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Background and Aims Recently, more elderly patients who are independent or able to live at home with support of family are opting for peritoneal dialysis (PD). And assisted PD becomes the useful cure in the super-aging society. Japanese nursing-care insurance system which began in 2000 is useful for the spread of PD in the elderly. A purpose of this study is to check the current situation of the PD therapy in the elderly needing care. And it is to plan the spread of assisted PD in the elderly patients. Method Of the 789 elderly patients controlled by dialysis at our hospital between 2000 and 2018, 265 patients (33.6%) selected PD. 106 patients (30.1%) of young-old group (65-74 years, n=352), 108 patients (32.6%) of old group (75-84 years, n=331), and 51 patients (48.1%) of oldest old (≧85 years, n=106) started PD. We studied total Kt/V, total Ccr, volume of urine, volume of dialysate, the bag exchange number and dialysate retention time in 90 PD patients. We estimated total Kt/V and relations of the nursing care level in elderly PD patients. The data of patients divided into 4 groups: young group (≦64 years, n=30), young-old group (65-74 years, n=19), old group (75-84 years, n=27) and oldest-old group (≧85 years, n=14). Total Kt/V and relations of the nursing care level between 1 and 5 based on assessment of care requirements in PD patients with or without assisted PD were studied. Results The nursing-care insurance acquisition rate of each age group was 3.3%, 18.8%, 51.9%, 78.6% and assisted PD rate was 0%, 21.1%, 55.6%, 92.9%, respectively. Total urine volume was 759±506 L/day in the independent elderly patients and was 603±433 in the elderly patients with assisted PD. Dialysate volume was 5.5±2.0L/day in the independent elderly patients and was 4.0±2.1 in the elderly patients with assisted PD (p The daily bag exchange number of times was 3.6±1.0 in the independent elderly patients and was 2.9±1.1 in the elderly patients with assisted PD (p Though total Kt/V did not have the difference in each age group, total Kt/V was 1.74±0.36 in the non-need of nursing care elderly patients and was 1.37±0.30 (p Total Kt/V was 1.72±0.30 in the independent elderly PD patients and was 1.53±0.44 in the elderly patients with assisted PD. Total Kt/V and the nursing care level were significantly inversely correlated (p = 0.011). Total Kt/V and the life independence degree of patients with dementia were significantly inversely correlated (p = 0.001) Conclusion Elderly PD patients can achieve improved levels of well-being with low volume peritoneal dialysates. The application of dialysis prescriptions using APD and and/or icodextorin decrease the burden of changing PD bags for elderly patients, nurses and families who support them (assisted PD). PD for elderly patients will create a paradigm shift of dialysis therapy in the super aging society.

Current guidelines for dialysis specify a minimum Kt/V. For haemodialysis (HD) patients, minimum treatment time and frequency is also specified. The guidelines allow for modification to take account of renal function. The guidelines are not specifically aimed at the elderly and may not be appropriate for all patients in this group. Increasing age is accompanied by physiological and pathological changes that may modify the patient's response to uraemia and dialysis. Frailty and multi-morbidity are likely, but to a variable extent. Elderly patients could be more susceptible to the effects of uraemia and require a higher dose of dialysis. Conversely, the generation rate of uraemic toxins is lower in elderly patients, potentially reducing the need for dialysis. In the elderly, quality of life may be more adversely affected by multimorbidity than uraemic symptoms, thus the dose of dialysis may be less relevant. Higher doses of dialysis may be more difficult to achieve in the elderly and may be less well tolerated. We conclude that the prescription of dialysis in the elderly should be individualized, taking multiple factors into account. An individualized Kt/V may be useful in controlling dialysis dose and detecting problems in delivery. However, achievement of a specified Kt/V may not result in any benefit to an elderly patient and could be counterproductive.

