Association of Ultrafiltration Rate with Mortality in Incident Hemodialysis Patients

Association of net ultrafiltration intensity and clinical outcomes among critically ill patients receiving continuous renal replacement therapy: A systematic review, meta-analysis, and trial sequential analysis

BACKGROUND

Net ultrafiltration (UFnet) has been used in the fluid management of critically ill patients undergoing continuous renal replacement therapy for an extended duration. Despite its widespread application, the correlation between UFnet intensity and clinical outcomes remains controversial.

METHODS

Electronic databases (PubMed, Embase, Web of Science, and the Cochrane database) were searched from inception to November 30, 2023. All possible studies that examined the following outcomes were included: all-cause mortality, recovery of kidney function, and length of hospital stay.

RESULTS

A total of 6209 patients from six cohort studies were included. There was no significant association observed between UFnet intensity and either mortality (odds ratio [OR] = 0.90, 95% confidence interval [CI] = 0.68-1.21, p = 0.49, I2 = 84%) or renal recovery (OR = 0.96, 95% CI = 0.57-1.61, p = 0.87, I2 = 75%) among critically ill patients. However, a high intensity of UFnet was associated with lower mortality in patients with acute kidney injury (AKI) (OR = 0.73, 95% CI = 0.59-0.90, p = 0.004, I2 = 67%). Furthermore, the study revealed a noteworthy correlation between a high UFnet intensity and a longer length of hospital stay (weighted mean difference = 3.34 d, 95% CI = 2.64-4.03, p2 = 0%).

CONCLUSIONS

The association between UFnet intensity and mortality or renal recovery in critically ill patients is insufficient. However, a high UFnet intensity is associated with an increasing length of hospital stay among critically ill patients.

Prognostic Significance of Visit-to-Visit Ultrafiltration Volume Variability in Hemodialysis Patients

Introduction: Patients on chronic hemodialysis (HD) have significantly higher mortality compared with the general population. Cardiovascular (CV) disease is the primary reason for death in these patients. Suboptimal extracellular fluid management increases the CV risk of HD patients. We aimed to study the effect of visit-to-visit ultrafiltration volume (UV) variability on CV events and mortality in chronic HD patients. Patients and Methods: In our study, 173 chronic HD patients were included (median age: 63 ± 13 years; 53% men). Ultrafiltration volume (UV) variability was analyzed retrospectively for 24 months. The standard deviation (SD) and coefficient of variation (CV) were calculated using the indices of UV variability. CV is the SD divided by the mean. The obtained parameters were SD and CV of the UV: UVSD and UVCV. UV data during the observation period were recorded and used to calculate UV variability. Routine transthoracal echocardiography was performed. Results: Patients were divided into groups based on the median of UVSD, low-UVSD (<568 mL) and high-UVSD (≥568 mL) group; and also based on the median of UVCV, low- (<0.29) and high-UVCV (≥0.29) group. All-cause mortality was significantly higher in the high compared to the low-UVSD (21/84 vs. 9/89; p < 0.001) group. Similarly, mortality was higher in the high-UVCV group compared to the low-UVCV group (18/78 vs. 12/95; p = 0.005) after 24 months. Major adverse CV event (MACE) rates were also significantly higher in the high- compared to the low-UVSD group (20/84 vs. 8/89; p < 0.001). Similarly, the MACE rate was significantly higher in the high-UVCV group compared to the low-UVCV group (15/78 vs. 13/95; p = 0.029) after 24 months. There was no significant difference between the groups in CV mortality. UVSD correlated with parathormone (PTH) level (r = 0.416; p = 0.015), and UVCV with total cholesterol (r = 0.419; p = 0.015). Left ventricular end-diastolic diameter (LVEDD) and end-systolic diameter (LVESD) were higher in the high-UVCV group compared to the low-UVCV group (49.95 vs. 52.08; p = 0.013 and 32.19 vs. 34.13; p = 0.034). Conclusions: According to our results, high UVSD and UVCD are associated with increased all-cause mortality and MACE rates but not CV mortality in chronic HD patients. Cardiovascular changes caused by increased UF volume variability during HD may contribute to higher CV morbidity and mortality in these patients.

Assessment and management of emergencies during haemodialysis

The haemodialysis unit is a complex clinical environment. Medical emergencies complicating haemodialysis treatment are relatively infrequent but are associated with high morbidity and mortality. The management of intradialytic emergencies is challenging and relevant to the practice of all nephrology and critical care clinicians. There are no dedicated resuscitation guidelines for this unique patient population. This review article provides an outline of the assessment and treatment of important intradialytic emergencies (hypotension, hypertension, haemorrhage, hypoxia, neurologic disturbances, cardiac arrest) based on the best available evidence.

Prognostic Features for Overall Survival in Male Diabetic Patients Undergoing Hemodialysis Using Elastic Net Penalized Cox Regression; A Machine Learning Approach

BACKGROUND

Diabetics constitute a significant percentage of hemodialysis (HD) patients with higher mortality, especially among male patients. A machine learning algorithm was used to optimize the prediction of time to death in male diabetic hemodialysis (MDHD) patients.

METHODS

This multicenter retrospective study was conducted on adult MDHD patients (2011-2019) from 34 HD centers affiliated with Shiraz University of Medical Sciences. As a special type of machine learning approach, an elastic net penalized Cox proportional hazards (EN-Cox) regression was used to optimize a predictive regression model of time to death. To maximize the generalizability and simplicity of the final model, the backward elimination method was used to reduce the estimated predictive model to its core covariates.

