Epidemiology of renal recovery after acute renal failure

Renal Recovery in Critically Ill Adult Patients Treated with Veno-Venous Or Veno-Arterial Extra Corporeal Membrane Oxygenation: a Retrospective Cohort Analysis

Introduction

Patients on extracorporeal membrane oxygenator (ECMO) therapy are critically ill and often develop acute kidney injury (AKI) during hospitalisation. Little is known about the association of exposure to and the effect of the type of ECMO and extent of renal recovery after AKI development.

Aim of the study

In patients who developed AKI, renal recovery was characterised as complete, partial or dialysis-dependent at the time of hospital discharge in both the Veno-Arterial (VA) and Veno-Venous (VV) ECMO treatment groups.

Material and methods

The study consisted of a single-centre retrospective cohort that includes all adult patients (n=125) who received ECMO treatment at a tertiary academic medical centre between 2015 to 2019. Data on demographics, type of ECMO circuit, comorbidities, exposure to nephrotoxic factors and receipt of renal replacement therapy (RRT) were collected as a part of the analysis. Acute Kidney Injury Network (AKIN) criteria were used for the diagnosis and classification of AKI. Group differences were assessed using Fisher’s exact tests for categorical data and independent t-tests for continuous outcomes.

Results

Sixty-four patients received VA ECMO, and 58 received VV ECMO. AKI developed in 58(91%) in the VA ECMO group and 51 (88%) in the VV ECMO group (p=0.77). RRT was prescribed in significantly higher numbers in the VV group 38 (75%) compared to the VA group 27 (47%) (p=0.0035). At the time of discharge, AKI recovery rate in the VA group consisted of 15 (26%) complete recovery and 5 (9%) partial recovery; 1 (2%) remained dialysis-dependent. In the VV group, 22 (43%) had complete recovery (p=0.07), 3(6%) had partial recovery (p=0.72), and 1 (2%) was dialysis-dependent (p>0.99). In-hospital mortality was 64% in the VA group and 49% in the VV group (p=0.13).

Conclusions

Renal outcomes in critically ill patients who develop AKI are not associated with the type of ECMO used. This serves as preliminary data for future studies in the area.

Predictors and Outcomes of Dengue-Associated Acute Kidney Injury

Dengue viral infections present with a wide clinical spectrum ranging from asymptomatic to severe manifestations with organ involvement. The term "expanded dengue syndrome" has been commonly used to illustrate the unusual or atypical manifestations; acute kidney injury (AKI) is one of the atypical manifestations of this syndrome. The use of heterogeneous criteria to determine the presence of AKI in dengue patients due to the vast diversity in populations led to difficulties in assessing the true incidence of dengue-associated AKI. This review presents a variable, but often high, frequency of dengue-associated AKI among vastly diverse populations with various disease severities. Dengue-associated AKI is not an uncommon complication, and its importance has often been neglected during the management of dengue patients. The risk factors and certain clinical and laboratory findings commonly reported among dengue patients with AKI should be considered to support a timely diagnosis and case management. This review highlights the need for clinicians to be aware of dengue-associated AKI to reduce the morbidity and mortality associated with this common and important tropical disease.

Long-term consequences of acute kidney injury: a narrative review

The incidence of acute kidney injury (AKI) has increased in the past decades. AKI complicates up to 15% of hospitalizations and can reach up to 50-60% in critically ill patients. Besides the short-term impact of AKI in patient outcomes, several studies report the association between AKI and adverse long-term outcomes, such as recurrent AKI episodes in 25-30% of cases, hospital re-admissions in up to 40% of patients, an increased risk of cardiovascular events, an increased risk of progression of chronic kidney disease (CKD) after AKI and a significantly increased long-term mortality. Despite the long-term impact of AKI, there are neither established guidelines on the follow-up care of AKI patients, nor treatment strategies to reduce the incidence of sequelae after AKI. Only a minority of patients have been referred to nephrology post-discharge care, despite the evidence of improved outcomes associated with nephrology referral by addressing cardiovascular risk and risk of progression to CKD. Indeed, AKI survivors should have specialized nephrology follow-up to assess kidney function after AKI, perform medication reconciliation, educate patients on nephrotoxic avoidance and implement strategies to prevent CKD progression. The authors provide a comprehensive review of the transition from AKI to CKD, analyse the current evidence on the long-term outcomes of AKI and describe predisposing risk factors, highlight the importance of follow-up care in these patients and describe the current therapeutic strategies which are being investigated on their impact in improving patient outcomes.

