The 3rd International Consensus Conference of the Acute Dialysis Quality Initiative (ADQI)

Insights of Worsening Renal Function in Type 1 Cardiorenal Syndrome: From the Pathogenesis, Biomarkers to Treatment

Type-1 cardiorenal syndrome refers to acute kidney injury induced by acute worsening cardiac function. Worsening renal function is a strong and independent predictive factor for poor prognosis. Currently, several problems of the type-1 cardiorenal syndrome have not been fully elucidated. The pathogenesis mechanism of renal dysfunction is unclear. Besides, the diagnostic efficiency, sensitivity, and specificity of the existing biomarkers are doubtful. Furthermore, the renal safety of the therapeutic strategies for acute heart failure (AHF) is still ambiguous. Based on these issues, we systematically summarized and depicted the research actualities and predicaments of the pathogenesis, diagnostic markers, and therapeutic strategies of worsening renal function in type-1 cardiorenal syndrome.

Acute Kidney Injury Affects Mid-Term Outcomes of Thoracoabdominal Aortic Aneurysms Repair

The effect of acute kidney injury (AKI) on mid-term outcomes following thoracoabdominal aortic aneurysm (TAAA) repair is not well known. We hypothesized that postoperative AKI would reduce mid-term survival and aimed to analyze the effect of AKI on mid-term outcomes after TAAA repair. This retrospective study identified 294 consecutive TAAA repairs at Kobe University Hospital from October 1999 to March 2019. Patients with preexisting end-stage renal disease that required hemodialysis (n = 11) and patients who died intraoperatively (n = 2) were excluded. Finally, 281 patients were analyzed. AKI was defined according to Kidney Disease: Improving Global Outcomes guidelines (KDIGO) classification. Of the 281 patients, 178 (63.3%) developed AKI, of which 98 (34.9%) had mild, 34 (12.1%) had moderate, and 46 (16.4%) had severe AKI. Twenty-six patients (12.8%) required renal replacement therapy after surgery. Twenty-three in-hospital deaths (8.2%) were recorded, including 2 (0.7%) without AKI, 0 (0%) with mild AKI, 1 (0.4%) with moderate AKI, and 20 (7.1%) with severe AKI (p < .001). The 4-year survival was 91.9 ± 3.0% for no AKI, 91.3 ± 3.2% for mild AKI, 72.4 ± 8.5% for moderate AKI and 32.6 ± 7.4% for severe AKI (p < .001). Multivariable Cox-hazard regression analysis demonstrated that moderate and severe AKI, older age and emergency surgery were significant risk factors for mid-term survival. In patients undergoing TAAA repair, severe AKI was associated with an increase in in-hospital mortality and both moderate and severe AKI were negatively associated with mid-term survival. Preventing moderate/severe AKI may improve mid-term survival after TAAA repair.

Development and Validation of a Model for Predicting the Risk of Acute Kidney Injury Associated With Contrast Volume Levels During Percutaneous Coronary Intervention

Importance

Determining the association of contrast volume during percutaneous coronary intervention (PCI) with the risk of acute kidney injury (AKI) is important for optimizing PCI safety.

Objective

To quantify how the risk of AKI is associated with contrast volume, accounting for the possibility of nonlinearity and heterogeneity among different baseline risks.

Design, Setting, and Participants

This prognostic study used data from the American College of Cardiology National Cardiovascular Data Registry CathPCI Registry for 1694 US hospitals. Derivation analysis included 2 076 694 individuals who underwent PCI from July 1, 2011, to June 30, 2015. Validation analysis included 961 863 individuals who underwent PCI from July 1, 2015, to March 31, 2017. Data analysis took place from July 2018 to May 2019.

Exposure

Contrast volume during PCI.

Main Outcomes and Measures

Acute kidney injury was defined using 3 thresholds for preprocedure to postprocedure creatinine level increase (ie, ≥0.3 mg/dL, ≥0.5 mg/dL, and ≥1.0 mg/dL). A model quantifying the association of contrast volume with AKI was developed, and the existence of nonlinearity and heterogeneity were examined by likelihood ratio tests. The model was derived in the training set (a random 50% of the derivation cohort), and performance was evaluated in the test set (the remaining 50% of the derivation cohort) and an independent validation set by area under the receiver operating characteristic curve (AUC) and calibration slope of observed vs predicted risks.