Morbid obesity is reported to be a survival factor for haemodialysis patients compared with those with a normal body mass index (BMI), yet morbid obesity (BMI35) is a mortality risk factor for obese patients in the general population. Traditionally, haemodialysis dosing is prescribed to achieve a target Kt/V corrected for total body water (TBW). As obese patients typically have increased body fat, which contains less water than muscle, then obese patients may have lower levels of body water than their slimmer counterparts, and as such delivered Kt/V could be greater than that estimated using standard anthropomorphic equations, and so increased dialysis dose may help explain the increased survival reported for obese patients.We compared multi-frequency bioelectrical impedance analysis (MF-BIA) measurements of TBW in healthy haemodialysis outpatients, and compared TBW with that calculated from the Watson equation derived from anthropomorphic measurements.Three hundred and sixty-three adult patients, mean age 58.1 ± 16.7 years, 60.9% male and 29.9% diabetic were studied. MF-BIA-measured body composition showed that as BMI increased from20 to35, the percentage skeletal muscle mass fell from 42.8 ± 4.9 to 29.2 ± 5.5% (P0.01) whereas the % fat mass increased from 24.5 ± 11.6 to 46.7 ± 6.8% (P0.01). As such, TBW measured by MF-BIA was significantly lower from that predicted by the Watson equation at higher BMIs (BMI35; 38.9 ± 6.8 versus 44.7 ± 6.9 L, P0.01 and BMI = 30-35; 37.2 ± 7.5 versus 41.9 ± 7.3 L, P0.01), and as such the delivered Kt/V using MF-BIA was much greater than that using the Watson-based urea volume of distribution for the obese patients (BMI35; spKt/V 1.63 ± 0.48 versus 1.41 ± 0.35 and BMI 30-35; 1.65 ± 0.3 versus 1.46 ± 0.26, both P0.01).Prescribing dialysis or quantifying on-line clearance based on the anthropomorphically derived Watson equation leads to underestimation of the delivered dose to obese patients, due to changes in underlying body composition. As such, when using a 'one size fits all' target Kt/V, obese patients have an advantage over patients with normal BMI, in that they will receive a greater delivered dose of dialysis, and this may potentially explain the paradoxical survival advantage of the morbidly obese haemodialysis patient.

BACKGROUND: The recommended parameter of dialysis dose differs between K-DOQI and the European Best Practice Guidelines. It is not well known to what extent an agreement exists between the different parameters, nor if target and delivered dialysis dose are prescribed according to the urea reduction rate (URR), single-pool Kt/V (spKt/V) or equilibrated double-pool Kt/V (eKt/V) and which parameter is most strongly related to mortality. METHODS: In 830 haemodialysis patients from the NECOSAD cohort URR, spKt/V and eKt/V were calculated and compared according to a classification regarding the recommended treatment targets (70%, 1.4 and 1.2, respectively) as well as minimum delivered dialysis dose (65%, 1.2 and 1.05, respectively). Moreover, the relation between treatment dose and survival was assessed using Cox regression analysis. RESULTS: A spKt/V of >/=1.4 and URR >/=70% corresponded with eKt/V >/=1.20 (as reference method) in, respectively, 98.0 and 90.6% of patients. spKt/V of >/=1.2 and URR >/=65% corresponded with eKt/V >/=1.05 in, respectively, 95.5 and 91.2% of patients. Deviations from the reference method were significantly related to differences in urea distribution volume (spKt/V), treatment time (URR) and ultrafiltration volume (URR). The adjusted HR (95% CI) was 0.98 (0.96, 0.99) for URR, 0.51 (0.31, 0.84) for spKt/V and 0.46 (0.30, 0.80) for the eKt/V. CONCLUSION: The use of URR leads to larger disagreement with the reference method (eKt/V) treatment target as compared to spKt/V. Low urea distribution volume, short treatment time and low ultrafiltration volumes are predictive parameters for overestimation of dialysis dose when utilizing the alternative methods spKt/V and URR instead of eKt/V. Delivered eKt/V, spKt/V and URR were all positively related to survival.