Mortality and Recovery Associated with Kidney Failure due to Acute Kidney Injury

BACKGROUND AND OBJECTIVES

AKI requiring dialysis is a contributor to the growing burden of kidney failure, yet little is known about the frequency and patterns of recovery of AKI and its effect on outcomes in patients on incident dialysis.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

Using the US Renal Data System, we evaluated a cohort of 1,045,540 patients on incident dialysis from January 1, 2005 to December 31, 2014, retrospectively. We examined the association of kidney failure due to AKI with the outcome of all-cause mortality and the associations of sex and race with kidney recovery.

RESULTS

Mean age was 63±15 years, and 32,598 (3%) patients on incident dialysis had kidney failure due to AKI. Compared with kidney failure due to diabetes mellitus, kidney failure attributed to AKI was associated with a higher mortality in the first 0-3 months following dialysis initiation (adjusted hazard ratio, 1.28; 95% confidence interval, 1.24 to 1.32) and 3-6 months (adjusted hazard ratio, 1.16; 95% confidence interval, 1.11 to 1.20). Of the patients with kidney failure due to AKI, 11,498 (35%) eventually recovered their kidney function, 95% of those within 12 months. Women had a lower likelihood of kidney recovery than men (adjusted hazard ratio, 0.86; 95% confidence interval, 0.83 to 0.90). Compared with whites, blacks (adjusted hazard ratio, 0.68; 95% confidence interval, 0.64 to 0.72), Asians (adjusted hazard ratio, 0.82; 95% confidence interval, 0.69 to 0.96), Hispanics (adjusted hazard ratio, 0.82; 95% confidence interval, 0.76 to 0.89), and Native Americans (adjusted hazard ratio, 0.72; 95% confidence interval, 0.54 to 0.95) had lower likelihoods of kidney recovery.

CONCLUSIONS

Kidney failure due to AKI confers a higher risk of mortality in the first 6 months compared with kidney failure due to diabetes or other causes. Recovery within 12 months is common, although less so among women than men and among black, Asian, Hispanic, and Native American patients than white patients.

Diagnostics, Risk Factors, Treatment and Outcomes of Acute Kidney Injury in a New Paradigm

Acute kidney injury (AKI) is a common clinical condition among patients admitted in the hospitals. The condition is associated with both increased short-term and long-term mortality. With the development of a standardized definition for AKI and the acknowledgment of the impact of AKI on patient outcomes, there has been increased recognition of AKI. Two advances from past decades, the usage of computer decision support and the discovery of AKI biomarkers, have the ability to advance the diagnostic method to and further management of AKI. The increasingly widespread use of electronic health records across hospitals has substantially increased the amount of data available to investigators and has shown promise in advancing AKI research. In addition, progress in the finding and validation of different forms of biomarkers of AKI within diversified clinical environments and has provided information and insight on testing, etiology and further prognosis of AKI, leading to future of precision and personalized approach to AKI management. In this this article, we discussed the changing paradigms in AKI: from mechanisms to diagnostics, risk factors, and management of AKI.

The Association of Angiogenesis Markers With Acute Kidney Injury and Mortality After Cardiac Surgery

RATIONALE & OBJECTIVE

The process of angiogenesis after kidney injury may determine recovery and long-term outcomes. We evaluated the association of angiogenesis markers with acute kidney injury (AKI) and mortality after cardiac surgery.

STUDY DESIGN

Prospective cohort.

SETTING & PARTICIPANTS

1,444 adults undergoing cardiac surgery in the TRIBE-AKI (Translational Research Investigating Biomarker Endpoints for Acute Kidney Injury) cohort.

