***TASK*** the task is to summarize an input biomedical literature in six sentences 
    ***INPUT*** the input is a biomedical literature 
    ***OUTPUT*** the output is the summary of an input biomedical literature in six sentences 
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    Input: CONTEXT Although acute renal failure ( ARF ) is believed to be common in the setting of critical illness and is associated with a high risk of death , little is known about its epidemiology and outcome or how these vary in different regions of the world . OBJECTIVES To determine the period prevalence of ARF in intensive care unit ( ICU ) patients in multiple countries ; to characterize differences in etiology , illness severity , and clinical practice ; and to determine the impact of these differences on patient outcomes . DESIGN , SETTING , AND PATIENTS Prospect i ve observational study of ICU patients who either were treated with renal replacement therapy ( RRT ) or fulfilled at least 1 of the predefined criteria for ARF from September 2000 to December 2001 at 54 hospitals in 23 countries . MAIN OUTCOME MEASURES Occurrence of ARF , factors contributing to etiology , illness severity , treatment , need for renal support after hospital discharge , and hospital mortality . RESULTS Of 29 269 critically ill patients admitted during the study period , 1738 ( 5.7 % ; 95 % confidence interval [ CI ] , 5.5%-6.0 % ) had ARF during their ICU stay , including 1260 who were treated with RRT . The most common contributing factor to ARF was septic shock ( 47.5 % ; 95 % CI , 45.2%-49.5 % ) . Approximately 30 % of patients had preadmission renal dysfunction . Overall hospital mortality was 60.3 % ( 95 % CI , 58.0%-62.6 % ) . Dialysis dependence at hospital discharge was 13.8 % ( 95 % CI , 11.2%-16.3 % ) for survivors . Independent risk factors for hospital mortality included use of vasopressors ( odds ratio [ OR ] , 1.95 ; 95 % CI , 1.50 - 2.55 ; P<.001 ) , mechanical ventilation ( OR , 2.11 ; 95 % CI , 1.58 - 2.82 ; P<.001 ) , septic shock ( OR , 1.36 ; 95 % CI , 1.03 - 1.79 ; P = .03 ) , cardiogenic shock ( OR , 1.41 ; 95 % CI , 1.05 - 1.90 ; P = .02 ) , and hepatorenal syndrome ( OR , 1.87 ; 95 % CI , 1.07 - 3.28 ; P = .03 ) . CONCLUSION In this multinational study , the period prevalence of ARF requiring RRT in the ICU was between 5 % and 6 % and was associated with a high hospital mortality rate Objectives To evaluate the association of RIFLE classification with the outcomes of critically ill patients with acute kidney injury ( AKI ) who require renal replacement therapy ( RRT ) . Design and setting Prospect i ve cohort study in the medical-surgical ICUs at three tertiary hospitals . Patients 214 patients over 1 year ( mean age 71.4 ± 15.8 years ) .  Continuous RRT was used in 179 ( 84 % ) ; patients were classified as risk ( 25 % ) , injury ( 27 % ) , or failure ( 48 % ) . Overall mortality was 76 % . Measurements and results There were no significant differences according to RIFLE classification ( risk 72 % , injury 79 % , failure 76 % ) . Variables selected in multivariate analysis were : older age ( OR 1.03 , 95 % CI 1.01–1.06 ) , presence of comorbidity ( 3.15 , 1.10–9.02 ) , poor chronic health status ( 6.51 , 1.95–21.71 ) , number of associated organ dysfunctions ( patients with one or two organ dysfunctions 5.93 , 2.03–17.33 ; patients with three or more organ dysfunctions 26.76 , 6.28–114.11 ) , and start of RRT after the first day of ICU ( 2.46 , 1.09–5.53 ) . RIFLE classification was forced into the model and was not selected . However , a subgroup analysis of 150 patients who received mechanical ventilation and vasopressors found failure to be associated with increased mortality ( 3.58 , 1.08–11.80 ) . Conclusions Older age , number of organ dysfunctions , presence of comorbidities , and reduced functional capacity were the main prognostic factors . Patients who required RRT after the first day of ICU had a worse outcome . The RIFLE classification did not discriminate the prognosis in