Results

The 2 076 694 patients in the derivation set had a mean (SD) age of 65.1 (12.1) years, and 662 525 (31.9%) were women; 133 306 (6.4%) had creatinine level increases of at least 0.3 mg/dL, 66 626 (3.2%) had creatinine level increases of at least 0.5 mg/dL, and 28 378 (1.4%) had creatinine level increases of at least 1.0 mg/dL. In the validation set of 961 843 patients (mean [SD] age, 65.7 [12.1] years; 305 577 [31.8%] women), these rates were 62 913 (6.5%), 34 229 (3.6%), and 15 555 (1.6%), respectively. The association of contrast volume and AKI risk was nonlinear (χ226 = 1436.2; P < .001) and varied by preprocedural risk (χ220 = 105.6; P < .001). In the test set, the model yielded an AUC of 0.777 (95% CI, 0.775-0.779) for predicting risk of a creatinine level increase of at least 0.3 mg/dL, 0.839 (95% CI, 0.837-0.841) for predicting risk of a creatinine level increase of at least 0.5 mg/dL, and 0.870 (95% CI, 0.867-0.873) for predicting risk of a creatinine level increase of at least 1.0 mg/dL; it achieved a calibration slope of 0.998 (95% CI, 0.989-1.007), 0.999 (95% CI, 0.989-1.008), and 0.986 (95% CI, 0.973-0.998), respectively, for the AKI severity levels. The model had similar performance in the validation set (creatinine level increase of ≥0.3 mg/dL: AUC, 0.794; 95% CI, 0.792-0.795; calibration slope, 1.039; 95% CI, 1.030-1.047; creatinine level increase of ≥0.5 mg/dL: AUC, 0.845; 95% CI, 0.843-0.848; calibration slope, 1.063; 95% CI, 1.054-1.074; creatinine level increase of ≥1.0 mg/dL: AUC, 0.872; 95% CI, 0.869-0.875; calibration slope, 1.103; 95% CI, 1.089-1.117).

Conclusions and Relevance

The association of contrast volume with AKI risk is complex, varies by baseline risk, and can be predicted by a model. Future research to evaluate the effect of the model on AKI is needed.

The use of prophylactic intra-aortic balloon pump in high-risk patients undergoing coronary artery bypass grafting

Objective

Intra-aortic balloon pump (IABP) is one of the most commonly used mechanical circulatory assist devices for high-risk patients undergoing cardiac surgery. In an effort to validate previously reported clinical outcomes, we describe the preoperative characteristics and outcomes of patients who underwent prophylactic IABP in high-risk patients undergoing coronary artery bypass grafting (CABG).

Design

A prospective observational study

Methods

From 2005 to 2017, 471 patients underwent either isolated or combined CABG at our institution. Of those, 393 patients underwent isolated CABG and were included for the analysis. Eighty-five patients (22%) were considered high-risk and underwent prophylactic IABP, with subsequent review of surgical morbidity and mortality rates.

Results

The 30-day postoperative mortality (prophylactic IABP group vs non prophylactic IABP group: 0% vs 1.6%, p = 0.589) and major adverse cardiac or cerebrovascular events (5.9% vs 3.3%, p = 0.333) were not significantly different between the two groups. Prolonged mechanical ventilation (>72 hours) (12.5% vs 4.2%, p = 0.014) occurred more frequently in the prophylactic IABP group.

Conclusions

No IABP-related complications were noted, emphasizing that the use of prophylactic IABP in high-risk patients undergoing CABG is an acceptable option.

Stratification and Risk Reduction of Perioperative Acute Kidney Injury: An Update

Perioperative acute kidney injury is associated with morbidity and mortality. Several definitions have been proposed, incorporating small changes of serum creatinine and urinary output reduction as diagnostic criteria. In the surgical patient, comorbidities, type and timing of surgery, and nephrotoxins are important. Patient comorbidities remain a significant risk factor. Urgent or emergent surgery and cardiac or transplantation procedures are associated with a higher risk of acute kidney injury. Nephrotoxic drugs, contrast dye, and diuretics worsen preexisting kidney dysfunction or act as an adjunctive insult to perioperative injury. This review includes preoperative, intraoperative, and postoperative issues that can be mitigated.

Methods used to assess the performance of biomarkers for the diagnosis of acute kidney injury: a systematic review and meta-analysis

PURPOSE

Methods used to explore biomarkers for acute kidney injury (AKI) might have a major impact on the results and the use of these biomarkers. We evaluated the methods used to investigate biomarkers of AKI.

MATERIALS AND METHODS

A systematic review and meta-analysis were performed using a computerized search of the MEDLINE and the EMBASE databases (PROSPERO CRD42017059618). Articles reporting biomarker's performance to diagnose AKI were included. The outcome included a description of the methods used to assess the performance of biomarkers to diagnose AKI.

