney function and impairments are advantages of this setup. Thus, our described method may serve as a new standard for experimental investigations of septic AKI.

Diagnostic and short-term prognostic utility of plasma pro-enkephalin (pro-ENK) for acute kidney injury in patients admitted with sepsis in the emergency department

BACKGROUND

Acute kidney injury (AKI) aggravates the prognosis of patients with sepsis. Reliable biomarkers for early detection of AKI in this setting are lacking. Enkephalins influence kidney function, and may have a role in AKI from sepsis. We utilized a novel immunoassay for plasma proenkephalin (pro-ENK), a stable surrogate marker for endogenous enkephalins, in patients hospitalized with sepsis, in order to assess its clinical utility.

METHODS

In an observational retrospective study we enrolled 101 consecutive patients admitted to the emergency department (ED) with suspected sepsis. Plasma levels of pro-ENK and neutrophil gelatinase-associated lipocalin (NGAL) were evaluated at ED arrival for their association with presence and severity of AKI and 7-day mortality.

RESULTS

pro-ENK was inversely correlated to creatinine clearance (r = -0.72) and increased with severity of AKI as determined by RIFLE (risk, injury, failure, loss of function, end-stage renal disease) stages (p < 0.0001; pro-ENK median [interquartile range, IQR]) pmol/l: no AKI: 71 [41-97]; risk: 72 [51-120]; injury: 200 [104-259]; failure: 230 [104-670]; loss of function: 947 [273-811]. The majority of septic patients without AKI or at risk had pro-ENK concentrations within the normal range. While NGAL was similarly associated with AKI severity, it was strongly elevated already in septic patients without AKI. pro-ENK added predictive information to NGAL for detecting kidney dysfunction (added χ (2) 10.0, p = 0.0016). Admission pro-ENK outperformed creatinine clearance in predicting 7-day mortality (pro-ENK: χ (2) 13.4, p < 0.001, area under curve, AUC 0.69; creatinine clearance: χ (2) 4, p = 0.045, AUC: 0.61), and serial measurement improved prediction.

CONCLUSIONS

Use of pro-ENK in septic patients can detect the presence and severity of AKI. Moreover, pro-ENK is highly predictive of short-term mortality and could enable early identification of patients at risk of death.

Oxidative stress contributes to orthopedic trauma-induced acute kidney injury in obese rats

After trauma, obese patients have an increased risk of developing acute kidney injury (AKI). We have demonstrated that obese Zucker (OZ) rats, but not lean Zucker (LZ) rats, develop AKI 24 h after orthopedic trauma. ROS have been implicated in the pathophysiology of AKI in models of critical illness. However, the contribution of ROS to trauma-induced AKI in the setting of obesity has not been determined. We hypothesized that AKI in OZ rats after trauma is mediated by increased oxidative stress. Male LZ and OZ rats were divided into control and trauma groups, with a subset receiving treatment after trauma with the antioxidant apocynin (50 mg/kg ip, 2 mM in drinking water). The day after trauma, glomerular filtration rate, plasma creatinine, urine kidney injury molecule-1, and albumin excretion as well as renal oxidant and antioxidant activity were measured. After trauma, compared with LZ rats, OZ rats exhibited a significant decrease in glomerular filtration rate along with significant increases in plasma creatinine and urine kidney injury molecule-1 and albumin excretion. Additionally, oxidative stress was significantly increased in OZ rats, as evidenced by increased renal NADPH oxidase activity and urine lipid peroxidation products (thiobarbituric acid-reactive substances), and OZ rats also had suppressed renal superoxide dismutase activity. Apocynin treatment significantly decreased oxidative stress and AKI in OZ rats but had minimal effects in LZ rats. These results suggest that ROS play an important role in AKI in OZ rats after traumatic injury and that ROS may be a potential future therapeutic target in the obese after trauma.

Long-term risk of chronic kidney disease and mortality in children after acute kidney injury: a systematic review

BACKGROUND

Acute kidney injury (AKI) is associated with significant short-term morbidity and mortality in children. However, the risk for long-term outcomes after AKI is largely unknown.

METHODS

We performed a systematic review and meta-analysis to determine the cumulative incidence rate of proteinuria, hypertension, decline in glomerular filtration rate (GFR), and mortality after an episode of AKI. After screening 1934 published articles from 1985-2013, we included 10 cohort studies that reported long-term outcomes after AKI in children.

RESULTS

A total of 346 patients were included in these studies with a mean follow-up of 6.5 years (range 2-16) after AKI. The studies were of variable quality and had differing definitions of AKI with five studies only including patients who required dialysis during an AKI episode. There was a substantial discrepancy in the outcomes across these studies, most likely due to study size, disparate outcome definitions, and methodological differences. In addition, there was no non-AKI comparator group in any of the published studies. The cumulative incidence rates for proteinuria, hypertension, abnormal GFR (<90 ml/min/1.73 m2), GFR < 60 ml/min/1.73 m2, end stage renal disease, and mortality per 100 patient-years were 3.1 (95% CI 2.1-4.1), 1.4 (0.9-2.1), 6.3 (5.1-7.5), 0.8 (0.4 -1.4), 0.9 (0.6-1.4), and 3.7 (2.8-4.5) respectively.

