Fluid overload at initiation of renal replacement therapy is associated with lack of renal recovery in patients with acute kidney injury

Chloride-liberal fluids are associated with acute kidney injury after liver transplantation

Introduction

Acute kidney injury (AKI) occurs frequently after liver transplantation and is associated with significant morbidity and mortality. Recent evidence has linked the predominant usage of ‘chloride-liberal’ intravenous fluids, such as 0.9% saline to the development of renal dysfunction in general critically ill patients. We compared the effects of perioperative fluid types on AKI in liver transplant recipients.

Methods

An observational analysis of liver transplant recipients over a 33-month period, between January 2010 and September 2013, was performed. Intensive care unit database and patient records were analyzed for determinants of early postoperative AKI. Univariate and multivariate regression analysis was carried out using a two-tailed P value less than 0.05 to establish significance. The institutional Research Ethics Committee approved the study methodology (RAC no. 2131 073).

Results

One hundred and fifty-eight liver transplants were performed, AKI developed in 57 (36.1%) patients: 39 (68.4%) fully recovered, 13 (22.8%) developed chronic renal failure and 10 (17.5%) required long-term hemodialysis. On univariate regression analysis, AKI was significantly associated with greater than 3,200 ml of chloride-liberal fluids infused within the first postoperative day (HR 5.9, 95% CI 2.64, 13.2, P <0.001), greater than 1,500 ml colloids received in the operating room (hazard ratio (HR) 1.97, 95% CI 1.01, 3.8, P = 0.046), vasopressor requirement for 48 hours posttransplant (HR 3.34, 95% CI 1.55, 7.21, P = 0.002), hyperchloremia at day 2 (HR 1.09, 95% CI 1.01, 1.18, P = 0.015) and preoperative model for end-stage liver disease (MELD) score (HR 1.08, 95% CI 1.03, 1.13, P <0.001).

After stepwise multivariate regression, infusion of greater than 3,200 ml of chloride-liberal fluids (HR 6.25, 95% CI 2.69, 14.5, P <0.000) and preoperative MELD score (HR 1.08, 95% CI 1.02, 1.15, P = 0.004) remained significant predictors for AKI.

Conclusions

In a sample of liver transplant recipients, infusion of higher volumes of chloride-liberal fluids and preoperative status was associated with an increased risk for postoperative AKI.

The incidence and risk factors of acute kidney injury after hepatobiliary surgery: a prospective observational study

BACKGROUND

Although intraperitoneal surgery is a major operation associated with postoperative acute kidney injury (AKI), the incidence, risk factors, and long-term renal outcome are not well known. We aimed to determine the risk factors and 6 months renal outcome in patients with clinical or subclinical AKI after hepatobiliary surgery. We also assessed the validity of urine neutrophil gelatinase-associated lipocalin (NGAL) in the early detection of AKI or prediction of renal outcome.

METHODS

This prospective observational study enrolled patients with normal renal function who underwent hepatobiliary surgeries. Urine and serum samples were collected for NGAL measurement.

RESULTS

Among 131 patients, 10 (7.6%) developed postoperative AKI. Urine NGAL at 12 h postsurgery was the most predictive parameter for the diagnosis of AKI (cutoff, 92.85 ng/mL). With the cutoff value, subclinical AKI was diagnosed in 42 (32.1%) patients. Patients with clinical AKI and those with subclinical AKI were assigned to the AKI group. The AKI group had significantly higher model for end-stage liver disease and sodium (MELD-Na) score, lower albumin level, and longer hospital stay after surgery than the non-AKI group. Older age and higher MELD-Na score were independent risk factors for the development of postoperative AKI. At 6 months postsurgery, the estimated glomerular filtration rate (eGFR) in the AKI group was significantly lower than that in the non-AKI group, although the baseline eGFR was not different. In multiple linear regression analysis, the maximum urine NGAL level during 24 h postsurgery, intraoperative fluid balance, and having liver transplantation were significantly associated with a poor 6 months renal outcome.

CONCLUSION

Urine NGAL was useful in the early diagnosis of postoperative AKI as well as in predicting the 6 months renal outcome after hepatobiliary surgery. A considerable proportion of patients developed subclinical AKI, and these patients showed worse renal outcome compared with the non-AKI group.