RESULTS

Among the 295 included studies, assessment of biomarkers was the primary endpoint in 284 with sample size calculation in only 8% of cases. Eighty-five percent of the studies summarized the performance of biomarkers with receiver operating characteristic (ROC) curves; however, 74 studies (25%) did not provide the threshold, sensibility or specificity. A total of 176 studies evaluated more than one biomarker, and only 25% combined biomarkers to increase diagnostic performance. We determined that the definition of AKI and study design impacted the diagnostic performance using uNGAL (urinary neutrophil gelatinase-associated lipocalin) as an example. Major publication bias was identified.

CONCLUSIONS

Most articles that reported biomarkers of AKI performance present methodological weaknesses. Basic rules should be provided to increase the quality of reporting in this area.

The Clinical Epidemiology and 30-Day Outcomes of Emergency Department Patients With Acute Kidney Injury

BACKGROUND

Acute kidney injury (AKI) is associated with increased mortality and dialysis in hospitalized patients but has been little explored in the emergency department (ED) setting.

OBJECTIVE

The objective of this study was to describe the risk factors, prevalence, management, and outcomes in the ED population, and to identify the proportion of AKI patients who were discharged home with no renal-specific follow-up.

DESIGN

This is a retrospective cohort study using administrative and laboratory databases.

SETTING

Two urban EDs in Vancouver, British Columbia, Canada.

PATIENTS

We included all unique ED patients over a 1-week period.

METHODS

All patients had their described demographics, comorbidities, medications, laboratory values, and ED treatments collected. AKI was defined pragmatically, based upon accepted guidelines. The cohort was then probabilistically linked to the provincial renal database to ascertain renal replacement (transplant or dialysis) and the provincial vital statistics database to obtain mortality. The primary outcome was the prevalence of AKI; secondary outcomes included (1) the proportion of AKI patients who were discharged home with no renal-specific follow-up and (2) the combined 30-day rate of death or renal replacement among AKI patients.

RESULTS

There were 1651 ED unique patients, and 840 had at least one serum creatinine (SCr) obtained. Overall, 90 patients had AKI (10.7% of ED patients with at least one SCr, 95% confidence interval [CI], 8.7%-13.1%; 5.5% of all ED patients, 95% CI, 4.4%-6.7%) with a median age of 74 and 70% male. Of the 31 (34.4%) AKI patients discharged home, 4 (12.9%) had renal-specific follow-up arranged in the ED. Among the 90 AKI patients, 11 died and none required renal replacement at 30 days, for a combined outcome of 12.2% (95% CI, 6.5%-21.2%).

LIMITATIONS

Sample sizes may be small. Nearly half of ED patients did not obtain an SCr. Many patients did not have sequential SCr testing, and a modified definition of AKI was used.

Volume-related weight gain as an independent indication for renal replacement therapy in the intensive care units

Attempts to identify specific therapies to reverse acute kidney injury (AKI) have been unsuccessful in the past; only modifying risk profile or addressing the underlying disease processes leading to AKI proved efficacious. The current thinking on recognizing AKI is compromised by a "kidney function percent-centered" viewpoint, a paradigm further reinforced by the emergence of serum creatinine-based automated glomerular filtration reporting over the last two decades. Such thinking is, however, grossly corrupted for AKI and poorly applicable in critically ill patients in general. Conventional indications for renal replacement therapy (RRT) may have limited applicability in critically ill patients and there has been a relative lack of progress on RRT modalities in these patients. AKI in critically ill patients is a highly complex syndrome and it may be counterproductive to produce complex clinical practice guidelines, which are labor and resource-intensive to maintain, difficult to memorize or may not be immediately available in all settings all over the world. Additionally, despite attempts to develop reliable and reproducible biomarkers to replace serum creatinine as a guide to therapy such biomarkers failed to materialize. Under such circumstances, there is an ongoing need to reassess the practical value of simple measures, such as volume-related weight gain (VRWG) and urine output, both for prognostic markers and clinical indicators for the need for RRT. This current paper reviews the practical utility of VRWG as an independent indication for RRT in face of reduced urine output and hemodynamic instability.

Intra-day variability of cystatin C, creatinine and estimated GFR in intensive care patients

BACKGROUND

Markers of renal function are widely used in intensive care and sudden changes are important indicators of acute kidney injury. The problem is to distinguish between disease progression/improvement from the natural variation in the patient. The aim of the present study was thus to study the normal intraday variation in ICU patients.