BACKGROUND Urea standard Kt/V (stdKt/V) provides a tool to normalize weekly small solute clearance for patients dialysed at various intervals, but it has not been studied in the paediatric haemodialysis (HD) population. METHODS Using retrospective monthly adequacy data from children with end-stage renal disease receiving chronic thrice-weekly haemodialysis (n = 30), single-pool (spKt/V), equilibrated (eKt/V) and standard Kt/V (stdKt/V) were calculated for each individual HD session. eKt/V was estimated using Goldstein's logarithmic extrapolation method. Standard Kt/V was calculated using Leypoldt's formula based on eKt/V, duration and dialysis frequency. A spKt/V vs stdKt/V dose/frequency table was then derived from our thrice-weekly data. RESULTS Using spKt/V of >or=1.2 as the minimal acceptable HD dose, receiver operating characteristic curve analysis was used to determine the corresponding target stdKt/V across a number of potential cutoff values. Single-pool Kt/V >or=1.2 was delivered with near certainty [sensitivity: 93.5%, specificity: 96.7%, area under the curve (AUC): 0.98] when a stdKt/V >or=2.0 was targeted. For a spKt/V >or=1.4, a target of stdKt/V >or=2.2 provided sensitivity and specificity of 73.4 and 96.1%, respectively, with an AUC of 0.94. CONCLUSIONS Our data demonstrate that one should deliver a stdKt/V >or=2.0 for thrice-weekly paediatric HD in order to achieve a spKt/V >or=1.2; and if one wishes to ensure a spKt/V >or=1.4, then the stdKt/V must be >or=2.2. For children receiving a spKt/V >or=1.6 more than thrice weekly, the currently published adult dose/frequency table will overestimate the stdKt/V dose delivered and should be replaced by paediatric derived values.

Background. We examined the sensitivity of three different equivalent clearances to the spacing of haemodialysis treatments as well as to frequency. One would expect that a well-spaced schedule would be beneficial, and an optimal clearance measure should reflect this. Methods. Using a variable volume two-pool urea kinetic model, we derived clearances based on G [urea nitrogen (UN) generation rate] divided by time-averaged UN (G/TAC), mean predialysis UN (G/meanpre or ‘standard’ Kt/V) or peak UN (G/peak) when identical dialysis treatments were given on a poorly spaced (Monday—Tuesday—Wednesday) versus a well-spaced (Monday—Wednesday—Friday) schedule. We also calculated the ‘gain’ in each clearance when well-spaced treatments were given six versus three times a week. Modelling parameters were diffusive dialyser clearance = 283 ml/min, session length = 210 min (105 min for 6/week), G = 7 mg/min, V = 35 l and weight gain = 10 l/week. Results. The ‘standard’ Kt/V (G/meanpre) was the same with the poorly spaced (Monday—Tuesday—Wednesday) and well-spaced (Monday—Wednesday—Friday) schedules. In contrast, the G/TAC- and G/peak-based clearances were higher with the well-spaced schedule (+20% and +37%, respectively). When total treatment time was held constant at 630 min/week, the gain of moving from three to six treatments per week was lower with G/TAC (+9%) than with G/meanpre (+29%) or with G/peak (+18%). When 6/week treatment time was doubled to 1260 min/week, the gains with G/TAC and G/pre (relative to 3/week with 630 min/week dialysis) were similar (about +94% to 97%), but were lower with G/peak (+55%). Conclusions. All three equivalent clearances increased on moving from three to six sessions per week, with standard Kt/V having the greatest increase. Standard Kt/V is not at all sensitive to spacing. Alternative clearances based on the TAC or peak concentration have the advantage of taking both spacing and frequency into account.

