Relationship of urine output to dialysis initiation and mortality in acute renal failure

Predictors of Mortality in Patients with Acute Renal Failure

Mortality associated with acute renal failure (ARF) remains high despite of developments in therapy strategies and definition of different prognostic factors. Therefore, this study focused on to define new prognostic factors and especially regional characteristics of the ARF patients. One hundred fifteen ARF patients, diagnosed from November 1998 to May 2003, were included to this prospective and observational study. Clinical features, laboratory parameters, Acute Physiology and Chronic Health Evaluation (APACHE) III scores and co-morbid conditions of the patients were examined. Clinical and laboratory data, and APACHE III scores were recorded at the first nephrology consult day. Thirty of the patients (26%) died. APACHE III scores, presence and the total number of co-morbid conditions and serum albumin levels at the time of first nephrology consultation were found as independent predictors of mortality. There was a negative correlation between APACHE III scores and serum albumin levels. Not only increased APACHE III score and presence of co-morbid conditions but also low serum albumin level was found as the predictors of mortality. However, only serum albumin level is seen as modifiable prognostic factor among these parameters. Therefore, further studies are necessary to determine the causes of hypoalbuminemia in patients with ARF and the effect of it’s effective treatment on patients outcome.

Fluid overload and outcomes in neonates receiving continuous renal replacement therapy

BACKGROUND

Continuous renal replacement therapy (CRRT) has emerged as the modality of choice for the management of high-risk neonates with acute kidney injury (AKI), inborn errors of metabolism and multi-organ dysfunction. The aim of this study was to evaluate fluid overload (FO) and investigate the factors associated with outcomes in neonates undergoing CRRT.

METHODS

We retrospectively reviewed the medical records of 34 neonates with AKI who were admitted to the neonatal intensive care unit (NICU) of Samsung Medical Center, Seoul, Republic of Korea between January 2007 and December 2014 where they underwent at least 24 h of CRRT.

RESULTS

The survival rates of patients with an FO of ≥30 % at the time of CRRT initiation were lower than those of patients with an FO of <30 % at the same time-point. Univariate Cox regression analysis revealed that a higher percentage FO at CRRT initiation and decreased urine output at the end of CRRT were associated with mortality, and multivariate Cox regression analysis indicated that mortality was associated with decreased urine output at the end of CRRT. Univariate linear regression analysis revealed that the length of hospital stay was associated with higher levels of serum creatinine at CRRT initiation, longer stay in the NICU prior to initiation of CRRT, longer duration of CRRT and lower body weight at the time of NICU admission.

CONCLUSIONS

Neonates with a higher percentage FO and higher levels of serum creatinine at CRRT initiation showed poor outcomes. Early initiation of CRRT before the development of severe FO or azotemia might improve the outcomes of neonates requiring CRRT.

Massive blood transfusion after the first cut in liver transplantation predicts renal outcome and survival

INTRODUCTION

Transfusion requirements of blood products may provide useful prognostic factors for the prediction of short-term patient mortality and renal outcome after liver transplantation.

PATIENTS AND METHODS

Two hundred ninety-one consecutive liver transplants in adults were analysed retrospectively. Combined and living-related liver transplants were excluded. The amount of transfused packed red blood cells (PRBC) and units of platelets (UP) within the first 48 h were investigated as prognostic factors to predict short-term patient mortality and renal outcome. Receiver operating characteristic (ROC) curve analysis with area under the curve (AUC), Hosmer-Lemeshow tests and Brier scores were used to calculate overall model correctness, model calibration and accuracy of prognostic factors. Cut-off values were determined with the best Youden index.

RESULTS

The potential clinical usefulness of PRBC as a prognostic factor to predict 30-day mortality (cut-off 17.5 units) and post-transplant haemodialysis (cut-off 12.5 units) could be demonstrated with AUCs >0.7 (0.712 and 0.794, respectively). Hosmer-Lemeshow test results and Brier scores indicated good overall model correctness, model calibration and accuracy. The UP proved as an equally clinically useful prognostic factor to predict end-stage renal disease (cut-off 3.5 units; AUC = 0.763). The association of cut-off levels of PRBC with patient survival (p < 0.001, log-rank test) and dialysis-free survival (p < 0.001, log-rank test) was significant (cut-off levels 17.5 and 12.5 units, respectively) as well as the association of UP with dialysis-free survival (p < 0.001, log-rank test) (cut-off level 3.5 units).