CONCLUSIONS

AKI appears to be associated with a high risk of long-term renal outcomes in children. These findings may have implications for care after an episode of AKI in children. Future prospective studies with appropriate non-AKI comparator groups will be required to confirm these results.

Impact of partial nephrectomy on kidney function in patients with renal cell carcinoma

BACKGROUND

This study aimed to compare the changes in kidney function and the association of tumor size and renal outcomes between patients with renal cell carcinoma (RCC) who underwent radical nephrectomy (RN) and those who underwent partial nephrectomy (PN).

METHODS

A retrospective cohort study was conducted for 557 patients with an RCC of ≤7 cm in diameter and normal contralateral kidney function who underwent PN or RN. PN was performed for 218 (39%) patients. Renal outcomes included the incidence of acute kidney injury (AKI), new-onset chronic kidney disease (CKD), and a ≥25% decline in eGFR 1 year after surgery.

RESULTS

Serial changes in eGFR were compared during the 3 years of follow-up. Postoperative eGFR was significantly lower in patients undergoing RN than in those undergoing PN. The incidence of AKI and new-onset CKD was significantly higher in patients after RN (70.1% vs. 24.3%, respectively; P<0.001) than after PN (55.7% vs. 6.2%, respectively; P<0.001). According to the multivariable logistic regression analysis, RN was an independent risk factor for a ≥25% decline in kidney function after 1 year regardless of the tumor size, even after adjusting for various covariates.

CONCLUSIONS

Compared to PN, RN for even a moderate sized RCC leads to an increased incidence of AKI and new-onset CKD, and is a significant risk factor for kidney function decline. Therefore, PN should be considered as the choice of surgical treatment for RCCs that are ≤7 cm in diameter in order to preserve renal function postoperatively.

Prostatic surgery associated acute kidney injury

Acute kidney injury (AKI) is associated with extended hospital stays, high risks of in-hospital and long-term mortality, and increased risk of incident and progressive chronic kidney disease. Patients with urological diseases are a high-risk group for AKI owing to the coexistence of obstructive uropathy, older age, and preexistent chronic kidney disease. Nonetheless, precise data on the incidence and outcomes of postoperative AKI in urological procedures are lacking. Benign prostatic hyperplasia and prostate cancer are common diagnoses in older men and are frequently treated with surgical procedures. Whereas severe AKI after prostate surgery in general appears to be unusual, AKI associated with transurethral resection of the prostate (TURP) syndrome and with rhabdomyolysis (RM) after radical prostatectomy have been frequently described. The purpose of this review is to discuss the current knowledge regarding the epidemiology, risk factors, outcomes, prevention, and treatment of AKI associated with prostatic surgery. The mechanisms of TURP syndrome and RM following prostatic surgeries will be emphasized.

Biomarkers and physiopathology in the cardiorenal syndrome

Acute cardiorenal syndrome (CRS) corresponds to an association of acute heart failure and a worsening of renal function. The detection of acute kidney injury (AKI) unfortunately occurs at a late stage of CRS, leading to an increased mortality of the patients. In this review, we described the pathophysiology of CRS and discussed the potential interest of biochemical biomarkers (namely creatinine, cystatin C, NGAL, KIM-1, fatty acid binding protein, Nacetyl-β-D-glucosaminidase and IL-18) that could potentially help to detect AKI earlier and thus reduce the morbi-mortality of the patients suffering from CRS.

Nursing essential principles: continuous renal replacement therapy

AIMS

This article aims to guide critical care nurses with the care and management of patients on continuous renal replacement therapy (CRRT).

BACKGROUND

CRRT, a highly specialized therapy involving complex nursing care, is used widely in the intensive care unit to treat patients with acute kidney injury.

METHODS

A literature search was conducted using CINAHL, Medline from PubMed and BNI using the search terms CRRT or continuous veno-venous haemofiltration and nursing or nurses from 2000 onwards and limited to the English language. The appraised evidence and expert opinion is used in this article.

RESULTS

Four essential nursing principles for CRRT are reviewed (1) the importance of continuous assessment of the indications to influence the appropriate mode; (2) ensuring good vascular access; (3) the avoidance of unnecessary interruptions and (4) the prevention of complications.

CONCLUSION

The identified four essential nursing principles provide guidance on this complex aspects of nursing practice. Specific nursing research to guide the care and management of this therapy is limited so should be explored in the future.

RELEVANCE TO CLINICAL PRACTICE

Critical care nurses caring for and managing patients on CRRT require an understanding of how to deliver safe CRRT.

Year in review 2013: Critical Care - nephrology

We review original research in the field of critical care nephrology accepted or published in 2013 in Critical Care and, when considered relevant or linked to these studies, in other journals. Three main topics have been identified and are discussed for a rapid overview: acute kidney injury (diagnosis, risk factors and outcome); timing and modality of renal replacement therapy; and extracorporeal membrane oxygenation and renal dysfunction.