RESULTS

Out of 442 patients, 308 eligible cases were used in the final analysis. Their death proportion was estimated to be 28.2%. The estimated overall one-, two-, three-, and eight-year survival rates were 87.6%, 74.4%, 67.2%, and 53.9%, respectively. The EN-Cox regression model retained 14 (out of 35) candidate predictors of death. Five variables were excluded through backward elimination technique in the next step. Only 6 of the remaining 9 variables were statistically significant at the level of 5%. Body mass index (BMI)<25 kg/m2 (HR=2.75, P<0.001), vascular access type (HR=2.60, P<0.001), systolic blood pressure (1.02, P=0.003), hemoglobin (11≤Hb≤12.5 g/dL: HR=3.00, P=0.028 and Hb<11 g/dL: HR=2.95, P=0.021), dialysis duration in each session≥4hour (HR=2.95, P<0.001), and serum high-density lipoprotein cholesterol (HDL-C) (HR=1.02, P=0.022) had significant effects on the overall survival (OS) time.

CONCLUSION

Anemia, hypotension, hyperkalemia, having central venous catheter (CVC) as vascular access, a longer dialysis duration in each session, lower BMI and HDL-C were associated with lower mortality in MDHD patients.

Feasibility of the McIntyre audit tool for haemodialysis nurses

BACKGROUND

Nurse-sensitive indicators (NSI) assess the quality of nursing care provided to patients. These indicators assess the structures (supportive measures), processes (nursing actions) and outcomes of care. The McIntyre Audit Tool (MAT) was developed to measure haemodialysis NSIs.

OBJECTIVES

The objective of this study is to evaluate the feasibility and utility of the MAT in measuring haemodialysis NSIs in clinical practice.

DESIGN

Multisite nonrandomized feasibility study.

PARTICIPANTS

A convenience sample of nurses (n = 30) were recruited from two haemodialysis units in Australia.

MEASUREMENTS

Participants completed the MAT once daily for 1 week, to measure the extent the clinical indicators were being met. Feasibility data including utility and acceptability of the tool was collected once from each participant. Data were analysed descriptively.

RESULTS

Participants completed a total of 97 audits. Results revealed the majority of structural (75%) and process indicators (73%) were being achieved although some variation between sites was observed. Results for the outcome indicators showed more variation (5.9%-94.1). Feasibility results found most nurses (79%) took <5 min to complete the MAT and found the tool easy to use (91.7%). Most participants (83.3%) reported audits could be completed during a shift and auditing was easily implemented (79.2%).

CONCLUSION

Use of the MAT in clinical practice is a feasible and acceptable way of auditing the quality of haemodialysis nursing practice. The tool could be used to establish minimum standards and improve the quality of nursing care in haemodialysis units, also enabling benchmarking between services.

Coronary Artery Disease Assessment and Cardiovascular Events in Middle-Aged Patients on Hemodialysis

OBJECTIVE

To explore whether, in younger patients on dialysis with longer life expectancy, assessment of coronary artery disease (CAD) could identify individuals at higher risk of events and revascularization might improve outcomes in selected patients contrary to what had been observed in elderly patients.

METHODS

From August 1997 to January 2019, 2265 patients with stage 5 chronic kidney disease were prospectively referred for cardiovascular assessment. For this study, we selected 1374 asymptomatic patients aged between 18 and 64 years. After clinical risk stratification and cardiac scintigraphy by single-photon emission computed tomography, 866 patients underwent coronary angiography. The primary end point was the composite incidence of nonfatal/fatal major adverse cardiovascular events during a follow-up period of 0.1 to 189.7 months (median, 26 months). The secondary end point was all-cause mortality.

RESULTS

The primary end point occurred in 327 (23.8%) patients. Clinically stratified high-risk patients had a 3-fold increased risk of the primary end point. The prevalence of abnormal findings on perfusion scans was 29.2% (n=375), and significant CAD was found in 449 (51.8%) of 866 patients who underwent coronary angiography. An abnormal finding on myocardial perfusion scan and the presence of CAD were significantly associated with a 74% and 22% increased risk of cardiovascular events, respectively. In patients undergoing percutaneous coronary intervention or coronary artery bypass grafting (n=99), there was an 18% reduction in the risk of all-cause death relative to patients receiving medical treatment (P=.03).

CONCLUSION

In this cohort of middle-aged, asymptomatic patients on dialysis, assessment of CAD identified individuals at higher risk of events, and coronary intervention was associated with reducing the risk of death in selected patients.

Health inequities in dialysis care: A scoping review

MAIN PROBLEM

We aim to look at potential gaps in current dialysis literature on inequities and explore future research that could contribute to more equitable care.

METHODS

Following guidelines from the Joanna Briggs Institute (JBI) and the Preferred Reporting Items for Systematic reviews and Meta Analyses extension for Scoping Reviews (PRISMA-ScR), we conducted a scoping review of health inequities in dialysis. PubMed and Ovid Embase were searched in July 2022 for articles published between 2016 and 2022 that examined at least one of the following NIH defined health inequities: race/ethnicity, sex/gender, LGBTQ+ identity, underserved rural populations, education level, income, and occupation status. Frequencies of each health inequity as well as trends over time of the four most examined inequities were analyzed.

RESULTS

In our sample of 69 included studies, gaps were identified in LGBTQ+ identity and patient education. Inequities pertaining to race/ethnicity, sex/gender, underserved rural populations, and income were sufficiently reported. No trends between inequities investigated over time were identified.