EXPOSURES

Plasma concentrations of 2 proangiogenic markers (vascular endothelial growth factor A [VEGF] and placental growth factor [PGF]) and 1 antiangiogenic marker (soluble VEGF receptor 1 [VEGFR1]), measured pre- and postoperatively within 6 hours after surgery.

OUTCOMES

AKI, long AKI duration (≥7 days), and 1-year all-cause mortality.

ANALYTICAL APPROACH

Multivariable logistic regression.

RESULTS

Following cardiac surgery, plasma VEGF concentrations decreased 2-fold, and PGF and VEGFR1 concentrations increased 1.5- and 8-fold, respectively. There were no meaningful associations of preoperative concentrations of angiogenic markers with outcomes of AKI and mortality. Higher postoperative VEGF and PGF concentrations were independently associated with lower odds of AKI (adjusted ORs of 0.89 [95% CI, 0.82-0.98] and 0.69 [95% CI, 0.55-0.87], respectively), long AKI duration (0.65 [95% CI, 0.49-0.87] and 0.48 [95% CI, 0.28-0.82], respectively), and mortality (0.74 [95% CI, 0.62-0.89] and 0.46 [95% CI, 0.31-0.68], respectively). In contrast, higher postoperative VEGFR1 concentrations were independently associated with higher odds of AKI (1.56; 95% CI, 1.31-1.87), long AKI duration (1.75; 95% CI, 1.09-2.82), and mortality (2.28; 95% CI, 1.61-3.22).

LIMITATIONS

Angiogenesis markers were not measured after hospital discharge, so we were unable to determine long-term trajectories of angiogenesis marker levels during recovery and follow-up.

CONCLUSIONS

Higher levels of postoperative proangiogenic markers, VEGF and PGF, were associated with lower AKI and mortality risk, whereas higher postoperative antiangiogenic VEGFR1 levels were associated with higher risk for AKI and mortality.

Short-term renal outcomes following acute kidney injury among dengue patients: A follow-up analysis from large prospective cohort

BACKGROUND

Despite myriad improvements in the care of dengue patients, acute kidney injury (AKI) remained least appreciated intricacy of dengue infection. Exiting literature does not provide any information on renal outcomes among dengue patients surviving an episode of AKI.

METHODS

Dengue patients who developed AKI were followed up for post-discharge period of three months and renal recovery was assessed by using recovery criteria based on different thresholds of serum creatinine (SCr) and estimated glomerular filtration rates (eGFR).

RESULTS

Out of the 526 dengue participants, AKI was developed in 72 (13.7%) patients. Renal recovery was assessed among AKI survivors (n = 71). The use of less (±50% recovery to baseline) to more (±5% recovery to baseline) stringent definitions of renal recovery yielded recovery rates from 88.9% to 2.8% by SCr and 94.4% to 5.6% by eGFR, as renal function biomarkers. At the end of study, eight patients had AKI with AKIN-II (n = 7) and AKIN-III (n = 1). Approximately 50% patients (n = 36/71) with AKI had eGFR primitive to CKD stage 2, while 18.3% (n = 13/71) and 4.2% (n = 3/71) patients had eGFR corresponding to advanced stages of CKD (stage 3 & 4). Factors such as renal insufficiencies at hospital discharge, multiple organ involvements, advance age, female gender and diabetes mellitus were associated with poor renal outcomes.

CONCLUSIONS

We conclude that dengue patients with AKI portend unsatisfactory short-term renal outcomes and deserve a careful and longer follow-up, especially under nephrology care.