Effects of renal replacement therapy on renal recovery after acute kidney injury

Recovery of kidney function following an episode of acute kidney injury (AKI) is now acknowledged as a vital patient-centered outcome with clear health economic implications. In approximately 5-8% of critically ill patients with more severe forms of AKI, support with renal replacement therapy (RRT) is provided. Recent data have suggested that rates of RRT utilization in AKI are increasing. Despite advances in our understanding of how best to prescribe acute RRT in critically ill patients with AKI, additional aspects remain uncertain, predisposing to suboptimal delivery and variation in practice. Importantly, if, when, how, and by what principles we apply acute RRT for AKI are all treatment decision-related factors that are modifiable and may interact with recovery of kidney function. Limited data, mostly from observational studies and secondary analyses, have explored the specific association between acute RRT and recovery. Available data are not able to clarify whether providing any RRT in otherwise eligible patients with AKI impacts recovery. They are also unable to inform whether the timing or circumstance under which RRT is started impacts recovery. No studies have evaluated whether there is an optimal time to start RRT to maximize the probability of recovery. Accumulated evidence, mostly derived from observational studies, suggests initial therapy in critically ill patients with AKI with continuous RRT, compared with intermittent modalities, improves the probability of recovery to dialysis independence. Evidence from high-quality randomized trials failed to show any association between delivered dose intensity of RRT and recovery. The use of biocompatible membranes for acute RRT may improve recovery in AKI; however, data are inconsistent. Limited data have evaluated the impact of membrane flux properties on recovery. Preliminary data have suggested that circuit anticoagulation with citrate, which results in a reduction in membrane-induced oxidative stress and leukocyte activation, may be associated with improved recovery; however, further corroborative data are needed. Additional evidence, ideally from randomized trials, is clearly needed to inform best practice in the delivery of acute RRT to optimize probability of recovery of kidney function for survivors of AKI.

Clinical determinants of renal recovery

Acute kidney injury (AKI) is associated with increased mortality, prolonged hospitalization, and renal replacement therapy. Until recently, it was believed that the vast majority of patients recover from AKI without subsequent consequences. It is now recognized that patients with AKI may have very different renal outcomes, including complete recovery, incipient and progressive chronic kidney disease, and end-stage renal disease. Factors that influence these different outcomes have not been thoroughly evaluated and so are not currently understood. The patient's baseline demographic characteristics, subsequent clinical evolution, and factors associated with the treatment of these patients may all influence global and renal outcomes. Recovery from AKI is a potentially modifiable event and should be targeted for therapy. Useful tools are needed to monitor renal recovery and identify the patients at high risk for adverse outcomes.

Therapeutic strategies for clinical trials targeting renal recovery

Although at present we have developed consensus definitions for acute kidney injury (AKI) and there is a major focus on the treatment and prevention of AKI in high-risk populations, little is known about renal recovery per se and the impact of therapies on renal recovery. Here, we will focus on the specifics of clinical trial design relevant to studies of AKI recovery. While certain design considerations will be common to all trials, others elements will be more specific for studies focused on best practice or novel therapeutics. We will first discuss clinical trial considerations for all studies followed by specific proposals for best practice trials and therapy trials. Other presentations during this round table have focused on other aspects that are highly important for clinical trial design, including definitions for recovery, the potential use of biomarkers, as well as clinical trial endpoints, so we will not address these issues here.

Indications and management of mechanical fluid removal in critical illness

BACKGROUND

The Acute Dialysis Quality Initiative (ADQI) dedicated its Twelfth Consensus Conference (2013) to all aspects of fluid therapy, including the management of fluid overload (FO). The aim of the working subgroup 'Mechanical fluid removal' was to review the indications, prescription, and management of mechanical fluid removal within the broad context of fluid management of critically ill patients.

METHODS

The working group developed a list of preliminary questions and objectives and performed a modified Delphi analysis of the existing literature. Relevant studies were identified through a literature search using the MEDLINE database and bibliographies of relevant research and review articles.

RESULTS

After review of the existing literature, the group agreed the following consensus statements: (i) in critically ill patients with FO and with failure of or inadequate response to pharmacological therapy, mechanical fluid removal should be considered as a therapy to optimize fluid balance. (ii) When using mechanical fluid removal or management, targets for rate of fluid removal and net fluid removal should be based upon the overall fluid balance of the patient and also physiological variables, individualized, and reassessed frequently. (iii) More research on the role and practice of mechanical fluid removal in critically ill patients not meeting fluid balance goals (including in children) is necessary.

CONCLUSION

Mechanical fluid removal should be considered as a therapy for FO, but more research is necessary to determine its exact role and clinical application.

Fluid balance, change in serum creatinine and urine output as markers of acute kidney injury post cardiac surgery: an observational study

Background

Acute kidney injury (AKI) is defined as oliguria or rise in serum creatinine but oliguria alone as a diagnostic criterion may over-diagnose AKI.

Objectives

Given the association between fluid overload and AKI, we aimed to determine if positive fluid balance can complement the known parameters in assessing outcomes of AKI.

Design

Prospective observational study.

Setting

Teaching hospital in Vancouver, Canada.

Patients

111 consecutive patients undergoing elective cardiac surgery from January to April 2012.

Measurements

Outcomes of cardiac surgery intensive care unit (CSICU) and hospital length of stay (LOS) in relation to fluid balance, urine output and serum creatinine.

Methods

All fluid input and output was recorded for 72 hours post-operatively. Positive fluid balance was defined as >6.5 cc/kg. Daily serum creatinine and hourly urine output were recorded and patients were defined as having AKI according to the AKIN criteria.