CONCLUSIONS

Our scoping review examined current literature on health inequities pertaining to dialysis and found gaps concerning LGBTQ+ and patients with lower levels of education. To help fill these gaps, and possibly alleviate additional burden to these patients, we recommend cultural competency training for providers and dialysis center staff as well as community-based educational programs to improve dialysis patients' health literacy.

Ultrafiltration Rate Levels in Hemodialysis Patients Associated with Weight-Specific Mortality Risks

BACKGROUND

We hypothesized that the association of ultrafiltration rate with mortality in hemodialysis patients was differentially affected by weight and sex and sought to derive a sex- and weight-indexed ultrafiltration rate measure that captures the differential effects of these parameters on the association of ultrafiltration rate with mortality.

METHODS

Data were analyzed from the US Fresenius Kidney Care (FKC) database for 1 year after patient entry into a FKC dialysis unit (baseline) and over 2 years of follow-up for patients receiving thrice-weekly in-center hemodialysis. To investigate the joint effect of baseline-year ultrafiltration rate and postdialysis weight on survival, we fit Cox proportional hazards models using bivariate tensor product spline functions and constructed contour plots of weight-specific mortality hazard ratios over the entire range of ultrafiltration rate values and postdialysis weights (W).

RESULTS

In the studied 396,358 patients, the average ultrafiltration rate in ml/h was related to postdialysis weight (W) in kg: 3W+330. Ultrafiltration rates associated with 20% or 40% higher weight-specific mortality risk were 3W+500 and 3W+630 ml/h, respectively, and were 70 ml/h higher in men than in women. Nineteen percent or 7.5% of patients exceeded ultrafiltration rates associated with a 20% or 40% higher mortality risk, respectively. Low ultrafiltration rates were associated with subsequent weight loss. Ultrafiltration rates associated with a given mortality risk were lower in high-body weight older patients and higher in patients on dialysis for more than 3 years.

CONCLUSIONS

Ultrafiltration rates associated with various levels of higher mortality risk depend on body weight, but not in a 1:1 ratio, and are different in men versus women, in high-body weight older patients, and in high-vintage patients.

High Ultrafiltration Rate Is Associated with Increased All-Cause Mortality in Incident Hemodialysis Patients with a High Cardiothoracic Ratio

A high ultrafiltration rate (UFR) is associated with increased mortality in hemodialysis patients. However, whether a high UFR itself or heart failure with fluid overload followed by a high UFR causes mortality remains unknown. In this study, 2615 incident hemodialysis patients were categorized according to their initial cardiothoracic ratios (CTRs) to assess whether UFR was associated with mortality in patients with high or low CTRs. In total, 1317 patients (50.4%) were women and 1261 (48.2%) were diabetic. During 2246 (1087−3596) days of follow-up, 1247 (47.7%) cases of all-cause mortality were noted. UFR quintiles 4 and 5 were associated with higher risks of all-cause mortality than UFR quintile 2 in fully adjusted Cox regression analysis. As the UFR increased by 1 mL/kg/h, the risk of all-cause mortality increased 1.6%. Subgroup analysis revealed that in UFR quintile 5, hazard ratios (HRs) for all-cause mortality were 1.91, 1.48, 1.22, and 1.10 for CTRs of >55%, 50−55%, 45−50%, and <45%, respectively. HRs for all-cause mortality were higher in women and patients with high body weight. Thus, high UFRs may be associated with increased all-cause mortality in incident hemodialysis patients with a high CTR, but not in those with a low CTR.

Proportion of Hemodialysis Treatments with High Ultrafiltration Rate and the Association with Mortality

Background

Rapid fluid removal during hemodialysis has been associated with increased mortality. The limit of ultrafiltration rate (UFR) monitored by the Centers for Medicare & Medicaid Services is 13 ml/kg per hour. It is not clear if the proportion of treatments with high UFR is associated with higher mortality. We examined the association of proportion of dialysis treatments with high UFR and mortality in end stage kidney failure patients receiving hemodialysis.

Methods

This was a retrospective study of incident patients initiating hemodialysis between January 1, 2010, and December 31, 2019, at Emory dialysis centers. The proportion of treatments with high UFR (>13 ml/kg per hour) per patient was calculated using data from the initial 3 months of dialysis therapy. Patients were categorized on the basis of quartiles of proportion of dialysis sessions with high UFR. Risk of death and survival probabilities were calculated and compared for all quartiles.

Results

Of 1050 patients eligible, the median age was 59 years, 56% were men, and 91% were Black. The median UFR was 6.5 ml/kg per hour, and the proportion of sessions with high UFR was 5%. Thirty-one percent of patients never experienced high UFR. Being a man, younger age, shorter duration of hemodialysis sessions, lower weight, diabetic status, higher albumin, and history of heart failure were associated with a higher proportion of sessions with high UFR. Patients in the higher quartile (26% dialysis with high UFR, average UFR 9.8 ml/kg per hour, median survival of 5.6 years) had a higher risk of death (adjusted hazard ratio 1.54; 95% CI, 1.13 to 2.10) compared with those in the lower quartile (0% dialysis with high UFR, average UFR 4.7 ml/kg per hour, median survival 8.8 years).

Conclusions

Patients on hemodialysis who did not experience frequent episodes of elevated UFR during the first 3 months of their dialysis tenure had a significantly lower risk of death compared with patients with frequent episodes of high UFR.

