Acute Kidney Injury Network Classification Research Articles

Congenital heart surgery in infants: Effects of acute kidney injury on outcomes

We sought to characterize factors and outcomes associated with postoperative acute kidney injury in infants undergoing cardiac surgery. We retrospectively studied 430 infants (<90 days) who underwent heart surgery for congenital defects. With a pediatric modified version of the Acute Kidney Injury Network classification, we performed statistical analyses to detect factors and outcomes associated with postoperative acute kidney injury. Postoperative acute kidney injury occurred in 225 patients (52%): 135 patients (31%) reached maximum acute kidney injury stage I, 59 (14%) reached stage II, and 31 (7%) reached stage III. On multivariable analysis, single-ventricle status (odds ratio, 1.6; 95% confidence interval, 1.08-2.37; P = .02), cardiopulmonary bypass (odds ratio, 1.2; 95% confidence interval 1.01-1.47; P = .04), and higher reference serum creatinine (odds ratio, 5.1; 95% confidence interval, 1.94-13.2; P = .0009) were associated with postoperative acute kidney injury. Thirty-two (7%) patients died in the hospital. Multivariable logistic regression showed that more severe acute kidney injury was associated with in-hospital mortality (maximum acute kidney injury stage II odds ratio, 5.1; 95% confidence interval, 1.7-15.2; P = .004; maximum acute kidney injury stage III odds ratio, 9.46; 95% confidence interval, 2.91-30.7; P = .0002) and longer mechanical ventilation and inotropic support. All acute kidney injury stages were associated with longer intensive care durations. Stage III acute kidney injury was associated with systemic ventricular dysfunction at hospital discharge. Perioperative acute kidney injury is common in infant heart surgery and portends a poor clinical outcome.

Acute Kidney Injury Network definition of contrast-induced nephropathy in the critically ill: Incidence and outcome

Introduction Contrast-induced nephropathy (CIN) has been extensively studied in the ward but only scarcely in intensive care unit (ICU) patients, even if they may be particularly prone to develop or to worsen acute kidney insufficiency. We aimed to measure the incidence of CIN in a large ICU population using the Acute Kidney Injury Network (AKIN) definition and to investigate its impact on patients' outcome. Methods In this 3-year retrospective study, we included all patients undergoing, during their stay in our medical ICU, a contrast media–enhanced computed tomographic scan. Change in serum creatinine between baseline (24 hours before to 12 hours after contrast media injection) and its maximum value over the 96 hours after contrast media injection was recorded. Contrast-induced nephropathy was defined as a 44.2- μmol/L absolute or a 25% relative minimal increase in serum creatinine over 48, 72, or 96 hours and according to the stage 1 of the AKIN classification (at least 26.4 μmol/L or 50% increase over 48 hours). Results A total of 398 contrast-enhanced computed tomographic scans performed among 299 patients were analyzed. Incidence of CIN was 14% according to the AKIN definition and ranged from 8% (48-hour absolute definition) to 23% (96-hour relative definition). The need for renal replacement therapy and ICU mortality were significantly higher in case of CIN. After adjusting for other variables associated with ICU mortality, the occurrence of at least 1 CIN episode during the ICU stay (AKIN criteria) was independently associated with ICU mortality (odds ratio, 3.85; 95% confidence interval, 1.85-8.00). Conclusions Even if incidence varied greatly depending on the definition, CIN appeared frequent in our critically ill patients. The AKIN definition, independently associated with ICU mortality, may allow unifying diagnostic criteria to further evaluate this condition that impacts morbidity and mortality.