patients with AKI in need for RRT BACKGROUND Acute renal failure ( ARF ) is associated with high mortality . Presently , no specific therapy for ARF exists . Therefore , early detection of ARF is critical to prevent its progression . However , serum creatinine , the st and ard marker to detect ARF , demonstrates major limitations . We prospect ively evaluated whether serum cystatin C detected ARF earlier than serum creatinine . METHODS In 85 patients at high risk to develop ARF , serum creatinine and cystatin C were determined daily . ARF was defined according to the Risk of renal dysfunction , Injury to the kidney , Failure of kidney function , Loss of kidney function  , and ESRD  ( RIFLE ) classification when creatinine increased by > /=50 % ( R- criteria ) , by > /=100 % ( I- criteria ) , or by > /=200 % ( F- criteria ) . In analogy , ARF was detected when cystatin C increased by > /=50 % , by > /=100 % , or by > /=200 % . RESULTS Forty-four patients developed ARF and 41 served as controls . In ARF by R- , I- , and F- criteria , the increase of cystatin C significantly preceded that of creatinine . Specifically , serum cystatin C increased already by > /=50 % 1.5 + /- 0.6 days earlier compared to creatinine . Serum cystatin C demonstrated a high diagnostic value to detect ARF as indicated by area under the curve of the ROC analysis of 0.82 and 0.97 on the two days before the R- criteria was fulfilled by creatinine . Cystatin C detected ARF according to the R- criteria with a sensitivity of 55 % and 82 % on these days , respectively . Cystatin C also performed excellently , detecting ARF defined by the I- and F- criteria two days prior to creatinine , and moderately well predicting renal replacement therapy in the further course of ARF . Additionally , low T(3)- or T(3)/T(4 ) syndrome , glucocorticoid deficiency and excess did not affect cystatin C levels , adding to its usefulness in critically ill patients with ARF . CONCLUSION Serum cystatin C is a useful detection marker of ARF , and may detect ARF one to two days earlier than creatinine OBJECTIVES To evaluate the incidence of kidney injury and acute renal dysfunction ( ARD ) and associated risk factors in open abdominal aortic surgery . MATERIAL S AND METHODS 69 patients undergoing elective infrarenal aortic repair  were included in a prospect i ve study . Anaesthesia and haemodynamic management were st and ardised targeting a mean arterial pressure ( MAP ) of 70 - 90 mmHg , pulmonary artery occlusion pressure of 12 - 14 mmHg and cardiac index > or=2.4 l/min/m(2 ) . Urinary albumin-creatinine and N-acetyl-B-D-glucosaminidase-creatinine ratios were measured as indicators of kidney injury . The definition of ARD was based on the RIFLE criteria . RESULTS Kidney injury was found in most patients . ARD developed in 22 % of the patients , and acute renal failure in 4 % . The patients with ARD were older , and had lower plasma creatinine and estimated GFR before surgery . ARD was associated with intraoperative hypotension ( MAP < 60 mmHg > 15 min ) , low cardiac index ( < 2.4 l/min/m(2 ) ) , rhabdomyolysis , and early reoperation . Intraoperative hypotension and postoperative low cardiac output were independent risk factors for ARD in multivariate analysis . CONCLUSIONS Kidney injury occurs in most patients undergoing infrarenal aortic surgery , but only 22 % develop acute renal dysfunction . Hypotension and low cardiac output are risk factors that could be avoided by optimizing perioperative management Objective Because acute renal failure ( ARF ) is frequent in septic shock , an early marker of ARF could impact on management of such patients . High renal arterial resistive index ( RI ) is associated with parenchymatous renal failure . We assessed whether Doppler-measured RI on day 1 ( D1 ) of septic shock can predict ARF . Design Prospect i ve descriptive clinical study . Setting A 20-bed medical intensive care unit in a university hospital . Patients All patients with septic shock , excluding those with chronic renal failure ( serum