The clinical relevance of oliguria in the critically ill patient: analysis of a large observational database.

BACKGROUND: Urine output is widely used as one of the criteria for the diagnosis and staging of acute renal failure, but few studies have specifically assessed the role of oliguria as a marker of acute renal failure or outcomes in general intensive care unit (ICU) patients. Using a large multinational database, we therefore evaluated the occurrence of oliguria (defined as a urine output < 0.5 ml/kg/h) in acutely ill patients and its association with the need for renal replacement therapy (RRT) and outcome. METHODS: International observational study. All adult (> 16 years) patients in the ICON audit who had a urine output measurement on the day of admission were included. To investigate the association between oliguria and mortality, we used a multilevel analysis. RESULTS: Of the 8292 patients included, 2050 (24.7%) were oliguric during the first 24 h of admission. Patients with oliguria on admission who had at least one additional 24-h urine output recorded during their ICU stay (n = 1349) were divided into three groups: transient-oliguria resolved within 48 h after the admission day (n = 390 [28.9%]), prolonged-oliguria resolved > 48 h after the admission day (n = 141 [10.5%]), and permanent-oliguria persisting for the whole ICU stay or again present at the end of the ICU stay (n = 818 [60.6%]). ICU and hospital mortality rates were higher in patients with oliguria than in those without, except for patients with transient oliguria who had significantly lower mortality rates than non-oliguric patients. In multilevel analysis, the need for RRT was associated with a significantly higher risk of death (OR = 1.51 [95% CI 1.19-1.91], p = 0.001), but the presence of oliguria on admission was not (OR = 1.14 [95% CI 0.97-1.34], p = 0.103). CONCLUSIONS: Oliguria is common in ICU patients and may have a relatively benign nature if only transient. The duration of oliguria and need for RRT are associated with worse outcome.

Oliguria in critically ill patients: a narrative review.

Oliguria is often observed in critically ill patients. However, different thresholds in urine output (UO) have raised discussion as to the clinical importance of a transiently reduced UO of less than 0.5 ml/kg/h lasting for at least 6 h. While some studies have demonstrated that isolated oliguria without a concomitant increase in serum creatinine is associated with higher mortality rates, different underlying pathophysiological mechanisms suggest varied clinical importance of reduced UO, as some episodes of oliguria may be fully reversible. We aim to explore the clinical relevance of oliguria in critically ill patients and propose a clinical pathway for the diagnostic and therapeutic management of an oliguric, critically ill patient.

Effect of high-dose furosemide on the prognosis of critically ill patients.

PURPOSE: Diuretics are used frequently in critically ill patients. We investigated the effects of furosemide on the prognosis. MATERIALS AND METHODS: Following a retrospective review of patients admitted to the medical intensive care unit (ICU), we analyzed risk factors with variables including initial furosemide dose for ICU mortality. RESULTS: A total of 448 patients were included. Total furosemide dose during the first three days of the ICU stay (odds ratio (OR) 2.35, 95% confidence interval (CI) 1.01-5.02) and fluid balance during the same period (OR 3.04, 95% CI 1.46-6.31) were associated with ICU mortality, as were malignancy, chronic furosemide use, and APACHE II score. However, in oliguric patients, positive fluid balance was associated with ICU mortality (OR 22.33, 95% CI 1.82-273.72) but the high-dose furosemide was not. In contrast, in non-oliguric patients, high-dose furosemide was associated with ICU mortality (OR 2.47, 95% CI 1.01-5.68); however, the positive fluid balance showed only a trend for high ICU mortality. CONCLUSION: Early high-dose furosemide use is associated with ICU mortality, particularly in non-oliguric patients. We suggest that furosemide should be used with caution even in non-oliguric critically ill patients until the safety is confirmed in powered study.

Targeting urine output and 30-day mortality in goal-directed therapy: a systematic review with meta-analysis and meta-regression.