RIFLE and Acute Kidney Injury Network classifications predict mortality in leptospirosis‐associated acute kidney injury

Acute kidney injury (AKI) is a common complication in leptospirosis. The aim of this study is to investigate the association between RIFLE and AKIN classifications with mortality in leptospirosis-associated AKI. A retrospective study was conducted in patients with leptospirosis admitted to tertiary hospitals in Brazil. The association between RIFLE and AKIN classifications with mortality was investigated. Univariate and multivariate analysis was performed to investigate risk factors for death. A total of 287 patients were included, with an average age of 37 ± 16 years, and 80.8% were male. Overall mortality was 13%. There was a significant association between these classifications and death. Among non-survivors, 86% were in the class 'failure' and AKIN 3. Increased mortality was observed according to the worse classifications: 'risk' (R; 2%), 'injury' (I; 8%) and 'failure' (F; 23%), as well as in AKIN 1 (2%), AKIN 2 (8%) and AKIN 3 (23%) (P < 0.0001). The worst classifications were significantly associated with death: RIFLE F (odds ratio = 11.6, P = 0.018) and AKIN 3 (odds ratio = 12.8, P = 0.013). Receiver-operator curve for patients with AKI showed high areas under the curve (0.71, 95% confidence interval = 0.67-0.74) for both RIFLE and AKIN classifications in determining the sensitivity for mortality. There is a significant association between RIFLE and AKIN classifications with mortality in patients with leptospirosis. Initiation of dialysis in patients with RIFLE F and AKIN 3 should always be considered.

Acute Kidney Injury in Patients with Severe Traumatic Brain Injury: Implementation of the Acute Kidney Injury Network Stage System

There is limited information on the incidence and effect of acute kidney injury (AKI) in patients with severe traumatic brain injury (TBI), although AKI may affect outcome. Recently, acute kidney injury network (AKIN) classification has been widely accepted as a consensus definition for AKI. The aim of this study is to estimate the frequency and level of severity of AKI in patients with severe TBI by using AKIN criteria and to study whether AKI affects outcome. The authors retrospectively identified a total of 136 patients with severe TBI admitted to the neurosurgical center during a 3-year period ending May 2010. Demographic data, severity of TBI, serum creatinine, urine output, outcome at 6 month, and death were collected. Renal function was assessed by using AKIN criteria. Thirty-one patients (23%) were classified as having AKI by using AKIN criteria during their hospitalization. Of them, 21 patients (68%) were stratified as stage 1, 7 patients (22%) as stage 2, and 3 patients (10%) as stage 3. Patients who developed AKI were older, had lower Glasgow coma scale at admission, and had higher level of admission serum creatinine and blood urea nitrogen. Patients with AKI had higher mortality and worse outcome when compared with patients with normal renal function. Furthermore, patients with mild renal dysfunction (stage 1 AKI) are also found having increased mortality and worse long-term outcome, compared with patients without renal dysfunction. It is demonstrated using the newly defined AKIN criteria for renal dysfunction that AKI is a relatively common feature in patients with severe TBI, and even seemingly insignificant decrease in renal function may be associated with worse outcome. This study highlights the importance of close surveillance of renal function and stresses the value of renal hygiene in the severe TBI population.

Challenges of defining acute kidney injury

Until recently, there was a lack of a uniform definition for acute kidney injury (AKI). The 'acute renal injury/acute renal failure syndrome/severe acute renal failure syndrome' criteria, the Risk - Injury - Failure - Loss of kidney function - End stage renal disease (RIFLE) criteria and the Acute Kidney Injury Network (AKIN) classification were the most recent proposals. To compare the performance of the different AKI definitions. Application of the three most recent AKI definitions to 41 972 critically ill ICU patients and comparison of their performance. Incidence and outcome of AKI varied depending on the criteria. The RIFLE and AKIN classification led to similar total incidences of AKI (35.9 vs. 35.4%) but different incidences and outcomes of the individual AKI stages. Multivariate analysis showed that the different stages of AKI were independently associated with mortality. The worst stage of AKI was associated with an increased odds ratio for mortality of 1.59-2.27. Non-surgical admission, maximum number of associated failed organ systems, emergency surgery and mechanical ventilation were consistently associated with the highest risk of hospital mortality. The proposed AKI definitions differ in the cut-off values of serum creatinine, the suggested time frame, the approach towards patients with missing baseline values and the method of classifying patients on renal replacement therapy. All classifications can miss patients with definite AKI. The three most recent definitions of AKI confirmed a correlation between severity of AKI and outcome but have limitations and the potential to miss patients with definite AKI. These limitations need to be considered when using the criteria in clinical practice.

