Urea Kinetic Modelling in Chronic Hemodialysis: Benefits, Problems, and Practical Solutions

Fatigue characteristics on dialysis and non-dialysis days in patients with chronic kidney failure on maintenance hemodialysis

BACKGROUND

Fatigue is prevalent in hemodialysis patients who for survival follow a strict dialysis treatment regimen - dialysis and non-dialysis days. As a result, the daily activities, symptom burden, and clinical outcomes of hemodialysis patients vary significantly between dialysis and non-dialysis days. Fatigue is one of the most reported debilitating symptoms by hemodialysis patients with profound negative impact on their quality of life. Prior studies assessed fatigue during the preceding 7 or 30 days and did not discriminate fatigue characteristics between dialysis and non-dialysis days. We aimed to characterize and compare fatigue severity and fatigue interference with daily activities between dialysis and non-dialysis days.

METHODS

Hemodialysis patients self-reported fatigue on consecutive dialysis and non-dialysis days using the 9-item Brief Fatigue Inventory. The differences in fatigue characteristics between dialysis and non-dialysis days were analyzed using one-way ANCOVA.

RESULTS

Global fatigue burden was worse on a dialysis day compared to a non-dialysis day (P for all < 0.001). Age and education were associated with fatigue, but hemodialysis-related variables were not. A significant inverse association of physical activity with fatigue severity observed on non-dialysis day; there was also a negative association between the normalized protein catabolic rate and fatigue severity on both dialysis and non-dialysis days. The positive association of depression with fatigue severity and fatigue interference were consistent on both dialysis and non-dialysis days. None of these factors, however, explained differences in fatigue characteristics between dialysis and non-dialysis days.

CONCLUSIONS

Fatigue, measured in severity and interference, was more pronounced on a dialysis day relative to a non-dialysis day. These differences were not explained by age, sex, education, hemodialysis-related variables, habitual exercise, nutritional status, and or depression. The quantitative measures of fatigue characteristics may facilitate future interventional trials design and better fatigue management for hemodialysis patients.

Low Intracellular Water, Overhydration, and Mortality in Hemodialysis Patients

Background: In hemodialysis patients, extracellular water (ECW) overload predicts all-cause and cardiovascular mortality. The primary aim of the present study was to analyze changes in post-dialysis (i.e., following removal of excess ECW) ECW, intracellular water (ICW), and the overhydration (OH) parameter over time. Additionally, the association of these parameters with mortality was explored. Patients and methods: Prospective study of prevalent hemodialysis patients (n = 124) followed for a median of 20 (interquartile range (IQR) 8–31) months. In three visits, inflammation (C-reactive protein) and post-dialysis fluid status (bioimpedance, BIS) were assessed. Results: During follow-up, the overhydration (OH) parameter increased (−0.696 ± 1.6 vs. 0.268 ± 1.7 L; p = 0.007) at the expense of a decrease in intracellular water (ICW) (19.90 ± 4.5 vs. 18.72 ± 4.1 24 L; p = 0.006) with a non-significant numerical increase in ECW/ICW ratio (0.795 ± 0.129 vs. 0.850 ± 0.143; p = 0.055). Baseline ICW positively correlated with muscle mass and energy intake and negatively with C-reactive protein and it was lower in those who died than in survivors (15.09 ± 2.36 vs. 18.87 ± 4.52 L; p = 0.004). In Kaplan–Meier analysis, patients with low baseline ICW (≤17 L) and high ECW/ICW ratio (≥0.84) were at an increased risk of death. Baseline ICW was also associated with the risk of death in adjusted Cox proportional hazards models (HR 0.62 (0.40–0.98) p = 0.04). Conclusions: In hemodialysis patients, the post-dialysis OH parameter increased over time while ICW decreased, without changes in ECW. Low baseline post-dialysis ICW correlated with muscle wasting and inflammation and was an independent risk factor for mortality.

Metabolic and volume status evaluation of hemodialysis patients with and without residual renal function in the long interdialytic interval

Introduction:

It is unclear whether residual renal function (RRF) in dialysis patients can attenuate the metabolic impact of the long 68-hour interdialytic interval, in which water, acid, and electrolyte accumulation occurs.

Objective:

to evaluate serum electrolyte levels, water balance, and acid-base status in dialytic patients with and without RRF over the long interdialytic interval (LII).

Methodology:

this was a single-center, cross-sectional, and analytical study that compared patients with and without RRF, defined by diuresis above 200 mL in 24 hours. Patients were weighed and serum samples were collected for biochemical and gasometric analysis at the beginning and at the end of the LII.

Results:

27 and 24 patients with and without RRF were evaluated, respectively. Patients without RRF had a higher increase in serum potassium during the LII (2.67 x 1.14 mEq/L, p < 0.001), reaching higher values at the end of the study (6.8 x 5.72 mEq/L, p < 0.001) and lower pH value at the beginning of the interval (7.40 x 7.43, p = 0.018). More patients with serum bicarbonate < 18 mEq/L (50 x 14.8%, p = 0.007) and mixed acid-base disorder (57.7 x 29.2%, p = 0.042), as well as greater interdialytic weight gain (14.67 x 8.87 mL/kg/h, p < 0.001) and lower natremia (137 x 139 mEq/L, p = 0.02) at the end of the interval. Calcemia and phosphatemia were not different between the groups.

Conclusion:

Patients with RRF had better control of serum potassium, sodium, acid-base status, and volemia throughout the LII.

Investigating Physical and Nutritional Changes During Prolonged Intermittent Fasting in Hemodialysis Patients: A Prospective Cohort Study

OBJECTIVE

Studies investigating the health effects of prolonged intermittent fasting during Ramadan among Muslim patients on hemodialysis (HD) are limited and reported heterogeneous findings. This study aimed to evaluate the effects of intermittent fasting during Ramadan on nutritional and functional status of patients on maintenance HD.