Characteristics and clinical outcome of nonsteroidal anti-inflammatory drug-induced acute hepato-nephrotoxicity among Chinese patients

AIM: To determine the clinicopathological characteristics of nonsteroidal anti-inflammatory drug (NSAID)-induced acute hepato-nephrotoxicity among Chinese patients.

METHODS: We conducted a retrospective chart review of patients using the International Classification of Diseases, Ninth Revision diagnosis code for acute kidney injury (AKI) (584.5 or 584.9) and for acute liver injury (ALI) (570.0 or 573.3) from January 2004 to December 2013. Medical records were reviewed to confirm the diagnosis of AKI and ALI and to quantify NSAID administration.

RESULTS: Seven of 59 patients (11.8%) were identified with acute hepato-nephrotoxicity induced by NSAIDs. Five patients (71.4%) received over the recommended NSAIDs dose. Compared with NSAIDs-associated mere AKI, the risk factors of NSAIDs-induced acute hepato-nephrotoxicity are age older than 60 years (57.1%), a high prevalence of alcohol use (71.4%) and positive hepatitis B virus (HBV) markers (85.7%). Compared with NSAIDs-associated mere ALI, the risk factors of NSAIDs-induced acute hepato-nephrotoxicity are age older than 60 years (57.1%), increased extracellular volume depletion (71.4%), and renin-angiotensin-aldosterone system (RAAS) inhibitor combined use (57.1%). Acute interstitial nephritis and acute tubulointerstitial disease were apparent in three out of six (42.9%) kidney biopsy patients, respectively. Acute hepatitis was found in four out of six (66.7%) liver biopsy patients. Overall complete recovery occurred in four patients within a mean of 118.25 ± 55.42 d.

CONCLUSION: The injury typically occurred after an overdose of NSAIDs. The risk factors include age older than 60 years, alcohol use, positive HBV markers, extracellular volume depletion and RAAS inhibitor combined use.

The lower limit of intensity to control uremia during continuous renal replacement therapy

Introduction

The recommended lower limit of intensity during continuous renal replacement therapy (CRRT) is 20 or 25 mL/kg/h. However, limited information is available to support this threshold. We aimed to evaluate the impact of different intensities of CRRT on the clearance of creatinine and urea in critically ill patients with severe acute kidney injury (AKI).

Methods

This is a multicenter retrospective study conducted in 14 Japanese ICUs in 12 centers. All patients older than 18 years and treated with CRRT due to AKI were eligible. We evaluated the effect of CRRT intensity by two different definitions: daily intensity (the mean intensity over each 24-h period) and average intensity (the mean of daily intensity during the period while CRRT was performed). To study the effect of different CRRT intensity on clearance of urea and creatinine, all patients/daily observations were arbitrarily allocated to one of 4 groups based on the average intensity and daily intensity: <10, 10–15, 15–20, and >20 mL/kg/h.

Results

Total 316 patients were included and divided into the four groups according to average CRRT intensity. The groups comprised 64 (20.3%), 138 (43.7%), 68 (21.5%), and 46 patients (14.6%), respectively. Decreases in creatinine and urea increased as the average intensity increased over the first 7 days of CRRT. The relative changes of serum creatinine and urea levels remained close to 1 over the 7 days in the “<10” group. Total 1,101 daily observations were included and divided into the four groups according to daily CRRT intensity. The groups comprised 254 (23.1%), 470 (42.7%), 239 (21.7%), and 138 observations (12.5%), respectively. Creatinine and urea increased (negative daily change) only in the “<10” group and decreased with the increasing daily intensity in the other groups.

Conclusions

The lower limit of delivered intensity to control uremia during CRRT was approximately between 10 and 15 mL/kg/h in our cohort. A prescribed intensity of approximately 15 mL/kg/h might be adequate to control uremia for patients with severe AKI in the ICU. However, considering the limitations due to the retrospective nature of this study, prospective studies are required to confirm our findings.

Propensity-based study of aminoglycoside nephrotoxicity in patients with severe sepsis or septic shock

To assess the risk of acute kidney injury (AKI) attributable to aminoglycosides (AGs) in patients with severe sepsis or septic shock, we performed a retrospective cohort study in one medical intensive care unit (ICU) in France. Patients admitted for severe sepsis/septic shock between November 2008 and January 2010 were eligible. A propensity score for AG administration was built using day 1 demographic and clinical characteristics. Patients still on the ICU on day 3 were included. Patients with renal failure before day 3 or endocarditis were excluded. The time window for assessment of renal risk was day 3 to day 15, defined according to the RIFLE (risk, injury, failure, loss, and end-stage renal disease) classification. The AKI risk was assessed by means of a propensity-adjusted Cox proportional hazards regression analysis. Of 317 consecutive patients, 198 received AGs. The SAPS II (simplified acute physiology score II) score and nosocomial origin of infection favored the use of AGs, whereas a preexisting renal insufficiency and the neurological site of infection decreased the propensity for AG treatment. One hundred three patients with renal failure before day 3 were excluded. AGs were given once daily over 2.6 ± 1.1 days. AKI occurred in 16.3% of patients in a median time of 6 (interquartile range, 5 to 10) days. After adjustment to the clinical course and exposure to other nephrotoxic agents between day 1 and day 3, a propensity-adjusted Cox proportional hazards regression analysis showed no increased risk of AKI in patients receiving AGs (adjusted relative risk = 0.75 [0.32 to 1.76]). In conclusion, in critically septic patients presenting without early renal failure, aminoglycoside therapy for less than 3 days was not associated with an increased risk of AKI.