Obesity and acute kidney injury: reply to Dr. Robert and coworkers

Dear Editor, We thank Dr. Robert and colleagues [1] for their comments on our study on the impact of BMI on the evolution and prognosis of acute kidney injury (AKI) [2]. We remind the readers that in this study the impact of BMI on the evolution AKI was corrected for by several potential confounders, such as age, severity of disease, diabetes status, or comorbidities. Dr. Robert raises another possibility for a bias, i.e., the criteria for AKI diagnosis used in the Risk, Injury, Failure, Loss, and End-Stage Kidney (RIFLE) classification. They discuss whether urinary output should—as required in both RIFLE and Acute Kidney Injury Network (AKIN) classifications—be corrected for by body weight which might introduce a bias in obese patients. Our diagnosis of AKI, however (as in most studies), was not based on urine criterion but on the creatinine criterion and the necessity of renal replacement therapy. Dr. Robert also questions the validity of the creatinine criterion because obese persons also have a higher muscle mass and thus a higher creatinine formation. This fact—they argue—may result in an erroneous allocation of several subjects into the F category and also in an earlier initiation of renal replacement therapy in obese patients. This is certainly a point well taken; it is a problem which is inherent to currently used AKI classifications which all are based on serum creatinine. However, we only included patients in a really ‘‘failure’’ situation and the necessity of renal replacement therapy, a decision which rarely is based on creatinine concentration alone. A substantial impact of this potential bias on our results can largely be ruled out. References

Acute kidney injury network classification predicts in-hospital and long-term mortality in patients undergoing elective coronary artery bypass grafting surgery☆

Acute kidney injury (AKI) is a highly prevalent complication after cardiac surgery. It is associated with substantial morbidity and mortality. However, the definition of AKI has not been well established until the Acute Kidney Injury Network group outlined an easily used consentaneous staging system. The study aims to evaluate the association between this determination and in-hospital as well as long-term mortality in patients receiving elective coronary artery bypass grafting (CABG) surgery. Patients undergoing elective CABG surgery from January 2003 to December 2007 in a tertiary medical center were studied. The Acute Kidney Injury Network classification was applied for the diagnosis of perioperative AKI. Medical history and intra-operative variables were collected retrospectively. Multivariate analysis was used to identify the independent risk factors of in-hospital and long-term mortality. Long-term survival rates were calculated using the Kaplan-Meier method. This study included 964 patients. The incidence of AKI following elective CABG was 19.8%. Only 7% of the study population developed AKI requiring renal replacement therapy after surgery. The overall in-hospital mortality rate was 5.1%. Significant independent risk factors for in-hospital mortality include increasing age, higher serum uric acid, postoperative requirement of intra-aortic balloon pumping (IABP) and extracorporeal membrane oxygenation (ECMO), perioperative AKI, and chronic dialysis (all p<0.05). Significant independent risk factors for long-term mortality include increasing age, lower serum albumin, higher serum uric acid, postoperative requirement of IABP and ECMO, perioperative AKI, and chronic dialysis (all p < 0.005). Acute Kidney Injury Network classification is a powerful tool to evaluate the prognostic impact of AKI on both in-hospital and long-term mortality among patients undergoing elective CABG surgery.

Biomarkers of Acute Kidney Injury

ESPITE more than half a century of investigation,acute kidney injury (AKI) remains a major healthcareissue in medicine today. Reported to occur in 1–32% of allhospital admissions and 10–90% of intensive care unit ad-missions, the wide variation reflects different criteria used todefineAKI.However,independentofdefinition,adiagnosisof AKI is consistently associated with an increase in bothshort- and long-term morbidity and mortality. Even themildest forms of AKI are independently associated with in-creased early as well as long-term mortality, the risk increas-ing as severity of renal injury increases.