BACKGROUND: Oliguria is associated with a decreased kidney- and organ perfusion, leading to organ damage and increased mortality. While the effects of correcting oliguria on renal outcome have been investigated frequently, whether urine output is a modifiable risk factor for mortality or simply an epiphenomenon remains unclear. We investigated whether targeting urine output, defined as achieving and maintaining urine output above a predefined threshold, in hemodynamic management protocols affects 30-day mortality in perioperative and critical care. METHODS: We performed a systematic review with a random-effects meta-analyses and meta-regression based on search strategy through MEDLINE, EMBASE and references in relevant articles. We included studies comparing conventional fluid management with goal-directed therapy and reporting whether urine output was used as target or not, and reporting 30-day mortality data in perioperative and critical care. RESULTS: We found 36 studies in which goal-directed therapy reduced 30-day mortality (OR 0.825; 95% CI 0.684-0.995; P = 0.045). Targeting urine output within goal-directed therapy increased 30-day mortality (OR 2.66; 95% CI 1.06-6.67; P = 0.037), but not in conventional fluid management (OR 1.77; 95% CI 0.59-5.34; P = 0.305). After adjusting for operative setting, hemodynamic monitoring device, underlying etiology, use of vasoactive medication and year of publication, we found insufficient evidence to associate targeting urine output with a change in 30-day mortality (goal-directed therapy: OR 1.17; 95% CI 0.54-2.56; P = 0.685; conventional fluid management: OR 0.74; 95% CI 0.39-1.38; P = 0.334). CONCLUSIONS: The principal finding of this meta-analysis is that after adjusting for confounders, there is insufficient evidence to associate targeting urine output with an effect on 30-day mortality. The paucity of direct data illustrates the need for further research on whether permissive oliguria should be a key component of fluid management protocols.

Long-term outcome in ICU patients with acute kidney injury treated with renal replacement therapy: a prospective cohort study.

BACKGROUND: In intensive care unit (ICU) patients, acute kidney injury treated with renal replacement therapy (AKI-RRT) is associated with adverse outcomes. The aim of this study was to evaluate variables associated with long-term survival and kidney outcome and to assess the composite endpoint major adverse kidney events (MAKE; defined as death, incomplete kidney recovery, or development of end-stage renal disease treated with RRT) in a cohort of ICU patients with AKI-RRT. METHODS: We conducted a single-center, prospective observational study in a 50-bed ICU tertiary care hospital. During the study period from August 2004 through December 2012, all consecutive adult patients with AKI-RRT were included. Data were prospectively recorded during the patients' hospital stay and were retrieved from the hospital databases. Data on long-term follow-up were gathered during follow-up consultation or, in the absence of this, by consulting the general physician. RESULTS: AKI-RRT was reported in 1292 of 23,665 first ICU admissions (5.5 %). Mortality increased from 59.7 % at hospital discharge to 72.1 % at 3 years. A Cox proportional hazards model demonstrated an association of increasing age, severity of illness, and continuous RRT with long-term mortality. Among hospital survivors with reference creatinine measurements, 1-year renal recovery was complete in 48.4 % and incomplete in 32.6 %. Dialysis dependence was reported in 19.0 % and was associated with age, diabetes, chronic kidney disease (CKD), and oliguria at the time of initiation of RRT. MAKE increased from 83.1 % at hospital discharge to 93.7 % at 3 years. Multivariate regression analysis showed no association of classical determinants of outcome (preexisting CKD, timing of initiation of RRT, and RRT modality) with MAKE at 1 year. CONCLUSIONS: Our study demonstrates poor long-term survival after AKI-RRT that was determined mainly by severity of illness and RRT modality at initiation of RRT. Renal recovery is limited, especially in patients with acute-on-chronic kidney disease, making nephrological follow-up imperative. MAKE is associated mainly with variables determining mortality.

Derivation of urine output thresholds that identify a very high risk of AKI in patients with septic shock.