Ultrafiltration rate thresholds associated with increased mortality risk in hemodialysis, unscaled or scaled to body size

Introduction

One proposed threshold ultrafiltration rate (UFR) of concern in hemodialysis patients is 13 ml/h per kg. We evaluated associations among UFR, postdialysis weight, and mortality to determine whether exceeding such a threshold would result in similar levels of risk for patients of different body weights.

Methods

Data were analyzed in this retrospective cohort study for 1 year following dialysis initiation (baseline) and over 2 years of follow-up in incident patients receiving thrice-weekly in-center hemodialysis. Patient-level UFR was averaged over the baseline period. To investigate the joint effect of UFR and postdialysis weight on survival, we fit Cox proportional hazards models using bivariate tensor product spline functions, adjusting for sex, race, age, diabetes, and predialysis serum albumin, phosphorus, and systolic blood pressure (BP). We constructed contour plots of mortality hazard ratios (MHRs) over the entire range of UFR values and postdialysis weights.

Results

In the studied 2542 patients, UFR not scaled to body weight was strongly associated with MHR, whereas postdialysis weight was inversely associated with MHR. MHR crossed 1.5 when unscaled UFR exceeded 1000 ml/h, and this relationship was largely independent of postdialysis weight in the range of 80 to 140 kg. A UFR warning level associated with a lower MHR of 1.3 would be 900 ml/h, whereas the UFR associated with an MHR of 1.0 was patient-size dependent. The MHR when exceeding a UFR threshold of 13 ml/h per kg was dependent on patient weight (MHR = 1.20, 1.45, and >2.0 for a 60, 80, and 100 kg patient, respectively).

Conclusion

UFR thresholds based on unscaled UFR give more uniform risk levels for patients of different sizes than thresholds based on UFR/kg.

Ultrafiltration rate and incident atrial fibrillation among older individuals initiating hemodialysis

BACKGROUND

Higher ultrafiltration (UF) rates are associated with numerous adverse cardiovascular outcomes among individuals receiving maintenance hemodialysis. We undertook this study to investigate the association of UF rate and incident atrial fibrillation in a large, nationally representative US cohort of incident, older hemodialysis patients.

METHODS

We used the US Renal Data System linked to the records of a large dialysis provider to identify individuals ≥67 years of age initiating hemodialysis between January 2006 and December 2011. We applied an extended Cox model as a function of a time-varying exposure to compute adjusted hazard ratios (HRs) and 95% confidence intervals (CIs) for the association of delivered UF rate and incident atrial fibrillation.

RESULTS

Among the 15 414 individuals included in the study, 3177 developed atrial fibrillation. In fully adjusted models, a UF rate >13 mL/h/kg (versus ≤13 mL/h/kg) was associated with a higher hazard of incident atrial fibrillation [adjusted HR 1.19 (95% CI 1.07-1.30)]. Analyses using lower UF rate thresholds (≤10 versus >10 mL/h/kg and ≤8 versus >8 mL/h/kg, separately) yielded similar results. Analyses specifying the UF rate as a cubic spline (per 1 mL/h/kg) confirmed an approximately linear dose-response relationship between the UF rate and the risk of incident atrial fibrillation: risk began at UF rates of ~6 mL/h/kg and the magnitude of this risk flattened, but remained elevated, at rates ≥9 mL/h/kg.

CONCLUSION

In this observational study of older individuals initiating hemodialysis, higher UF rates were associated with higher incidences of atrial fibrillation.

Toward an individualized determination of dialysis adequacy: a narrative review with special emphasis on incremental hemodialysis

INTRODUCTION

The search for the 'perfect' renal replacement therapy has been paralleled by the search for the perfect biomarkers for assessing dialysis adequacy. Three main families of markers have been assessed: small molecules (prototype: urea); middle molecules (prototype β2-microglobulin); comprehensive and nutritional markers (prototype of the simplified assessment, albumin levels; composite indexes as malnutrition-inflammation score). After an era of standardization of dialysis treatment, personalized dialysis schedules are increasingly proposed, challenging the dogma of thrice-weekly hemodialysis.

AREAS COVERED

In this review, we describe the advantages and limitations of the approaches mentioned above, focusing on the open questions regarding personalized schedules and incremental hemodialysis.

EXPERT OPINION

In the era of personalized dialysis, the assessment of dialysis adequacy should be likewise personalized, due to the limits of 'one size fits all' approaches. We have tried to summarize some of the relevant issues regarding the determination of dialysis adequacy, attempting to adapt them to an elderly, highly comorbidity population, which would probably benefit from tailor-made dialysis prescriptions. While no single biomarker allows precisely tailoring the dialysis dose, we suggest using a combination of clinical and biological markers to prescribe dialysis according to comorbidity, life expectancy, residual kidney function, and small and medium-size molecule depuration.

Mediators of the Impact of Hourly Net Ultrafiltration Rate on Mortality in Critically Ill Patients Receiving Continuous Renal Replacement Therapy

OBJECTIVES

During continuous renal replacement therapy, a high net ultrafiltration rate has been associated with increased mortality. However, it is unknown what might mediate its putative effect on mortality. In this study, we investigated whether the relationship between early (first 48 hr) net ultrafiltration and mortality is mediated by fluid balance, hemodynamic instability, or low potassium or phosphate blood levels using mediation analysis and the primary outcome was hospital mortality.

DESIGN

Retrospective, observational study.

SETTING

Mixed medical and surgical ICUs at Austin hospital, Melbourne, Australia.