ACUTE KIDNEY INJURY CLASSIFICATION

The Acute Kidney Injury Network (AKIN) group has recently proposed modifications to the risk of renal failure, injury to kidney, failure of kidney function, loss of kidney function, and end-stage renal failure (RIFLE) classification system. The few studies that have compared the two classifications have revealed no substantial differences. This study aimed to compare the AKIN and RIFLE classifications for predicting outcome in critically ill patients. This retrospective study investigated the medical records of 291 critically ill patients who were treated in medical intensive care units of a tertiary care hospital between March 2003 and February 2006. This study compared performance of the RIFLE and AKIN criteria for diagnosing and classifying AKI and for predicting hospital mortality. Overall mortality rate was 60.8% (177/291). Increased mortality was progressive and significant (chi-square for trend; P < 0.001) based on the severity of AKIN and RIFLE classification. Hosmer and Lemeshow goodness-of-fit test results demonstrated good fit in both systems. The AKIN and RIFLE scoring systems displayed good areas under the receiver operating characteristic curves (0.720 + or - 0.030, P = 0.001; 0.738 + or - 0.030, P = 0.001, respectively). Compared with RIFLE criteria, this study indicated that AKIN classification does not improve the sensitivity and ability of outcome prediction in critically ill patients.

A comparison of the RIFLE and Acute Kidney Injury Network classifications for cardiac surgery–associated acute kidney injury: A prospective cohort study

There is an intense debate on whether the RIFLE (R-renal risk, I-injury, F-failure, L-loss of kidney function, E-end-stage renal disease) classification or its recent modification, the Acute Kidney Injury Network definition and classification system should be used to standardize research on acute kidney injury. In this study we compared these classifications with regard to (1) the detection of acute kidney injury, (2) their agreement according to the grading of acute kidney injury across classes, and (3) their prognostic value. We prospectively enrolled 282 cardiac surgery patients undergoing cardiopulmonary bypass and assigned a RIFLE and Acute Kidney Injury Network class to each patient. The incidence of acute kidney injury and in-hospital mortality across classes was compared by using the chi(2) test, and their prognostic value was compared by using the area under the curve receiver-operating characteristic for in-hospital mortality. According to the RIFLE (45.8%) or Acute Kidney Injury Network (44.7%) classification, a similar proportion of patients had acute kidney injury. There was large agreement between classifications according to patients graded as having nonacute kidney injury; however, there was some disagreement across classes for staging the severity of acute kidney injury. The area under the curve for in-hospital mortality was similar for all classifications: 0.91 for the RIFLE classification (95% confidence interval, 0.82-0.99) and 0.94 for the Acute Kidney Injury Network classification (95% confidence interval, 0.81-0.97; P = .6 for area under the curve comparison). In patients undergoing cardiac surgery, modifications of the RIFLE classification for acute kidney injury do not materially improve the clinical usefulness of the definition. Other factors, such as the applicability of the acute kidney injury definition and classification system to be applied, need to be considered.

Miniaturized Cardiopulmonary Bypass and Acute Kidney Injury in Coronary Artery Bypass Graft Surgery

Acute kidney injury (AKI) is one of the most important complications after on-pump coronary artery bypass graft surgery (CABG). Miniaturized cardiopulmonary bypass (mini-CPB) systems have been developed to allow the ease of on-pump surgery but tempering the disadvantages. Whether mini-CPB reduces the incidence of AKI remains to be determined. Using a propensity score matched analysis, we investigated the occurrence of AKI among patients undergoing CABG on mini-CPB (n = 104) versus conventional CPB (n = 601). Acute kidney injury was defined according to the recent Acute Kidney Injury Network classification. Overall, acute kidney injury developed in 274 of 705 patients (38.8%). A total of 27 of 705 patients (3.8%) required renal replacement therapy. The median postoperative length of intensive care unit stay in survivors with AKI was 5.4 (3.9 to 6.8) days compared with 2.0 (1.0 to 3.0) days for patients without AKI (p = 0.0002). The overall incidence of AKI for patients undergoing mini-CPB was 30 of 104 (28.8%) compared with 244 of 601 (40.5%) for patients undergoing conventional CPB (p = 0.03). In the propensity score matched-pair statistical analysis, mini-CPB was independently associated with a decreased incidence of AKI (adjusted odds ratio [OR] 0.61; 95% confidence interval [CI]: 0.38 to 0.97). Other variables independently associated with AKI were preoperative glomerular filtration rate (OR 0.988 for 1 mL.min(-1).1.73 m(-2) increase; 95% CI: 0.98 to 0.99), postoperative red blood cell transfusion (OR 1.58; 95% CI: 1.12 to 2.23); CPB time (OR 1.005 for 1-minute increase; 95% CI: 1.0 to 1.009), and postoperative low output syndrome (OR 1.72; 95% CI: 1.23 to 2.41). The present study showed that mini-CPB is associated with a lower incidence of AKI when compared with conventional CPB among patients undergoing CABG.