Results

Of the patients who were oliguric, those with fluid overload trended towards longer LOS than those without fluid overload [CSICU LOS: 62 and 39 hours (unadjusted p-value 0.02, adjusted p-value 0.58); hospital LOS: 13 and 9 days (unadjusted p-value: 0.05, adjusted p-value: 0.16)]. Patients with oliguria who were fluid overloaded had similar LOS to patients with overt AKI (change in serum creatinine ≥ 26.5 µmol/L), [CSICU LOS: 62 and 69 hours (adjusted p value: 0.32) and hospital LOS: 13 and 14 days (adjusted p value: 0.19)]. Patients with oliguria regardless of fluid balance had longer CSICU LOS (adjusted p value: 0.001) and patients who were fluid overloaded in the absence of AKI had longer hospital LOS (adjusted p value: 0.02).

Limitations

Single centre, small sample, LOS as outcome.

Conclusions

Oliguria and positive fluid balance is associated with a trend towards longer LOS as compared to oliguria alone. Fluid balance may therefore be a useful marker of AKI, in addition to urine output and serum creatinine.

Renal recovery after acute kidney injury: choice of initial renal replacement therapy modality still matters

Renal replacement therapy can be applied either in an intermittent fashion or in a continuous fashion in severe acute kidney injury. To date, no modality has been shown to consistently improve patient survival. In the study recently reported by Sun and colleagues, continuous application of renal replacement therapy was associated with improved renal recovery, defined by lower risk of long-term need for chronic dialysis therapy. This association between nonrecovery and intermittent renal replacement therapy may be explained by a higher rate of hypotensive episodes and the lower capacity for fluid removal during the first 72 hours of therapy. Altogether, this study adds to the growing body of evidence to suggest improved likelihood of recovery of kidney function in critically ill survivors of AKI with continuous modalities for renal replacement therapy.

Prognostic factors in continuous hemofiltration therapy for patients with cardiorenal syndrome

AIMS

The aims of this study were to investigate the efficacy and identify the prognostic factors of continuous hemofiltration in patients with cardiorenal syndrome (CRS) and, finally, to optimally select patients who could benefit more from this therapy.

METHODS

A total of 59 patients with CRS type 1 or type 2 treated with continuous hemofiltration were enrolled. We collected their clinical data and divided them into 2 groups according to their survival or death during hospitalization to conduct a retrospective analysis on factors affecting mortality.

RESULTS

The following items were significantly different between the survival (n = 30) and death (n = 29) groups: serum creatinine, serum total bilirubin, direct bilirubin, white blood cells, hemoglobin, hematocrit, left ventricular end-diastolic diameter, left ventricular end-systolic diameter, systolic blood pressure and mean arterial pressure before hemofiltration, and average dehydration volume during the hemofiltration process. Leukocytosis was a risk factor for death (OR 1.242, 95% CI 1.242-1.480), and elevated sCr was not a key negative factor in the prognosis of CRS (OR 0.994, 95% CI 0.989-1.000).

CONCLUSIONS

Cardiac function before hemofiltration and the amount of dehydration during the hemofiltration process both affected the prognosis. Infection and fluid overload condition at the beginning of hemofiltration were independently associated with mortality during hospitalization.

Limited echocardiography-guided therapy in subacute shock is associated with change in management and improved outcomes

PURPOSE

The purpose of the study was to compare the effect of limited echocardiography (LE)-guided therapy to standard management on 28-day mortality, intravenous fluid prescription, and inotropic dosing following early resuscitation for shock.

MATERIALS AND METHODS

Two hundred twenty critically ill patients with undifferentiated shock from a quaternary intensive care unit were included in the study. The LE group consisted of 110 consecutive patients prospectively studied over a 12-month period receiving LE-guided management. The standard management group consisted of 110 consecutive patients retrospectively studied with shock immediately prior to the LE intervention.

RESULTS

In the LE group, fluid restriction was recommended in 71 (65%) patients and initiation of dobutamine in 27 (25%). Fluid prescription during the first 24 hours was significantly lower in LE patients (49 [33-74] vs 66 [42-100] mL/kg, P = .01), whereas 55% more LE patients received dobutamine (22% vs 12%, P = .01). The LE patients had improved 28-day survival (66% vs 56%, P = .04), a reduction in stage 3 acute kidney injury (20% vs 39%), and more days alive and free of renal support (28 [9.7-28] vs 25 [5-28], P = .04).

CONCLUSIONS

Limited echocardiography-guided management following early resuscitation is associated with improved survival, less fluid, and increased inotropic prescription. A prospective randomized control trial is required to verify these results.