PATIENTS

Critically ill patients treated with continuous renal replacement therapy within 14 days of ICU admission who survived greater than 48 hours.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

We studied 347 patients (median [interquartile range] age: 64 yr [53-71 yr] and Acute Physiology and Chronic Health Evaluation III score: 73 (54-90)]. After adjustment for confounders, compared with a net ultrafiltration less than 1.01 mL/kg/hr, a net ultrafiltration rate greater than 1.75 mL/kg/hr was associated with significantly greater mortality (adjusted odds ratio, 1.15; 95% CI, 1.03-1.29; p = 0.011). Adjusted univariable mediation analysis found no suggestion of a causal mediation pathway for this effect by blood pressure, vasopressor therapy, or potassium levels, but identified a possible mediation effect for fluid balance (average causal mediation effect, 0.95; 95% CI, 0.89-1.00; p = 0.060) and percentage of phosphate measurements with hypophosphatemia (average causal mediation effect, 0.96; 95% CI, 0.92-1.00; p = 0.055). However, on multiple mediator analyses, these two variables showed no significant effect. In contrast, a high net ultrafiltration rate had an average direct effect of 1.24 (95% CI, 1.11-1.40; p < 0.001).

CONCLUSIONS

An early net ultrafiltration greater than 1.75 mL/kg/hr was independently associated with increased hospital mortality. Its putative effect on mortality was direct and not mediated by a causal pathway that included fluid balance, low blood pressure, vasopressor use, hypokalemia, or hypophosphatemia.

Ultrafiltration in critically ill patients treated with kidney replacement therapy

Management of fluid overload is one of the most challenging problems in the care of critically ill patients with oliguric acute kidney injury. Various clinical practice guidelines support fluid removal using ultrafiltration during kidney replacement therapy. However, ultrafiltration is associated with considerable risks. Emerging evidence from observational studies suggests that both slow and fast rates of net fluid removal (that is, net ultrafiltration (UFNET)) during continuous kidney replacement therapy are associated with increased mortality compared with moderate UFNET rates. In addition, fast UFNET rates are associated with an increased risk of cardiac arrhythmias. Experimental studies in patients with kidney failure who were treated with intermittent haemodialysis suggest that fast UFNET rates are also associated with ischaemic injury to the heart, brain, kidney and gut. The UFNET rate should be prescribed based on patient body weight in millilitres per kilogramme per hour with close monitoring of patient haemodynamics and fluid balance. Dialysate cooling and sodium modelling may prevent haemodynamic instability and facilitate large volumes of fluid removal in patients with kidney failure who are treated with intermittent haemodialysis, but the effects of this strategy on organ injury are less well studied in critically ill patients treated with continuous kidney replacement therapy. Randomized trials are required to examine whether moderate UFNET rates are associated with a reduced risk of haemodynamic instability, organ injury and improved outcomes in critically ill patients.

Kidney Replacement Therapy for Fluid Management

Emerging evidence from observational studies suggests that both slower and faster net ultrafiltration rates during kidney replacement therapy are associated with increased mortality in critically ill patients with acute kidney injury and fluid overload. Faster rates are associated with ischemic organ injury. The net ultrafiltration rate should be prescribed based on patient body weight in milliliters per kilogram per hour, with close monitoring of patient hemodynamics and fluid balance. Randomized trials are required to examine whether moderate net ultrafiltration rates compared with slower and faster rates are associated with reduced risk of hemodynamic instability, organ injury, and improved outcomes.

Net ultrafiltration prescription survey in Europe

Background

Fluid overload is common in patients in the intensive care unit (ICU) and ultrafiltration (UF) is frequently required. There is lack of guidance on optimal UF practice. We aimed to explore patterns of UF practice, barriers to achieving UF targets, and concerns related to UF practice among practitioners working in Europe.

Methods

This was a sub-study of an international open survey with focus on adult intensivists and nephrologists, advanced practice providers, and ICU and dialysis nurses working in Europe.

Results

Four hundred eighty-five practitioners (75% intensivists) from 31 countries completed the survey. The most common criteria for UF initiation was persistent oliguria/anuria (45.6%), followed by pulmonary edema (16.7%). Continuous renal replacement therapy was the preferred initial modality (90.0%). The median initial and maximal rate of net ultrafiltration (UF^NET) prescription in hemodynamically stable patients were 149 mL/hr. (IQR 100–200) and 300 mL/hr. (IQR 201–352), respectively, compared to a median UF^NET rate of 98 mL/hr. (IQR 51–108) in hemodynamically unstable patients and varied significantly between countries.

Two-thirds of nurses and 15.5% of physicians reported assessing fluid balance hourly. When hemodynamic instability occurred, 70.1% of practitioners reported decreasing the rate of fluid removal, followed by starting or increasing the dose of a vasopressor (51.3%). Most respondents (90.7%) believed in early fluid removal and expressed willingness to participate in a study comparing protocol-based fluid removal versus usual care.

Conclusions

There was a significant variation in UF practice and perception among practitioners in Europe. Future research should focus on identifying the best strategies of prescribing and managing ultrafiltration in critically ill patients.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12882-020-02184-y.

Heterogeneity of Effect of Net Ultrafiltration Rate among Critically Ill Adults Receiving Continuous Renal Replacement Therapy

INTRODUCTION

In continuous renal replacement therapy (CRRT)-treated patients, a net ultrafiltration (NUF) rate >1.75 mL/kg/h has been associated with increased mortality. However, there may be heterogeneity of effect of NUF rate on mortality, according to patient characteristics.