METHODS

We studied the intra-day variation of creatinine, cystatin C and estimated GFR based on these two markers in 28 clinically stable ICU patients.

RESULTS

The median diurnal coefficient of variation sCV) for creatinine was 3.70% (1.92-9.25%) while the median CV for cystatin C was 3.66% (1.36-8.11%). The corresponding CVs for the estimated GFRs were 2.00% (0.89-9.82%) for eGFRcreatinine and 4.60% (1.65-10.24%) for eGFRcystc.

CONCLUSIONS

The eGFRcreatinine values in individual patients were clearly higher than the eGFRcystc values. The median CV for creatinine, cystatin C and the eGFR measurements were below 5% which means that 95% of the test results will vary by <10% between sampling times in stable ICU patients. Differences >10% between sampling times are thus likely to be an indication of changes in biomarker levels due to the disease/treatment.

Recent Successes in the Identification, Development, and Qualification of Translational Biomarkers

The development of novel safety or efficacy biomarkers has increasingly been used to improve safety monitoring and minimize attrition during drug development; however, for new biomarkers, the failure rate can equal or exceed that of new chemical entities. Drug-induced kidney injury is recognized to occur throughout the drug development process, with histopathology considered to be the gold standard for preclinical toxicologic screening. Renal biomarkers used clinically are primarily biomarkers of renal function and are considered insensitive for the detection of drug-induced kidney injury during first-in-man studies, particularly for compounds known to induce renal injury in preclinical species. Recent efforts by public–private partnerships have led to unprecedented success in the identification, development, and qualification of several new translatable biomarkers of kidney injury in the rat. To optimize the chance of success in current and future biomarker efforts in preclinical species and man, selection and development of biomarkers should emphasize biological considerations including marker variability and biology in both health and disease. The research to support the qualification of novel renal safety markers for routine use in the clinical setting is currently underway, and results from this work are greatly anticipated.

Prioritizing a research agenda: a Delphi study of the better outcomes through research for newborns (BORN) network

BACKGROUND

There is a paucity of evidence to guide clinical management for term and late preterm newborns. The Better Outcomes through Research for Newborns (BORN) network is a national collaborative of clinicians formed to increase the evidence-base for well newborn care.

OBJECTIVE

To develop a consensus-based, prioritized research agenda for well newborn care.

DESIGN

A two-round modified Delphi survey of BORN members was conducted. Round 1 was an open-ended survey soliciting 5 clinical questions identified as important and under-researched. Using qualitative methods, 20 most common themes were extracted and transformed into research questions. Round 2 survey respondents ranked the top 20 questions using a 5- point Likert scale and a quantitative analysis was conducted.

RESULTS

Round 1 survey generated 439 unique research questions that fell into 57 themes. In the Round 2 survey, the highest rated questions were: 1) At what weight-loss percentage is it medically necessary to formula supplement a breastfeeding infant? 2) What is the optimal management of infants with neonatal abstinence syndrome? 3) How and when should we initiate a workup for sepsis, and how should these newborns be managed?

CONCLUSIONS

Research priorities of clinicians include criteria for medically indicated formula supplementation of the breastfed newborn, management of neonatal abstinence syndrome and management of newborns at-risk for sepsis.

Procalcitonin levels predict acute kidney injury and prognosis in acute pancreatitis: a prospective study

Background

Acute kidney injury (AKI) has been proposed as a leading cause of mortality for acute pancreatitis (AP) patients admitted to the intensive care unit (ICU). This study investigated the predictive value of procalcitonin (PCT) for AKI development and relevant prognosis in patients with AP, and compared PCT’s predictive power with that of other inflammation-related variables.

Methods

Between January 2011 and March 2013, we enrolled 305 cases with acute pancreatitis admitted to ICU. Serum levels of PCT, serum amyloid A (SAA), interleukin-6 (IL-6), and C reactive protein (CRP) were determined on admission. Serum PCT was tested in patients who developed AKI on the day of AKI occurrence and on either day 28 after occurrence (for survivors) or on the day of death (for those who died within 28 days).