A patient with AKI after cardiac surgery

Up to 30% of patients undergoing cardiac surgery develop AKI, with 1% requiring RRT. AKI is an independent risk factor for morbidity and mortality. Postoperatively, even minimal changes in serum creatinine are associated with a substantial increase in mortality. No intervention has been definitely proven effective in reducing kidney injury. The successful prevention and management of AKI involves identifying patients at risk for AKI, recognizing subtle abnormalities in a timely manner, performing basic clinical assessments, and responding appropriately to data obtained. With that in mind, in this Attending Rounds, a woman with AKI in the setting of cardiac surgery is presented to highlight the use of history, physical exam, hemodynamic monitoring, laboratory data trends, and urine indices in establishing the correct diagnosis and appropriate management.

Fluid administration and the kidney

PURPOSE OF REVIEW

To review recent studies and information on the relationship between fluid administration and kidney function in critically ill patients.

RECENT FINDINGS

There is little evidence from large multicenter trials to direct fluid therapy in patients at risk of acute kidney injury (AKI). Evidence of benefit for fluid administration from single center studies of fluid resuscitation to hemodynamic goals needs to be weighed against evidence of harm associated with fluid overload in large observational studies. The composition of intravenous fluid may affect the risk of AKI. Even latest-generation hydroxyethyl starches increase the risk of severe AKI in general and septic ICU patients. Isotonic saline has been associated with greater incidence of AKI in comparison to buffered crystalloids. Experimentally, infusion of saline results in reduction in renal perfusion in comparison to buffered solutions.

SUMMARY

Clinicians need to weigh the balance between adequate resuscitation of cardiac output and avoidance of fluid overload. Protocolized resuscitation to hemodynamic goals may help achieve these conflicting goals at least in the early phases of critical illness. In critically ill patients with, or at risk of, AKI, clinicians should avoid starch and, possibly, saline solutions.

Fluids are drugs: type, dose and toxicity

PURPOSE OF REVIEW

We discuss the formulation of a prescription for intravenous (i.v.) fluid therapy (a 'volume prescription') for critically ill patients: pros/cons of different fluid types; accurate dosing; and qualitative and quantitative toxicities. Updated physiologic concepts are invoked and results of recent major clinical trials on i.v. fluid therapy in the acutely ill are interpreted.

RECENT FINDINGS

Context is vital and any fluid can be harmful if dosed incorrectly. When contrasting 'crystalloid versus colloid', differences in efficacy are modest, but differences in safety are significant. Differences in chloride load and strong ion difference appear to be clinically important. Quantitative toxicity is mitigated when dosing is based on dynamic parameters that predict volume responsiveness. Qualitative toxicity for colloids (even with newer hydroxyethyl starch 130/0.4 solutions) and isotonic saline remain a concern.

SUMMARY

Similar to any drug used in acutely ill patients, clinicians ordering a volume prescription must recognize that context is crucial. Physiologically balanced crystalloids may be the 'default' fluid for acutely ill patients, and the role for colloids is unclear. Optimal dosing involves assessment of volume responsiveness.

Controversies in fluid therapy: Type, dose and toxicity

Fluid therapy is perhaps the most common intervention received by acutely ill hospitalized patients; however, a number of critical questions on the efficacy and safety of the type and dose remain. In this review, recent insights derived from randomized trials in terms of fluid type, dose and toxicity are discussed. We contend that the prescription of fluid therapy is context-specific and that any fluid can be harmful if administered inappropriately. When contrasting ‘‘crystalloid vs colloid’’, differences in efficacy are modest but differences in safety are significant. Differences in chloride load and strong ion difference across solutions appear to be clinically important. Phases of fluid therapy in acutely ill patients are recognized, including acute resuscitation, maintaining homeostasis, and recovery phases. Quantitative toxicity (fluid overload) is associated with adverse outcomes and can be mitigated when fluid therapy based on functional hemodynamic parameters that predict volume responsiveness and minimization of non-essential fluid. Qualitative toxicity (fluid type), in particular for iatrogenic acute kidney injury and metabolic acidosis, remain a concern for synthetic colloids and isotonic saline, respectively. Physiologically balanced crystalloids may be the ‘‘default’’ fluid for acutely ill patients and the role for colloids, in particular hydroxyethyl starch, is increasingly unclear. We contend the prescription of fluid therapy is analogous to the prescription of any drug used in critically ill patients.

Acute kidney injury-epidemiology, outcomes and economics

Acute kidney injury (AKI) is a widespread problem of epidemic status. Compelling evidence indicates that the incidence of AKI is rapidly increasing, particularly among hospitalized patients with acute illness and those undergoing major surgery. This increase might be partially attributable to greater recognition of AKI, improved ascertainment in administrative data and greater sensitivity of consensus diagnostic and classification schemes. Other causes could be an ageing population, increasing incidences of cardiovascular disease, diabetes mellitus and chronic kidney disease (CKD), and an expanding characterization of modifiable risk factors, such as sepsis, administration of contrast media and exposure to nephrotoxins. The sequelae of AKI are severe and characterized by increased risk of short-term and long-term mortality, incident CKD and accelerated progression to end-stage renal disease. AKI-associated mortality is decreasing, but remains unacceptably high. Moreover, the absolute number of patients dying as a result of AKI is increasing as the incidence of the disorder increases, and few proven effective preventative or therapeutic interventions exist. Survivors of AKI, particularly those who remain on renal replacement therapy, often have reduced quality of life and consume substantially greater health-care resources than the general population as a result of longer hospitalizations, unplanned intensive care unit admissions and rehospitalizations.