DESIGN AND METHODS

This was a 12-week, multicenter, prospective observational study. The study setting included three HD centers. Adult Muslim patients, who were undergoing HD session thrice weekly and planned to fast during Ramadan, were screened for eligibility and recruited. Nutritional and functional status assessments were carried out 2 weeks before (V₀), at the fourth week of Ramadan (V₁), and 4 weeks after Ramadan (V₂). Nutritional status parameters included anthropometry (body mass index, interdialytic weight gain, waist circumference), body composition (mid-arm circumference, triceps skinfold, body fat percentage), blood biochemistry (albumin, renal profile, lipid profile, and inflammatory markers), blood pressure, dietary intake, and handgrip strength. Changes in nutritional and functional status parameters across study timepoints were analyzed using repeated-measures analysis of variance.

RESULTS

A total of 87 patients completed the study, with 68 patients (78.2%) reporting fasting ≥20 days. Ramadan fasting led to significant reductions (all P < .05) in body mass index, interdialytic weight gain, waist circumference, mid-arm circumference, fat tissue mass, and body fat percentage, but these were not accompanied by any significant change in lean tissue mass (P > .05). Significant improvement was observed in serum phosphate levels, but serum albumin, urea, and creatinine were also reduced significantly during Ramadan (P < .05). There were no significant changes in lipid profile and inflammatory markers. Interestingly, energy and protein intakes remain unchanged during Ramadan. Handgrip strength improved significantly during Ramadan and further improved after Ramadan.

CONCLUSION

Intermittent Ramadan fasting leads to temporary changes in nutritional status parameters and poses nondetrimental nutritional risk for patients on maintenance HD.

Prediction equation for calculating residual kidney urea clearance using urine collections for different hemodialysis treatment frequencies and interdialytic intervals

Background

The purpose of the study was to explore the precision of an equation designed to estimate residual kidney urea clearance (KRU) from interdialytic urine collection data and pre-hemodialysis (HD) serum urea nitrogen (SUN) in different hemodialysis treatment schedules.

Methods

The generalizability of the proposed equation was tested in 32 731 HD treatments where urine was collected prior to a dialysis session, mostly for 24 h but sometimes longer, in patients being dialyzed 1-4 times/week.

Results

The residual kidney urea clearance estimating equation predicted a KRU that matched the one computed by formal modeling within 5% in >98% of sessions analyzed. The errors in estimated versus modeled KRU for interdialytic intervals (IDIs) of 2, 3, 4 and 7 days, were 1.6 ± 1.5%, -0.4 ± 1.6%, 0.9 ± 1.6%, and 1.5 ± 1.2%, respectively. Percent errors were similar for schedules of 1-4/week with the exception of urine collection during the 2-day interval of a 2:5-day twice-weekly schedule; here error averaged 5.0 ± 1.2%. Use of the average of the SUN values at the start and end of the collection period overestimated modeled KRU by 11.3 ± 4.5%, whereas an equation suggested by others underestimated modeled KRU by -9.9 ± 3.4%.

Conclusions

The equation tested predicts values for KRU that are similar to those obtained from formal urea kinetic modeling, with percent errors that only rarely exceed 5%. It gives relatively precise results for a wide range of HD treatment schedules, IDIs and urine collection periods.

Keywords

chronic hemodialysis, clearance, guidelines, hemodialysis, predialysis.

Criteria for classification of protein-energy wasting in dialysis patients: impact on prevalence

Malnutrition is highly prevalent in dialysis patients and associated with poor outcomes. In 2008, protein-energy wasting (PEW) was coined by the International Society of Renal Nutrition and Metabolism (ISRNM), as a single pathological condition in which undernourishment and hypercatabolism converge. In 2014, a new simplified score was described using serum creatinine adjusted for body surface area (sCr/BSA) to replace a reduction of muscle mass over time in the muscle wasting category. We have now compared PEW-ISRNM 2008 and PEW-score 2014 to evaluate the prevalence of PEW and the risk of death in 109 haemodialysis patients. This was a retrospective analysis of cross sectional data with a median prospective follow-up of 20 months. The prevalence of PEW was 41 % for PEW-ISRNM 2008 and 63 % for PEW-score 2014 (P &lt;0·002). Using PEW-score 2014: twenty-nine patients (27 %) had severe malnutrition (PEW-score 2014 0-1) and forty (37 %) with moderate malnutrition (score 2). Additionally, thirty-three (30 %) patients had mild wasting and only seven patients (6 %) presented a normal nutritional status. sCr/BSA correlated with lean total mass (R 0·46. P&lt;0·001). A diagnosis of PEW according to PEW-score 2014, but not according to PEW-ISRNM 2008, was significantly associated with short-term mortality (P=0·0349) in univariate but not in multivariate analysis (P=0·069). In conclusion, the new PEW-score 2014 incorporating sCr/BSA identifies a higher number of dialysis PEW patients than PEW-ISRNM 2008. Whereas PEW-score-2014 provides timelier and therefore more clinically relevant information, its association with early mortality needs to be confirmed in larger studies.

Individualized Hemodialysis Treatment: A Perspective on Residual Kidney Function and Precision Medicine in Nephrology

Background: Residual kidney function (RKF) is often expected to inevitably and rapidly decline among hemodialysis patients and, hence, has been inadvertently ignored in clinical practice. The importance of RKF has been revisited in some recent studies. Given that patients with end-stage renal disease now tend to initiate maintenance hemodialysis therapy with higher RKF levels, there seem to be important opportunities for incremental hemo­dialysis by individualizing the dose and frequency according to their RKF levels. This approach is realigned with precision medicine and patient-centeredness. Summary: In this article, we first review the available methods to estimate RKF among hemodialysis patients. We then discuss the importance of maintaining and monitoring RKF levels based on a variety of clinical aspects, including volume overload, blood pressure control, mineral and bone metabolism, nutrition, and patient survival. We also review several potential measures to protect RKF: the use of high-flux and biocompatible membranes, the use of ultrapure dialysate, the incorporation of hemodiafiltration, incremental hemodialysis, and a low-protein diet, as well as general care such as avoiding nephrotoxic events, maintaining appropriate blood pressure, and better control of mineral and bone disorder parameters. Key Message: Individualized hemodialysis regimens may maintain RKF, lead to a better quality of life without compromising long-term survival, and ensure precision medicine and patient-centeredness in nephrology practice.

