A positive fluid balance is associated with a worse outcome in patients with acute renal failure

Volume-related weight gain and subsequent mortality in acute renal failure patients treated with continuous renal replacement therapy

Fluid overload is a frequent finding in critically ill patients suffering from acute kidney injury (AKI). To assess the impact of fluid overload on the mortality of AKI patients treated with continuous renal replacement therapy (CRRT), we used a registry of 81 critically ill patients with AKI initiated on CRRT assembled over an 18-month period to conduct a cross- sectional analysis using volume-related weight gain (VRWG) of > or =10% and > or =20% of body weight and oliguria (< or =20 ml/h) as the principal variables, with the primary outcome measure being mortality at 30 days. Mean Apache II scores were 27.5 +/- 6.9 with overall cohort mortality of 50.6%. Mean (+/-SD) VRWG was 8.3 +/- 9.6 kg, representing a 10.2% +/- 13.5% increase since admission. Oliguria was present in 65.4% of patients. Odds ratio (OR) for mortality on univariate analysis was increased to 2.62 [95% confidence interval (CI): 1.07-6.44] by a VRWG > or =10% and to 3.22 (95% CI: 1.23-8.45) by oliguria. VRWG > or =20% had OR of 3.98 (95% CI: 1.01-15.75; p = 0.049) for mortality. Both VRWG > or =10% (OR 2.71, p = 0.040) and oliguria (OR 3.04, p = 0.032) maintained their statistically significant association with mortality in multivariate models that included sepsis and Apache II score. In conclusion, fluid overload is an important prognostic factor for survival in critically ill AKI patients treated with CRRT. Further studies are needed to elicit mechanisms and develop appropriate interventions.

Adequacy of haemodialysis and or haemofiltration treatments for patients with acute kidney injury

Traditionally, the dose of haemodialysis or haemofiltration delivered to patients with kidney failure is assessed by urea clearance. For patients with chronic kidney disease below a critical urea clearance threshold, patient wellbeing is compromised. It was suggested, therefore, that the dose of dialysis or haemofiltration delivered could also affect outcomes for patients with acute kidney injury. Two major prospective multicentre clinical trials have recently reported that a higher intensity of renal support, by either intermittent haemodialysis or continuous renal replacement therapy, did not improve patient survival or recovery from dialysis. It must be recognised, however, that urea clearance is only one component of renal supportive therapy, and other aspects, including volume control, electrolyte homeostasis and acid-base balance, may be equally important targets for patients with acute kidney injury.

The SPARK Study: a phase II randomized blinded controlled trial of the effect of furosemide in critically ill patients with early acute kidney injury

BACKGROUND

Furosemide is commonly prescribed in critically ill patients with acute kidney injury (AKI). Existing data from observational studies and small clinical trials have significant limitations and have reported conflicting findings. There remains controversy on whether furosemide can impact clinical outcomes in critically ill patients with AKI; however, a survey of intensivists and nephrologists showed equipoise for high-quality evidence on this important issue.

DESIGN/METHODS

This protocol summarizes the rationale and design of a phase II randomized, blinded, placebo-controlled trial of a low-dose continuous infusion of furosemide, titrated to the physiology parameter of urine output, in critically ill patients with early AKI. Two hundred sixteen adult critically ill patients with early evidence of AKI, defined by the RIFLE criteria, will be enrolled. Included patients will also have fulfilled >or=2 criteria of the systemic inflammatory response syndrome and achieved immediate goals of acute resuscitation. The primary outcome is progression in severity of kidney injury. Secondary outcomes include: safety, fluid balance, electrolyte balance, the need for renal replacement therapy, duration of AKI, rate of renal recovery, mortality and changes in novel serum and urine biomarkers of AKI. The primary analysis will be intention-to-treat. Planned recruitment will be complete by June 2011 and results available by December 2011.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier NCT00978354.