Renal recovery

Acute kidney injury (AKI) research in the past decade has mostly focused upon development of a standard AKI definition, validation of early novel biomarkers to predict AKI prior to serum creatinine rise and predict AKI severity, and assessment of aspects of renal replacement therapies and their impact on survival. Given the independent association between AKI and mortality in the acute phase, such focus makes imminent sense. More recently, the recognition that AKI is associated with subsequent development of chronic kidney disease and end-stage renal disease, with the attendant increase in mortality, has led to interest in the clinical epidemiology and the mechanistic understanding of renal recovery after an AKI episode in critically ill patients. We review the current knowledge surrounding renal recovery after an AKI episode, including renal replacement therapy initiation timing and modality impact, biomarker assessment and mechanistic targets to guide potential future clinical trials.

Acute kidney injury: an intensivist's perspective

The changing epidemiology of acute kidney injury (AKI) in adults and children has resulted in more patients being treated for kidney injury occurring in the context of multi-organ failure requiring treatment in the intensive care unit (ICU). AKI complicating critical illness has complex, multi-factorial etiology, and supportive care, including organ support, remains the mainstay of therapy. In the day-to-day management of AKI in the ICU two of the major challenges are the inadequacy of current diagnostics for the early identification of AKI and the relationship between hemodynamic resuscitation strategies and the development of AKI. This review focuses on these areas from the intensivist's perspective. Given that the diagnosis of AKI is often delayed, the prevention of complications and limitation of secondary renal injury are of particular importance. Fluid overload is increasingly being associated with adverse patient outcomes in critical illness and may contribute to persistent renal dysfunction. Thus, hemodynamic management strategies in AKI should be tailored to limit fluid overload as much as possible.

Acute kidney injury: quoi de neuf?

BACKGROUND

Acute kidney injury (AKI) is frequently encountered in the nephrology practice. Serum creatinine, with its many shortcomings, is still the main biomarker used to detect AKI.

METHODS

This review focuses on recent advances in definition, diagnosis, risk factors, and molecular mechanisms of AKI. In addition, specific AKI syndromes such as contrast-induced AKI, hepatorenal syndrome, and acute decompensated heart failure are discussed. The connection between AKI and subsequent chronic kidney disease and recent developments in renal replacement therapy are also covered.

RESULTS

Novel biomarkers such as cystatin C and neutrophil gelatinase-associated lipocalin (NGAL) are being investigated to replace serum creatinine in the detection of AKI. Recent studies suggest that intravenous (IV) fluid use is beneficial for the prevention of contrast-induced AKI, while N-acetylcysteine use is not as well established. Diuretics are clearly beneficial in the treatment of acute decompensated heart failure. Ultrafiltration is less promising and can lead to adverse side effects. Although terlipressin use in hepatorenal syndrome is associated with reduced mortality, it is not available in the United States; combination therapy with midodrine, octreotide, and albumin provides an alternative. Fluid resuscitation is frequently used in critically ill patients with AKI; however, overly aggressive fluid resuscitation is frequently associated with an increased risk of mortality. A 3-step approach that combines guided fluid resuscitation, establishment of an even fluid balance, and an appropriate rate of fluid removal may be beneficial. If fluid resuscitation is needed, crystalloid solutions are preferred over hetastarch solutions. Renal replacement therapy is the last resort in AKI treatment, and timing, modality, and dosing are discussed. Research suggests that AKI leads to an increased incidence of subsequent chronic kidney disease. However, this relationship has not been fully established and additional studies are needed for clarification.

CONCLUSION

Despite major advances in AKI research, serum creatinine remains the major biomarker for the detection of AKI. The following interventions have shown to be beneficial: IV fluids for contrast-induced AKI; diuretics for acute decompensated heart failure/cardiorenal syndrome; and combination therapy with midodrine, octreotide, and albumin for hepatorenal syndrome. Fluid resuscitation in a patient with AKI should be used with caution because too liberal use of fluids can be associated with increased mortality. AKI appears to be related to increased rates of subsequent chronic kidney disease, and patients with AKI should therefore be monitored closely. Recent studies on renal replacement therapy have neither revealed an optimal timing for initiation of dialysis nor a clear advantage for a specific dialysis modality.