Points of Concern in Post Acute Kidney Injury Management

The incidence of acute kidney injury (AKI) will in the future remain high, partly due to an increase in comorbidities and other AKI favoring factors such as the rise in high-risk diagnostic and therapeutic interventions. AKI has emerged as a major public health concern with high human and financial costs. It has recently been demonstrated that patients surviving an AKI episode show increased all-cause mortality, chronic kidney disease (CKD), ESRD, cardiovascular events, and reduced quality of life. Although it is important to acknowledge that, after an AKI episode, the risk of dying by far exceeds the risk of developing incident or progressive CKD and/or entering a maintenance renal replacement therapy (RRT) program, currently only a minority of patients are referred for renal follow-up, even after AKI-requiring RRT. On the other hand, renal follow-up for all AKI survivors might not be necessary and would represent an overwhelming work load for the health care system. There are at present no clear guidelines on which patients should be referred and on the elements of post AKI care that may improve non-renal and renal outcomes. In this review, we discuss several points of concern in post-AKI management and propose an algorithm on post-AKI care, mainly based on the renal recovery pattern at discharge from the hospital. Potential opportunities to improve care include appropriate risk stratification, close monitoring of kidney function, management of CKD complications, blood pressure control, medication reconciliation, and education of patients and non-nephrologists on AKI and its downstream complications.

The association between renal recovery after acute kidney injury and long-term mortality after transcatheter aortic valve replacement

Background

This study aimed to examine the association between renal recovery status at hospital discharge after acute kidney injury (AKI) and long-term mortality following transcatheter aortic valve replacement (TAVR).

Methods

We screened all adult patients who survived to hospital discharge after TAVR for aortic stenosis at a quaternary referral medical center from January 1, 2008, through June 30, 2014. An AKI was defined as an increase in serum creatinine level of 0.3 mg/dL or a relative increase of 50% from baseline. Renal outcome at the time of discharge was evaluated by comparing the discharge serum creatinine level to the baseline level. Complete renal recovery was defined as no AKI at discharge, whereas partial renal recovery was defined as AKI without a need for renal replacement therapy at discharge. No renal recovery was defined as a need for renal replacement therapy at discharge.

Results

The study included 374 patients. Ninty-eight (26%) patients developed AKI during hospitalization: 55 (56%) had complete recovery; 39 (40%), partial recovery; and 4 (4%), no recovery. AKI development was significantly associated with increased risk of 2-year mortality (hazard ratio [HR], 2.20 [95% CI, 1.37–3.49]). For patients with AKI, the 2-year mortality rate for complete recovery was 34%; for partial recovery, 43%; and for no recovery, 75%; compared with 20% for patients without AKI (P < .001). In adjusted analysis, complete recovery (HR, 1.87 [95% CI, 1.03–3.23]); partial recovery (HR, 2.65 [95% CI, 1.40–4.71]) and no recovery (HR, 10.95 [95% CI, 2.59–31.49]) after AKI vs no AKI were significantly associated with increased risk of 2-year mortality.

Conclusion

The mortality rate increased for all patients with AKI undergoing TAVR. A reverse correlation existed for progressively higher risk of death and the extent of AKI recovery.

Renal recovery after acute kidney injury

Acute kidney injury (AKI) is a frequent complication of critical illness and carries a significant risk of short- and long-term mortality, chronic kidney disease (CKD) and cardiovascular events. The degree of renal recovery from AKI may substantially affect these long-term endpoints. Therefore maximising recovery of renal function should be the goal of any AKI prevention and treatment strategy. Defining renal recovery is far from straightforward due in part to the limitations of the tests available to assess renal function. Here, we discuss common pitfalls in the evaluation of renal recovery and provide suggestions for improved assessment in the future. We review the epidemiology of renal recovery and of the association between AKI and the development of CKD. Finally, we stress the importance of post-discharge follow-up of AKI patients and make suggestions for its incorporation into clinical practice. Summary key points are that risk factors for non-recovery of AKI are age, CKD, comorbidity, higher severity of AKI and acute disease scores. Second, AKI and CKD are mutually related and seem to have a common denominator. Third, despite its limitations full recovery of AKI may best be defined as the absence of AKI criteria, and partial recovery as a fall in AKI stage. Fourth, after an episode of AKI, serial follow-up measurements of serum creatinine and proteinuria are warranted to diagnose renal impairment and prevent further progression. Measures to promote recovery are similar to those preventing renal harm. Specific interventions promoting repair are still experimental.