METHODS

To investigate the presence and impact of heterogeneity of effect, we performed a secondary analysis of the "Randomized Evaluation of Normal versus Augmented Level of Renal Replacement Therapy" (RENAL) trial. Exposure was NUF rate (weight-adjusted fluid volume removed per hour) stratified into tertiles (<1.01 mL/kg/h; 1.01-1.75 mL/kg/h; or >1.75 mL/kg/h). Primary outcome was 90-day mortality. Patients were clustered according to baseline characteristics. Heterogeneity of effect was assessed according to clusters and baseline edema and related to the additional impact of baseline cardiovascular Sequential Organ Failure Assessment (SOFA) score. We excluded patients with missing values for baseline weight and/or treatment duration.

RESULTS

We identified 2 clusters. The largest (cluster 1; n = 941) included more severely ill patients, with more sepsis, more edema, and more vasopressor therapy (all p < 0.001). Compared to the middle tertile, the probability of harm was greater with the high tertile of NUF rate in patients in cluster 1 and in patients with baseline edema (probability of harm, cluster 1: 99.9%; edema: 99.1%). Moreover, higher baseline cardiovascular SOFA score also increased mortality risk with both high and low compared to middle NUF rates in cluster 1 patients and in patients with edema.

CONCLUSIONS

In CRRT patients, both high and low NUF rates may be harmful, especially in those with edema, sepsis, and greater illness severity. Cardiovascular SOFA scores modulate this association. Additional studies are needed to test these hypotheses, and targeted trials of NUF rates based on risk stratification appear justified.

TRIAL REGISTRATION

ClinicalTrials.gov identifier: NCT00221013.

Association between Ultrafiltration Rate and Clinical Outcome Is Modified by Muscle Mass in Hemodialysis Patients

BACKGROUND

The association between ultrafiltration rate (UFR) and mortality may be affected by the muscle mass or volume status in hemodialysis (HD) patients. However, there is an absence of data regarding this association.

METHODS

We performed an observational study on patients (≥18 years old) who had been on HD for at least 3 months. A body composition monitor (BCM) was used for baseline bioimpedance analysis measurement. The primary composite outcome was defined as the time to death or the first cardiovascular event.

RESULTS

The median (interquartile range) UFR, volume excess measured by the BCM, and lean tissue index (LTI) (calculated as lean tissue mass/height2) were 11.4 (8.0-15.0) mL/h/kg, 2.4 (1.4-4.1) L, and 12.5 (10.4-14.4) kg/m2, respectively. During 284 person-years of follow-up, the primary outcome occurred in 44 of the 167 patients (26%). Higher UFR was associated with an increased outcome of death or cardiovascular event; the adjusted hazard ratio (HR) was 1.044 (95% confidence interval [CI]: 1.006-1.083). This association remained consistent even after adjusting for volume excess. However, the association between UFR and the primary outcome was modified by LTI (pinteraction = 0.027); the association was significant in patients with LTI < 12.5 kg/m2, and the HR (95% CI) was 1.050 (1.001-1.102).

CONCLUSION

Higher UFR was associated with an increased risk of a composite outcome of death or cardiovascular event regardless of volume status in HD patients. However, muscle mass may modify the association between higher UFR and increased risk of a composite outcome.

Early net ultrafiltration rate and mortality in critically ill patients receiving continuous renal replacement therapy

BACKGROUND

In patients treated with continuous renal replacement therapy (CRRT), early net ultrafiltration (NUF) rates may be associated with differential outcomes. We tested whether higher early NUF rates are associated with increased mortality in CRRT patients.

METHODS

We performed a retrospective, observational study of all patients treated with CRRT within 14 days of intensive care unit admission. We defined the early (first 48 h) NUF rate as the volume of fluid removed per hour adjusted for patient body weight and analysed as a categorical variable (>1.75, 1.01-1.75 and <1.01 mL/kg/h). The primary outcome was 28-day mortality. To deal with competing risk, we also compared different time epochs.

RESULTS

We studied 347 patients {median age 64 [interquartile range (IQR) 53-71] years and Acute Physiology and Chronic Health Evaluation III score 73 [IQR 54-90]}. Compared with NUF rates <1.01 mL/kg/h, NUF rates >1.75 mL/kg/h were associated with greater mortality rates in each epoch: Days 0-5, adjusted hazard ratio (aHR) 1.27 [95% confidence interval (CI) 1.21-1.33]; Days 6-10, aHR 1.62 (95% CI 1.55-1.68); Days 11-15, aHR 1.87 (95% CI 1.79-1.94); Days 16-26, aHR 1.92 (95% CI 1.84-2.01) and Days 27-28, aHR 4.18 (95% CI 3.98-4.40). For every 0.5 mL/kg/h NUF rate increase, mortality similarly increased during these epochs.

CONCLUSION

Compared with early NUF rates <1.01 mL/kg/h, NUF rates >1.75 mL/kg/h are associated with increased mortality. These observations provide the rationale for clinical trials to confirm or refute these findings.

Net Ultrafiltration Prescription and Practice Among Critically Ill Patients Receiving Renal Replacement Therapy: A Multinational Survey of Critical Care Practitioners

OBJECTIVES

To assess the attitudes of practitioners with respect to net ultrafiltration prescription and practice among critically ill patients with acute kidney injury treated with renal replacement therapy.

DESIGN

Multinational internet-assisted survey.