The dark side of high-intensity renal replacement therapy of acute kidney injury in critically ill patients

The impact of intensity or dose of renal replacement therapy (RRT) on outcome of critically ill patients has been a matter of controversy. Most definitions of an adequate dose of acute RRT are based on urea removal, while ignoring other crucial aspects of RRT adequacy in acute kidney injury (AKI). Although some clinical trials have found an improvement in survival with higher doses of intermittent hemodialysis or continuous RRT, results have not been consistent across all studies. The largest trials suggest that there is no additional survival benefit with doses of 35-45 ml/kg/h (CRRT) or daily intermittent hemodialysis. On the other hand, high-intensity treatment may cause life-threatening complications and thereby counteract the benefits of higher small-solute clearance. One important area for future investigations is the need to characterize the potential harm of high-dose RRT for AKI in critically ill patients.

Clinical course and mortality risk factors in critically ill children requiring continuous renal replacement therapy

OBJECTIVE

To study the clinical course in children requiring continuous renal replacement therapy (CRRT) and to analyse factors associated with mortality.

DESIGN

Prospective observational study.

SETTING

Paediatric intensive care department of a tertiary university hospital.

PATIENTS

Critically ill children with CRRT were included in the study.

INTERVENTION

Continuous renal replacement therapy.

MEASUREMENTS AND RESULTS

Univariate and multivariate analyses were performed to analyse the influence of each factor on mortality. The ability of the PRISM, PIM II and PELOD severity of illness scores to predict mortality was tested using receiver-operating characteristic curve statistics. A total of 174 children aged between 1 month and 22 years were treated with CRRT. Mortality was 35.6%, and multiorgan failure and haemodynamic disturbances were the principal causes of death. Mortality was higher in children less than 12 months of age (44.7%; P = 0.037) and in patients with a diagnosis of sepsis (44.1%; P = 0.001). Haemodynamic disturbances at the time of starting CRRT (hypotension or need for adrenaline >0.6 microg/kg/min) and the presence of multiorgan failure were the factors associated with an increased risk of mortality. The PRISM scale was the severity score with the best predictive capacity, although all three scales underestimated the actual mortality.

CONCLUSIONS

Mortality in children who require CRRT is high. Haemodynamic disturbances and the presence of multiorgan failure at the time of starting the technique are the factors associated with a higher mortality. The clinical severity scores underestimate mortality in children requiring CRRT.

[Acute renal failure in critically ill patients]

BACKGROUND

Acute renal failure is common in critically ill patients and is associated with a high mortality rate. This paper reviews current management of patients with acute renal failure admitted to an intensive care unit.

MATERIAL AND METHODS

Literature search in databases (Medline, Cochrane database of systematic reviews, UpToDate).

RESULTS

The prevalence of acute renal failure is 5-20 % in patients admitted to intensive care units; the associated hospital mortality is 30-60 %. The aetiology is usually multifactorial; inflammation (sepsis, surgery), hypovolaemia and drug toxicity commonly precipitate acute renal failure. There is no effective drug treatment, but early onset of renal replacement therapies with haemodialysis or haemofiltration is likely to prolong survival.

INTERPRETATION

Despite modern intensive care, mortality is high in acute renal failure and preventive measures should therefore be vigorously pursued. Haemodialysis and haemofiltration should be introduced early in acute renal failure, and should be available in all intensive care units.

Early vs late start of dialysis: it's all about timing

Acute kidney injury (AKI) is now well recognized as an independent risk factor for increased morbidity and mortality, particularly when dialysis is needed. The wide variation in dialysis utilization contributes to a lack of consensus on what parameters should guide the decision to start dialysis. While the association of early initiation of dialysis with survival benefit was first demonstrated four decades ago, few studies in the modern era of dialysis have addressed time of dialysis initiation. Though listed as one of the top priorities in research on AKI, timing of dialysis initiation has not been included as a factor in any of the large, randomized controlled trials in this area.