The growth of acute kidney injury: a rising tide or just closer attention to detail?

Acute kidney injury (AKI), previously termed acute renal failure, is associated with increased mortality, prolonged hospital stay, and accelerated chronic kidney disease (CKD). Over the past 2 decades, dramatic rises in the incidences of AKI have been reported, particularly within the United States. The question arises as to whether these changes reflect actual increases in disease incidence, or are potentially explained by the introduction of consensus definitions that rely on small standardized changes in serum creatinine, changes in coding and reimbursement, or increasingly available and more liberal use of dialysis. In this review, we explore the secular trends in AKI incidence in North America and Western Europe and its potential contributors.

Acute kidney injury in the neonate

Critically ill neonates are at risk for acute kidney injury (AKI). AKI has been associated with increased risk of morbidity and mortality in adult and pediatric patients, and increasing evidence suggests a similar association in the neonatal population. This article describes the current AKI definitions (including their limitations), work on novel biomarkers to define AKI, diagnosis and management strategies, long-term outcomes after AKI, and future directions for much-needed research in this important area.

Laboratory test surveillance following acute kidney injury

BACKGROUND

Patients with hospitalized acute kidney injury (AKI) are at increased risk for accelerated loss of kidney function, morbidity, and mortality. We sought to inform efforts at improving post-AKI outcomes by describing the receipt of renal-specific laboratory test surveillance among a large high-risk cohort.

METHODS

We acquired clinical data from the Electronic health record (EHR) of 5 Veterans Affairs (VA) hospitals to identify patients hospitalized with AKI from January 1st, 2002 to December 31st, 2009, and followed these patients for 1 year or until death, enrollment in palliative care, or improvement in renal function to estimated GFR (eGFR) ≥ 60 L/min/1.73 m(2). Using demographic data, administrative codes, and laboratory test data, we evaluated the receipt and timing of outpatient testing for serum concentrations of creatinine and any as well as quantitative proteinuria recommended for CKD risk stratification. Additionally, we reported the rate of phosphorus and parathyroid hormone (PTH) monitoring recommended for chronic kidney disease (CKD) patients.

RESULTS

A total of 10,955 patients admitted with AKI were discharged with an eGFR<60 mL/min/1.73 m2. During outpatient follow-up at 90 and 365 days, respectively, creatinine was measured on 69% and 85% of patients, quantitative proteinuria was measured on 6% and 12% of patients, PTH or phosphorus was measured on 10% and 15% of patients.

CONCLUSIONS

Measurement of creatinine was common among all patients following AKI. However, patients with AKI were infrequently monitored with assessments of quantitative proteinuria or mineral metabolism disorder, even for patients with baseline kidney disease.

Explaining the racial difference in AKI incidence

African Americans face higher risk of AKI than Caucasians. The extent to which this increased risk is because of differences in clinical, socioeconomic, or genetic risk factors is unknown. We evaluated 10,588 African-American and Caucasian participants in the Atherosclerosis Risk in Communities study, a community-based prospective cohort of middle-aged individuals. Participants were followed from baseline study visit (1996-1999) to first hospitalization for AKI (defined by billing code), ESRD, death, or December 31, 2010. African-American participants were slightly younger (61.7 versus 63.1 years, P<0.001), were more often women (64.5% versus 53.2%, P<0.001), and had higher baseline eGFR compared with Caucasians. Annual family income, education level, and prevalence of health insurance were lower among African Americans than Caucasians. The unadjusted incidence of hospitalized AKI was 7.4 cases per 1000 person-years among African Americans and 5.8 cases per 1000 person-years among Caucasians (P=0.002). The elevated risk of AKI among African Americans persisted after adjustment for demographics, cardiovascular risk factors, kidney markers, and time-varying number of hospitalizations (adjusted hazard ratio, 1.20; 95% confidence interval [95% CI], 1.01 to 1.43; P=0.04); however, accounting for differences in income and/or insurance by race attenuated the association (P>0.05). High-risk APOL1 variants did not associate with AKI among African Americans (demographic-adjusted hazard ratio, 1.07; 95% CI, 0.69 to 1.65; P=0.77). In summary, the higher risk of AKI among African Americans may be related to disparities in socioeconomic status.