Background. From the beginning of the dialysis era, the issue of optimal dialysis dose and frequency has been a central topic in the delivery of dialysis treatment. Methods. We undertook a discussion to achieve a consensus on key points relating to dialysis dose and frequency, focusing on the relationships with clinical and patient outcomes. Results. Traditionally, dialysis adequacy has been quantified referring to the kinetics of urea, taken as a paradigm of all uraemic toxins, and applying the principles of pharmacokinetics using either single- or double-pool variable volume models. An index of dialysis dose is the fractional clearance of urea, which is commonly expressed as Kt/V. It can be calculated from blood urea concentration and haemodialysis (HD) parameters, according to the respective urea kinetic model or by means of simplified formulas. Similar principles are applicable to peritoneal dialysis (PD), where weekly Kt/V and creatinine clearance are used. Recommended minimal targets for dialysis adequacy have been defined by both American and European guidelines (DOQI and European Best Practice Guidelines, respectively). The question of how to improve the severe outcome of dialysis patients has recently come back to the fore, since the results of two recent randomized controlled trials led to the conclusion that, in thrice weekly HD and in PD, increasing the dialysis dose well above the minimum requirements of current American guidelines did not improve patient outcome. Daily HD (defined as a minimum of six HD sessions per week), in the form of either short daytime HD or long slow nocturnal HD, is regarded as a possibility to improve dialysis patient outcome. The results of the studies published so far indicate excellent results with respect to all outcomes analysed: optimal blood pressure control, regression of left ventricular hypertrophy and amelioration of left ventricular performance, improvement of renal anaemia, optimal hyperphosphataemia control, improvement of nutritional status, reduction in oxidative stress indices and improvement in quality of life. The basis for these beneficial effects is thought to be a more physiological clearance of solutes and water, with reduced pre- and post-HD solute concentrations and interdialytic oscillation, compared with traditional HD. Apart from concerns regarding reimbursement and organizational issues, no serious adverse effects have been described with daily HD. However, the evidence accumulated is limited mainly to retrospective cohorts, with small patient numbers and no adequate controls in most instances. Therefore, large prospective studies with adequate controls are required to make daily HD accepted by reimbursing authorities and patients. Conclusions. Given the available observational and interventional body of evidence, there is no reason to reduce arbitrarily dialysis dose, particularly dialysis treatment time in HD patients treated three times weekly. Daily HD represents a very promising tool for improving dialysis outcomes and quality of life, although its impact on patient survival has not yet been proven definitively.

Background. C-reactive protein (CRP) levels, an acute phase response index, predict cardiovascular outcome and are inversely related to visceral proteins, including albuminaemia in haemodialysis patients. Less definite is the relationship between inflammation and markers of somatic proteins such as serum creatinine in such patients. To explore these questions, a cross-sectional analysis of potential predictors of serum creatinine was performed. Methods. One hundred and seventy-nine prevalent haemodialysis patients as of June 2001 were included in the cohort. Midweek pre-dialysis blood samples were collected during the months of June, September through to December 2001 inclusive, and determinations of serum urea (urease method), creatinine (alkaline picrate method) and CRP levels by means of a high sensitivity immunonephelometric method were performed. Furthermore, pre- and post-dialysis body weights were recorded and 2 min post-dialysis serum urea levels were determined three times. They were utilized for the calculation of single pool KtuV and of normalized protein catabolic rate (nPCR). Each of the data represents the mean of three determinations made every 3 months in the study period. Results. The analysis of multivariate linear regression was able to validate our model characterized by a dependent variable, serum creatinine and four independent variables (age, CRP, KtuV and nPCR) (R 2 s0.60; Fs24.10; P-0.00001; SEs1.94). Age (0.08 mgudl decrease in serum creatinine per 1-year increase in age), Ktu V( 0.25 mgudl decrease in serum creatinine per 0.1 increase in KtuV) and nPCR (0.10 mgudl increase in serum creatinine per 0.1 g proteinukguday increase in nPCR) were independently predictive of serum creatinine (P-0.00001). CRP and dialysis vintage did not predict serum creatinine. Stratifying the patients for the effects of CRP, only CRP values O 4m gul were directly predictive of serum creatinine (P-0.00001), whereas CRP values ) 4m gul were not. A further insight was given by the stratification of the patients for the effects of the interquartile ranges of CRP: it showed a progressive and statistically significant reduction of b-coefficient inversely related to the increasing CRP values (Ps0.003). Thus, the nature of the correlation between CRP and serum creatinine changes with increasing CRP values: from being a direct one, it shows a trend towards a transformation into an indirect one with bs 0a t a CRP value of ; 9m gul. However, this indirect relationship does not reach statistical significance. Conclusions. The present cross-sectional study suggests that the activation of acute phase response does not influence creatinine metabolism in haemodialysis patients; in contrast, age, KtuV and nPCR predict serum creatinine levels. Larger prospective trials are needed to achieve a definitive answer about the relationship between somatic proteins, acute phase response activation and nutrition in dialysis patients.