SETTING

Critical care practitioners involved with 14 societies in 80 countries.

SUBJECTS

Intervention: MEASUREMENT AND MAIN RESULTS:: Of 2,567 practitioners who initiated the survey, 1,569 (61.1%) completed the survey. Most practitioners were intensivists (72.7%) with a median duration of 13.2 years of practice (interquartile range, 7.2-22.0 yr). Two third of practitioners (71.0%; regional range, 55.0-95.5%) reported using continuous renal replacement therapy with a net ultrafiltration rate prescription of median 80.0 mL/hr (interquartile range, 49.0-111.0 mL/hr) for hemodynamically unstable and a maximal rate of 299.0 mL/hr (interquartile range, 200.0-365.0 mL/hr) for hemodynamically stable patients, with regional variation. Only a third of practitioners (31.5%; range, 13.7-47.8%) assessed hourly net fluid balance during continuous renal replacement therapy. Hemodynamic instability was reported in 20% (range, 20-38%) of patients and practitioners decreased the rate of fluid removal (70.3%); started or increased the dose of a vasopressor (51.5%); completely stopped fluid removal (35.8%); and administered a fluid bolus (31.6%), with significant regional variation. Compared with physicians, nurses were most likely to report patient intolerance to net ultrafiltration (73.4% vs 81.3%; p = 0.002), frequent interruptions (40.4% vs 54.5%; p < 0.001), and unavailability of trained staff (11.9% vs 15.6%; p = 0.04), whereas physicians reported unavailability of dialysis machines (14.3% vs 6.1%; p < 0.001) and costs associated with treatment as barriers (12.1% vs 3.0%; p < 0.001) with significant regional variation.

CONCLUSIONS

Our study provides new knowledge about the presence and extent of international practice variation in net ultrafiltration. We also identified barriers and specific targets for quality improvement initiatives. Our data reflect the need for evidence-based practice guidelines for net ultrafiltration.

Solute and Volume Dosing during Kidney Replacement Therapy in Critically Ill Patients with Acute Kidney Injury

Among critically ill patients with severe acute kidney injury either continuous kidney replacement therapy (CKRT) or intermittent hemodialysis (IHD) can be performed to provide optimal solute and volume control. The modality of KRT should be chosen based on the needs of the patient, hemodynamic status, clinician expertise, and resource available under a particular setting and consideration of costs. Evidence from high-quality randomized trials suggests that an effluent flow rate of 25 mL/kg/hour per day using CKRT and Kt/V of 1.3 per session of IHD provide optimal solute control. For volume dosing, the net ultrafiltration (UF_NET) rate should be prescribed based on patient body weight in milliliters per kilogram per hour, with close monitoring of patient hemodynamics and fluid balance. Emerging evidence from observational studies suggests a “J”-shaped association between UF_NET rate and outcomes with both faster and slower UF_NET rates being associated with increased mortality compared with moderate UF_NET rates. Thus, randomized trials are required to determine optimal UF_NET rates in critically ill patients.

Ultrafiltration Rate, Residual Kidney Function, and Survival Among Patients Treated With Reduced-Frequency Hemodialysis

RATIONALE & OBJECTIVE

Patients receiving twice-weekly or less-frequent hemodialysis (HD) may need to undergo higher ultrafiltration rates (UFRs) to maintain acceptable fluid balance. We hypothesized that higher UFRs are associated with faster decline in residual kidney function (RKF) and a higher rate of mortality.

STUDY DESIGN

Retrospective cohort study.

SETTING & PARTICIPANTS

1,524 patients with kidney failure who initiated maintenance HD at a frequency of twice or less per week for at least 6 consecutive weeks at some time between 2007 and 2011 and for whom baseline data for UFR and renal urea clearance were available.

PREDICTOR

Average UFR during the first patient-quarter during less-frequent HD (<6, 6-<10, 10-<13, and≥13mL/h/kg).

OUTCOME

Time to all-cause and cardiovascular death, slope of decline in RKF during the first year after initiation of less-frequent HD (with slopes above the median categorized as rapid decline).

ANALYTICAL APPROACH

Cox proportional hazards regression for time to death and logistic regression for the analysis of rapid decline in RKF.

RESULTS

Among 1,524 patients, higher UFR was associated with higher all-cause mortality; HRs were 1.43 (95% CI, 1.09-1.88), 1.51 (95% CI, 1.08-2.10), and 1.76 (95% CI, 1.23-2.53) for UFR of 6 to<10, 10 to<13, and≥13mL/h/kg, respectively (reference: UFR < 6mL/h/kg). Higher UFR was also associated with higher cardiovascular mortality. Baseline RKF modified the association between UFR and mortality; the association was attenuated among patients with renal urea clearance≥5mL/min/1.73m². Higher UFR had a graded association with rapid decline in RKF; ORs were 1.73 (95% CI, 1.18-2.55), 1.89 (95% CI, 1.12-3.17), and 2.75 (95% CI, 1.46-5.18) at UFRs of 6 to<10, 10 to<13, and≥13mL/h/kg, respectively (reference: UFR < 6mL/h/kg).

LIMITATIONS

Residual confounding from unobserved differences across exposure categories.

CONCLUSIONS

Higher UFR was associated with worse outcomes, including shorter survival and more rapid loss of RKF, among patients receiving regular HD treatments at a frequency of twice or less per week.