Fluid management for the prevention and attenuation of acute kidney injury

In patients with acute kidney injury (AKI), optimization of systemic haemodynamics is central to the clinical management. However, considerable debate exists regarding the efficacy, nature, extent and duration of fluid resuscitation, particularly when the patient has undergone major surgery or is in septic shock. Crucially, volume resuscitation might be required to maintain or restore cardiac output. However, resultant fluid accumulation and tissue oedema can substantially contribute to ongoing organ dysfunction and, particularly in patients developing AKI, serious clinical consequences. In this Review, we discuss the conflict between the desire to achieve adequate resuscitation of shock and the need to mitigate the harmful effects of fluid overload. In patients with AKI, limiting and resolving fluid overload might prompt earlier use of renal replacement therapy. However, rapid or early excessive fluid removal with diuretics or extracorporeal therapy might lead to hypovolaemia and recurrent renal injury. Optimal management might involve a period of guided fluid resuscitation, followed by management of an even fluid balance and, finally, an appropriate rate of fluid removal. To obtain best clinical outcomes, serial fluid status assessment and careful definition of cardiovascular and renal targets will be required during fluid resuscitation and removal.

Continuous renal replacement therapy outcomes in acute kidney injury and end-stage renal disease: a cohort study

INTRODUCTION

Continuous renal replacement therapy (CRRT) is a widely used but resource-intensive treatment. Despite its broad adoption in intensive care units (ICUs), it remains challenging to identify patients who would be most likely to achieve positive outcomes with this therapy and to provide realistic prognostic information to patients and families.

METHODS

We analyzed a prospective cohort of all 863 ICU patients initiated on CRRT at an academic medical center from 2008 to 2011 with either new-onset acute kidney injury (AKI) or pre-admission end-stage renal disease (ESRD). We examined in-hospital and post-discharge mortality (for all patients), as well as renal recovery (for AKI patients). We identified prognostic factors for both in-hospital and post-discharge mortality separately in patients with AKI or ESRD.

RESULTS

In-hospital mortality was 61% for AKI and 54% for ESRD. In patients with AKI (n=725), independent risk factors for mortality included age over 60 (OR 1.9, 95% CI 1.3, 2.7), serum lactate over 4 mmol/L (OR 2.2, 95% CI 1.5, 3.1), serum creatinine over 3 mg/dL at time of CRRT initiation (OR 0.63, 95% CI 0.43, 0.92) and comorbid liver disease (OR 1.75, 95% CI 1.1, 2.9). Among patients with ESRD (n=138), liver disease was associated with increased mortality (OR 3.4, 95% CI 1.1, 11.1) as was admission to a medical (vs surgical) ICU (OR 2.2, 95% CI 1.1, 4.7). Following discharge, advanced age became a predictor of mortality in both groups (AKI: HR 1.9, 95% CI 1.2, 3.0; ESRD: HR 4.1, 95% CI 1.5, 10.9). At the end of the study period, only 25% (n=183) of patients with AKI achieved dialysis-free survival.

CONCLUSIONS

Among patients initiating CRRT, risk factors for mortality differ between patients with underlying ESRD or newly acquired AKI. Long-term dialysis-free survival in AKI is low. Providers should consider these factors when assessing prognosis or appropriateness of CRRT.

Fluid overload and mortality are associated with acute kidney injury in sick near-term/term neonate

BACKGROUND

Acute kidney injury (AKI) is common and portends mortality in several neonatal cohorts. Fluid overload is independently associated with poor outcomes in children and adults but has not been extensively studied in neonates.

METHODS

Between February 2010 and May 2011, we followed 58 neonates who met the following criteria: birth weight >2,000 g, gestational age ≥ 34 weeks, 5-min Apgar ≤ 7, and parental consent. Serum creatinine (SCr) was measured daily for first 4 days of life. AKI was defined as a rise in SCr of > 0.3 mg/dl or persistent SCr above 1.5 mg/dl.

RESULTS

AKI was present in 9/58 (15.6 %) neonates and was associated with higher birth weight, being male, lower 5-min Apgar scores, lower cord pH, delivery room intubation, and absence of maternal pre-eclampsia. Percent weight accumulation at day 3 of life was higher in those with AKI [median=8.2, interquartile range (IQR) =4.4-21.6)] than without AKI (median= -4 (IQR= -6.5 to 0.0) (p<0.001). Infants with AKI had lower survival rates than those without AKI [7/9 (72 %) vs. 49/49 (100 %) (p<0.02)].

CONCLUSIONS

AKI incidence in this neonatal population is similar to other neonatal cohorts. Near-term/term infants with AKI have a higher mortality rate and a net positive fluid balance over the first few days of life.

Renal dysfunction in burns: a review

Acute kidney injury (AKI), although rare, is a major complication of burn injury that commonly leads to mortality. It results from a complex interplay of various cellular and neuro-humoral changes affecting burn patients. Guidelines for the treatment of this entity are still not well defined; therefore, prevention and early diagnosis are key to avoid the unfavorable prognosis of AKI. These entail a comprehensive understanding of the global physiologic changes underlying the condition of burn patients and a judicious interpretation of their continuous homeostatic alterations. The aim of this review is to present the salient features in burn patient physiology that contribute to AKI. Strategies for identifying early AKI are presented. Finally, the different treatment modalities are revisited.