Dosing of renal replacement therapy in acute kidney injury: lessons learned from clinical trials

Prescribing dialysis to manage acute kidney injury (AKI) is common and recently has become a controversial area for physicians. The concept of dialysis "dose" initially was developed for end-stage renal disease and has been extended to AKI in the last decade. Urea kinetic modeling has been the mainstay of dose quantification in end-stage renal disease. Extrapolation of these techniques to critically ill patients with AKI is difficult because of a non-steady state leading to a variable increase in urea generation rate, alterations in total-body water and its compartmental distribution, and changing renal excretory capacity. Additional challenges are imposed when dose is considered for different modalities of dialysis that vary in operational characteristics (diffusion, convection, and adsorption), duration (intermittent and continuous), and frequency. The purpose of this article is to review the concept of dialysis dose, perform a critical assessment of the most important clinical trials of dialysis dose in AKI, summarize clinical evidence from these trials, and define key research issues that should be addressed in the future.

Fluid accumulation and acute kidney injury: consequence or cause

PURPOSE OF REVIEW

Fluid accumulation and fluid overload are frequent findings in critically ill patients and in those suffering from severe acute kidney injury. This review focuses on the consequences associated with fluid overload in critically ill patients with or without associated acute kidney injury and discusses the potential mechanisms by which acute kidney injury can contribute to fluid overload and whether fluid overload can also contribute to kidney dysfunction.

RECENT FINDINGS

Fluid overload has recently been linked to adverse outcomes in critically ill patients suffering from acute kidney injury. However, whether significant fluid accumulation can contribute to acute kidney injury has not been investigated.

SUMMARY

Fluid overload is independently associated with increased mortality in patients with acute kidney injury and contributes to worsen outcomes in critically ill patients. Further studies are required to determine the influence of fluid overload on organ function and overall prognosis.

Fluid overload and mortality in children receiving continuous renal replacement therapy: the prospective pediatric continuous renal replacement therapy registry

BACKGROUND

Critically ill children with hemodynamic instability and acute kidney injury often develop fluid overload. Continuous renal replacement therapy (CRRT) has emerged as a favored modality in the management of such children. This study investigated the association between fluid overload and mortality in children receiving CRRT.

STUDY DESIGN

Prospective observational study.

SETTING & PARTICIPANTS

297 children from 13 centers across the United States participating in the Prospective Pediatric CRRT Registry.

PREDICTOR

Fluid overload from intensive care unit (ICU) admission to CRRT initiation, defined as a percentage equal to (fluid in [L] - fluid out [L])/(ICU admit weight [kg]) x 100%.

OUTCOME & MEASUREMENTS

The primary outcome was survival to pediatric ICU discharge. Data were collected regarding demographics, CRRT parameters, underlying disease process, and severity of illness.

RESULTS

153 patients (51.5%) developed < 10% fluid overload, 51 patients (17.2%) developed 10%-20% fluid overload, and 93 patients (31.3%) developed > or = 20% fluid overload. Patients who developed > or = 20% fluid overload at CRRT initiation had significantly higher mortality (61/93; 65.6%) than those who had 10%-20% fluid overload (22/51; 43.1%) and those with < 10% fluid overload (45/153; 29.4%). The association between degree of fluid overload and mortality remained after adjusting for intergroup differences and severity of illness. The adjusted mortality OR was 1.03 (95% CI, 1.01-1.05), suggesting a 3% increase in mortality for each 1% increase in severity of fluid overload. When fluid overload was dichotomized to > or = 20% and < 20%, patients with > or = 20% fluid overload had an adjusted mortality OR of 8.5 (95% CI, 2.8-25.7).

LIMITATIONS

This was an observational study; interventions were not standardized. The relationship between fluid overload and mortality remains an association without definitive evidence of causality.

CONCLUSIONS

Critically ill children who develop greater fluid overload before initiation of CRRT experience higher mortality than those with less fluid overload. Further goal-directed research is required to accurately define optimal fluid overload thresholds for initiation of CRRT.