Acute kidney injury in critically ill patients classified by AKIN versus RIFLE using the SAPS 3 database

Acute kidney injury (AKI) is associated with significantly increased morbidity and mortality. To provide a uniformly accepted definition, the RIFLE classification was introduced by the Acute Dialysis Quality Initiative, recently modified by the Acute Kidney Injury Network (AKIN), suggesting staging of AKI based on dynamic changes within 48 h. This study compares these two classification systems with regard to outcome. Cohort analysis of SAPS 3 database. Sixteen thousand seven hundred and eighty-four ICU patients from 303 ICUs were analysed. Classification was performed according to RIFLE (Risk, Injury, Failure) or according to AKIN (stage 1, 2, 3) without including a requirement of renal replacement therapy in the analysis. Changes of serum creatinine as well as urinary output were assessed for both AKIN and RIFLE during the first 48 h of ICU admission. Primary endpoint was hospital mortality. Incidence of AKI in our population of critically ill patients was found to range between 28.5 and 35.5% when applying AKIN and RIFLE criteria, respectively, associated with increased hospital mortality averaging 36.4%. Observed-to-expected mortality ratios revealed excess mortality conferred by any degree of AKI increasing from 0.81 for patients classified as non-AKI up to 1.31 and 1.23 with AKIN stage 3 or RIFLE Failure, respectively. AKIN misclassified 1,504 patients as non-AKI compared to RIFLE which misclassified 504 patients. Acute kidney injury classified by either RIFLE or AKIN is associated with increased hospital mortality. Despite presumed increased sensitivity by the AKIN classification, RIFLE shows better robustness and a higher detection rate of AKI during the first 48 h of ICU admission.

Does perioperative hemodynamic optimization protect renal function in surgical patients? A meta-analytic study

Postoperative acute deterioration in renal function, producing oliguria and/or increase in serum creatinine, is one of the most serious complication in surgical patients. Most cases are due to renal hypoperfusion as a consequence of systemic hypotension, hypovolemia, and cardiac dysfunction. Although some evidence suggests that perioperative monitoring and manipulation of oxygen delivery by volume expansion and inotropic drugs may decrease mortality in surgical patients, no study analyzed this approach on postoperative renal dysfunction. The objective of this investigation is to perform a meta-analysis on the effects of perioperative hemodynamic optimization on postoperative renal dysfunction. DATA SOURCES, STUDY SELECTION, DATA EXTRACTION: A systematic literature review, using MEDLINE, EMBASE, and The Cochrane Library databases through January 2008 was conducted and 20 studies met the inclusion criteria (4220 participants). Data synthesis was obtained by using odds ratio (OR) with 95% confidence interval (CI) by random-effects model. Postoperative acute renal injury was significantly reduced by perioperative hemodynamic optimization when compared with control group (OR 0.64; CI 0.50-0.83; p = 0.0007). Perioperative optimization was effective in reducing renal injury defined consistently with risk, injury, failure, and loss and end-stage kidney disease and Acute Kidney Injury Network classifications, and in studies defining renal dysfunction by serum creatinine and/or need of renal replacement therapy only (OR 0.66; CI 0.50-0.88; p = 0.004). The occurrence of renal dysfunction was reduced when treatment started both preoperatively and intraoperatively or postoperatively, was performed in high-risk patients, and was obtained by fluids and inotropes. Mortality was significantly reduced in treatment group (OR 0.50; CI 0.31-0.80; p = 0.004), but statistical heterogeneity was observed. Surgical patients receiving perioperative hemodynamic optimization are at decreased risk of renal impairment. Because of the impact of postoperative renal complications on adverse outcome, efforts should be aimed to identify patients and surgery that would most benefit from perioperative optimization.