Peritoneal dialysis was first introduced in Romania in 1995. We are reporting data on patient and technique outcomes, based on the 5-year experience of one of the first two Romanian continuous ambulatory peritoneal dialysis (CAPD) centres. During this period, Romania had the highest rate of increase in renal replacement therapy (RRT) and CAPD (28 times over baseline) in Europe: CAPD increase in Romania vs s Eastern Europe was 6.7 compared to a similarly defined ratio of 5.6 for haemodialysis (HD). Between 1995 and 2000, at the C. I. Parhon' Hospital in Iasi, 259 patients were started on HD and 102 on CAPD. The 90 CAPD patients we followed were treated for a total of 1896 months. 86.7% of the patients were alive on 31 July 2000-67.8% continuing on CAPD, 15.6% on HD and 3.3% transplanted. The 61 patients still on PD on that date, represented 11.1% of the actual Romanian CAPD population and 31% of our RRT population (compared to 13.7% nationwide). The gross mortality rate was comparable to the mean calculated for the HD population nationwide. Mean survival of the CAPD patients was 45.4±2.6 months (95% CI=40.4-50.4 months). One-year and 5-year patient survival rates were 97.5% and 52.7% respectively, superior and similar to mean figures nationwide. Mean technique survival was 36.6±0.6 months (95% CI=31.5 41.6 months). One- and 5-year technique survival rates were 83.1% and 34.3% respectively. Technique failure was mainly due to dialysis inefficiency: 50% of cases. Mean weekly Kt V for the 5-year period was 1.92±0.21 while mean weekly creatinine clearance was 61.2±12.4 ml/1.73 m 2 week. Eighty-four episodes of peritonitis were recorded in 46 patients (0.25 episodes/patient/year); mean duration to peritonitis was 23 months (95% CI = 18.2-27.5). Malnutrition was noted (SGA score) in 25.5% of the cases. Blood pressure (assessed by 24-h ABPM) was adequately controlled in 83.3% of the patients. Left ventricular hypertrophy was ubiquitous (77.7%), but left ventricular dilatation and systolic dysfunction (fractioning shortening index

Background. The potential superiority of various renal replacement treatment modalities consisting largely of convective mass transfer as opposed to primarily diffusive mass transfer, is still a matter of debate. The objective of the present study was to evaluate acute and long-term clinical effects of varying degrees of convection and diffusion in a group of 24 clinically stable patients with end-stage renal disease. Methods. The patients were prospectively assigned to three consecutive treatment schedules of 6 months each: phase I (HF1) (on-line predilution haemofiltration)→ phase II (HD) (high-flux haemodialysis)→ phase III (HF2; as phase I). We used the AK 100/200 ULTRA monitor (Gambro), which prepares ultrapure dialysis fluid for HD and sterile, pyrogen-free substitution solution for HF. The membrane (polyamide), fluid composition, and treatment time were the same on HF and HD. The targeted equilibrated Kt/V was 1.2 for both treatment modes, creating a similar urea clearance. Results. Fifteen patients, mean age 62.8 ± 8.4 years, completed the study according to the above conditions. Urea kinetics, nutritional parameters, and dry weight were similar in the three periods. The frequency of intra-treatment episodes of hypotension/patient/month was significantly lower on HF1 (1.24) and HF2 (1.27) than on H D (1.80) (P < 0.04). It decreased progressively on HF1, then increased on HD, and decreased again during HF2. Patients had fewer muscular cramps on HF than on HD (P < 0.03) and required significantly less saline and plasma expander during HF than HD sessions. The prevalence of inter-treatment symptoms, including fatigue and hypotension, was lower on HF than on HD (score difference P = 0.04). Quality of life, determined by the Laupacis method in all three periods, showed a tendency towards improvement during the study, reaching the best values during HF2. Conclusions. HF has a progressive stabilizing haemodynamic effect, producing a more physiological cardiovascular profile than HD. This long-term effect, observed in stable patients treated under strictly identical conditions, is probably due to the mechanism of convection, and is different from the acute effect observed mainly in unstable patients.