Leptin and ghrelin in chronic kidney disease: their associations with protein-energy wasting

BACKGROUND

This study aimed to evaluate plasma concentrations of leptin and total ghrelin in children with chronic kidney disease (CKD) and assess their roles in protein-energy wasting (PEW).

METHODS

This study consisted of three different CKD populations [CKD group (20 patients with non-dialysis CKD), dialysis group (39 patients on dialysis), and kidney transplant (KTx) group (35 KTx recipients)] and control group (18 healthy children). Plasma leptin and total ghrelin levels were measured. Multi-frequency bioimpedance analysis was used for the assessment of fat and lean mass. PEW was defined using criteria including body mass, muscle mass, growth, serum albumin level, and protein intake.

RESULTS

While plasma leptin levels did not differ among the study groups, total ghrelin levels were significantly higher in the dialysis group (P < 0.001). Seven dialysis patients (18%) and one CKD patient (5%) but none of the KTx recipients met the criteria of PEW. Dialysis patients with PEW had lower plasma leptin levels compared to their counterparts (P = 0.018); however, total ghrelin levels did not differ between the two groups (P = 0.10). Low leptin level in dialysis patients was independently associated with lower fat mass index (P < 0.001) and lower height-specific SD scores of BMI (P = 0.019).

CONCLUSIONS

PEW is prevalent in dialysis patients. Low levels of leptin seem to be associated with PEW. Our result suggests that low leptin levels may be a consequence rather than a cause of PEW. Longitudinal studies are required to investigate this complex relationship between leptin and PEW in pediatric dialysis patients.

Differences between KT/V Measured during Dialysis and KT/V Predicted from Manufacturer Clearance Data

We retrospectively analyzed data from 3,863 dialysis treatments in 329 end-stage renal disease patients over a period of 33 months to evaluate the accuracy of in vitro KT/V estimated by manufacturer's urea clearance data in relation to in vivo measured KT/V. In 1,087 urea clearances measured, mean actual clearance was 87% of predicted. At all blood flows, actual clearances were significantly lower than predicted (8-16% lower than predicted). In 2,807 KT/V measurements, predicted KT/V was 1.238 ± 0.005 whereas the mean of actual measured KT/V was 16% lower or 1.024 ± 0.005 (P < 0.0001). At different blood flows and with different dialyzers, predicted KT/V overestimated actual values. With increasing numbers of reuse, actual/predicted clearance ratios and actual/predicted KT/V ratios progressively dropped. Prescribing dialysis treatments using manufacturer's in vitro generated clearance data can lead to marked underdialysis of patients.

Nutritional Status of Maintenance Dialysis Patients: Low Lean Body Mass Index and Obesity Are Common, Protein-Energy Wasting Is Uncommon

BACKGROUND AND AIMS

Maintenance dialysis patients are at increased risk of abnormal nutritional status due to numerous causative factors, both nutritional and non-nutritional. The present study assessed the current prevalence of protein-energy wasting, low lean body mass index and obesity in maintenance dialysis patients, and compared different methods of nutritional assessment.

METHODS

In a cross-sectional study conducted in 2014 at Roskilde Hospital, Denmark, we performed anthropometry (body weight, skinfolds, mid-arm, waist, and hip circumferences), and determined plasma albumin and normalized protein catabolic rate in order to assess the prevalence of protein-energy wasting, low lean body mass index and obesity in these patients.

RESULTS

Seventy-nine eligible maintenance dialysis patients participated. The prevalence of protein-energy wasted patients was 4% (95% CI: 2-12) as assessed by the coexistence of low lean body mass index and low fat mass index. Low lean body mass index was seen in 32% (95% CI: 22-44). Obesity prevalence as assessed from fat mass index was 43% (95% CI: 32-55). Coexistence of low lean body mass index and obesity was seen in 10% (95% CI: 5-19). The prevalence of protein-energy wasting and obesity varied considerably, depending on nutritional assessment methodology.

CONCLUSIONS

Our data indicate that protein-energy wasting is uncommon, whereas low lean body mass index and obesity are frequent conditions among patients in maintenance dialysis. A focus on how to increase and preserve lean body mass in dialysis patients is suggested in the future. In order to clearly distinguish between shortage, sufficiency and abundance of protein and/or fat deposits in maintenance dialysis patients, we suggest the simple measurements of lean body mass index and fat mass index.

Precedent fluctuation of serum hs-CRP to albumin ratios and mortality risk of clinically stable hemodialysis patients

Background

A high sensitivity C-reactive protein to albumin ratio (hs-CRP/Alb) predicts mortality risk in patients with acute kidney injury. However, it varies dynamically. This study was conducted to evaluate whether a variation of this marker was associated with long-term outcome in clinically stable hemodialysis (HD) patients.

Methods

hs-CRP/Alb was checked bimonthly in 284 clinically stable HD outpatients throughout all of 2008. Based on the “slope” of trend equation derived from 5–6 hs-CRP/alb ratios for each patient, the total number of patients was divided into quartiles—Group 1: β≦ −0.13, n = 71; group 2: β>-0.13≦0.003; n = 71, group 3: β>0.003≦0.20; and group 4: β>0.20, n = 71. The observation period was from January 1, 2009 to August 31, 2012.