Acute kidney injury in patients with sepsis: a contemporary analysis

To analyze the clinical characteristics of septic acute kidney injury (AKI) according to the Acute Kidney Injury Network (AKIN) classification, and to evaluate the capacity of this system in predicting in-hospital mortality of septic patients. Patients with sepsis admitted to the infectious diseases intensive care unit (ICU) of our hospital between January 2004 and June 2007 were retrospectively studied. Maximum AKIN stage within the first three days of hospitalization was recorded. Three hundred fifteen patients were evaluated. According to AKIN criteria, 99 patients (31.4%) had AKI: 26.2% at stage 1, 20.2% at stage 2, and 53.6% at stage 3. Four patients (1.9%) with no AKI progressed to stage 1, two patients (7.7%) at stage 1 progressed to stage 2, one patient (3.8%) at stage 1 progressed to stage 3, and one patient at stage 2 (5%) progressed to stage 3. The mortality rate was 25.3% and increased significantly from normal renal function to stage 3 (normal, 12.5%; stage 1, 34.6%; stage 2, 45%; stage 3, 64.1%; p<0.0001). After adjusting for age, gender, race, pre-existing chronic kidney disease, illness severity as evaluated by acute physiology and chronic health evaluation, version II (APACHE II) score, need for mechanical ventilation, and vasopressor use, AKIN stage 1 (odds ratio (OR) 3.03, 95% confidence interval (CI) 1.12-8.19, p=0.029), stage 2 (OR 3.3, 95% CI 1.11-9.78, p=0.031), and stage 3 (OR 7.35, 95% CI 3.13-17.25, p<0.0001) predicted mortality. AKIN criteria are a useful tool to characterize and stratify septic patients according to the risk of death.

Impact of minimal increases in serum creatinine on outcome in patients after cardiothoracic surgery: Do we have to revise current definitions of acute renal failure?*

Traditional cutoff values of serum creatinine considered to define postoperative acute renal failure have been challenged recently. In a previous investigation we demonstrated that minimal changes in serum creatinine concentration were associated with a substantial decrease in survival after cardiac surgery. In this investigation, we assessed the impact of minimal absolute increases in serum creatinine in a second institution, and we analyzed whether relative changes, as in the RIFLE classification and, partially, in Acute Kidney Injury Network (AKIN) classification, confer a different prognostic potential. Prospective analysis. University hospital. All consecutive patients undergoing cardiac surgery in the University Hospital of Zurich (Center USZ) over a 46-month period. Patients were prospectively documented. We analyzed maximal changes in serum creatinine in the first 48 hrs postoperatively (DeltaCrea) regarding death within 30 days. Results were compared with those of the University Hospital Vienna (Center AKH). Moreover, the prognostic potential of DeltaCrea within 48 hrs vs. serum creatinine elements according to RIFLE and AKIN classifications was assessed. A total of 3,123 patients were evaluated from USZ. The majority of patients had decreased postoperative serum creatinine values (negative DeltaCrea) and the lowest mortality (1.8%). Minimal increases, [0, 0.5) mg x dL(-1), were associated with a more than doubled mortality in both centers (5%/6%). Mortality, according to RIFLE and AKIN classifications for both populations combined, was as follows: 7,023 (3.6%), 160 (29%), 43 (19%), and 15 (33%) for RIFLE Normal, Risk, Injury, and Failure; 6,644 (2.8), 463 (16.4), 3 (66.7), and 131 (1.8) for AKIN stage 0, 1, 2, and 3. Measuring repeat serum creatinine concentrations within 48 hrs and determining DeltaCrea were the most effective discrimination method to find patients at risk for adverse postoperative outcome after cardiac surgery, better than application of this sole criterion to the RIFLE (least discriminatory) or the AKIN classification.