Fluid balance and acute kidney injury

Intravenous fluids are widely administered to patients who have, or are at risk of, acute kidney injury (AKI). However, deleterious consequences of overzealous fluid therapy are increasingly being recognized. Salt and water overload can predispose to organ dysfunction, impaired wound healing and nosocomial infection, particularly in patients with AKI, in whom fluid challenges are frequent and excretion is impaired. In this Review article, we discuss how interstitial edema can further delay renal recovery and why conservative fluid strategies are now being advocated. Applying these strategies in critical illness is challenging. Although volume resuscitation is needed to restore cardiac output, it often leads to tissue edema, thereby contributing to ongoing organ dysfunction. Conservative strategies of fluid management mandate a switch towards neutral balance and then negative balance once hemodynamic stabilization is achieved. In patients with AKI, this strategy might require renal replacement therapy to be given earlier than when more-liberal fluid management is used. However, hypovolemia and renal hypoperfusion can occur in patients with AKI if excessive fluid removal is pursued with diuretics or extracorporeal therapy. Thus, accurate assessment of fluid status and careful definition of targets are needed at all stages to improve clinical outcomes. A conservative strategy of fluid management was recently tested and found to be effective in a large, randomized, controlled trial in patients with acute lung injury. Similar randomized, controlled studies in patients with AKI now seem justified.

Microcirculation and mitochondria in sepsis: getting out of breath

PURPOSE OF REVIEW

To present the recent findings obtained in clinical and experimental studies examining microcirculatory alterations in sepsis, their link to mitochondrial dysfunction, and current knowledge regarding the impact of these alterations on the outcome of septic patients.

RECENT FINDINGS

Interlinked by a mutual cascade effect and driven by the host-pathogen interaction, microcirculatory and mitochondrial functions are impaired during sepsis. Mitochondrial respiration seems to evolve during the course of sepsis, demonstrating a change from reversible to irreversible inhibition. The spatiotemporal heterogeneity of microcirculatory and mitochondrial dysfunction suggests that these processes may be compartmentalized. Although a causal relationship between mitochondrial and microcirculatory dysfunction and organ failure in sepsis is supported by an increasing number of studies, adaptive processes have also emerged as part of microcirculatory and mitochondrial alterations. Treatments for improving or preserving microcirculatory, mitochondrial function, or both seem to yield a better outcome in patients.

SUMMARY

Even though there is evidence that microcirculatory and mitochondrial dysfunction plays a role in the development of sepsis-induced organ failure, their interaction and respective contribution to the disease remains poorly understood. Future research is necessary to better define such relationships in order to identify therapeutic targets and refine treatment strategies.

Effect of fluid resuscitation on mortality and organ function in experimental sepsis models

INTRODUCTION

Several recent studies have shown that a positive fluid balance in critical illness is associated with worse outcome. We tested the effects of moderate vs. high-volume resuscitation strategies on mortality, systemic and regional blood flows, mitochondrial respiration, and organ function in two experimental sepsis models.

METHODS

48 pigs were randomized to continuous endotoxin infusion, fecal peritonitis, and a control group (n = 16 each), and each group further to two different basal rates of volume supply for 24 hours [moderate-volume (10 ml/kg/h, Ringer's lactate, n = 8); high-volume (15 + 5 ml/kg/h, Ringer's lactate and hydroxyethyl starch (HES), n = 8)], both supplemented by additional volume boli, as guided by urinary output, filling pressures, and responses in stroke volume. Systemic and regional hemodynamics were measured and tissue specimens taken for mitochondrial function assessment and histological analysis.

RESULTS

Mortality in high-volume groups was 87% (peritonitis), 75% (endotoxemia), and 13% (controls). In moderate-volume groups mortality was 50% (peritonitis), 13% (endotoxemia) and 0% (controls). Both septic groups became hyperdynamic. While neither sepsis nor volume resuscitation strategy was associated with altered hepatic or muscle mitochondrial complex I- and II-dependent respiration, non-survivors had lower hepatic complex II-dependent respiratory control ratios (2.6 +/- 0.7, vs. 3.3 +/- 0.9 in survivors; P = 0.01). Histology revealed moderate damage in all organs, colloid plaques in lung tissue of high-volume groups, and severe kidney damage in endotoxin high-volume animals.

CONCLUSIONS

High-volume resuscitation including HES in experimental peritonitis and endotoxemia increased mortality despite better initial hemodynamic stability. This suggests that the strategy of early fluid management influences outcome in sepsis. The high mortality was not associated with reduced mitochondrial complex I- or II-dependent muscle and hepatic respiration.