Continuous renal replacement therapy-related strategies to avoid colistin toxicity: a clinically orientated review

Polymyxins are 'old' antimicrobials which were abandoned for almost 30 years because of significant renal and neurological toxicity. However, the alarming rise in multiresistant Gram-negative bacterial infections worldwide has revived interest in these 'forgotten' agents. Colistin (polymyxin E) is one of the main antibiotics of this class. It is most often administered as the prodrug colistimethate sodium. Doses for treatment of systemic infections in adults range between 3 and 9 million IU per day. Colistin is increasingly used to treat pneumonia and bacteremia in critically ill patients. During their intensive care unit stay, many of these patients will need continuous renal replacement therapy (CRRT) because of acute kidney injury or an unstable hemodynamic condition. Based on recent pharmacological data and our own experience, we postulate that patients undergoing CRRT may receive substantially higher doses of colistin (i.e. a high loading dose, followed by a maintenance dose of up to 4.5 million IU t.i.d.). Treatment can be continued for a prolonged time period without increasing toxicity. CRRT counteracts colistin accumulation because the drug is continuously filtered and also significantly adsorbed in the bulk of the dialysis membrane. Implementing such a 'CRRT rescue' therapy does require the strict use of highly adsorptive dialysis membranes in association with citrate anticoagulation to increase membrane performance.

Renal function, acute kidney injury and hospital mortality in patients with acute myocardial infarction

OBJECTIVES

To examine retrospectively the relationship between acute kidney injury (AKI) and acute myocardial infarction (AMI), and the association between estimated glomerular filtration rate (eGFR) at admission and AKI outcome.

METHODS

AKI was defined as an increase in serum creatinine (SCr) by ≥ 0.3 mg/dl within 48 h or an increase in SCr to ≥ 1.5 times baseline within the first 7 days of hospitalization. Patients with AMI were divided into subgroups according to their eGFR at admission and the development of AKI.

RESULTS

This study enrolled 396 patients with AMI; 48 (12.1%) developed AKI. In-hospital mortality was 39.6% (19/48) for patients with AKI compared with 7.5% (26/348) in those without AKI (odds ratio [OR] 8.11; 95% confidence interval [CI] 4.02, 16.39). The mortality rate was 35.7% (five of 14) in the eGFR ≥ 60 ml/min/1.73 m(2) with AKI group (OR 6.21, 95% CI 1.50, 25.69) and 41.2% (14/34) in the eGFR <60 ml/min/1.73 m(2) with AKI group (OR 12.62, 95% CI 5.54, 28.74).

CONCLUSIONS

AKI development was common and associated with mortality in AMI patients with either preserved or impaired eGFR levels.

Renal function-adjusted contrast volume redefines the baseline estimation of contrast-induced acute kidney injury risk in patients undergoing primary percutaneous coronary intervention

BACKGROUND

Age, estimated glomerular renal function (eGFR), and ejection fraction are preprocedural predictors of contrast-induced acute kidney injury (CI-AKI) after primary percutaneous coronary intervention. The effect of renal function-adjusted contrast volume (CV) remains not totally explored, and a threshold has not yet been established.

METHODS AND RESULTS

Logistic regression and receiver-operating characteristic curve analyses were used to assess whether CV/eGFR was an independent predictor of CI-AKI. The increased discriminative value of CV/eGFR over the preprocedural model based on age, eGFR, and ejection fraction was examined using the net reclassification improvement analysis. Of 470 patients enrolled, we observed 25 (5.3%) cases of CI-AKI. Patients with CI-AKI had received a higher renal function-adjusted CV (CV/eGFR 3.62 versus 1.96; P<0.001), and CI-AKI incidence was higher (15%; P<0.001) in patients in the highest quartile of CV/eGFR, corresponding to the cutoff indicated by the receiver-operating characteristic curve (>2.5; area under the curve, 0.77). At multivariable analysis, CV/eGFR above the cutoff (odds ratio, 5.57; P=0.002) remained an independent predictor of CI-AKI. The model with CV/eGFR demonstrated a statistically significantly net reclassification improvement of 0.23 (P=0.021) over the baseline preprocedural model, largely driven by a correct decrease in risk estimates for patients not experiencing CI-AKI, with a likelihood ratio χ(2) of 5.973 (P=0.029).

CONCLUSIONS

CV remains a key risk factor for CI-AKI after primary percutaneous coronary intervention and our study supports the need for minimizing CV, independently from baseline preprocedural risk. A CV restricted to no more than twice and a half the baseline eGFR might be valuable in reducing the risk of CI-AKI.

Effects of ghrelin on sepsis-induced acute kidney injury: one step forward

BACKGROUND

Among the several disorders induced by sepsis, acute kidney injury (AKI) represents the most important economic burden problem that is associated with high mortality and morbidity rates. The aim of this study was to investigate the anti-inflammatory effects of ghrelin in sepsis-induced AKI and the possible role of vagus nerve.

METHODS

Five groups were included: sham, cecal ligation and puncture (CLP), CLP-ghrelin, CLP-vagotomy and CLP-vagotomy-ghrelin group.