Kt/V is the main index of adequacy for diffusive and diffusive convective methods of extracorporeal depuration, yet there exists no universally acceptable validation of an adequacy index for the solely convective methods such as haemofiltration (HF). The aim of the present study is to analyse which of the parameters of adequacy used in two multicentre HF studies, Kt/V for urea or infusion volume, correlate best with nutritional parameters and can therefore be utilized for the evaluation of treatment dose in on-line pre-dilution HF. Twenty-three clinically stable patients were enrolled in the first study [3 months of haemodialysis (HD)+ 3 months of HF]. In the second study, 24 stable patients were studied in three phases: 6 months in HF, 6 months in HD and a further 6 months in HF; in this study, a target of Kt/V= 1.2 in all three periods was preestablished: 15 patients completed the full study. In both studies, we utilized the same monitor (AK 100/200 Ultra, Gambro), the same membrane (polyamide) and the same on-line prepared ultrapure dialysis fluid and sterile infusion solution. In both studies, we ensured that HF fulfilled the following parameters of adequacy: urea kinetics, cardiovascular and blood pressure stability (better in HF than in HD), common haematochemical and nutritional parameters, reduction in beta2-microglobulin levels, a good intra- and extra-session clinical outcome, and a good quality of life with morbidity and mortality rates no different from those of HD. HF proved to be an efficacious method of ensuring adequate depuration and a good quality of life for uraemic patients. We have shown that in longer periods of HF, a notable correlation between Kt/V and normalized protein catabolic rate (nPCR) and an equally good correlation between total ultrafiltration (UF)/dry weight ratio and nPCR could be achieved. In both studies, the patients showed a good level of epuration adequacy when total UF per session was at least 1.3 times the dry body weight. The total UF/body weight ratio thus seems to be an easy method in HF because of its greater ease of predictability and measurement, also when it is used independently of the Kt/V index.

Background. The efforts to improve the quality of haemodialysis (HD) has renewed the interest in the consequences of blood-flow distribution for removal of solutes. Methods. To test the effects of HD time per se, 10 patients were studied in a cross-over fashion with HD for 3 h and 1 week later for 6 h, with similar blood urea Kt/Vs, achieved by adjusting the blood flow rate to 290 and 120 ml/min respectively. Injections of iohexol (MW 821 Dalton) were given 2 days prior to the dialysis sessions. Blood samples were taken before, during (6/HD), 1 and 24 h after the HD and analysed for concentrations of urea and iohexol. A urea on-line monitor (Gambro) was used for continuous recordings and sampling of dialysate. Results. According to the study design the blood Kt/V for urea (Daugirdas II) was similar for 3 and 6 h HD, close to 1.0 (n.s), while the removed mass of urea showed that Kt/V was slightly and significantly higher for the 6 h HD. The 'apparent' mass of iohexol, defined as plasma concentration times estimated distribution volume, fell to 29% and 21% of pre-dialysis levels after 3 h and 6 h HD, respectively (P