Recovery from AKI in the critically ill: potential confounders in the evaluation

PURPOSE

Studies on recovery from acute kidney injury (AKI) in ICU patients yield variable results. We assessed the impact of different recovery definitions, of different exclusion criteria, and of imputing missing baseline creatinine on AKI recovery in a heterogeneous ICU population.

METHODS

Secondary analysis of the EPaNIC database. Recovery of kidney function in patients who developed AKI in ICU was assessed at hospital discharge. We studied recovery rates of different AKI stages with different definitions of recovery after inclusion or exclusion of non-survivors and in patients with or without chronic kidney disease (CKD). In addition, the impact of imputing missing baseline creatinine was investigated.

RESULTS

A total of 1310 AKI patients were studied of which 977 were discharged alive from hospital. Rate of complete recovery (absence of KDIGO criteria) was markedly higher in survivors than in all AKI patients (79.5 vs 67.0%), especially for more severe forms of AKI. For patients with CKD, only the need for renal replacement therapy worsened kidney outcome as compared with no-CKD patients. Using stricter definitions of complete recovery significantly reduced its occurrence. New or worsening CKD occurred in 30% of AKI survivors. In no-CKD patients with available baseline creatinine, using an imputed baseline did not affect recovery. Patients with unavailable baseline creatinine were different from those with known baseline and revealed different recovery patterns.

CONCLUSION

These results indicate the need for rigorous description of AKI severity, the included population, definitions, and baseline creatinine handling in reports on AKI recovery.

Predictors of outpatient kidney function recovery among patients who initiate hemodialysis in the hospital

BACKGROUND

Recent policy clarifications by the Centers for Medicare & Medicaid Services have changed access to outpatient dialysis care at end-stage renal disease (ESRD) facilities for individuals with acute kidney injury in the United States. Tools to predict "ESRD" and "acute" status in terms of kidney function recovery among patients who previously initiated dialysis therapy in the hospital could help inform patient management decisions.

STUDY DESIGN

Historical cohort study.

SETTING & PARTICIPANTS

Incident hemodialysis patients in the Mayo Clinic Health System who initiated in-hospital renal replacement therapy (RRT) and continued outpatient dialysis following hospital dismissal (2006 through 2009).

PREDICTOR

Baseline estimated glomerular filtration rate (eGFR), acute tubular necrosis from sepsis or surgery, heart failure, intensive care unit, and dialysis access.

OUTCOMES

Kidney function recovery defined as sufficient kidney function for outpatient hemodialysis therapy discontinuation.

RESULTS

Cohort consisted of 281 patients with a mean age of 64 years, 63% men, 45% with heart failure, and baseline eGFR≥30mL/min/1.73m(2) in 46%. During a median of 8 months, 52 (19%) recovered, most (94%) within 6 months. Higher baseline eGFR (HR per 10-mL/min/1.73m(2) increase eGFR, 1.27; 95% CI, 1.16-1.39; P<0.001), acute tubular necrosis from sepsis or surgery (HR, 3.34; 95% CI, 1.83-6.24; P<0.001), and heart failure (HR, 0.40; 95% CI, 0.19-0.78, P=0.007) were independent predictors of recovery within 6 months, whereas first RRT in the intensive care unit and catheter dialysis access were not. There was a positive interaction between absence of heart failure and eGFR≥30mL/min/1.73m(2) for predicting kidney function recovery (P<0.001).

LIMITATIONS

Sample size.

CONCLUSIONS

Kidney function recovery in the outpatient hemodialysis unit following in-hospital RRT initiation is not rare. As expected, higher baseline eGFR is an important determinant of recovery. However, patients with heart failure are less likely to recover even with a higher baseline eGFR. Consideration of these factors at hospital discharge informs decisions on ESRD status designation and long-term hemodialysis care.

The impact of acute kidney injury on the long-term risk of stroke

BACKGROUND

The incidence of acute kidney injury (AKI) requiring dialysis in hospitalized patients is increasing; however, information on the long-term incidence of stroke in patients surviving to discharge after recovering from AKI after dialysis has not been reported.