RESULTS

Ghrelin treatment immediately after induction of CLP, significantly improved renal Glomerular filtration rate (GFR), serum creatinine, BUN and renal necrosis score as compared to the unprotected CLP group. In addition, ghrelin significantly decreased renal TNF alpha (111.5 ± 10.35 vs. 291.8 ± 15.8 pg/mg ptn), VCAM1 (6.28 ± 1.7 vs. 12.9 ± 1.2 µ/g ptn) and MPO (0.95 ± 0.13 vs. 2.5 ± 0.4 µ/g ptn) without significant increase in renal IL-10. Those effects were abolished by vagotomy.

CONCLUSION

We concluded that ghrelin could represent new therapeutic window in early treatment of sepsis-induced AKI and this could be mainly due to its anti-inflammatory effects.

Small acute increases in serum creatinine are associated with decreased long-term survival in the critically ill

RATIONALE

Long-term outcomes after acute kidney injury (AKI) are poorly described.

OBJECTIVES

We hypothesized that one single episode of minimal (stage 1) AKI is associated with reduced long-term survival compared with no AKI after recovery from critical illness.

METHODS

A prospective cohort of 2,010 intensive care unit (ICU) patients admitted to the ICU between years 2000 and 2009 at a provincial tertiary care hospital. Development of AKI was determined according to the KDIGO classification and mortality up to 10 years after ICU admission was recorded.

MEASUREMENTS AND MAIN RESULTS

Of the 1,844 eligible patients, 18.4% had AKI stage 1, 12.1% had stage 2, 26.5% had stage 3, and 43.0% had no AKI. The 28-day, 1-year, 5-year, and 10-year survival rates were 67.1%, 51.8%, 44.1%, and 36.3% in patients with mild AKI, which was significantly worse compared with the critically ill patients with no AKI at any time (P < 0.01). The unadjusted 10-year mortality hazard ratio was 1.53 (95% confidence interval, 1.2-2.0) for 28-day survivors with stage 1 AKI compared with critically ill patients with no AKI. Adjusted 10-year mortality risk was 1.26 (1.0-1.6). After propensity matching stage 1 AKI with no AKI patients, mild AKI was still significantly associated with decreased 10-year survival (P = 0.036).

CONCLUSIONS

Patients with one episode of mild AKI have significantly lower long-term survival rates than critically ill patients with no AKI. Close medical follow-up of these patients may be warranted and mechanistic research is required to understand how AKI influences long-term events.

Using inflammatory and oxidative biomarkers in urine to predict early acute kidney injury in patients undergoing liver transplantation

OBJECTIVE

We examined the value of inflammatory and oxidative biomarkers in predicting acute kidney injury (AKI) following orthotopic liver transplantation (OLT).

METHODS

Urinary excretion of tumour necrosis factor-α (TNF-α), interleukin-8 (IL-8), interleukin-10 (IL-10), superoxide dismutase (SOD), malondialdehyde (MDA), 6-keto prostaglandin F1α (6-keto-PGF1α), hydrogen peroxide (H2O2), and 8-keto prostaglandin F2α (8-iso-PGF2α), serum creatinine (SCr), blood urea nitrogen (BUN), urinary N-acetyl-beta-D-glucosaminidase (NAG), β2-microglobulin (β2-MG) and γ-glutamyl-transferase (γ-GT), were measured before surgery (baseline), at 2 h after graft reperfusion and 24 h after OLT in 28 liver transplantation patients.

RESULTS

The levels of TNF-α, IL-8, IL-10, SOD, MDA, 6-keto-PGF1α, H2O2 and 8-iso-PGF2α in urine were all significantly higher in patients who had AKI than in those who did not at 2 h after graft reperfusion and 24 h after OLT (p < 0.01).

Incidence and consequence of acute kidney injury in unselected emergency admissions to a large acute UK hospital trust

BACKGROUND

AKI is common among hospital in-patients and places a huge financial burden on the UK National Health Service, causing increased length of hospital stay and use of critical care services, with increased requirement for complex interventions including dialysis. This may account for up to 0.6% of the total Health Service budget. To investigate the incidence and consequences of AKI, all unselected emergency admissions to a large acute UK single centre University Teaching Hospital over two separate 7 day periods were reviewed.

METHODS

A retrospective audit of 745 case records was undertaken (54.6% male) including laboratory data post-discharge or death, with classification of AKI by RIFLE, AKIN and AKIB criteria. Participants were included whether admitted via their general practitioners, the emergency department, or as tertiary specialty transfers. Outcome measures were presence or absence of AKI recorded using each of the three AKI criteria, length of hospital stay (LOS), admission to, and LOS in critical care, and mortality. The most severe grade of AKI only, at any time during the admission, was recorded to prevent double counting. Renal outcome was determined by requirement for renal replacement therapy (RRT), and whether those receiving RRT remained dialysis dependent or not.