Mechanical ventilation and the kidney

Acute lung injury (ALI) and acute kidney injury (AKI) are complications often encountered in the setting of critical illness. Both forms of end-organ injury commonly occur in similar settings of systemic inflammatory response syndrome, shock, and evolving multiple organ dysfunction. Recent elucidation of the pathobiology of critical illness has led to a more basic mechanistic understanding of the complex interplay between injured organs in patients with multiple organ dysfunction syndrome; this has been aptly called 'the slippery slope of critical illness' [Kidney Int Suppl 1998;66:S25-S33]. Distant organ effects of apparently isolated injuries to the lungs, gut, and kidneys have all been discovered in recent years. In this article, we will review the harmful bidirectional interaction between ALI and AKI, which appears to be a common clinical syndrome with routine clinical implications. We will review the current understanding of lung-kidney interactions from both perspectives, including the renal effects of ALI and mechanical ventilation, and the pulmonary sequelae of AKI. In this review of the emerging evidence of deleterious bidirectional organ cross talk between lung and kidney, we will focus on the role of ventilator-induced kidney injury in the pathogenesis of AKI in patients with ALI.

A proposed algorithm for initiation of renal replacement therapy in adult critically ill patients

Critically ill patients whose course is complicated by acute kidney injury often receive renal replacement therapy (RRT). For these patients, initiation of RRT results in a considerable escalation in both the complexity and associated cost of care. While RRT is extensively used in clinical practice, there remains uncertainty about the ideal circumstances of when to initiate RRT and for what indications. The process of deciding when to initiate RRT in critically ill patients is complex and is influenced by numerous factors, including patient-specific and clinician-specific factors and those related to local organizational/logistical issues. Studies have shown marked variation between clinicians, and across institutions and countries. As a consequence, analysis of ideal circumstances under which to initiate RRT is challenging. Recognizing this limitation, we review the available data and propose a clinical algorithm to aid in the decision for RRT initiation in critically ill adult patients. The algorithm incorporates several patient-specific factors, based on evidence when available, that may decisively influence when to initiate RRT. The objective of this algorithm is to provide a starting point to guide clinicians on when to initiate RRT in critically ill adult patients. In addition, the proposed algorithm is intended to provide a foundation for prospective evaluation and the development of a broad consensus on when to initiate RRT in critically ill patients.

[Acute perioperative disturbances of renal function. Strategies for prevention and therapy]

The increasing life expectancy in industrial nations leads to an increase in the number of elderly and aged persons treated in hospital. Increasingly more complex operations are being carried out on this group of patients. Renal dysfunction in the preoperative situation increases morbidity and mortality. Acute kidney injury (AKI) is nearly always part of a multi-organ dysfunction syndrome in critically ill patients. The treatment strategy of the AKI should be oriented to the degree of organ dysfunction. However, the stage of organ dysfunction is mostly unknown so that the therapeutically exploitable interval is often missed. The same therapy is practically always used for all patients: administration of fluids and diuretics often under the premise of "the kidneys must be rinsed". A unified classification of the continuation of kidney function disorders using the RIFLE criteria (risk, injury, failure, loss, endstage kidney disease) can assist recognition of early stages of kidney failure in order to react correspondingly with therapeutic measures and to critically question or optimize the use of conservative treatment strategies.

Year in review 2008: Critical Care--nephrology

We summarize original research in the field of critical care nephrology accepted or published during 2008 in Critical Care and, when considered relevant or directly linked to this research, in other journals. Three main topics have been identified for a rapid overview. (1) The classification of acute kidney injury, with particular attention to differences and similarities between the RIFLE and AKIN classifications. (2) Fluid balance in patients requiring renal replacement therapy (RRT) has been shown as an independent risk factor for mortality in critically ill patients: current evidence and uncertainties are described. (3) Management of anticoagulation during RRT has been explored by several researchers in 2008: diagnosis of heparin-induced thrombocytopenia, the use of tirofiban and optimal anticoagulation during drotrecogin A activated treatment have been evaluated.

ARDS of early or late onset: does it make a difference?