BACKGROUND AND OBJECTIVES: To promote early detection of AKI, recently proposed pretest probability models combine sub-Kidney Disease Improving Global Outcomes (KDIGO) AKI criteria with baseline AKI risk. The primary objective of this study was to determine sub-KDIGO thresholds that identify patients with septic shock at highest risk for AKI. DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS: This was a retrospective analysis of 390 adult patients admitted to the medical intensive care unit (ICU) of a tertiary, academic medical center with septic shock between January 2008 and December 2010. Hourly urine output was collected from the time of septic shock recognition (hour 0) to hour 96, urine catheter removal, or ICU discharge (whichever occurred first). All available serum creatinine (SCr) measurements were collected until hour 96. The AKI pretest probability model was assessed during the first 12 hours of resuscitation and included the initial episode of oliguria, increase from baseline to peak SCr level, and Acute Physiology and Chronic Health Evaluation (APACHE) III score in a multivariable receiver-operator characteristic (ROC) analysis. The primary outcome was the incidence of stage II or III (stage II+) AKI defined by KDIGO criteria. Secondary outcomes included the need for RRT and 28-day mortality. RESULTS: Ninety-eight (25%) patients developed stage II+ AKI after septic shock recognition. APACHE III score and increase in SCr level in the first 12 hours were not statistically associated with stage II+ AKI in multivariable ROC analysis. Consecutive oliguria for 3 hours had fair predictive ability for achieving stage II+ AKI criteria (area under ROC curve, 0.73; 95% confidence interval [95% CI], 0.68 to 0.78), and oliguria for 5 hours demonstrated optimal accuracy (82%; 95% CI, 79% to 86%). CONCLUSIONS: Three to 5 hours of consecutive oliguria in patients with septic shock may provide a valuable measure of AKI risk. Further validation to support this finding is needed.

Defining reduced urine output in neonatal ICU: importance for mortality and acute kidney injury classification.

BACKGROUND: Acute kidney injury (AKI) is an independent risk factor for mortality in adults and children. Generally, urine output (UO) < 1 mL/kg/h is accepted as oliguria in neonates, although it has not been systematically studied. pRIFLE criteria suggest UO cut-offs similar to those of the adult population (0.3 and 0.5 mL/kg/h). The aim of the present study was to investigate UO in correlation with mortality in critically ill neonates and suggest changes in the pRIFLE definition of reduced diuresis. METHODS: A retrospective cohort study was performed in an eight-bed neonatal intensive care unit (NICU). UO was systematically measured by diaper weight each 3 h. Discriminatory capacity to predict mortality of UO was measured and patients were divided according to UO ranges: G1 > 1.5 mL/kg/h; G2 1.0-1.5 mL/kg/h; G3 0.7-1.0 mL/kg/h and G4 < 0.7 mL/kg/h. These ranges were incorporated to pRIFLEGFR criteria and its performance was evaluated. RESULTS: Of 384 patients admitted at the NICU during the study period, 72 were excluded and overall mortality was 12.8%. UO showed good performance for mortality prediction (area under the curve 0.789, P < 0.001). There was a stepwise increase in hospital mortality according to UO groups after controlling for SNAPPE-II and diuretic use. Using these UO ranges with pRIFLE improves its discriminatory capacity (area under the receiver operating characteristic curve 0.882 versus 0.693, P < 0.05). CONCLUSIONS: UO is a predictor of mortality in NICU. An association between a UO threshold < 1.5 mL/kg/h and mortality was observed, which is higher than the previously published pRIFLE thresholds. Adopting higher values of UO in pRIFLE criteria can improve its capacity to detect AKI severity in neonates.

Empirical relationships among oliguria, creatinine, mortality, and renal replacement therapy in the critically ill.