CONCLUSIONS

The impressive discriminative power of these simple prognostic factors for the prediction of outcome after liver transplantation emphasizes the relevance of strategies to avoid excessive transfusion requirements.

When should renal replacement therapy be initiated for acute kidney injury?

Acute kidney injury (AKI) is now well recognized as an independent risk factor for increased morbidity and mortality particularly when dialysis is needed. Although renal replacement therapy (RRT) has been used in AKI for more than five decades, there is no standard methodology to predict which AKI patients will need dialysis and who will recover renal function without requiring dialysis. The lack of consensus on what parameters should guide the decision to start dialysis has led to a wide variation in dialysis utilization. A contributing factor is the lack of studies in the modern era evaluating the relationship of timing of dialysis initiation and outcomes. Although listed as one of the top priorities in research on AKI, timing of dialysis initiation has not been included as a factor in large, randomized controlled trials in this area. In this review we will discuss the criteria that have been used to define early vs. late initiation in previous studies on dialysis initiation. In addition, we propose a patient-centered approach to define early and late initiation that could serve as framework for managing patients and for future studies in this area.

Clinical factors associated with initiation of renal replacement therapy in critically ill patients with acute kidney injury-a prospective multicenter observational study

PURPOSE

Our objective was to describe the current practice for initiation of RRT in this population. There is uncertainty regarding the optimal time to initiate renal replacement therapy (RRT) in critically ill patients with acute kidney injury (AKI).

METHODS

Prospective study of patients receiving RRT in 6 intensive care units (ICUs) at 3 hospitals from July 2007 to August 2008. We characterized factors associated with start of RRT and evaluated their relationship with mortality.

RESULTS

We included 234 patients. RRT was initiated 1 day (0-4) after ICU admission (median [interquartile range]). Median creatinine was 331 μmol/L (225-446 μmol/L), urea 22.9 mmol/L (13.9-32.9 mmol/L), and RIFLE-Failure in 76.9%. Of traditional indications, Pao(2)/Fio(2) < 200 (54.5%) and oliguria (32.9%) were most common. ICU and hospital mortality were 45.3% and 51.9%, respectively. In adjusted analysis, mortality at RRT initiation was associated with creatinine <332 μmol/L (odds ratio [OR] 2.8; 95% confidence interval [CI] 1.5-5.4), change in urea from admission >8.9 mmol/L (OR 1.8; 95% CI, 1.0-3.4), urine output <82 mL/24 hours (OR 3.0; 95% CI, 1.4-6.5), fluid balance >3.0 L/24 hours (OR 2.3; 95% CI, 1.2-4.5), percentage of fluid overload >5% (OR 2.3; 95% CI, 1.2-4.7), 3 or more failing organs (OR 4.5; 95% CI, 1.2-4.2), Sequential Organ Failure Assessment score >14 (OR 2.3; 95% CI, 1.3-4.3), and start 4 days or more after admission (OR 4.3; 95% CI, 1.9-9.5). Mortality was higher as factors accumulated.

CONCLUSION

In ICU patients requiring RRT, there was marked variation in factors that influence start of RRT. RRT initiation with fewer clinical triggers was associated with lower mortality. Timing of RRT may modify survival but requires appraisal in a randomized trial.

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%.

Mechanisms of the urinary concentration defect and effect of desmopressin during endotoxemia in rats

Acute renal failure during human sepsis is often nonoliguric. To study the underlying mechanisms, renal function was assessed in endotoxic and control male Wistar rats during and after saline loading and treatment with the selective V2 receptor agonist desmopressin. Escherichia coli endotoxin (dose, 8 mg/kg) was administered from time (t)=0 to t=60 min; saline loading (rate, 5 mL/100 g per hour) was administered from t=0 to t=120 min. Thereafter, half of each group received desmopressin (dose, 10 microg) for 1 h. The inner medullary (IM) osmolality, hematocrit, plasma, and urinary concentrations of sodium, potassium, urea, and osmolality were measured; then, aquaporin 2 (AQP2) immunohistochemistry was performed. Plasma vasopressin concentrations were measured at t=180 min. Saline loading increased urine volume in all rats. In the endotoxic group, mean arterial pressure decreased when saline loading was stopped. Despite increased hematocrit and vasopressin levels (>16 pg/mL), the endotoxin group had a low IM osmolality (mean +/- SEM, 412+/-0.04 mOsm/kg H2O) in comparison with the control group (mean +/- SEM, 1,094+/-0.17 mOsm/kg H2O) and was not able to either decrease urine volume or raise urine osmolality. Desmopressin treatment in endotoxin-treated rats maintained mean arterial pressure, increased sodium reabsorption, IM osmolality, and urine osmolality, and decreased urine flow. The AQP2 intensity decreased in the endotoxin group, and the apical localization disappeared; both were not affected by desmopressin. Our results indicate that endotoxemia in rats acutely diminishes renal urinary concentration capacity and is associated with a decreased IM osmolality and diminished apical AQP2 localization. These findings may help to explain nonoliguric acute renal failure in human septic shock.