BACKGROUND

Differences in outcomes have been demonstrated for critically ill patients with late-onset compared with early-onset renal failure and late-onset compared with early-onset shock, which could cause a lead-time bias in clinical trials assessing potential therapies for these conditions. We used data from a large, multicenter observational study to assess whether late-onset ARDS was similarly associated with worse outcomes compared with early-onset ARDS.

METHODS

Data were extracted from the Sepsis Occurrence in Acutely Ill Patients (SOAP) study, which involved 198 ICUs from 24 European countries. All adult patients admitted to a participating ICU between May 1, 2002 and May 15, 2002, were eligible, except those admitted for uncomplicated postoperative surveillance. Early/late onset acute lung injury (ALI)/ARDS was defined as ALI/ARDS occurring within/after 48 h of ICU admission.

RESULTS

Of the 3,147 patients included in the SOAP study, 393 (12.5%) had a diagnosis of ALI/ARDS; 254 had early-onset ALI/ARDS (64.6%), and 139 (35.5%) late-onset. Patients with early-onset ALI/ARDS had higher Simplified Acute Physiology II scores on admission and higher initial Sequential Organ Failure Assessment scores. Patients with late-onset ALI/ARDS had longer ICU and hospital lengths of stay than patients with early-onset ALI/ARDS. ICU and hospital mortality rates were, if anything, lower in late-onset ALI/ARDS than in early-onset ALI/ARDS, but these differences were not statistically significant.

CONCLUSIONS

There were no significant differences in mortality rates between early- and late-onset ARDS, but patients with late-onset ALI/ARDS had longer ICU and hospital lengths of stay.

Mechanisms of the cardiorenal syndromes

The kidney and heart have essential roles in maintaining blood volume homeostasis and in the regulation of systemic blood pressure. Acute or chronic dysfunction in either the heart or kidneys can induce dysfunction in the other organ, resulting in the so-called cardiorenal syndromes, which are classified into five different types. Abrupt worsening of cardiac function predisposes an individual to acute kidney injury from renal hypoperfusion or renal congestion. Progressive, sometimes permanent, chronic kidney impairment can result from chronic renal hypoperfusion or congestion. Heart failure is common in patients with acute kidney injury. Chronic kidney disease predisposes individuals to atherosclerotic, arteriosclerotic and cardiomyopathic disease. Finally, both cardiac and renal disease can also occur secondary to systemic conditions, such as diabetes or autoimmune disease. This Review examines the mechanisms presiding over the first four types of cardiorenal syndromes. These mechanisms provide a template that accounts for the heart-kidney interactions that occur in patients whose concomitant cardiac and renal conditions result from a third cause.

Mortality in sepsis versus non-sepsis induced acute lung injury

Introduction

Sepsis-induced acute lung injury (ALI) has been reported to have a higher case fatality rate than other causes of ALI. However, differences in the severity of illness in septic vs. non-septic ALI patients might explain this finding.

Methods

520 patients enrolled in the Improving Care of ALI Patients Study (ICAP) were prospectively characterized as having sepsis or non sepsis-induced ALI. Biologically plausible risk factors for in-hospital death were considered in multiple logistic regression models to evaluate the independent association of sepsis vs. non-sepsis ALI risk factors with mortality.

Results

Patients with sepsis-induced ALI had greater illness severity and organ dysfunction (APACHE II and SOFA scores) at ALI diagnosis and higher crude in-hospital mortality rates compared with non-sepsis ALI patients. Patients with sepsis-induced ALI received similar tidal volumes, but higher levels of positive end expiratory pressure, and had a more positive net fluid balance in the first week after ALI diagnosis. In multivariable analysis, the following variables (odds ratio, 95% confidence interval) were significantly associated with hospital mortality: age (1.04, 1.02 to 1.05), admission to a medical intensive care unit (ICU) (2.76, 1.42 to 5.36), ICU length of stay prior to ALI diagnosis (1.15, 1.03 to 1.29), APACHE II (1.05, 1.02 to 1.08), SOFA at ALI diagnosis (1.17, 1.09 to 1.25), Lung Injury Score (2.33, 1.74 to 3.12) and net fluid balance in liters in the first week after ALI diagnosis (1.06, 1.03 to 1.09). Sepsis did not have a significant, independent association with mortality (1.02, 0.59 to 1.76).