PURPOSE: The observation periods and thresholds of serum creatinine and urine output defined in the Acute Kidney Injury Network (AKIN) criteria were not empirically derived. By continuously varying creatinine/urine output thresholds as well as the observation period, we sought to investigate the empirical relationships among creatinine, oliguria, in-hospital mortality, and receipt of renal replacement therapy (RRT). METHODS: Using a high-resolution database (Multiparameter Intelligent Monitoring in Intensive Care II), we extracted data from 17,227 critically ill patients with an in-hospital mortality rate of 10.9 %. The 14,526 patients had urine output measurements. Various combinations of creatinine/urine output thresholds and observation periods were investigated by building multivariate logistic regression models for in-hospital mortality and RRT predictions. For creatinine, both absolute and percentage increases were analyzed. To visualize the dependence of adjusted mortality and RRT rate on creatinine, the urine output, and the observation period, we generated contour plots. RESULTS: Mortality risk was high when absolute creatinine increase was high regardless of the observation period, when percentage creatinine increase was high and the observation period was long, and when oliguria was sustained for a long period of time. Similar contour patterns emerged for RRT. The variability in predictive accuracy was small across different combinations of thresholds and observation periods. CONCLUSIONS: The contour plots presented in this article complement the AKIN definition. A multi-center study should confirm the universal validity of the results presented in this article.

Aminophylline improves urine flow rates but not survival in childhood oliguric/anuric acute kidney injury.

INTRODUCTION: Acute kidney injury (AKI) morbidity and mortality rates remain high. Variable AKI outcomes have been reported in association with aminophylline treatment. This study evaluated AKI outcome in a group of Nigerian children treated with aminophylline. METHODS: This is a retrospective study of AKI in children treated with (N=9) and without (N=8) aminophylline. Studied outcome indices comprised urine flow rate (UFR), duration of oliguria/anuria, progression through AKI stages, number of patients requiring dialysis and mortality. RESULTS: Mean ages for the control and aminophylline arms were 4.6±2.7 and 4.9±2.1 years (P=0.7), respectively. All patients progressed to stage-3 AKI. Baseline median UFRs in the aminophylline and control arms were similar (0.13 Vs 0.04 ml/kg/hour respectively, P=0.5). The median UFR was significantly higher on day-5 (0.8 Vs 0.1; P=0.03), day-6 (1.0 Vs 0.2; P=0.02), and day-7 (1.2 Vs 0.2; P=0.03) in the aminophylline than the control arm, respectively. Short duration of oliguria/anuria (≤ 6 days) was more frequently observed in aminophylline- treated patients compared to controls (77.8% Vs 25.0%; odds ratio 0.09; 95% CI: 0.01-0.89; P=0.04). Only the aminophylline group maintained steady serum creatinine levels. Four out of five patients in the control group were dialyzed compared to only one out of eight patients in the aminophylline group (odds ratio 0.16; 95% CI: 0.04-0.71; P=0.03). Mortality rates were similar in aminophylline- treated and control patients (33% Vs 25%; hazard ratio 0.8; 95% CI: 0.1-5.5; P=0.8). CONCLUSION: Aminophylline therapy was beneficial for patients with AKI in terms of improved UFR and reduced need for dialysis, but failed to impact positively on survival.

Oliguria: an earlier and accurate biomarker of acute kidney injury?

In the context of the critically ill patient, the onset of consistent oliguria is an ominous sign that requires immediate attention. Without intervention, intermittent oliguria may turn into persistent oliguria or evolve to acute kidney injury (AKI), with severe associated morbidity and mortality. Whether the addition of urine output to the serum creatinine criteria permits earlier and more specific detection of AKI is controversial, but current evidence supports its importance in early diagnosis and management.

Oliguria is an early predictor of higher mortality in critically ill patients.