Results

Group 1+4 showed a worse long-term survival (p = 0.04) and a longer 5-year hospitalization stay than Group 2+3 (38.7±44.4 vs. 16.7±22.4 days, p<0.001). Group 1+4 were associated with older age (OR = 1.03, 95% CI = 1.01–1.05) and a high prevalence of congestive heart failure (OR = 2.02, 95% CI = 1.00–4.11). Standard deviation (SD) of hs-CRP/Alb was associated with male sex (β = 0.17, p = 0.003), higher Davies co-morbidity score (β = 0.16, p = 0.03), and baseline hs-CRP (β = 0.39, p<0.001). Patients with lower baseline and stable trend of hs-CRP/Alb had a better prognosis. By multivariate Cox proportional methods, SD of hs-CRP/alb (HR: 1.05, 95% CI: 1.01–1.08) rather than baseline hs-CRP/Alb was an independent predictive factor for long-term mortality after adjusting for sex and HD vintage.

Conclusion

Clinically stable HD patients with a fluctuating variation of hs-CRP/Alb are characterized by old age, and more co-morbidity, and they tend to have longer subsequent hospitalization stay and higher mortality risk.

Protein-energy wasting, as well as overweight and obesity, is a long-term risk factor for mortality in chronic hemodialysis patients

INTRODUCTION

In patients with end-stage renal disease on chronic hemodialysis (HD), protein-energy wasting (PEW) is very common and is associated with increased morbidity and mortality. Evaluation of nutritional status should be performed regularly in all such patients, using multiple methods. In this study, we analyzed the influence of several nutritional markers on long-term (5 years) survival of HD patients in one center. This is the first study on the long-term influence of nutritional status on mortality in dialysis patients ever conducted in Romania.

MATERIALS AND METHODS

We included all prevalent HD patients in our center. Those with ongoing acute illnesses and with inflammation (C-reactive protein ≥ 6.0 mg/l) were excluded. In the remaining subjects (N = 149, 82 males, mean age 55 years old), we performed the following measurements of nutritional status: estimation of dietary protein intake by normalized protein equivalent of nitrogen appearance (nPNA), subjective global assessment (SGA), body mass index (BMI), tricipital skinfold thickness, mid-arm circumference, assessment of body composition by bioelectrical impedance analysis (BIA), and pre-dialysis serum creatinine, albumin, and total cholesterol. We used receiver operating characteristic curves to determine the cutoff points for most of the variables, and we applied the Kaplan-Meier estimator and the Cox's proportional hazards model (stepwise method) to analyze the influence of these variables on survival.

RESULTS

In univariate analysis, general factors including age ≥ 65 years, male gender, dialysis vintage ≥ 2 years, and the presence of diabetes and heart failure were all significant predictors of mortality. Among nutritional parameters, BMI ≥ 25 kg/m(2), SGA-B (mild PEW), nPNA < 1.15 g/kg per day, and the BIA-derived phase angle (PhA) <5.58° were also significantly associated with reduced survival. All of these factors maintained statistical significance in multivariate analysis, except for male gender and heart failure.

CONCLUSION

We showed that low values of SGA, nPNA, and PhA independently predict mortality in HD patients. In conjunction with an earlier study, we demonstrated that the relative risk of death associated with these markers is highest during the first year of monitoring and it decreases in the following 4 years, although it still remains significantly increased. On the other hand, overweight and obesity were also associated with lower survival after 5 years, whereas this association was not apparent after 1 year.

Malnutrition and its association with inflammation and vascular disease in children on maintenance dialysis

BACKGROUND

Malnutrition is associated with both inflammation and atherosclerotic cardiovascular disease in adults with chronic kidney disease. We studied the prevalence of malnutrition and its possible associations with inflammation and vascular disease in children on chronic dialysis.

METHODS

Thirty-three patients on maintenance dialysis (18 peritoneal dialysis, 15 hemodialysis) and 19 age- and gender- matched healthy controls were studied. Nutritional status was assessed by anthropometric measurements including body mass index (BMI), upper arm measurements, multifrequency bioimpedance analysis (BIA) and serum levels of albumin, prealbumin, and cholesterol. Inflammation was assessed by serum levels of C-reactive protein (CRP), interleukin (IL)-6, and tumor necrosis factor (TNF)-alpha. The carotid artery intima thickness (cIMT) was measured to assess vascular disease.

RESULTS

Compared with healthy children, patients had lower anthropometric measurements (P < 0.05) and serum albumin level (P < 0.001), and higher CRP and TNF-alpha (P = 0.030 and P = 0.007, respectively), and higher cIMT-SDS (P < 0.001). Malnutrition was present in 8 (24%) and lower BIA-based fat mass was independently associated with higher IL-6 levels (P = 0.035). An increased cIMT was present in 16 (48.5%); however, there was no difference in cIMT-SDS between patients with and without malnutrition. Carotid IMT did not show any association with nutritional indices; but positively correlated with serum IL-6 (P = 0.037), CRP (P = 0.012), and iPTH (P = 0.009), and independently associated with only iPTH (P = 0.018).

CONCLUSIONS

Children on dialysis are at an increased risk of malnutrition, inflammation, and vascular disease. Although each of these three conditions exists, there is no interaction among them all. We postulate that the malnutrition-inflammation-atherosclerosis (MIA) complex might not exist in pediatric dialysis patients.

Interdialytic creatinine change versus predialysis creatinine as indicators of nutritional status in maintenance hemodialysis

BACKGROUND

Protein-energy wasting is common in patients on maintenance hemodialysis and is strongly associated with poor quality of life and mortality. However, clinical assessment of protein-energy wasting remains difficult. Predialysis creatinine levels are associated with mortality risk but may be influenced by both muscle mass and dialysis dose. This might be overcome by examining the rate of rise in creatinine between dialysis sessions.