A comparison of the RIFLE and AKIN criteria for acute kidney injury in critically ill patients

The Acute Dialysis Quality Initiative Group has published a consensus definition/classification system for acute kidney injury (AKI) termed the RIFLE criteria. The Acute Kidney Injury Network (AKIN) group has recently proposed modifications to this system. It is currently unknown whether there are advantages between these criteria. We interrogated the Australian New Zealand Intensive Care Society (ANZICS) Adult Patient Database (APD) for all adult admissions to 57 ICUs from 1 January 2000 to 31 December 2005. We compared the performance of the RIFLE and AKIN criteria for diagnosis and classification of AKI and for robustness of hospital mortality. We included 120 123 critically ill patients, of which 27.8% had a primary diagnosis of sepsis. We found only small differences (<1%) in the number of patients classified as having some degree of kidney injury using either the AKIN or RIFLE definition or classification systems. AKIN slightly increased the number of patients classified as Stage I injury (category R in RIFLE) (from 16.2 to 18.1%) but decreased the number of patients classified as having Stage II injury (category I in RIFLE) (13.6% versus 10.1%). The area under the ROC curve for hospital mortality was 0.66 for RIFLE and 0.67 for AKIN in all patients and it was 0.65 for both in septic patients. Compared to the RIFLE criteria, the AKIN criteria do not materially improve the sensitivity, robustness and predictive ability of the definition and classification of AKI in the first 24 h after admission to ICU.

Acute kidney injury in intensive care unit patients: a comparison between the RIFLE and the Acute Kidney Injury Network classifications

IntroductionWhether discernible advantages in terms of sensitivity and specificity exist with Acute Kidney Injury Network (AKIN) criteria versus Risk, Injury, Failure, Loss of Kidney Function, End-stage Kidney Disease (RIFLE) criteria is currently unknown. We evaluated the incidence of acute kidney injury and compared the ability of the maximum RIFLE and of the maximum AKIN within intensive care unit hospitalization in predicting inhospital mortality of critically ill patients.MethodsPatients admitted to the Department of Intensive Medicine of our hospital between January 2003 and December 2006 were retrospectively evaluated. Chronic kidney disease patients undergoing dialysis or renal transplant patients were excluded from the analysis.ResultsIn total, 662 patients (mean age, 58.6 ± 19.2 years; 392 males) were evaluated. AKIN criteria allowed the identification of more patients as having acute kidney injury (50.4% versus 43.8%, P = 0.018) and classified more patients with Stage 1 (risk in RIFLE) (21.1% versus 14.7%, P = 0.003), but no differences were observed for Stage 2 (injury in RIFLE) (10.1% versus 11%, P = 0.655) and for Stage 3 (failure in RIFLE) (19.2% versus 18.1%, P = 0.672). Mortality was significantly higher for acute kidney injury defined by any of the RIFLE criteria (41.3% versus 11%, P < 0.0001; odds ratio = 2.78, 95% confidence interval = 1.74 to 4.45, P < 0.0001) or of the AKIN criteria (39.8% versus 8.5%, P < 0.0001; odds ratio = 3.59, 95% confidence interval = 2.14 to 6.01, P < 0.0001). The area under the receiver operator characteristic curve for inhospital mortality was 0.733 for RIFLE criteria (P < 0.0001) and was 0.750 for AKIN criteria (P < 0.0001). There were no statistical differences in mortality by the acute kidney injury definition/classification criteria (P = 0.72).ConclusionsAlthough AKIN criteria could improve the sensitivity of the acute kidney injury diagnosis, it does not seem to improve on the ability of the RIFLE criteria in predicting inhospital mortality of critically ill patients.