METHODS AND RESULTS

Patients that survived after recovery from dialysis-requiring AKI during index hospitalizations from 1999 to 2008 were identified in nationwide administrative registries. The risk of de novo stroke and death were analyzed with time-varying Cox proportional hazard models. The results were validated by a critical care database. We enrolled 4315 patients in the AKI-recovery group (men, 57.7%; mean age, 62.8±16.8 years) and matched 4315 control subjects as the non-AKI group by propensity scores. After a median follow-up period of 3.36 years, the incident stroke rate was 15.6 per 1000 person-years. The AKI-recovery group had higher risk (hazard ratio: 1.25; P=0.037) and higher severity of stroke events than the non-AKI group, regardless of progression to subsequent chronic kidney disease. The rate of incident stroke was not statistically different in those with diabetes alone (without AKI) and in those with AKI alone (without diabetes) after hospital discharge (P=0.086). Furthermore, the risk of mortality in the AKI-recovery group was higher than in the non-AKI group (hazard ratio: 2.4; P<0.001).

CONCLUSIONS

The patients who recovered from AKI had a higher incidence of developing incident stroke and mortality than the patients without AKI, and the impact was similar to diabetes. Our results suggest that a public health initiative is needed to enhance postdischarge follow-up of renal function and to control the subsequent incidence of stroke among patients who recover from AKI after dialysis.

Long-term follow-up of patients after acute kidney injury: patterns of renal functional recovery

BACKGROUND AND OBJECTIVES

Patients who survive acute kidney injury (AKI), especially those with partial renal recovery, present a higher long-term mortality risk. However, there is no consensus on the best time to assess renal function after an episode of acute kidney injury or agreement on the definition of renal recovery. In addition, only limited data regarding predictors of recovery are available.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

From 1984 to 2009, 84 adult survivors of acute kidney injury were followed by the same nephrologist (RCRMA) for a median time of 4.1 years. Patients were seen at least once each year after discharge until end stage renal disease (ESRD) or death. In each consultation serum creatinine was measured and glomerular filtration rate estimated. Renal recovery was defined as a glomerular filtration rate value ≥60 mL/min/1.73 m2. A multiple logistic regression was performed to evaluate factors independently associated with renal recovery.

RESULTS

The median length of follow-up was 50 months (30-90 months). All patients had stabilized their glomerular filtration rates by 18 months and 83% of them stabilized earlier: up to 12 months. Renal recovery occurred in 16 patients (19%) at discharge and in 54 (64%) by 18 months. Six patients died and four patients progressed to ESRD during the follow up period. Age (OR 1.09, p<0.0001) and serum creatinine at hospital discharge (OR 2.48, p = 0.007) were independent factors associated with non renal recovery. The acute kidney injury severity, evaluated by peak serum creatinine and need for dialysis, was not associated with non renal recovery.

CONCLUSIONS

Renal recovery must be evaluated no earlier than one year after an acute kidney injury episode. Nephrology referral should be considered mainly for older patients and those with elevated serum creatinine at hospital discharge.

Predicting restoration of kidney function during CRRT-free intervals

Background

Renal failure is common in critically ill patients and frequently requires continuous renal replacement therapy (CRRT). CRRT is discontinued at regular intervals for routine changes of the disposable equipment or for replacing clogged filter membrane assemblies. The present study was conducted to determine if the necessity to continue CRRT could be predicted during the CRRT-free period.

Materials and methods

In the period from 2003 to 2006, 605 patients were treated with CRRT in our ICU. A total of 222 patients with 448 CRRT-free intervals had complete data sets and were used for analysis. Of the total CRRT-free periods, 225 served as an evaluation group. Twenty-nine parameters with an assumed influence on kidney function were analyzed with regard to their potential to predict the restoration of kidney function during the CRRT-free interval. Using univariate analysis and logistic regression, a prospective index was developed and validated in the remaining 223 CRRT-free periods to establish its prognostic strength.