Conclusions

Greater severity of illness contributes to the higher case fatality rate observed in sepsis-induced ALI. Sepsis was not independently associated with mortality in our study.

Comparison of methods for estimating glomerular filtration rate in critically ill patients with acute kidney injury

BACKGROUND

In critically ill patients with acute kidney injury, estimates of kidney function are used to modify drug dosing, adjust nutritional therapy and provide dialytic support. However, estimating glomerular filtration rate is challenging due to fluctuations in kidney function, creatinine production and fluid balance. We hypothesized that commonly used glomerular filtration rate prediction equations overestimate kidney function in patients with acute kidney injury and that improved estimates could be obtained by methods incorporating changes in creatinine generation and fluid balance.

METHODS

We analysed data from a multicentre observational study of acute kidney injury in critically ill patients. We identified 12 non-dialysed, non-oliguric patients with consecutive increases in creatinine for at least 3 and up to 7 days who had measurements of urinary creatinine clearance. Glomerular filtration rate was estimated by Cockcroft-Gault, Modification of Diet in Renal Disease, Jelliffe equation and Jelliffe equation with creatinine adjusted for fluid balance (Modified Jelliffe) and compared to measured urinary creatinine clearance.

RESULTS

Glomerular filtration rate estimated by Jelliffe and Modification of Diet in Renal Disease equation correlated best with urinary creatinine clearances. Estimated glomerular filtration rate by Cockcroft-Gault, Modification of Diet in Renal Disease and Jelliffe overestimated urinary creatinine clearance was 80%, 33%, 10%, respectively, and Modified Jelliffe underestimated GFR by 2%.

CONCLUSION

In patients with acute kidney injury, glomerular filtration rate estimating equations can be improved by incorporating data on creatinine generation and fluid balance. A better assessment of glomerular filtration rate in acute kidney injury could improve evaluation and management and guide interventions.

Detecting volume responsiveness and unresponsiveness in intensive care unit patients: two different problems, only one solution

Policies of fluid administration/restriction in critically ill patients have evolved over recent years. Abundant fluid resuscitation is encouraged during the early stage of severe sepsis. But a conservative fluid strategy is recommended in later stages, in particular when lungs are injured. Both strategies are risky if uncontrolled. Tests detecting volume unresponsiveness at any moment of fluid resuscitation or detecting volume unresponsiveness at any moment of fluid restriction would help to better assess the benefit/risk ratio of continuing such strategies. Measuring the short-term hemodynamic changes during passive leg raising can be reliably used for that purpose in both situations, even when patients are breathing spontaneously.

Renal replacement therapy in the liver transplant candidate

Since the implementation of the model of end-stage liver disease score to prioritize patients for orthotopic liver transplantation (OLT), the number of liver transplant candidates with renal failure and on renal replacement therapy (RRT) has dramatically increased. This review is intended to discuss the indications and implications of RRT initiation, the different RRT modalities, and special problems encountered with RRT in OLT candidates.

Fluid accumulation, survival and recovery of kidney function in critically ill patients with acute kidney injury

Fluid accumulation is associated with adverse outcomes in critically ill patients. Here, we sought to determine if fluid accumulation is associated with mortality and non-recovery of kidney function in critically ill adults with acute kidney injury. Fluid overload was defined as more than a 10% increase in body weight relative to baseline, measured in 618 patients enrolled in a prospective multicenter observational study. Patients with fluid overload experienced significantly higher mortality within 60 days of enrollment. Among dialyzed patients, survivors had significantly lower fluid accumulation when dialysis was initiated compared to non-survivors after adjustments for dialysis modality and severity score. The adjusted odds ratio for death associated with fluid overload at dialysis initiation was 2.07. In non-dialyzed patients, survivors had significantly less fluid accumulation at the peak of their serum creatinine. Fluid overload at the time of diagnosis of acute kidney injury was not associated with recovery of kidney function. However, patients with fluid overload when their serum creatinine reached its peak were significantly less likely to recover kidney function. Our study shows that in patients with acute kidney injury, fluid overload was independently associated with mortality. Whether the fluid overload was the result of a more severe renal failure or it contributed to its cause will require clinical trials in which the role of fluid administration to such patients is directly tested.