Oliguria is a valuable marker of kidney function and a criterion for diagnosing and staging acute kidney injury (AKI). However, the utility of urine output as a specific metric for renal dysfunction is somewhat controversial. To study this issue further we tested whether urine output is a sensitive, specific, and early measure for diagnosing and staging AKI in 317 critically ill patients in a prospective observational study. Urine output was assessed every hour and serum creatinine every 12 to 24 h. The sensitivity and specificity of different definitions of oliguria for the diagnosis of AKI were compared with the Acute Kidney Injury Network serum creatinine criterion. The incidence of AKI increased from 24%, based solely on serum creatinine, to 52% by adding the urine output as a diagnostic criterion. Oliguric patients without a change in serum creatinine had an intensive care unit mortality rate (8.8%) significantly higher than patients without AKI (1.3%), and similar to oliguric patients with an increase in serum creatinine (10.4%). The diagnosis of AKI occurred earlier in oliguric than in non-oliguric patients. Oliguria of more than 12 h and oliguria of 3 or more episodes were associated with an increased mortality rate. Thus, urine output is a sensitive and early marker for AKI and is associated with adverse outcomes in intensive care unit patients.

Incidence and clinical outcomes of acute kidney injury requiring renal replacement therapy in Japan.

No population-based studies have described the prevalence of acute kidney injury (AKI) treated with renal replacement therapy (RRT) in Japan. This study prospectively examined the incidence of AKI requiring RRT by surveying 16 hospitals in Shizuoka prefecture from January to October 2006. The subjects comprised 242 patients treated with RRT during the observation period. The estimated incidence of AKI requiring RRT was 13.3 cases/100,000 persons/year in this area. Major contributing factors for AKI were sepsis (34%), cardiac shock (23%), and major surgery (12%). The in-hospital mortality rate was 47.1%, paralleling the increased number of insufficient organs. Oliguria was a risk factor for in-hospital mortality. These findings suggest that the incidence of AKI treated with RRT in Japan is comparable to those in Western countries, and the prognosis of AKI patients requiring RRT is also poor in Japanese patients.

A comparison of nonoliguric and oliguric severe acute kidney injury according to the risk injury failure loss end-stage (RIFLE) criteria.

BACKGROUND: Risk, Injury, Failure, Loss, and End-Stage (RIFLE) criteria have been proposed as a standard definition of acute kidney injury (AKI). The most severe form of AKI, class F AKI, can be defined by either severe oliguria or a 3-fold increase in serum creatinine concentrations. We hypothesized that the outcomes of patients with these 2 alternative criteria of severe AKI were different. METHODS: A prospective cohort study was conducted of all patients attaining RIFLE class F AKI during a 12-month period in a tertiary critical care facility. RESULTS: Among a total of 2,379 critical care admissions, 129 (5.4%) fulfilled the serum creatinine criteria without oliguria (RIFLE class F) and 99 (4.2%) fulfilled oliguric (RIFLE class F) AKI criteria. Patients with oliguric AKI suffered a more severe disease process than nonoliguric AKI. Oliguric AKI was associated with a significantly higher risk of requiring acute dialysis (70.7 vs. 22.4%, p = 0.001), long-term dialysis >90 days (15 vs. 1.9%, p = 0.006), and hospital mortality (adjusted hazard ratio 3.33, 95% confidence interval, p = 0.001) than nonoliguric AKI. CONCLUSIONS: Oliguric RIFLE class F AKI is a more severe form of AKI than nonoliguric class F AKI. These 2 forms of AKI should be considered separately when AKI is evaluated in a clinical trial.

Unspecific clinical presentation of bowel ischemia in the very old. Digitalis treatment--a reason for higher mortality?