Timing of renal replacement therapy initiation in acute renal failure: a meta-analysis

BACKGROUND

Some studies have suggested that early institution of renal replacement therapy (RRT) might be associated with improved outcomes in patients with acute renal failure (ARF).

STUDY DESIGN

A systematic review and meta-analysis of randomized controlled trials and cohort comparative studies to assess the effect of early RRT on mortality in patients with ARF.

SETTING & POPULATION

Hospitalized adult patients with ARF.

SELECTION CRITERIA FOR STUDIES

We searched several databases for studies that compared the effect of "early" and "late" RRT initiation on mortality in patients with ARF. We included studies of various designs.

INTERVENTION

Early RRT as defined in the individual studies.

OUTCOMES

The primary outcome measure was the effect of early RRT on mortality stratified by study design. The pooled risk ratio (RR) for mortality was compiled using a random-effects model. Heterogeneity was evaluated by means of subgroup analysis and meta-regression.

RESULTS

We identified 23 studies (5 randomized or quasi-randomized controlled trials, 1 prospective and 16 retrospective comparative cohort studies, and 1 single-arm study with a historic control group). By using meta-analysis of randomized trials, early RRT was associated with a nonsignificant 36% mortality risk reduction (RR, 0.64; 95% confidence interval, 0.40 to 1.05; P = 0.08). Conversely, in cohort studies, early RRT was associated with a statistically significant 28% mortality risk reduction (RR, 0.72; 95% confidence interval, 0.64 to 0.82; P < 0.001). The overall test for heterogeneity among cohort studies was significant (P = 0.005). Meta-regression yielded no significant associations; however, early dialysis therapy was associated more strongly with lower mortality in smaller studies (n < 100) by means of subgroup analysis.

LIMITATIONS

Paucity of randomized controlled trials, use of variable definitions of early RRT, and publication bias preclude definitive conclusions.

CONCLUSION

This hypothesis-generating meta-analysis suggests that early initiation of RRT in patients with ARF might be associated with improved survival, calling for an adequately powered randomized controlled trial to address this question.

Survival to discharge among patients treated with continuous renal replacement therapy

Continuous renal replacement therapy (CRRT) is widely used in critically ill patients with acute renal failure (ARF). The survival of patients who require CRRT and the factors predicting their outcomes are not well defined. We sought to identify clinical features to predict survival in patients treated with CRRT. We reviewed the charts of all patients who received CRRT at the Toronto General Hospital during the year 2002. Our cohort (n=85) represented 97% of patients treated with this modality in 3 critical care units. We identified demographic variables, underlying diagnoses, transplantation status, location (medical-surgical, coronary, or cardiovascular surgery intensive care units), CRRT duration, baseline estimated glomerular filtration rate (eGFR), and presence of oliguria (<400 mL/day) on the day of CRRT initiation. The principal outcome was survival to hospital discharge. Among those alive at discharge, we assessed whether there was an ongoing need for renal replacement therapy. Greater than one-third (38%, 32/85) of patients survived to hospital discharge. Three (9%) survivors remained dialysis-dependent at the time of discharge. Survivors were younger than nonsurvivors (mean age 56 vs. 60 years), were on CRRT for a shorter duration (7 vs. 13 days), and had a higher baseline eGFR (74 vs. 62 mL/min/m(2)). Patient survival varied among different critical care units (medical surgical 33%, coronary 38%, and cardiovascular surgery 45%). Multivariable logistic regression revealed that shorter duration of CRRT, nonoliguria, and baseline eGFR >60 mL/min/m(2) were independently associated with survival to hospital discharge (p<0.05). Critically ill patients with ARF who require CRRT continue to have high in-hospital mortality. A shorter period of CRRT dependence, nonoliguria and higher baseline renal function may predict a more favorable prognosis. The majority of CRRT patients who survive their critical illness are independent of dialysis at the time of hospital discharge.