Introduction. In Europe, especially in Germany, little is currently known about the relationship between urea kinetics delivered and predicted haemodialysis doses for patients on maintenance haemodialysis. We compared delivered and predicted Kt/V in patients of an outpa- Introduction tient dialysis centre in Berlin by calculating the ratio of delivered and predicted Kt/V, resulting in the eY- Comprehensive data from the United States Renal cacy quotient, Q E. Moreover, we studied the influence Data System ( USRDS ) provide evidence that morbidof technical and anthropometric parameters on both ity and mortality of patients with end-stage renal delivered Kt/V and Q E under routine clinical disease ( ESRD) are related to the amount of urea conditions. removed during haemodialysis (HD) [1]. Current Methods. Blood samples were taken after the long American guidelines [2] therefore place a strong interval in a thrice-weekly regimen before and 10 min emphasis on the use of Kt/V for the assessment of after ultrafiltration and 100 ml/min slow-pump dialysis adequacy. method. Delivered Kt/V was computed using the Apart from the general assessment of dialysis Daugirdas III formula. Predicted Kt/V was estimated adequacy, the Kt/V concept may also have considerfrom the dialysis filter urea clearance given by the able practical value for monitoring the technical eYmanufacturer, treatment time and the total body water cacy of dialysis in an individual patient. The aim of ( V ) computed by the Watson formula and was cor- the present study was therefore to examine the relationrected for real blood flow. As and when appropriate, ship between delivered Kt/ V( Kt/V del ) and predicted bivariate and multivariate regression analyses were Kt/ V( Kt/V pred ), expressed as an eYcacy quotient used to make comparisons. (Q E ), as a measure of technical performance. We Results. The mean quotient (Q E ) between delivered studied these parameters in a group of unselected and predicted Kt/V was 1.02±0.20. Mean delivered patients undergoing routine haemodialysis in an Kt/V in 377 treatments of 128 patients was 1.28±0.27. European outpatient dialysis unit in which dialysis Delivered Kt/V and Q E were positively associated dosage a priori was based on session time rather than (P

Inadequate dialysis dose is closely related to mortality and morbidity of maintenance haemodialysis (MHD) patients. According to the DOQI guidelines a minimum prescribed dialysis dose of single-pool Kt/V (Kt/Vsp)=1.3, equivalent to equilibrated double pool Kt/V (e-Kt/Vdp)=1.1, is recommended. Knowledge of patient-related risk factors for inadequate delivery of hacmodialysis would be helpful to select patient subgroups for intensive control ofdialysis adequacy.A retrospective survey was conducted to assess the prevalence of inadequate dialysis dose according to DOQI criteria during a 7-month period. A total of 320 e-Kt/Vdp measurements in 62 MHD patients were evaluated (mean effective dialysis time 222+/-32 min). Residual renal function (RRF) was expressed as renal weekly Kt/V (r-Kt/Vweek) and included into assessment of total weekly renal and dialytic Kt/V (t-Kt/Vweek).Inadequacy (e-Kt/Vdp1.10) was prevalent in 37.2% of all measurements and in 22/62 patients (35.5%). In 54% of underdialysed patients r-Kt/Vweek compensated for insufficient dialytic urea removal. Mean weekly Kt/V was inadequate (t-Kt/Vweek3.30) in 12/62 patients (19.4%) of whom 91.7% (11/12) were male. Body-weight, urea distribution volume (UDV). and body-surface area (BSA) were significantly higher in inadequately is adequately dialysed males. UDV42.0 litres or BSA2.0 m2 and a lack of RRF (r-Kt/Vweek0.3) put 'big men' at increased risk to receive an inadequate dose of dialysis.Our data identify patients at risk for inadequate haemodialysis treatment. Special attention should be focused on 'big men' with UDV42.0 litres or BSA2.0 m2. In this subset of patients frequent measurements of t-Kt/Vweek and assessment of RRF should be mandatory.