Anticoagulant properties of drotrecogin alfa (activated) during hemofiltration in patients with severe sepsis

In a retrospective study among 35 severely septic patients treated with drotrecogin alfa (activated) (DrotAA) and renal replacement therapy (RRT), Camporota and colleagues demonstrated that the addition of heparin, epoprostenol, or both to DrotAA during RRT did not improve filter survival. Furthermore, in a multivariate logistic regression analysis, they identified the minimum value in platelet count as the only predictive factor of filter clotting during DrotAA infusion. These findings are in line with the previously formulated suggestion that DrotAA alone is as effective as heparin in the prevention of coagulation in the extracorporeal circuit. They also confirm the importance of baseline platelet count in the pathogenesis of extracorporeal circuit thrombosis. In the study by Camporata and colleagues, DrotAA treatment was not associated with an increase in red blood cell requirements. The results of this study supply a background to clinical decision making when choosing an anticoagulant for RRT in septic patients.

Fluid balance and acute kidney injury: the missing link for predicting adverse outcomes?

This Practice Point commentary discusses the findings from the secondary analysis of a large systematic cohort study of critically ill patients that evaluated the influence of fluid overload on outcomes from acute kidney injury (AKI). Payen et al. reported a 36% incidence of AKI among the 3,147 patients enrolled in the Sepsis Occurrence in Acutely Ill Patients (SOAP) study. Mortality rate at 60 days was more than twofold higher among patients who had AKI than among those without AKI. Among patients with AKI, mortality rates were increased in patients with oliguria and in those treated with renal replacement therapy. A positive fluid balance was an independent risk factor for 60-day mortality. The interpretation and implications of these findings for clinical practice are highlighted in this commentary. Fluid balance is probably an important factor that determines outcomes in patients with AKI who are in an intensive care unit, but additional studies are required to confirm these findings.

Renal replacement therapies: physiological review

INTRODUCTION

A physiological review on renal replacement therapies (RRT) is a challenging task: there is nothing "physiologic" about RRT, since the most accurate, safe and perfectly delivered extracorporeal therapy would still be far from "physiologically" replacing the function of the native kidney.

METHODS

This review will address the issues of physiology of fluid and solute removal, acid base control and impact on mortality during intermittent and continuous therapies: different RRT modalities and relative prescriptions will provide different "physiological clinical effects" to critically ill patients with acute kidney injury (AKI), with the aim of restoring lost "renal homeostasis". On the other side, however, the "pathophysiology" of RRT, consists with unwanted clinical effects caused by the same treatments, generally under-recognized by current literature but often encountered in clinical practice. Physiology and pathophysiology of different RRT modalities have been reviewed.

CONCLUSION

Physiology and pathophysiology of RRT often coexist during dialysis sessions. Improvement in renal recovery and survival from AKI will be achieved from optimization of therapy and increased awareness of potential benefits and dangers deriving from different RRT modalities.

Fluid balance as a biomarker: impact of fluid overload on outcome in critically ill patients with acute kidney injury

Fluid therapy is fundamental to the acute resuscitation of critically ill patients. In general, however, early and appropriate goal-directed fluid therapy contributes to a degree of fluid overload in most if not all patients. Recent data imply that a threshold may exist beyond which, after acute resuscitation, additional fluid therapy may cause harm. In patients with acute kidney injury and/or oliguria, a positive fluid balance is almost universal. Few studies have examined the impact of fluid balance on clinical outcomes in critically ill adults with acute kidney injury. Payen and coworkers, in a secondary analysis of the SOAP (Sepsis Occurrence in Acutely Ill Patients) study, now present evidence that there is an independent association between mortality and positive fluid balance in a cohort of critically ill patients with acute kidney injury. In this commentary, we discuss these findings within the context of prior literature and propose that assessment of fluid balance should be considered as a potentially valuable biomarker of critical illness.