Results

Only three parameters showed an independent influence on the restoration of kidney function during CRRT-free intervals: the number of previous CRRT cycles (medians in the two outcome groups: 1 vs. 2), the "Sequential Organ Failure Assessment"-score (means in the two outcome groups: 8.3 vs. 9.2) and urinary output after the cessation of CRRT (medians in two outcome groups: 66 ml/h vs. 10 ml/h). The prognostic index, which was calculated from these three variables, showed a satisfactory potential to predict the kidney function during the CRRT-free intervals; Receiver operating characteristic (ROC) analysis revealed an area under the curve of 0.798.

Conclusion

Restoration of kidney function during CRRT-free periods can be predicted with an index calculated from three variables. Prospective trials in other hospitals must clarify whether our results are generally transferable to other patient populations.

Acute renal replacement therapy in pediatrics

Acute kidney injury (AKI) independently increases morbidity and mortality in children admitted to the hospital. Renal replacement therapy (RRT) is an essential therapy in the setting of AKI and fluid overload. The decision to initiate RRT is complex and often complicated by concerns related to patient hemodynamic and thermodynamic instability. The choice of which RRT modality to use depends on numerous criteria that are both patient and treatment center specific. Surprisingly, despite decades of use, no randomized, controlled trial study involving RRT in pediatrics has been performed. Because of these factors, clear-cut consensus is lacking regarding key questions surrounding RRT delivery. In this paper, we will summarize existing data concerning RRT use in children. We discuss the major modalities and the data-driven specifics of each, followed by controversies in RRT. As no standard of care is in widespread use for RRT in AKI or in multiorgan disease, we conclude in this paper that prospective studies of RRT are needed to identify best practice guidelines.

Organ failure in sepsis

The development of organ failure determines the course and prognosis of the septic patient. Although several successful clinical trials in recent years have raised the enthusiasm of intensivists, severe sepsis and septic shock still have an increasing incidence with more or less unchanged mortality. Recent sepsis research, including progress made in definitions, epidemiology, pathophysiology, diagnosis, standard and adjunctive therapy, and experimental approaches, is encouraging. This includes genomic information for stratifying subgroups of patients, a broader field of laboratory diagnostics due to clinical studies, and basic research on the cellular mechanisms of inflammation and organ dysfunction. Furthermore, new findings in pathogenesis and therapeutic approaches to organ failure merit attention. In this review, state-of-the-art publications are presented to elucidate the possible impact of sepsis-induced organ failure on clinical routine.

Acute kidney injury in the elderly population

The elderly population is more prone to acute kidney injury (AKI) than younger populations. Older patients have less renal reserve because of reduced glomerular filtration rates due to anatomic/functional changes, and concomitant diseases such as hypertension, diabetes, atherosclerosis, heart failure, ischemic renal disease, and obstructive uropathy. The risk of AKI may also increase as a result of aggressive diagnostic and therapeutic procedures, which include medical agents, radiology, and surgical intervention. AKI in the elderly has a multifactorial physiopathology due to different etiologies. Studies that have specifically compared prognosis of AKI in elderly versus young over the recent years suggest that age is a predictor of long-term outcome. In most cases, the treatment of AKI is similar for all age groups. The majority of critically ill patients with AKI will eventually need renal replacement therapy (RRT). The influence of RRT on renal outcome remains a subject of intense investigation and debate. Avoiding situations that could damage the kidney is an important strategy to prevent AKI development in the elderly, besides medical and interventional therapeutics.