creatinine > 120 μmol/l ) . Measurements and results RI was determined during the first 24 h ( D1 ) following vasopressor introduction , concomitant with recording of : age , SAPS II , mean arterial pressure , arterial lactate , catecholamine ( dose and type ) , urine output and serum creatinine . ARF was diagnosed according to the RIFLE classification . RI measurement was possible for 35 of 37 included patients . On day 5 ( D5 ) , 17 patients were without ARF ( RIFLE-0 or R ) and 18 patients were classified as having ARF ( RIFLE-I or F ) . On D1 , RI was higher in these latter 18 patients ( 0.77 ± 0.08 vs. 0.68 ± 0.08 , p < 0.001 ) . They also had higher SAPS II and arterial lactate concentration . RI > 0.74 on D1 had a positive likelihood ratio of 3.3 ( 95 % CI 1.1–35 ) for developing ARF on D5 . RI correlated inversely with mean arterial pressure ( ρ = –0.48 , p = 0.006 ) but not with catecholamine type or dose or with lactate concentration . Conclusion Doppler-based determination of RI on D1 in septic shock patients may help identify those who will develop ARF Acute kidney injury ( AKI ) in the intensive care unit ( ICU ) is associated with an enhanced mortality . The Acute Dialysis Quality Initiative group has proposed the RIFLE ( Risk-Injury-Failure-Loss-ESRD ) classification to st and ardize the approach to AKI . This study was performed to estimate the AKI incidence in ICU patients in northeastern Italy and describe clinical characteristics and outcomes of patients with AKI on the basis of their RIFLE class . A prospect i ve multicenter observational study was performed of patients who fulfilled AKI criteria in 19 ICU in northeastern Italy . Data were analyzed using multivariate logistic regression and survival curve analysis . Of 2164 ICU patients who were admitted during the study period , 234 ( 10.8 % ; 95 % confidence interval 9.5 to 12.1 % ) developed AKI ; 19 % were classified as risk ( R ) , 35 % as injury ( I ) , and 46 % as failure ( F ) . Preexisting kidney disease was present in 36.8 % . The most common causes of AKI were prerenal causes ( 38.9 % ) and sepsis ( 25.6 % ) . At diagnosis of AKI , median serum creatinine and urine output were 2.0 mg/dl and 1100 ml/d , respectively . ICU mortality was 49.5 % in class F , 29.3 % in I , and 20 % in R. Independent risk factors for mortality included RIFLE class , sepsis , and need for renal replacement therapy , whereas a postsurgical cause of AKI , exposure to nephrotoxins , higher serum creatinine , and urine output were associated with lower mortality risk . In this study , AKI incidence in the ICU was between 9 and 12 % , with 3.3 % of ICU patients requiring renal replacement therapy . Sepsis was a significant contributing factor . Overall mortality was between 30 and 42 % , and was highest among those in RIFLE class AIM The aim of this study was to determine the incidence of renal dysfunction according to the Acute-Dialysis- Quality Initiative-(ADQI)-RIFLE grading system in cardiac surgery in Germany in 2003 and to determine if variations in the incidence of renal dysfunction are related to clinical practice patterns . METHODS DESIGN prospect i ve cohort analysis and practice pattern survey . MEASUREMENTS 81 hospitals were requested to report prospect ively sample d quality -management- data on patient load , case mix , aortic-cross-clamp-time , baseline and maximal plasma creatinine ( CreaP ) , new-onset-renal-replacement-therapy , and clinical practice concerning the use of fluids , inotropic and vasopressor drugs , and diuretics .  Fifty-one ( 63 % ) centers answered the survey . Twenty-six centers (32%)(representative for 29 623 patients ( reported creatinine data . RES 
    Output:
    
The RIFLE classification is a simple , readily available clinical tool to classify AKI in different population s. It seems to be a good outcome predictor , with a progressive increase in mortality with worsening RIFLE class .
It also suggests that even mild degrees of kidney dysfunction may have a negative impact on outcome .