RESULTS

AKI incidence was 25.4% overall. With approximately one third present on admission and two thirds developing post admission. The AKI group had LOS almost three times higher than the non AKI group (10 vs 4 days). Requirement for critical care beds was 8.1% in the AKI group compared to 1.7% in non AKI group. Overall mortality was 5.5%, with the AKI group at 11.4% versus 3.3% in the non AKI group.

CONCLUSIONS

AKI in acute unselected hospital admissions is more common than existing literature suggests, affecting 25% of unselected admissions. In many this is relatively mild and may resolve spontaneously, but is associated with increased LOS, likelihood of admission to critical care, and risk of death. If targeted effective interventions can be developed it seems likely that substantial clinical benefits for the patient, as well as financial and structural benefits for the healthcare organisation may accrue.

HSP70, Peroxiredoxin-3 and -6 are upregulated during renal warm ischaemia in a donation after circulatory death model

BACKGROUND

The use of donation after circulatory death (DCD) kidneys for transplantation is increasing. Subsequent delayed graft function is related to ischaemia/reperfusion injury (I/R), warm ischaemia (WI) being one of the main contributing factors. This proteomics study aimed to identify candidate biomarkers of WI.

METHODS

Termination biopsies were obtained over 180min in 6 pigs. Proteins were subjected to differential in-gel electrophoresis (DIGE) and identified using LC MS/MS.

RESULTS

Thirty nine protein spots showed significant changes in expression (ANOVA, p<0.05). Peroxiredoxin-3 and -6 (PRX3 and PRX6) were expressed with a fold change (FD) of +1.8 (p=0.03 and 0.02 respectively). A significant upregulation of Alpha-2-HS-glycoprotein (A2HSG, FD+1.9, p=0.047) and heat-shock protein 70-1b (HSP70-1b, FD+2.1 p=0.002) was recorded.

CONCLUSIONS

The expression of PRX3, PRX6 and HSP70-1b during the first 30min of WI may be critical in measuring cellular responses. This is the first large animal model to describe the novel candidate biomarker, structural protein A2HSG. A2HSG upregulation during WI alone in this study is encouraging and further assessment in a DCD auto-transplant model is warranted.

BIOLOGICAL SIGNIFICANCE

Warm ischaemia (WI) during donation after circulatory death (DCD) organ retrieval is associated with higher rates of post transplant organ dysfunction. The cellular and molecular mechanism of this paradigm is poorly reported. The work carried out in this large animal study has been performed to enable better understanding of protein expression during DCD WI at the time of retrieval. We have identified differential increased expression of PRX3, PRX6 and HSP70 during the first 30min of WI. Observation of this behaviour has not been reported before. Application of these results in a reperfusion model or autograft animal study would further help study of the named proteins as clinical biomarkers of WI. Alpha 2-HS Glycoprotein (A2HSG) species were also differentially expressed during the WI period. This remains a novel finding. Assessment of A2HSG is also recommended for further study in a reperfusion context. Previous reports of A2HSG have suggested an association in chronic kidney disease and diabetes, but no association with WI has previously been noted in either small or large animals.

Comparative study of three methods of estimation of creatinine clearance in critically ill patients

BACKGROUND

At the bedside, the reference method for creatinine clearance determination is based on the measurement of creatinine concentrations in urine and serum (mCrCl). Several models are available to calculate the creatinine clearance from the serum creatinine concentration. This observational survey aimed at testing the hypothesis that the proposed equations are unreliable to determine accurate creatinine clearance in patients admitted to intensive care unit (ICU).

METHOD

Creatinine clearance was determined by the use of mCrCl. Then, we compared three equations: Cockcroft-Gault (CG), Simplified Modification of Diet in Renal Disease (MDRDs), and Chronic Kidney Disease Epidemiology (CKD-EPI) in 156 consecutive patients within the first 24hours after ICU admission. We tested the hypothesis that the three equations were equivalent. The agreement between the three equations was evaluated by linear regression and Bland and Altman analysis.

RESULTS

Bland and Altman analysis showed similar agreement between the three equations. The biases and precisions were -4.8±51, -1.3±50, and 8.2±44 for CG, MDRDs, and CKD-EPI equations, respectively (P>0.05). The precisions were similar for the three equations (P>0.05). The percentages of outliers at ±30% were 44%, 45%, and 49% for CG, MDRDs, and CKD-EPI, respectively (P>0.05).

CONCLUSION

Regarding the high percentage of outliers, the use of these equations cannot be recommended in ICU patients.

Safety and efficacy of intensive intraoperative glycaemic control in cardiopulmonary bypass surgery: a randomised trial

BACKGROUND

This study aimed to determine the safety and efficacy of intraoperative intensive glycaemic treatment with modified glucose-insulin-potassium solution by hyperinsulinemic normoglycaemic clamp in cardiopulmonary bypass surgery patients. We hypothesised that the treatment would reduce infection rates in this group of patients.