METHODS

We conducted an observational cohort study among 81 patients on maintenance hemodialysis at our Veterans Affairs unit. Predialysis serum creatinine and change in serum creatinine between midweek dialysis sessions served as the predictor variables of interest and clinically available proxies of nutritional status and time to mortality served as the outcome variables. Linear regression and Cox proportional hazards models evaluated relationships, respectively.

RESULTS

The mean age of the study participants was 63 ± 10 years, 77 (95%) were male, mean body mass index was 27 ± 6 kg/m(2) and 69% had diabetes. Median follow-up time was 13 months, during which 12 patients (15%) died. Interdialytic change in serum creatinine showed a strong direct correlation with predialysis serum creatinine (R = 0.96). Higher levels of both markers were associated with younger age, less residual urine volume and higher serum albumin, serum phosphorus and normalized protein catabolic rate (P < 0.05 for all). Both markers were approximately equally strongly associated with mortality. For example, compared to the highest predialysis creatinine tertile, participants in the lowest tertile (<6 mg/dL) had 5.5-fold [95% confidence interval (CI) 1.1, 26.6] higher risk of death. Similarly, participants in the lowest tertile of interdialytic change in creatinine (change <3.7 mg/dL/48 h), had 5.0-fold (95% CI 1.0, 24.4) higher death risk.

CONCLUSIONS

Predialysis creatinine and interdialytic change in creatinine are both strongly associated with proxies of nutritional status and mortality in hemodialysis patients and are highly correlated. Interdialytic change in creatinine provided little additional information about nutritional status or mortality risk above and beyond predialysis creatinine levels alone.

Validation of a Method to Predict Required Dialysis Time for Cases of Methanol and Ethylene Glycol Poisoning

BACKGROUND

Traditional dialysis management of ethylene glycol and methanol poisoning includes frequent intradialytic measurements of concentrations of the involved alcohol and its metabolite. A simple formula to predict the required dialysis time in advance by using patient age, sex, weight, height, dialyzer specifications, and initial toxin level was proposed and tested by us previously in 5 cases. To reach a 5-mmol/L-or-less toxin concentration target, required hemodialysis time, in hours, would be [-V ln (5/A)/0.06 k], where V is the Watson estimate of total-body water in liters, A is the initial toxin concentration in mmol/L, and k is 80% of the manufacturer-specified dialyzer urea clearance in milliliters per minute at the initial observed blood flow rate.

METHODS

We further assessed the accuracy of this formula by reviewing all dialyzed new patients with methanol or ethylene glycol poisoning from March 2001 to March 2004 (N = 13).

RESULTS

There were no clinically or statistically significant differences between mean predicted (8.7+/-3.4 [SD] hours) and required (8.4+/-3.2 hours) dialysis time. No rebound increase in toxin levels occurred.

CONCLUSION

The proposed formula is a simple, yet accurate, method to predict dialysis time for patients with methanol and ethylene glycol toxicity, confirmed by validation on an independent data set. Only initial, 2 hours before termination of dialysis, and 1 to 2 hours postdialysis measurements of toxin levels are required to ensure adequate dialysis therapy.

Quality of life of patients on haemodialysis for end-stage renal disease

AIM

The aims of the study were (a) to measure the overall quality of life of people receiving haemodialysis, (b) to compare the quality of life of the sample with that of the general population and (c) to identify any differences between the quality of life of people who are adequately dialysed and those inadequately dialysed, as determined by Kt/V(urea) (dialysis adequacy) measurements.

BACKGROUND

End stage renal disease is a progressive, debilitating, chronic illness requiring nursing and medical interventions. The development of the disease affects quality of life, potentially influencing physical and mental health, functional status, independence, general well-being, personal relationships and social functioning.

METHOD

A descriptive, cross-sectional, survey was carried out of the quality of life of patients undergoing haemodialysis treatment at a hospital in the Republic of Ireland. A non-probability sample of 97 patients was chosen. Health-related quality of life was assessed using the 36-item Short Form Health Survey questionnaire.

FINDINGS

Patients receiving haemodialysis identified limitations in a number of areas including vitality, physical functioning and physical role limitations. They also reported significantly lower physical functioning when compared with general population norm-based scores. Differences were also found in mental health scores between patients who were well-dialysed and those less well-dialysed.

CONCLUSION

End-stage renal disease and its ensuing treatments negatively affect quality of life. Nurses aware of this evidence can explore new ways to assess more accurately and identify specific problem areas for individual patients and take action to ameliorate these.

Artificial neural networks improve the prediction of Kt/V, follow-up dietary protein intake and hypotension risk in haemodialysis patients

BACKGROUND

Artificial neural networks (ANN) represent a promising alternative to classical statistical and mathematical methods to solve multidimensional non-linear problems. The aim of the study was to compare the performance of ANN in predicting the dialysis quality (Kt/V), the follow-up dietary protein intake and the risk of intradialytic hypotension in haemodialysis patients with that predicted by experienced nephrologists.

METHODS

A combined retrospective and prospective observational study was performed in two Swiss dialysis units (80 chronic haemodialysis patients, 480 monthly clinical observations and biochemical test results). Using mathematical models based on linear and logistic regressions as background, ANN were built and then prospectively compared with the ability of six experienced nephrologists to predict the Kt/V and the follow-up protein catabolic rate (PCR) and to detect a Kt/V < 1.30, a follow-up PCR < 1.00 g/kg/day and the occurrence of hypotension.

RESULTS

ANN compared with nephrologists gave a more accurate correlation between estimated and calculated Kt/V and follow-up PCR (P<0.001). The same superiority of ANN was also seen in the ability to detect a Kt/V < 1.30, a follow-up PCR < 1.00 g/kg/day and the occurrence of hypotension expressed as a percentage of correct answers, sensitivity, specificity and predictivity.