Results

Serum PCT levels were 100-fold higher in the AKI group than in the non-AKI group on the day of ICU admission (p<0.05). The area under the receiver-operating characteristic (ROC) curve of PCT for predicting AKI was 0.986, which was superior to SAA, CRP, and IL-6 (p<0.05). ROC analysis revealed all variables tested had lower predictive performance for AKI prognosis. The average serum PCT level on day 28 (2.67 (0.89, 7.99) ng/ml) was significantly (p<0.0001) lower than on the day of AKI occurrence (43.71 (19.24,65.69) ng/ml) in survivors, but the serum PCT level on death (63.73 (34.22,94.30) ng/ml) was higher than on the day of AKI occurrence (37.55 (18.70,74.12) ng/ml) in non-survivors, although there was no significant difference between the two days in the latter group (p = 0.1365).

Conclusion

Serum PCT is superior to CRP, IL-6, and SAA for predicting the development of AKI in patients with AP, and also can be used for dynamic evaluation of AKI prognosis.

A Comparison of Traditional and Novel Definitions (RIFLE, AKIN, and KDIGO) of Acute Kidney Injury for the Prediction of Outcomes in Acute Decompensated Heart Failure

AIMS

To determine if newer criteria for diagnosing and staging acute kidney injury (AKI) during heart failure (HF) admission are more predictive of clinical outcomes at 30 days and 1 year than the traditional worsening renal function (WRF) definition.

METHODS

We analyzed prospectively collected clinical data on 637 HF admissions with 30-day and 1-year follow-up. The incidence, stages, and outcomes of AKI were determined using the following four definitions: KDIGO, RIFLE, AKIN, and WRF (serum creatinine rise ≥0.3 mg/dl). Receiver operating curves were used to compare the predictive ability of each AKI definition for the occurrence of adverse outcomes (death, rehospitalization, dialysis).

RESULTS

AKI by any definition occurred in 38.3% (244/637) of cases and was associated with an increased incidence of 30-day (32.3 vs. 6.9%, χ(2) = 70.1; p < 0.001) and 1-year adverse outcomes (67.5 vs. 31.0%, χ(2) = 81.4; p < 0.001). Most importantly, there was a stepwise increase in primary outcome with increasing stages of AKI severity using RIFLE, KDIGO, or AKIN (p < 0.001). In direct comparison, there were only small differences in predictive abilities between RIFLE and KDIGO and WRF concerning clinical outcomes at 30 days (AUC 0.76 and 0.74 vs. 0.72, χ(2) = 5.6; p = 0.02) as well as for KDIGO and WRF at 1 year (AUC 0.67 vs. 0.65, χ(2) = 4.8; p = 0.03).

CONCLUSION

During admission for HF, the benefits of using newer AKI classification systems (RIFLE, AKIN, KDIGO) lie with the ability to identify those patients with more severe degrees of AKI who will go on to experience adverse events at 30 days and 1 year. The differences in terms of predictive abilities were only marginal.

Imperfect gold standards for kidney injury biomarker evaluation

Clinicians have used serum creatinine in diagnostic testing for acute kidney injury for decades, despite its imperfect sensitivity and specificity. Novel tubular injury biomarkers may revolutionize the diagnosis of acute kidney injury; however, even if a novel tubular injury biomarker is 100% sensitive and 100% specific, it may appear inaccurate when using serum creatinine as the gold standard. Acute kidney injury, as defined by serum creatinine, may not reflect tubular injury, and the absence of changes in serum creatinine does not assure the absence of tubular injury. In general, the apparent diagnostic performance of a biomarker depends not only on its ability to detect injury, but also on disease prevalence and the sensitivity and specificity of the imperfect gold standard. Assuming that, at a certain cutoff value, serum creatinine is 80% sensitive and 90% specific and disease prevalence is 10%, a new perfect biomarker with a true 100% sensitivity may seem to have only 47% sensitivity compared with serum creatinine as the gold standard. Minimizing misclassification by using more strict criteria to diagnose acute kidney injury will reduce the error when evaluating the performance of a biomarker under investigation. Apparent diagnostic errors using a new biomarker may be a reflection of errors in the imperfect gold standard itself, rather than poor performance of the biomarker. The results of this study suggest that small changes in serum creatinine alone should not be used to define acute kidney injury in biomarker or interventional studies.

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.