The widely used Kt/V concept for quantitating haemodialysis (HD) and ensuring adequate dialysis is based on several assumptions. In order to simplify the urea kinetic modelling, the body is assumed to be a single well-mixed compartment. Previously, more physiological two-compartment or blood flow distribution models have been used to explain the phenomenon of blood urea rebound after dialysis. This study attempts to evaluate the effects of a multi compartment model on the removal of urea, i.e. on the adequacy of dialysis. Four different tissue compartments of similar size are used, with flow rates between 40 and 3600 ml/min for a bodyweight around 70 kg, allowing for blood flow heterogeneity within and between skeletal muscles. Dialysis is simulated by removing blood containing urea and replacing it with blood free of urea, during isovolumetric conditions and assuming no diffusion barriers for urea. Several important conclusions can be drawn from the model. Firstly the removal of urea is dependent both on the time of dialysis and on the number of HD treatments per week despite constant Kt/V. Secondly the blood urea concentration is increased after dialysis-'urea rebound'-in accordance with clinical data. Thirdly the concept of blood flow distribution can fully explain the difference between haemodialysis and peritoneal dialysis in terms of Kt/V needed for adequate dialysis. Thus a weekly Kt/V of 3.6 for HD 4h 3 times per week removes the same amount of urea as CAPD and a Kt/V of 2.1. Also, nightly intermittent PD requires similar Kt/Vs (0.1 higher) as CAPD to obtain equivalent removal of urea. Finally the crucial point is that the Kt/V required for adequate dialysis must be increased if the dialysis treatment time is reduced. If not, the patient with renal insufficiency suffers the risk of being under-dialysed.

Kt/V urea (u) has been used as a measure of adequacy of haemodialysis (HD). However, the accurate assessment of its components is difficult and subject to error in a clinical setting. This study was designed to evaluate different forms of dialyser clearance (K) measurements and their influence on Kt/V. Sixteen patients on high-flux HD were studied at blood flow (Qb) rates of 250 and 350 ml/min and at constant dialysate flow rates. K of urea was measured by the arteriovenous blood sampling technique (Kbu), corrected for access recirculation (Kbru) and compared with K as determined by dialysate collection (Kdu) using a new sampling device. At Qb 250 and 350 ml/min, Kbu as based on dialysate collection was significantly lower than Kbru and Kbu as based on arteriovenous blood sampling: at Qb 250, Kdu 169.0 +/- 13.3, Kbru 191.2 +/- 11.5, and Kbu 203.0 +/- 9.3 ml/min (P < 0.0005); at Qb 350, Kdu 196.5 +/- 17.3, Kbru 227.7 +/- 15.5, and Kbu 243.6 +/- 12.7 ml/min (P < 0.0005). At Qb 250 ml/min Kbu t/V (1.33 +/- 0.17) overestimated Kdu t/V (1.11 +/- 0.13) by 16:8%, at Qb 350 ml/min by 19.3% (1.58 +/- 0.19 versus 1.27 +/- 0.15). Dialyser clearances based on arteriovenous differences in blood overestimate true clearances (and therefore Kt/V) as measured by dialysate collection. This overestimation is more marked with higher blood flow rates.

The estimation of Kt/V by utilization of the pre- and postdialysis urea concentrations (per cent reduction in urea and In(Upre/Upost)) provides a simple, quick technique that can be applied at the bedside. However, the accuracy of such techniques has been questioned. One possible reason for this inaccuracy may be the frequently observed postdialysis rebound in serum urea. We assessed the urea rebound at 30 min postdialysis in 34 haemodiafiltered patients and compared the calculation of Kt/V using this urea concentration with that using the immediate postdialysis concentration. These results were then compared to the Kt/V calculated by urea kinetic modelling (UKM), also utilizing the delayed serum urea concentration. The degree of urea rebound observed was large, 21.4%, being a reflection of the short-duration, rapid-flux dialysis. The formulae for calculation of Kt/V all significantly correlated with Kt/V by UKM but all gave results significantly different from Kt/V by UKM (P < 0.001 by paired t test). For assessment of Kt/V by these formulae or by UKM, the urea rebound is too large to ignore in the setting of short-duration, rapid-flux dialysis.