Continuous renal replacement therapy for children ≤10 kg: a report from the prospective pediatric continuous renal replacement therapy registry

OBJECTIVE

To report circuit characteristics and survival analysis in children weighing ≤10 kg enrolled in the Prospective Pediatric Continuous Renal Replacement Therapy (ppCRRT) Registry.

STUDY DESIGN

We conducted prospective cohort analysis of the ppCRRT Registry to: (1) evaluate survival differences in children ≤10 kg compared with other children; (2) determine demographic and clinical differences between surviving and non-surviving children ≤10 kg; and (3) describe continuous renal replacement therapy (CRRT) circuit characteristics differences in children ≤5 kg versus 5-10 kg.

RESULTS

The ppCRRT enrolled 84 children ≤10 kg between January 2001 and August 2005 from 13 US tertiary centers. Children ≤10 kg had lower survival rates than children >10 kg (36/84 [43%] versus 166/260 [64%]; P < .001). In children ≤10 kg, survivors were more likely to have fewer days in intensive care unit prior to CRRT, lower Pediatric Risk of Mortality 2 scores at intensive care unit admission and lower mean airway pressure (P(aw)), higher urine output, and lower percent fluid overload (FO) at CRRT initiation. Adjusted regression analysis revealed that Pediatric Risk of Mortality 2 scores, FO, and decreased urine output were associated with mortality. Compared with circuits from children 5-10 kg at CRRT initiation, circuits from children ≤5 kg more commonly used blood priming for initiation, heparin anticoagulation, and higher blood flows/effluent flows for body weight.

CONCLUSION

Mortality is more common in children who are ≤10 kg at the time of CRRT initiation. Like other CRRT populations, urine output and FO at CRRT initiation are independently associated with mortality. CRRT prescription differs in small children.

Volume management in the critically ill patient with acute kidney injury

Acute kidney injury (AKI) frequently occurs in the setting of critical illness and its management poses a challenge for the intensivist. Optimal management of volume status is critical in the setting of AKI in the ICU patient. The use of urine sodium, the fractional excretion of sodium (FeNa), and the fractional excretion of urea (FeUrea) are common clinical tools used to help guide fluid management especially further volume expansion but should be used in the context of the patient's overall clinical scenario as they are not completely sensitive or specific for the finding of volume depletion and can be misleading. In the case of oliguric or anuric AKI, diuretics are often utilized to increase the urine output although current evidence suggests that they are best reserved for the treatment of volume overload and hyperkalemia in patients who are likely to respond to them. Management of volume overload in ICU patients with AKI is especially important as volume overload has several negative effects on organ function and overall morbidity and mortality.

Fluid management and use of diuretics in acute kidney injury

Critically ill adult patients at risk for or with acute kidney injury (AKI) require careful attention to their hemodynamic status because hypotension and hypovolemia may contribute to or worsen kidney injury. Increasing evidence suggests that isotonic crystalloids should be used instead of colloids for initial expansion of intravascular volume in patients at risk for AKI or with AKI, such as those with sepsis, septic shock, or trauma. The timing and amount of volume to be administered to prevent AKI and other organ damage is still debated, but an aggressive fluid repletion in the early setting is probably beneficial. However, fluid overload has also been associated with increased mortality and reduced rate of kidney recovery in observational studies in critically ill patients with AKI. Diuretics may prevent or treat fluid overload and may also affect kidney function. The efficacy of these procedures in critically ill AKI patients need to be confirmed with randomized controlled trials. This review focuses on early volume resuscitation, overall fluid management, and use of diuretics in critically ill adult patients at risk for or with AKI and their effect on mortality and kidney function in this setting.

Fluid overload in AKI: epiphenomenon or putative effect on mortality?

PURPOSE OF REVIEW

The incidence of acute kidney injury (AKI) is increasing dramatically, and despite advances in dialytic therapy and critical care, there has been little improvement in associated morbidity and mortality. Recently, several articles have suggested that fluid overload in patients with AKI is associated with an increased risk of death.

RECENT FINDINGS

Observational studies have demonstrated an association between fluid overload and poor outcomes (including death) in patients with AKI; however, whether this association is causal or due to residual confounding is unknown. A recent study testing the impact of fluid overload and diuretics on outcomes in the context of a randomized controlled trial suggests that the beneficial impact of diuretics in those with AKI is mediated by reducing fluid overload. Finally, potential mechanisms by which fluid overload may contribute to death include failure to recognize AKI due to creatinine dilution, direct tissue edema leading to decreased renal perfusion, and an increased risk of other complications such as sepsis.