BACKGROUND AND AIMS: Ischemic bowel disease predominantly affects the elderly (>65 years). Early diagnosis and treatment are of vital importance for the outcome. The vague symptoms of ischemic bowel disease entail a risk of delayed diagnosis, with a subsequent risk of increased mortality. The aims of this retrospective study were to identify symptoms and prodromes, to study factors associated with mortality in ischemic bowel disease, and to describe the influence of age, by comparing patients <80 and > or = 80 years. METHODS: The subjects of the study were 135 patients, mean age 77 years, admitted to Malmö University Hospital, Sweden, between 1987 and 1996, with a ICD-9 diagnosis of acute or chronic splanchnic ischemia. RESULTS: Patients aged 80 years or more presented with a significantly higher prevalence of confusion (29% vs 12%), hematemesis (57% vs 14%), vomiting (82% vs 65%) and dehydration (58% vs 36%) at admission compared with patients aged under 80 years, and presented a higher mortality (87% compared with 65%, p=0.003). The prevalence of digitalis treatment was 34%, which was high compared with other Swedish cohort studies. Digitalis, adjusted for age, congestive heart failure and atrial fibrillation, was associated with increased mortality (odds ratio 4.6, 95% CI 1.3-16.1). Prodromal signs predicted poor outcome, and were found in one out of 4 patients, without any age differences. CONCLUSIONS: Bowel ischemia in the very old is associated with a different clinical presentation and a higher mortality compared with younger patients. Digitalis treatment seems to be associated with increased mortality in ischemic bowel disease. Prodromal signs are prognostically unfavorable.

Prognosis of patients with acute renal failure requiring dialysis: results of a multicenter study.

Despite several decades of clinical experience, the mortality rate for patients with acute renal failure (ARF) requiring dialysis remains high, and the evaluation of the patients prognosis has been difficult. To date, the Acute Physiology and Chronic Health Evaluation II (APACHE II) scoring system has been used more frequently for prediction in studies of ARF than any other scoring system, but has not been prospectively validated in controlled multicenter studies of this entity. In a multicenter, prospective, controlled trial evaluating the use of biocompatible hemodialysis membranes (BCMs) in patients with ARF, we evaluated the extent to which the APACHE II scoring system, based on the physiological variables in the 24 hours before the onset of dialysis and the presence or absence of oliguria, is predictive of outcome. Analysis of survival and recovery of renal function for the 153 patients treated in this study show that APACHE II scores are predictive both of survival and recovery of renal function, whether analyzed separately by type of dialysis membrane used (BCM or bioincompatible [BICM]) or for both groups combined (all P < 0.01). There was no evidence of a significant center effect or interaction of APACHE II score with dialysis membrane in our study. After adjusting for the APACHE II score, there was a positive effect of the BCM on both probability of survival (P < 0.05) and recovery of renal function (P < 0.01). In patients dialyzed with BCMs, oliguria at onset of dialysis had an adverse effect on both survival and recovery of renal function (both P < 0.01). Receiver operator curves (ROCs) using APACHE II score and the use of BCMs in nonoliguric patients yielded a statistically significant improvement versus the use of APACHE II score alone in the area under the curve (AUC) for survival (0.747 to 0.801; P < 0.05) and recovery of renal function (0.712 to 0.775; P < 0.05). We conclude that the use of the APACHE II score determined at the time of initiation of dialysis for patients with ARF is a statistically significant predictor of patient survival and recovery of renal function. The use of the APACHE II score measured at the time of dialysis initiation, especially when modified by the presence or absence of oliguria, should help in predicting outcome when evaluating interventions for patients with ARF.

A simple prognostic index for patients with acute renal failure requiring dialysis. French Multicentric Prospective Study on Furosemide in Acute Renal Failure Requiring Dialysis.

The probability of death in patients with acute renal failure (ARF) remains high. A valid prognostic index available on patient admission and during follow-up could be helpful for decision making. In this study, 94 ARF patients requiring dialysis (not responding to a previous single dose of furosemide 15 mg/kg) were included. On admission, patients were classified according to a Simplified Acute Physiology Score (SAPS) of < or = 15 or > 15. The prognostic value of 11 risk factors was analyzed. Only 6 in 11 risk factors were significant by univariate analysis: age (> 55 years) (0.02), mechanical ventilation (0.008), oliguria (< 500 mL/day during the first 5 days) (0.02), sepsis (0.001), shock (0.007), and serum bilirubin (> 30 mumol) (0.001). Only oliguria and sepsis were significant risk factors by multivariate analysis. Overall mortality rate was 41%. Mortality rate was higher in patients with SAPS > 15 (65%) than in those with SAPS < or = 15 (22%) (0.001). Patients with > 3 risk factors showed a significantly higher mortality rate than patients with < 3 risk factors (all patients disregarding SAPS) (0.001). Considering the worst combination of risk factors by univariate analysis, mortality prediction was 56% if oliguria, sepsis, and high serum bilirubin were present, and reached 80% if an older age was added (four risk factors). Ventilation increased probability of death to 92% (five risk factors). If all six risk factors were present, the probability rose to 96%. The corresponding observed mortality rate was 32% for three risk factors, 70% for four, 81% for five and 100% for six risk factors. The results suggest that probability of death in ARF requiring dialysis can be correctly estimated when more than three significant risk factors are present. If confirmed, they could avoid using a more complex severity scoring system in patients with ARF requiring dialysis.