METHODS

A prospective, randomised, double-blind trial was conducted in cardiopulmonary bypass surgery patients. A total of 199 adult patients (out of a planned 400) were randomly allocated to intensive or conventional treatment with target glucose levels of 4.4-8.3 mmol/l and < 13.8 mmol/l, respectively. The primary outcomes were clinical infection and cytokine levels, including interleukin (IL)-6 and IL-10. The secondary outcomes were morbidity and mortality.

RESULTS

The study was terminated early because of safety concerns (hypoglycaemia). The clinical post-operative infection rate was 17% in the intensive group and 13% in the conventional group (P = 0.53). The proportion of patients with hypoglycaemia was significantly higher in the intensive group (23%) compared with the conventional group (3%) (P < 0.001). Morbidity and mortality rates were similar for both groups. Anaesthetic duration > 2 h (vs. ≤ 2 h), pre-operative IL-6 level > 15 pg/ml (vs. ≤ 15 pg/ml) and post-operative IL-6 level 56-110 pg/ml (vs. ≤ 55 pg/ml) were independent predictors for post-operative infection.

CONCLUSIONS

Intraoperative intensive glycaemic treatment significantly increased the risk of hypoglycaemia, but its effect on post-operative infection by clinical assessment could not be determined. Anaesthetic duration, pre-operative and post-operative IL-6 levels can independently predict post-operative infection.

Perioperative organ injury

Despite the fact that a surgical procedure may have been performed for the appropriate indication and in a technically perfect manner, patients are threatened by perioperative organ injury. For example, stroke, myocardial infarction, acute respiratory distress syndrome, acute kidney injury, or acute gut injury are among the most common causes for morbidity and mortality in surgical patients. In the current review, the authors discuss the pathogenesis of perioperative organ injury, and provide select examples for novel treatment concepts that have emerged over the past decade. Indeed, the authors are of the opinion that research to provide mechanistic insight into acute organ injury and identification of novel therapeutic approaches for the prevention or treatment of perioperative organ injury represent the most important opportunity to improve outcomes of anesthesia and surgery.

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.

Incidence, predictive factors, and clinical outcomes of acute kidney injury after gastric surgery for gastric cancer

Background

Postoperative acute kidney injury (AKI), a serious surgical complication, is common after cardiac surgery; however, reports on AKI after noncardiac surgery are limited. We sought to determine the incidence and predictive factors of AKI after gastric surgery for gastric cancer and its effects on the clinical outcomes.

Methods

We conducted a retrospective study of 4718 patients with normal renal function who underwent partial or total gastrectomy for gastric cancer between June 2002 and December 2011. Postoperative AKI was defined by serum creatinine change, as per the Kidney Disease Improving Global Outcomes guideline.

Results

Of the 4718 patients, 679 (14.4%) developed AKI. Length of hospital stay, intensive care unit admission rates, and in-hospital mortality rate (3.5% versus 0.2%) were significantly higher in patients with AKI than in those without. AKI was also associated with requirement of renal replacement therapy. Multivariate analysis revealed that male gender; hypertension; chronic obstructive pulmonary disease; hypoalbuminemia (<4 g/dl); use of diuretics, vasopressors, and contrast agents; and packed red blood cell transfusion were independent predictors for AKI after gastric surgery. Postoperative AKI and vasopressor use entailed a high risk of 3-month mortality after multiple adjustments.

Conclusions

AKI was common after gastric surgery for gastric cancer and associated with adverse outcomes. We identified several factors associated with postoperative AKI; recognition of these predictive factors may help reduce the incidence of AKI after gastric surgery. Furthermore, postoperative AKI in patients with gastric cancer is an important risk factor for short-term mortality.

Year in review 2012: Critical Care--Nephrology

We summarize original research in the field of critical care nephrology accepted or published in 2012 in Critical Care and, when considered relevant or directly linked to this research, in other journals. Three main topics have been identified for a rapid overview: acute kidney injury, detailed in some pathogenetic and epidemiological aspects; fluid overload as a predictor of mortality both in acute kidney injury and renal replacement therapy (RRT) patients; and RRT, evaluating some features of citrate anticoagulation and describing the effects of RRT modalities or timing on survival.

Multiple myeloma and kidney disease

Multiple myeloma (MM) has a high incidence rate in the elderly. Responsiveness to treatments differs considerably among patients because of high heterogeneity of MM. Chronic kidney disease (CKD) is a common clinical feature in MM patients, and treatment-related mortality and morbidity are higher in MM patients with CKD than in patients with normal renal function. Recent advances in diagnostic tests, chemotherapy agents, and dialysis techniques are providing clinicians with novel approaches for the management of MM patients with CKD. Once reversible factors, such as hypercalcemia, have been corrected, the most common cause of severe acute kidney injury (AKI) in MM patients is tubulointerstitial nephropathy, which results from very high circulating concentrations of monoclonal immunoglobulin free light chains (FLC). In the setting of AKI, an early reduction of serum FLC concentration is related to kidney function recovery. The combination of extended high cutoff hemodialysis and chemotherapy results in sustained reductions in serum FLC concentration in the majority of patients and a high rate of independence from dialysis.