Acute kidney injury following coronary angiography is associated with a long-term decline in kidney function

To determine whether acute kidney injury results in later long-term decline in kidney function we measured changes in kidney function over a 3-year period in adults undergoing coronary angiography who had serum creatinine measurements as part of their clinical care. Acute kidney injury was categorized by the magnitude of increase in serum creatinine (mild (50-99% or >or=0.3 mg/dl) and moderate or severe (>or=100%)) within 7 days of coronary angiography. Compared to patients without acute kidney injury, the adjusted odds of a sustained decline in kidney function at 3 months following angiography increased more than 4-fold for patients with mild to more than 17-fold for those with moderate or severe acute kidney injury. Among those with an estimated glomerular filtration rate after angiography less than 90 ml/min per 1.73 m(2), the subsequent adjusted mean rate of decline in estimated glomerular filtration rate during long-term follow-up (all normalized to 1.73 m(2) per year) was 0.2 ml/min in patients without acute kidney injury, 0.8 ml/min following mild injury, and 2.8 ml/min following moderate to severe acute kidney injury. Thus, acute kidney injury following coronary angiography is associated with a sustained loss and a larger rate of future decline in kidney function.

Delivered dose of renal replacement therapy and mortality in critically ill patients with acute kidney injury

INTRODUCTION

The optimal dialysis dose for the treatment of acute kidney injury (AKI) is controversial. We sought to evaluate the relationship between renal replacement therapy (RRT) dose and outcome.

METHODS

We performed a prospective multicentre observational study in 30 intensive care units (ICUs) in eight countries from June 2005 to December 2007. Delivered RRT dose was calculated in patients treated exclusively with either continuous RRT (CRRT) or intermittent RRT (IRRT) during their ICU stay. Dose was categorised into more-intensive (CRRT >or= 35 ml/kg/hour, IRRT >or= 6 sessions/week) or less-intensive (CRRT < 35 ml/kg/hour, IRRT < 6 sessions/week). The main outcome measures were ICU mortality, ICU length of stay and duration of mechanical ventilation.

RESULTS

Of 15,200 critically ill patients admitted during the study period, 553 AKI patients were treated with RRT, including 338 who received CRRT only and 87 who received IRRT only. For CRRT, the median delivered dose was 27.1 ml/kg/hour (interquartile range (IQR) = 22.1 to 33.9). For IRRT, the median dose was 7 sessions/week (IQR = 5 to 7). Only 22% of CRRT patients and 64% of IRRT patients received a more-intensive dose. Crude ICU mortality among CRRT patients were 60.8% vs. 52.5% (more-intensive vs. less-intensive groups, respectively). In IRRT, this was 23.6 vs. 19.4%, respectively. On multivariable analysis, there was no significant association between RRT dose and ICU mortality (Odds ratio (OR) more-intensive vs. less-intensive: CRRT OR = 1.21, 95% confidence interval (CI) = 0.66 to 2.21; IRRT OR = 1.50, 95% CI = 0.48 to 4.67). Among survivors, shorter ICU stay and duration of mechanical ventilation were observed in the more-intensive RRT groups (more-intensive vs. less-intensive for all: CRRT (median): 15 (IQR = 8 to 26) vs. 19.5 (IQR = 12 to 33.5) ICU days, P = 0.063; 7 (IQR = 4 to 17) vs. 14 (IQR = 5 to 24) ventilation days, P = 0.031; IRRT: 8 (IQR = 5.5 to 14) vs. 18 (IQR = 13 to 35) ICU days, P = 0.008; 2.5 (IQR = 0 to 10) vs. 12 (IQR = 3 to 24) ventilation days, P = 0.026).

CONCLUSIONS

After adjustment for multiple variables, these data provide no evidence for a survival benefit afforded by higher dose RRT. However, more-intensive RRT was associated with a favourable effect on ICU stay and duration of mechanical ventilation among survivors. This result warrants further exploration.

TRIAL REGISTRATION

Cochrane Renal Group (CRG110600093).

Creatinine kinetics and the definition of acute kidney injury

Acute kidney injury (AKI) is a common and devastating medical condition, but no widely accepted definition exists. A recent classification system by the Acute Dialysis Quality Initiative (RIFLE) defines AKI largely by percentage increases in serum creatinine (SCr) over baseline. The Acute Kidney Injury Network defines the first stage by either an absolute or a percentage increase in SCr. To examine the implications of various definitions, we solved differential equations on the basis of mass balance principles. We simulated creatinine kinetics after AKI in the setting of normal baseline kidney function and stages 2, 3, and 4 chronic kidney disease (CKD). The percentage changes in SCr after severe AKI are highly dependent on baseline kidney function. Twenty-four hours after a 90% reduction in creatinine clearance, the rise in SCr was 246% with normal baseline kidney function, 174% in stage 2 CKD, 92% in stage 3 CKD, and only 47% in stage 4 CKD. By contrast, the absolute increase was nearly identical (1.8 to 2.0 mg/dl) across the spectrum of baseline kidney function. Time to reach a 50% increase in SCr was directly related to baseline kidney function: From 4 h (normal baseline) up to 27 h for stage 4 CKD. By contrast, the time to reach a 0.5-mg/dl increase in SCr was virtually identical after moderate to severe AKI (>50% reduction in creatinine clearance). We propose an alternative definition of AKI that incorporates absolute changes in SCr over a 24- to 48-h time period.