Acute renal failure in a teaching hospital.

This was a retrospective study of the clinical course of 164 adult inpatients with acute renal failure (ARF) at the Hospital of the University of Science Malaysia admitted from June 1986 to May 1990. The mean age was 49.8 +/- 17.2 years. 33.5%, 54.9% and 11.6% were surgical, medical and obstetrical patients respectively. Obstructive uropathy, poor cardiac output or decrease in intravascular volume and infection accounted for more than 67% of the cases. Acute renal failure was present at admission in 113 (69%) patients. The majority of the patients (80%) had nonoliguric acute renal failure with daily output of urine of more than 400 ml. Compared with nonoliguric patients, oliguric patients had higher mortality (56.3% vs 18.9%, p < 0.01), and needed dialysis more frequently (43.8% vs 12.9%, p < 0.01). Early recognition of acute renal failure, improvement in early treatment of renal stones and discerning use of nephrotoxic drugs could result in decrease in incidence and severity of renal failure.

The outcome of critically ill elderly patients with severe acute renal failure treated by continuous hemodiafiltration.

OBJECTIVES: To study the outcome of critically ill elderly patients with severe acute renal failure managed by continuous hemodiafiltration. DESIGN: Prospective study. SETTING: Intensive Care Unit of tertiary institution PATIENTS: Seventy-two consecutive critically ill patients of 65 years or older admitted to the ICU with severe acute renal failure. Seventy similar control patients of age < 65 years. INTERVENTION: Treatment of all patients with continuous hemodiafiltration. MEASUREMENTS AND MAIN RESULTS: Safety and effectiveness of therapy were assessed. Main outcome measures were duration of oliguria, of ICU stay, and hospital stay for survivors, and survival to ICU discharge and to hospital discharge. Mean APACHE II score on admission was 29.8 (95% confidence interval: 28.5 to 31.1) and mean organ failure score prior to initiation of continuous hemodiafiltration was 3.9 (95% confidence interval: 3.6 to 4.2). Sepsis was present in 51 cases (70.8%) and bacteremia or fungemia in 24 (33.3%). Fifty-three (73.6%) required mechanical ventilation for > 3 days. Vasopressor drugs were used in 65 (90.2%). Continuous hemodiafiltration controlled azotemia in all patients and was only associated with minor complications. Thirty-four patients (47.2%) survived to ICU discharge and 30 (41.6%) to hospital discharge. Among survivors, duration of oliguria was 11.6 days (95% confidence interval: 9.1 to 14.1), mean duration of ICU stay 8.6 days (95% confidence interval: 6.1 to 11.) and mean duration of hospital stay 33.1 days (95% confidence interval: 28.8 to 37.4). No statistically significant difference in survival was found when these patients were compared to a control group of similar but younger patients who also received ICU care and continuous hemodiafiltration for the treatment of severe acute renal failure. CONCLUSIONS: A greater than 40% survival was achieved in critically ill elderly patients with severe acute renal failure by the use of continuous hemodiafiltration. These patients had an in hospital survival comparable to that of younger patients. These findings support an aggressive renal replacement approach in such patients and suggest that continuous hemodiafiltration may be ideally suited to their management.