CONCLUSIONS

The use of ANN significantly improves the ability of experienced nephrologists to estimate the Kt/V and the follow-up PCR and to detect a Kt/V < 1.30, a follow-up PCR < 1.00 g/kg/day and the occurrence of intradialytic hypotension.

Normalized protein nitrogen appearance is correlated with hospitalization and mortality in hemodialysis patients with Kt/V greater than 1.20

OBJECTIVES

Normalized protein nitrogen appearance (nPNA), also known as protein catabolic rate (nPCR), reflects the daily protein intake in maintenance hemodialysis (MHD) patients. Several studies indicate that nPNA and Kt/V correlate with clinical outcome and also with each other. Thus, the relationship between low nPNA and poor outcome could be due to uremia, low Kt/V or due to reported mathematical coupling between nPNA and Kt/V. We therefore investigated whether nPNA is associated with outcome in patients who have adequate or high Kt/V.

DESIGN

Prospective cohort.

SETTINGS

Outpatient dialysis unit affiliated with a tertiary-care community medical center.

PATIENTS

From a pool of 135 MHD outpatients in one dialysis unit, 122 patients with a delivered, Kt/V(sp)>1.20, independent of their residual renal function, were evaluated. Patients (61 women, 61 men), aged from 23 to 89 years (53.4+/-14.0 years)(+/-SD), had been undergoing MHD for one month to 17 years.

INTERVENTION

Review of laboratory values and clinical outcome.

MAIN OUTCOME MEASURES

Twelve-month mortality and hospitalization.

RESULTS

Delivered Kt/V(sp) ranged from 1.23 to 2.71 (1.77+/-0.34), nPNA from 0.5 to 2.15 (1.13+/-0.29 g/kg/day), and serum albumin, from 1.9 to 4.6 (3.76+/-0.37 g/dL). During the 12-month follow-up, 55 patients were hospitalized overnight at least once; 12 patients died; 5 patients underwent renal transplantation, and 6 patients left the study. The nPNA and Kt/V(sp) did not correlate significantly (r=.09) except when analysis was limited to Kt/V values < 1.5 (r=.54). Serum nPNA and albumin were the only variables with statistically significant correlations with both mortality and 3 measures of hospitalization (H): total days of H (H(D)), total number of H (H(F)), and time to first H (H(T)). The case-mix adjusted correlations for serum albumin and nPNA versus total days (r(HD)) and frequency of H (r(HF)) were significant, and Cox analysis based on H(T) and time to death resulted in significant odds ratios for each standard deviation decrement for both serum albumin and nPNA. Serum total iron binding capacity (TIBC) and creatinine concentrations also correlated with some but not all outcome measures: lower serum concentrations of these values were each significantly associated with poor clinical outcomes.

CONCLUSIONS

Both nPNA and serum albumin predict prospective hospitalization and mortality in MHD patients with Kt/V > 1.20. Serum TIBC and creatinine concentrations appear to have association with some outcome measures as well. These data are consistent with the possibility that protein intake affects the clinical course even in the setting of an adequate to high hemodialysis dose. Studies based on randomized assignments to different protein intakes would be helpful to confirm these conclusions.

Artificial intelligence: a new approach for prescription and monitoring of hemodialysis therapy

The effect of dialysis on patients is conventionally predicted using a formal mathematical model. This approach requires many assumptions of the processes involved, and validation of these may be difficult. The validity of dialysis urea modeling using a formal mathematical model has been challenged. Artificial intelligence using neural networks (NNs) has been used to solve complex problems without needing a mathematical model or an understanding of the mechanisms involved. In this study, we applied an NN model to study and predict concentrations of urea during a hemodialysis session. We measured blood concentrations of urea, patient weight, and total urea removal by direct dialysate quantification (DDQ) at 30-minute intervals during the session (in 15 chronic hemodialysis patients). The NN model was trained to recognize the evolution of measured urea concentrations and was subsequently able to predict hemodialysis session time needed to reach a target solute removal index (SRI) in patients not previously studied by the NN model (in another 15 chronic hemodialysis patients). Comparing results of the NN model with the DDQ model, the prediction error was 10.9%, with a not significant difference between predicted total urea nitrogen (UN) removal and measured UN removal by DDQ. NN model predictions of time showed a not significant difference with actual intervals needed to reach the same SRI level at the same patient conditions, except for the prediction of SRI at the first 30-minute interval, which showed a significant difference (P = 0.001). This indicates the sensitivity of the NN model to what is called patient clearance time; the prediction error was 8.3%. From our results, we conclude that artificial intelligence applications in urea kinetics can give an idea of intradialysis profiling according to individual clinical needs. In theory, this approach can be extended easily to other solutes, making the NN model a step forward to achieving artificial-intelligent dialysis control.

A simple method to estimate the required dialysis time for cases of alcohol poisoning

BACKGROUND

Conventional dialysis management of ethylene glycol and methanol poisoning includes frequent intradialytic determinations of serum toxin concentration. Dialysis is continued until a target toxin concentration is reached. Initially, the required dialysis duration is unknown, making planning difficult. We devised a simple method to estimate the duration of dialysis required and avoid quantitation of multiple toxin samples.

METHODS

Using the assumption that toxic alcohols would have a dialysis clearance similar to urea, we proposed that required dialysis time (hours) to reach a 5 mmol/L toxin concentration target would be: [-V ln(5/A)]/0.06k, where V (liters) is the Watson estimate of total body water, A is the initial toxin concentration (mmol/L), and k is 80% of the manufacturer-specified dialyzer urea clearance (mL/min) at the initial observed blood flow rate. Directly measured dialysis and renal toxin clearance, and true dialysis requirement by conventional treatment protocol were compared with our estimate in two methanol and three ethylene glycol poisonings treated with Fresenius F8 dialyzers.