Renal replacement therapy in the critical care unit

Acute renal failure is common in critically ill patients. Many intensive care unit patients require renal replacement therapy (RRT). Hemodialysis can be performed as intermittent treatments or as continuous RRT, which can be customized to clinical goals by the use of carefully designed replacement fluids and hemodialysates. The available forms of RRT are reviewed, with emphasis on the clinical indications that contribute to the choice and design of therapy. Practical issues and troubleshooting are discussed, as are available options for anticoagulation during RRT. Consideration is given to modality choice, hemodynamic issues, costs, and physiologic outcomes.

Intermittent hemodialysis versus continuous renal replacement therapy for acute renal failure in the intensive care unit: an observational outcomes analysis

BACKGROUND

Studies have failed to show a survival difference between intermittent hemodialysis (IHD) and continuous renal replacement therapy (CRRT). Comparative cost analyses are limited and fail to control for differences in patient disease severity and comorbid conditions. The authors retrospectively estimated clinical and economic outcomes associated with CRRT and IHD among critically ill patients experiencing acute renal failure (ARF) in 2 tertiary care hospitals in Rochester, Minnesota, between January 1, 2000, and December 12, 2001.

METHODS

161 critically ill patients requiring dialysis for ARF were analyzed. Patient demographics, comorbid conditions, ARF etiology, mode of renal replacement therapy (RRT), renal recovery, and survival were abstracted from medical chart. APACHE II scores at dialysis initiation were calculated. Administrative data tracked length of stay (LOS) and direct medical costs from initiation of RRT to death or intensive care unit (ICU) and hospital discharge. Multivariate modeling was used to adjust outcomes for baseline differences.

RESULTS

84 (52%) of the patients received CRRT and 77 (48%) received IHD. CRRT-treated patients were younger (58 vs 65 years), less likely male (58% vs 77%), had higher APACHE II scores (32 vs 27) with a higher incidence of sepsis (46% vs 30%) and respiratory disease (56% vs 39%), and were less likely to have chronic renal insufficiency (32% vs 49%). With adjustment for differences in baseline patient characteristics, the RRT method did not affect the likelihood of renal recovery, in-hospital survival, or survival during follow-up. Mean adjusted ICU LOS was 9.5 days shorter for IHD-treated than CRRT-treated patients (P< .001), and the adjusted mean difference in hospital and total costs associated with ICU stay was $56,564 and $60 827, in favor of IHD (P< .001). Mean adjusted total costs through hospital discharge were $93 611 and $140,733 among IHD-treated and CRRT-treated patients, respectively (P< .001).

CONCLUSIONS

This observational study suggests that costs may significantly differ by mode of RRT despite similar severity-adjusted patient outcomes. Future prospective comparisons of renal replacement modalities will need to include both clinical and economic outcomes.

Acute Dialysis Quality Initiative (ADQI): methodology

The Acute Dialysis Quality Initiative (ADQI) is an ongoing process that seeks to produce evidence-based recommendations for the prevention and management of acute kidney injury (AKI) and on different issues concerning acute dialysis. Our methods involve a combination of both expert panel and evidence appraisal, and this approach was chosen to achieve the best of both options. This approach has led to important practice guidelines with wide acceptance and adoption into clinical practice. We further recognize that additional research will be needed and have proposed specific studies that will help move this field forward.

The future of extracorporeal support

Extracorporeal therapy has expanded significantly over the past few decades from solely artificial renal replacement therapy. In patients with multiple organ dysfunction syndrome, it becomes necessary to provide multiple organ support therapy. Technological advances have opened the door to a multifaceted intervention directed at supporting the function of multiple organs through the treatment of blood. Indications for "old" therapies such as hemofiltration and adsorption have been expanded, and using these therapies in combination further enhances blood detoxification capabilities. Furthermore, new devices are constantly in development. Nanotechnology allows us to refine membrane characteristics and design innovative monitoring/biofeedback devices. Miniaturization is leading down the path of wearable/implantable devices. With the incorporation of viable cells within medical devices, these instruments become capable not only of detoxification but synthetic functions as well, bringing us closer to the holy grail of complete replacement of organ function. This article provides a brief overview of current and future direction in extracorporeal support in the critical care setting.