Management of acute renal failure in the elderly patient: a clinician's guide

Numerous anatomical and functional changes occurring in the aging kidney lead to reduced glomerular filtration rate, lower renal blood flow and impaired renal autoregulation. The elderly are especially vulnerable to the development of renal dysfunction and in this population acute renal failure (ARF) is a common problem. ARF is often iatrogenic and multifactorial; common iatrogenic combinations include pre-existing renal dysfunction and exposure to nephrotoxins such as radiocontrast agents or aminoglycosides, use of NSAIDs in patients with congestive cardiac failure and use of ACE inhibitors and diuretics in patients with underlying atherosclerotic renal artery stenosis. The aetiology of ARF is classically grouped into three categories: prerenal, intrinsic and postrenal. Prerenal ARF is the second most common cause of ARF in the elderly, accounting for nearly one-third of all hospitalized cases. Common causes can be grouped into true volume depletion (e.g. decreased fluid intake), decreased effective blood volume (e.g. systemic vasodilation) and haemodynamic (e.g. renal artery stenosis, NSAID use). Acute tubular necrosis (ATN) is the most common cause of intrinsic ARF and is responsible for over 50% of ARF in hospitalized patients, and up to 76% of cases in patients in intensive care units. ATN usually occurs after an acute ischaemic or toxic event. The pathogenesis of ATN involves an interplay of processes that include endothelial injury, microvascular flow disruption, tubular hypoxia, dysfunction and apoptosis, tubular obstruction and trans-tubular back-leak. Vasculitis causing ARF should not be missed as this condition is potentially life threatening. The likelihood of a postrenal cause for ARF increases with age. Benign prostatic hypertrophy, prostatic carcinoma and pelvic malignancies are all important causes. Early identification of ARF secondary to obstruction with renal imaging is essential, and complete or partial renal recovery usually ensues following relief of the obstruction.A comprehensive medical and drug history and physical examination are all invaluable. Particular attention should be paid to the fluid status of the patient (skin turgor, jugular venous pressure, lying and standing blood pressure, urine output). Urinalysis should be performed to detect evidence of proteinuria and haematuria, which will aid diagnosis. Fractional excretion of sodium and urine osmolality may be measured but the widespread use of diuretics in the elderly gives rise to unreliable results. Renal imaging, usually ultrasound scanning, is routinely performed for assessment of renal size and to exclude urinary obstruction. In some cases, renal biopsy is necessary to provide specific diagnostic information. The general principles of managing ARF include treatment of life-threatening features such as shock, respiratory failure, hyperkalaemia, pulmonary oedema, metabolic acidosis and sepsis; stopping and avoiding administration of nephrotoxins; optimization of haemodynamic and fluid status; adjustment of drug dosage appropriate to glomerular filtration rate; early nutritional support; and early referral to nephrologists for diagnosis of ARF cause, timely initiation of dialysis and initiation of specific treatment. The treatment of prerenal and ATN ARF is largely supportive with little evidence of benefit from current pharmacological therapies. Despite advances in critical care medicine and renal replacement therapy, the mortality of ARF has not changed significantly over the last 40 years, with current mortality rates being up to 75%.

Risk factors of early redialysis after weaning from postoperative acute renal replacement therapy

OBJECTIVE

The aim of this study was to identify risk factors for redialysis in postoperative patients with acute renal failure (ARF) who had previously been weaned from acute dialysis. Although recovery of renal function is anticipated in patients with ARF, no data have been reported on successful weaning from acute dialysis.

DESIGN AND SETTING

Retrospective observational case-control study in a 64-bed surgical ICU.

PATIENTS AND METHODS

Success in discontinuing dialysis was defined as cessation from dialysis for at least 30 days. A total of 304 postoperative patients who underwent acute renal replacement therapy in a surgical ICU between July 2002 and April 2005 were included. SOFA score biochemical data and renal function parameters were assessed on the day after the last session of renal replacement therapy, designated as day 0 (D0).

RESULTS

We could wean 94 patients (30.9%) from acute dialysis for more than 5 days, and 64 of these (21.1%) were successfully weaned for at least 30days. The independent predictors for resuming dialysis within 30 days were: (a) longer duration of dialysis (OR 1.06), (b) higher SOFA score on D0 (OR 1.44), (c) oliguria (urine output <100cc/8h; OR 4.17) on D1, and (d) age over 65 years (OR 6.35). The area under the ROC curve was 0.880. Two-way analysis of variance with repeated measurements over time showed a larger decline in SOFA score and an increase in urine output in patients with successful cessation of dialysis. Kaplan-Meier analysis showed a significant difference in early resumption of dialysis between patients with or without oliguria at D0.

CONCLUSIONS

More than two-thirds of patients weaned from postoperative acute dialysis for more than 5 days were free of dialysis for at least 30 days. Less urine output, longer duration of dialysis, age over 65 years, and higher disease severity score are predictive of a patient's redialysis after initial weaning from acute dialysis.