RESULTS

There were no clinically or statistically significant differences between predicted dialysis duration (7.6 +/- 1.9 hours, +/-SD) and that actually provided using hourly toxin concentration sampling (7.4 +/- 1.9 hours). Renal toxin clearance was negligible compared to that of dialysis, and predicted dialysis clearance did not differ significantly from that observed.

CONCLUSIONS

The simple estimate method is sufficiently valid to guide the prescription of dialysis for toxic alcohol poisoning. Data required at dialysis start include only the initial toxin concentration, dialyzer manufacturer's specified urea clearance at initial observed blood pump speed, and patient demographics to estimate total body water. This approach allows for planned dialysis therapy, without the need for additional toxin concentration measurements until dialysis is completed.

[Conservative treatment of renal ptosis]

BACKGROUND

Nephroptosis or floating kidney is an acquired, caudal displacement of one or both kidneys, with differing stages and etiology. It has been almost completely ignored over the past few years. The general tendency to regard nephroptosis as a urological pathology has prompted researchers to look for resolutive surgical treatment. The existence of over 150 surgical techniques is a clear demonstration of the high failure rate with the result that surgeons are unwilling to tackle this pathology, often leaving the patient alone with his problems. The numerous nephrological complications caused by nephroptosis have prompted us to look for alternative therapies to propose to nephrologists for the consecutive treatment of the floating kidney, enabling the patient to live with his pathology.

METHODS

A longitudinal study was performed for 60 months in 102 patients with mono or bilateral nephroptosis. Hematuria, urinary cylindroids, asthenia, pain and the daily intake of antispastic lenitives were analysed at 6, 12, 24 and 60 months. Throughout this period all patients were treated with a water cure (31/day) and nocturnal decubitus in Trendelenburg's position (the foot of the bed is raised by 10 cm). Patients with primary or secondary kidney pathology, UTI and nephrolithiasis were excluded from the study.

RESULTS

All the parameters showed a marked and steady improvement. At one year, over half the patients treated had improved, and at two years over two thirds only complained of marginal symptoms.

CONCLUSIONS

Quali-quantitative and temporal values are reported in the light of which we can affirm that conservative treatment enables the patient to lead an almost normal life, as well as returning to work, with a reduced risk of complications.

Analysis of the relationship between chimerism and the allgeneic humoral response

BACKGROUND

Persistence of antigens has been suggested to play a role in two opposing immunological phenomena: tolerance and memory. Therefore, we studied the impact of chimerism on alloreactive antibody (allo-Ab) production in kidney transplant patients.

METHODS

Thirty-five female renal transplant recipients of male donor organs were classified into the following groups: group 1, 13 sensitized uremic patients on dialysis; group 2, 5 nonsensitized uremic patients on dialysis; group 3, six sensitized patients experiencing graft rejection (3 acute vascular, 1 acute cellular, and 2 chronic); and group 4, 11 nonsensitized with functioning allografts (9 with good function, 1 with acute cellular rejection, and 1 with chronic rejection). Mean duration of dialysis after graft failure was similar in groups 1 (56+/-29.7 months) and 2 (41.8+/-42.4 months), as was dialysis efficiency. Chimerism was measured indirectly in the peripheral blood lymphocytes by polymerase chain reaction amplification of a specific Y chromosome DNA gene sequence with a detection sensitivity limit of 1 male cell per 1 million female cells. Allo-Ab production was measured by the PRA-STAT enzyme-linked immunosorbent assay (Sangstat) method.

RESULTS

Chimerism was observed in 60% of groups 1 and 2, 83% of group 3, and 82% of group 4. Among all groups, graft existence, irrespective of its function, positively predicted chimerism in 92% with a sensitivity of 88% and a specificity of 78%. In group 3, all three patients with acute vascular rejection had chimerism and donor-specific allo-Abs. In group 4, eight of the nine patients with no rejection had chimerism.

CONCLUSION

Chimerism relates to persistence of allogeneic stimulus irrespective of its function. Chimerism did not confer protection against allo-Ab production or vascular rejection, and its existence was not crucial for sustenance of allo-Ab production.

Alloantigen-blocking antibodies in sera from highly sensitized uremic patients: antibody class and relationship with lymphocytotoxins

BACKGROUND

Previously, we identified an antimitogenic IgG antibody separated from sera of patients with known kidney transplant chronic rejection. This antibody inhibits individual patients' own unprimed T helper cell responses to alloantigens as well as a third-party mixed lymphocyte response, but does not inhibit autologous unprimed T helper cell proliferation to adherent anti-CD3 antibody. We suggest that the mechanism of inhibitory action is allogeneic-dependent.

METHODS

We used a series of similar experimental designs to test the presence of this antibody in uremic, sensitized patients and have studied its relationship to sensitization as defined by the presence of lymphocytotoxins in four uremic groups: highly sensitized with or without previous graft loss, moderately sensitized with or without graft loss, nonsensitized without previous graft loss, and nonsensitized with graft loss.

RESULTS

(1) Sensitization is associated with the presence of a potent antibody that blocks primary mixed lymphocyte response. Primed cells are less susceptible to its antimitogenic action. (2) The blocking antibody activity is present only in sensitized patients who have IgG lymphocytotoxic activity against the same HLA class I antigens. (3) The blocking activity is unequal in the following order: IgG 3 > IgG 1 > IgG 2. (4) Although IgG 1 and 2 fractions contain lymphocytotoxic activity against HLA class I antigens, the IgG 3 fraction does not.

CONCLUSIONS

The differential effect of IgG antibodies on naive and memory T cells may explain why humeral responses to alloantigens can be maintained in the presence of blocking antibodies.