Impact of residual kidney function on hemodialysis adequacy and patient survival

Background

Both dialysis dose and residual kidney function (RKF) contribute to solute clearance and are associated with outcomes in hemodialysis patients. We hypothesized that the association between dialysis dose and mortality is attenuated with greater RKF.

Methods

Among 32 251 incident hemodialysis patients in a large US dialysis organization (2007-11), we examined the interaction between single-pool Kt/V (spKt/V) and renal urea clearance (rCLurea) levels in survival analyses using multivariable Cox proportional hazards regression model.

Results

The median rCLurea and mean baseline spKt/V were 3.06 [interquartile range (IQR) 1.74-4.85] mL/min/1.73 m2 and 1.32 ± 0.28, respectively. A total of 7444 (23%) patients died during the median follow-up of 1.2 years (IQR 0.5-2.2 years) with an incidence of 15.4 deaths per 100 patient-years. The Cox model with adjustment for case-mix and laboratory variables showed that rCLurea modified the association between spKt/V and mortality (Pinteraction = 0.03); lower spKt/V was associated with higher mortality among patients with low rCLurea (i.e. <3  mL/min/1.73 m2) but not among those with higher rCLurea. The adjusted mortality hazard ratios (aHRs) and 95% confidence intervals of the low (<1.2) versus high (≥1.2) spKt/V were 1.40 (1.12-1.74), 1.21 (1.10-1.33), 1.06 (0.98-1.14), and 1.00 (0.93-1.08) for patients with rCLurea of 0.0, 1.0, 3.0 and 6.0 mL/min/1.73 m2, respectively.

Conclusions

Incident hemodialysis patients with substantial RKF do not exhibit the expected better survival at higher hemodialysis doses. RKF levels should be taken into account when deciding on the dose of dialysis treatment among incident hemodialysis patients.

Association of Net Ultrafiltration Rate With Mortality Among Critically Ill Adults With Acute Kidney Injury Receiving Continuous Venovenous Hemodiafiltration: A Secondary Analysis of the Randomized Evaluation of Normal vs Augmented Level (RENAL) of Renal Replacement Therapy Trial

IMPORTANCE

Net ultrafiltration (NUF) is frequently used to treat fluid overload among critically ill patients, but whether the rate of NUF affects outcomes is unclear.

OBJECTIVE

To examine the association of NUF with survival among critically ill patients with acute kidney injury being treated with continuous venovenous hemodiafiltration.

DESIGN, SETTING, AND PARTICIPANTS

The Randomized Evaluation of Normal vs Augmented Level (RENAL) of Renal Replacement Therapy trial was conducted between December 30, 2005, and November 28, 2008, at 35 intensive care units in Australia and New Zealand among critically ill adults with acute kidney injury who were being treated with continuous venovenous hemodiafiltration. This secondary analysis began in May 2018 and concluded in January 2019.

EXPOSURES

Net ultrafiltration rate, defined as the volume of fluid removed per hour adjusted for patient body weight.

MAIN OUTCOMES AND MEASURES

Risk-adjusted 90-day survival.

RESULTS

Of 1434 patients, the median (interquartile range) age was 67.3 (56.9-76.3) years; 924 participants (64.4%) were male; median (interquartile range) Acute Physiology and Chronic Health Evaluation III score was 100 (84-118); and 634 patients (44.2%) died. Using tertiles, 3 groups were defined: high, NUF rate greater than 1.75 mL/kg/h; middle, NUF rate from 1.01 to 1.75 mL/kg/h; and low, NUF rate less than 1.01 mL/kg/h. The high-tertile group compared with the low-tertile group was not associated with death from day 0 to 6. However, death occurred in 51 patients (14.7%) in the high-tertile group vs 30 patients (8.6%) in the low-tertile group from day 7 to 12 (adjusted hazard ratio [aHR], 1.51; 95% CI, 1.13-2.02); 45 patients (15.3%) in the high-tertile group vs 25 patients (7.9%) in the low-tertile group from day 13 to 26 (aHR, 1.52; 95% CI, 1.11-2.07); and 48 patients (19.2%) in the high-tertile group vs 29 patients (9.9%) in the low-tertile group from day 27 to 90 (aHR, 1.66; 95% CI, 1.16-2.39). Every 0.5-mL/kg/h increase in NUF rate was associated with increased mortality (3-6 days: aHR, 1.05; 95% CI, 1.00-1.11; 7-12 days: aHR, 1.08; 95% CI, 1.02-1.15; 13-26 days: aHR, 1.11; 95% CI, 1.04-1.18; 27-90 days: aHR, 1.13; 95% CI, 1.05-1.22). Using longitudinal analyses, increase in NUF rate was associated with lower survival (β = .056; P < .001). Hypophosphatemia was more frequent among patients in the high-tertile group compared with patients in the middle-tertile group and patients in the low-tertile group (high: 308 of 477 patients at risk [64.6%]; middle: 293 of 472 patients at risk [62.1%]; low: 247 of 466 patients at risk [53.0%]; P < .001). Cardiac arrhythmias requiring treatment occurred among all groups: high, 176 patients (36.8%); middle: 175 patients (36.5%); and low: 147 patients (30.8%) (P = .08).

CONCLUSIONS AND RELEVANCE

Among critically ill patients, NUF rates greater than 1.75 mL/kg/h compared with NUF rates less than 1.01 mL/kg/h were associated with lower survival. Residual confounding may be present from unmeasured risk factors, and randomized clinical trials are required to confirm these findings.

TRIAL REGISTRATION

ClinicalTrials.gov identifier: NCT00221013.