SUMMARY

On the basis of the current literature, the relative contributions of the direct effects of fluid overload versus the association of fluid overload with other patient characteristics associated with adverse outcome (e.g. sepsis) remain unknown. Additional human studies, including randomized controlled trials, are warranted to further clarify these issues.

Fluid management in acute kidney injury

Fluid management in critical illness has undergone extensive reevaluation in the past decade. Since a significant percentage of critically ill patients develop acute kidney injury (AKI), optimal fluid management is even more paramount to prevent the ill effects of either underhydration or overhydration. The concepts of early goal-directed fluid therapy (EGDT) and conservative late fluid management permeate current clinical research, and the independent association between fluid accumulation and mortality has been repeatedly demonstrated. A number of prospective randomized trials are planned to provide an adequately powered assessment of the effect of EGDT or earlier renal replacement therapy initiation in patients with, or at risk for AKI. The aim of this analytical review is to use existing clinical and physiological studies to support a 3-phase model of fluid management in the critically ill patient with AKI.

Fluid overload is associated with an increased risk for 90-day mortality in critically ill patients with renal replacement therapy: data from the prospective FINNAKI study

Introduction

Positive fluid balance has been associated with an increased risk for mortality in critically ill patients with acute kidney injury with or without renal replacement therapy (RRT). Data on fluid accumulation prior to RRT initiation and mortality are limited. We aimed to study the association between fluid accumulation at RRT initiation and 90-day mortality.

Methods

We conducted a prospective, multicenter, observational cohort study in 17 Finnish intensive care units (ICUs) during a five-month period. We collected data on patient characteristics, RRT timing, and parameters at RRT initiation. We studied the association of parameters at RRT initiation, including fluid overload (defined as cumulative fluid accumulation > 10% of baseline weight) with 90-day mortality.

Results

We included 296 RRT-treated critically ill patients. Of 283 patients with complete data on fluid balance, 76 (26.9%) patients had fluid overload. The median (interquartile range) time from ICU admission to RRT initiation was 14 (3.3 to 41.5) hours. The 90-day mortality rate of the whole cohort was 116 of 296 (39.2%; 95% confidence interval 38.6 to 39.8%). The crude 90-day mortality of patients with or without fluid overload was 45 of 76 (59.2%) vs. 65 of 207 (31.4%), P < 0.001. In logistic regression, fluid overload was associated with an increased risk for 90-day mortality (odds ratio 2.6) after adjusting for disease severity, time of RRT initiation, initial RRT modality, and sepsis. Of the 168 survivors with data on RRT use at 90 days, 34 (18.9%, 95% CI 13.2 to 24.6%) were still dependent on RRT.

Conclusions

Patients with fluid overload at RRT initiation had twice as high crude 90-day mortality compared to those without. Fluid overload was associated with increased risk for 90-day mortality even after adjustments.

Renal replacement therapy in critically ill patients receiving extracorporeal membrane oxygenation

Extracorporeal membrane oxygenation (ECMO) is a lifesaving procedure used in neonates, children, and adults with severe, reversible, cardiopulmonary failure. On the basis of single-center studies, the incidence of AKI occurs in 70%-85% of ECMO patients. Those with AKI and those who require renal replacement therapy (RRT) are at high risk for mortality, independent of potentially confounding variables. Fluid overload is common in ECMO patients, and is one of the main indications for RRT. RRT to maintain fluid balance and metabolic control is common in some but not all centers. RRT on ECMO can be performed via an in-line hemofilter or by incorporating a standard continuous renal replacement machine into the ECMO circuit. Both of these methods require specific technical considerations to provide safe and effective RRT. This review summarizes available epidemiologic data and how they apply to our understanding of AKI pathophysiology during ECMO, identifies indications for RRT while on ECMO, reviews technical elements for RRT application in the setting of ECMO, and finally identifies specific research-focused questions that need to be addressed to improve outcomes in this at-risk population.

Serum cystatin C is associated with renal function recovery in critically ill patients undergoing continuous renal replacement therapy

PURPOSE

Serum cystatin C (sCyC) has long been known as a reliable biomarker of renal injury. However, it remains to be tested whether sCyC is a reliable biomarker to predict renal recovery after continuous renal replacement therapy (CRRT).

METHODS

A retrospective analysis of patients admitted to a tertiary 18-bed intensive care unit from January 2008 to December 2011 was performed. Univariate and multivariate regression analyses were performed to test the independent predictors of renal recovery. The diagnostic value of sCyC in predicting renal recovery was assessed using a receiver operating characteristic curve (ROC).

RESULTS

Older age and higher sCyC were independent risk factors of renal nonrecovery (OR: 1.40 and 4.76, respectively). The area under the ROC of sCyC to predict renal recovery was 0.87 (95% CI: 0.82-0.92), with a sensitivity and specificity of 80.5% and 83.5% at the cutoff of 2.98 mg/l.

CONCLUSION

A high sCyC level at the initiation of CRRT is associated with poor renal outcome.