Hypotension during hemodialysis: role for nitric oxide

Hypotensive episodes during hemodialysis are a frequent complication in patients with end-stage renal disease. The possibility that nitric oxide (NO), a major regulator of cardiovascular hemodynamics, could be a factor was explored. Pre and postdialysis plasma samples from 17 hemodialysis patients were analyzed for the stable end products of NO,nitrite + nitrate (NO2 + NO3), by the Greiss method. Predialysis NO2 + NO3 levels were significantly higher in end-stage renal disease than in nine age-matched controls (44.08 +/- standard error of mean 5.74 versus 18.67 +/- 3.56 uM, P = 0.017). In more than half of the patients, postdialysis values dropped markedly, whereas in others the value change was far less; several rose above predialysis values. Depending on the nitrite + nitrate reduction ratio (pre minus postdialysis NO2 + NO3 divided by the predialysis value) patients were separated into two groups, A (n = 9 where nitrate + nitrate reduction ratio was > 0.5 and B (n = 8 where nitrate + nitrate reduction ratio was < 0.5). Whereas the mean predialysis NO2 + NO3 values between groups A and B did not differ significantly, postdialysis levels fell from a predialysis mean of 50 uM to 12 uM in group A but rose from 37 uM to 45 uM in group B. The difference between the postdialysis values of group A and group B was significant (P = 0.0264). In group B, mean systolic blood pressure dropped more than in group A, (57.8 mm Hg compared with 21.2 mm Hg, P = 0.0078). When measured by analysis of variance for repeated measures, skin and core temperatures and blood pressures were lower in group B than in group A. The volume of the ultrafiltrate was removed and dialysis duration and mean weight loss did not differ. Thus, in group B, apparently NO formation increased during hemodialysis exceeding the rate of removal or metabolism of the end products, whereas in group A, NO2 + NO3 removal or metabolism was without apparent increase in the formation of NO. The basis for this difference is unknown. Because vasodilation is a major effect of NO, the strong association of severe reduction in blood pressures and increased NO synthesis in subset B suggests a role for NO in hypotensive episodes during hemodialysis.

Fractional direct dialysis quantification: a new approach for prescription and monitoring hemodialysis therapy

We describe a new methodology, fractional direct dialysis quantification (FDDQ) utilizing the Fresinius Dialysate Sampling Module (DSM), for quantitating total solute removal during hemodialysis (HD). Our data demonstrate that this technique and Direct Dialysis Quantification (DDQ) yield virtually identical results. FDDQ, however, obviates the practical obstacles that have limited the applicability of DDQ. We discuss the theoretical and practical advantages of this methodology, as compared to urea kinetic modeling (UKM) with Kt/V, for prescribing and monitoring dialysis therapy. FDDQ provides reliable and accurate quantitative data of dialysis function and protein catabolic rate (PCR) independent of questionable theoretical assumptions and parameters required for UKM with Kt/V. It is simple to comprehend and apply. It permits easy comparison of standard and rapid high efficiency dialyses. It also facilitates the quantitative comparison of HD and continuous therapies (peritoneal dialysis and various types of continuous hemofiltration). FDDQ permits the use of other solutes, in place of or in addition to urea, for the quantitation of HD. Because of its simplicity and probable low cost, it can be used with each HD session. It will thus provide accurate data on delivered versus prescribed therapy. These features should permit more accurate monitoring and lead to a clearer understanding of the relationship of outcomes versus delivered dialysis dose, and consequently more effective adjustment of dialysis therapy.

Individualized use of hemodialysis and peritoneal dialysis

Over the past few years it has better been realized how individual the needs for the effectiveness ("dose") of dialytic therapy are and which treatment related factors affect the morbidity and mortality of dialysis patients. Although the role of urea, a marker of small molecular weight uremic toxins, has been challenged, most studies have been based on kinetics of urea during and between dialyses. The dose of dialysis affects also the nutritional status and a special role for "middle" molecules as anorectic factors has been suggested. This article gives an in-depth view of some factors which affect the needs for the effectiveness of dialytic therapy, a summary of the goals of the treatment, and some practical guidelines how to reach them.

Racial differences in the delivery of hemodialysis

Differences in the quality of medical care provided to black and white patients have been observed in the United States, but have not been studied in dialysis patients. We examined whether dialysis delivery, as measured by indirect determination of Kt/V, differs between black and white patients in New Jersey. Five hundred forty-four patients at 10 New Jersey dialysis units were randomly selected by the US Health Care Financing Administration as part of their Medical Case Review Study. Of these, 237 patients at eight units were classified as black or white and had urea kinetic data available. The mean Kt/V urea was higher for white than black patients at all facilities, averaging 1.03 for the 123 black patients and 1.20 for the 114 white patients (P = 0.0006). Black patients were 40% more likely than white patients to have a Kt/V less than 1.0 (45.6% of black patients v 32.5% of white patients, P = 0.038). Racial disparities in dialysis delivery exist, the causes and consequences of which need to be addressed.

Adequacy of hemodialysis

Despite technical advances in the delivery of hemodialysis over the past decade, the mortality rate of hemodialysis-dependent, end-stage renal disease (ESRD) patients in the United States remains high. The increase in the number and severity of comorbid conditions of patients entering ESRD is a factor contributing to this high mortality. Nevertheless, there is increasing evidence that the dose of dialysis received by US patients is inadequate and that this plays a major role in the observed high mortality. In this review, we examine some of the parameters used to judge the adequacy of dialysis, as well as factors that can result in differences between prescribed and delivered dose of hemodialysis. Based on available evidence, we propose that for most patients the optimum dose of dialysis, above which further improvement of morbidity and mortality is doubtful, is represented by a delivered dose of dialysis equivalent to a Kt/V of 1.4 or greater, using biocompatible membranes. The prescription of this optimal dose of dialysis must be coupled with an ongoing effort to monitor delivery of the appropriate dose.