Diagnosis, epidemiology and outcomes of acute kidney injury

Acute kidney injury is an increasingly common and potentially catastrophic complication in hospitalized patients. Early observational studies from the 1980s and 1990s established the general epidemiologic features of acute kidney injury: the incidence, prognostic significance, and predisposing medical and surgical conditions. Recent multicenter observational cohorts and administrative databases have enhanced our understanding of the overall disease burden of acute kidney injury and trends in its epidemiology. An increasing number of clinical studies focusing on specific types of acute kidney injury (e.g., in the setting of intravenous contrast, sepsis, and major surgery) have provided further details into this heterogeneous syndrome. Despite our sophisticated understanding of the epidemiology and pathobiology of acute kidney injury, current prevention strategies are inadequate and current treatment options outside of renal replacement therapy are nonexistent. This failure to innovate may be due in part to a diagnostic approach that has stagnated for decades and continues to rely on markers of glomerular filtration (blood urea nitrogen and creatinine) that are neither sensitive nor specific. There has been increasing interest in the identification and validation of novel biomarkers of acute kidney injury that may permit earlier and more accurate diagnosis. This review summarizes the major epidemiologic studies of acute kidney injury and efforts to modernize the approach to its diagnosis.

The incidence and prognostic significance of acute kidney injury

PURPOSE OF REVIEW

Acute kidney injury is an increasingly common and potentially catastrophic complication in hospitalized patients. This review summarizes the major epidemiologic studies that have informed our understanding of the incidence and prognostic significance of acute kidney injury.

RECENT FINDINGS

Early observational studies from the 1980s and 1990s established the general epidemiologic features of acute kidney injury, including the incidence, prognostic significance and predisposing medical and surgical conditions. Recent multicenter observational cohorts and administrative databases have enhanced our understanding of the overall disease burden of acute kidney injury and trends in its epidemiology. An increasing number of clinical studies focusing on specific types of acute kidney injury (e.g. following exposure to intravenous contrast, sepsis and major surgery) have provided further details into this heterogeneous syndrome.

SUMMARY

In light of the increasing incidence and prognostic significance of acute kidney injury, new strategies for prevention and treatment are desperately needed.

Acute kidney injury in critical care: time for a paradigm shift?

PURPOSE OF REVIEW

Acute alterations in renal function are commonly encountered in various settings with varied clinical manifestations ranging from a minimal elevation in serum creatinine to anuric renal failure. Our knowledge of human acute kidney injury has been fairly stagnant, until recently largely limited by a lack of concerted efforts in the field. This review summarizes the recent advances and provides an overview of emerging trends in this field.

RECENT FINDINGS

One of the limitations in our knowledge of human acute kidney injury has been the lack of a standardized definition and staging criteria for this disorder. New information on the epidemiology and outcomes of acute kidney injury has emerged providing an opportunity to reappraise our approach to this disease. Also, there has been new work on the relationship of alterations of renal function to short and long-term outcomes, particularly mortality.

SUMMARY

To translate advances from basic research to clinical application a multidisciplinary approach is required. New research in the field of biomarkers combined with clinical markers will lead to therapies that can be introduced earlier in the course of the disease and, hopefully, lead to a decrease in mortality from this potentially reversible condition.

Consensus development in acute renal failure: The Acute Dialysis Quality Initiative

PURPOSE OF REVIEW

Although acute renal failure is both common and highly lethal in the intensive care unit, our understanding of the epidemiology and pathophysiology of acute renal failure is limited, and treatment for acute renal failure is extremely variable around the world. The general lack of consensus with regard to definitions, prevention, and treatment of acute renal failure has limited progress in this field.

RECENT FINDINGS

Consensus in acute renal failure requires establishing a framework in which intensivists, nephrologists, pharmacologists, and others who care for critically ill patients with or at risk for acute renal failure can reach consensus and develop evidence-based practice guidelines. The Acute Dialysis Quality Initiative seeks to provide an objective, dispassionate distillation of the literature and description of the current state of practice of dialysis and related therapies as they are applied to acutely ill patients. The purposes of Acute Dialysis Quality Initiative are first, to develop a consensus of opinion, with evidence where possible, on best practice; and second, to articulate a research agenda to focus on important unanswered questions.

SUMMARY

Broad consensus in the diagnosis and management of acute renal failure and in the use of blood purification in nonrenal critical illness is achievable. Standardization of definitions, practice, and research methodology is urgently needed, and specific proposals have been made by an international, interdisciplinary group.