Longer treatment time and slower ultrafiltration in hemodialysis: associations with reduced mortality in the DOPPS

Longer treatment time (TT) and slower ultrafiltration rate (UFR) are considered advantageous for hemodialysis (HD) patients. The study included 22,000 HD patients from seven countries in the Dialysis Outcomes and Practice Patterns Study (DOPPS). Logistic regression was used to study predictors of TT > 240 min and UFR > 10 ml/h/kg bodyweight. Cox regression was used for survival analyses. Statistical adjustments were made for patient demographics, comorbidities, dose of dialysis (Kt/V), and body size. Europe and Japan had significantly longer (P < 0.0001) average TT than the US (232 and 244 min vs 211 in DOPPS I; 235 and 240 min vs 221 in DOPPS II). Kt/V increased concomitantly with TT in all three regions with the largest absolute difference observed in Japan. TT > 240 min was independently associated with significantly lower relative risk (RR) of mortality (RR = 0.81; P = 0.0005). Every 30 min longer on HD was associated with a 7% lower RR of mortality (RR = 0.93; P < 0.0001). The RR reduction with longer TT was greatest in Japan. A synergistic interaction occurred between Kt/V and TT (P = 0.007) toward mortality reduction. UFR > 10 ml/h/kg was associated with higher odds of intradialytic hypotension (odds ratio = 1.30; P = 0.045) and a higher risk of mortality (RR = 1.09; P = 0.02). Longer TT and higher Kt/V were independently as well as synergistically associated with lower mortality. Rapid UFR during HD was also associated with higher mortality risk. These results warrant a randomized clinical trial of longer dialysis sessions in thrice-weekly HD.     

Evidence for an independent role of metabolic acidosis on nutritional status in haemodialysis patients

Background: Malnutrition in haemodialysis (HD) patients has been referred to underdialysis with low protein intake, and to acidosis. However, the separate effects of underdialysis and acidosis on nutrition have not been clearly demonstrated. To evaluate the role of the dialysis dose and of metabolic acidosis on nutrition, we measured the predialysis serum HCO3, pH, serum albumin, PCRn, Kt/V, and BMI in 81 uraemic patients on maintenance bicarbonate, HD for 93±80 months. Patients with chronic liver diseases, malignancies, and cachexia were excluded. Results: Mean age was 59±17 years, Kt/V was 1.29±0.21, PCRn 1.06±0.22 g/kg/day, serum albumin 4.07plusmn;0.28 g/dl, BMI 23±4 kg/m², HCO3 21.1±1.9 mmol/l, pH 7.36±0.04. Serum albumin showed a significant direct correlation with: PCRn (P=0.001), HCO3 (P=0.001), pH (P=0.002), but no correlation with Kt/V and BMI. Serum HCO3 correlated inversely with PCRn (P=0.027). Multiple regression analysis confirmed the significant role of serum bicarbonate and age, but not of Kt/V, on serum albumin concentrations. The role of PCRn appeared to be marginal compared to serum bicarbonate in determining serum albumin levels. Dividing patients into two groups, serum albumin was 3.96±0.22 g/dl with HCO3 ⩽20 mmol/l and 4.18±0.31 g/dl in those with serum HCO3⩾23 mmol/l (P=0.002). PCRn in the same groups was respectively 1.14±0.24 g/kg/day and 1.01±0.23 g/kg/day (P=0.03). Most importantly, serum albumin levels did not appear to be affected by the dialysis dose, with Kt/V ranging from 0.90 to 1.88. Conclusions: In HD patients with adequate Kt/V, metabolic acidosis exerts a detrimental effect on serum albumin concentrations partially independently of the protein intake, as evaluated by PCRn. In the presence of moderate to severe metabolic acidosis, PCRn does not reflect the real dietary protein intake of the patients, probably as a result of increased catabolism of endogenous proteins. For this reason PCRn should be considered with caution as an estimate of the dietary protein intake in HD patients in the presence of metabolic acidosis.      

Correction of metabolic acidosis increases serum albumin concentrations and decreases kinetically evaluated protein intake in haemodialysis patients: a prospective study

Background: Metabolic acidosis in haemodialysis (HD) patients increases whole body protein degradation while the correction of acidosis reduces it. However, the effects of the correction of acidosis on nutrition have not been clearly demonstrated. Study design: In this study we have evaluated the effects of 3 months of correction of metabolic acidosis by oral sodium bicarbonate supplementation on protein catabolic rate (PCRn) and serum albumin concentrations in 12 uraemic patients on maintenance HD for at least 6 months (median 49 months; range 6-243 months). Pre-dialysis serum bicarbonate, arterial pH, serum albumin, total serum proteins, serum creatinine, plasma sodium, haemoglobin, PCRn, Kt/V, and TACurea, were evaluated before and after correction. Results: Serum bicarbonate levels and arterial pH increased respectively from 19.3±0.6 mmol/l to 24.4±1.2 mmol/l (P<0.0001) and 7.34±0.03 to 7.40±0.02 (P<0.0001). Serum albumin increased from 34.9±2.1 g/l to 37.9±2.9 g/l (P<0.01) while PCRn decreased from 1.11±0.17 g/kg/day to 1.03±0.17 g/kg/day (P<0.001). No changes in Kt/V, total serum proteins, serum creatinine, plasma sodium, haemoglobin, body weight, pre dialysis systolic and diastolic blood pressure, and intradialytic weight loss were observed. Conclusions: Our data demonstrate that correction of metabolic acidosis improves serum albumin concentration in HD patients. The correction of acidosis induced a decrease in PCRn values, as evaluated by kinetic criteria, suggesting that in the presence of moderate to severe acidosis this parameter does not reflect the real dietary protein intake of the patients probably as a result of increased catabolism of endogenous proteins. The correction of metabolic acidosis should be considered of paramount importance in HD patients.     

Continuous haematocrit monitoring during intradialytic hypotension: precipitous decline in plasma refill rates.

BACKGROUND: Intradialytic hypotension (IDH) during ultrafiltration remains a major source of haemodialysis related morbidity, despite technological advances including continuous haematocrit monitoring and automated blood volume controlled dialysis machines. We hypothesized that studying the relationship between ultrafiltration rate and plasma refill rate (UFR, PRR) before and during IDH would provide insight into its mechanism and possible prevention. METHODS: We retrospectively identified 17 patients (mean age 50 years) with IDH treated solely by turning off the ultrafiltration, none having received hypertonic saline, mannitol or albumin. All patients had archived data for continuous haematocrits, UFR, ultrafiltration goal, vital signs and symptoms. We used the Crit-Line III optical haematocrit monitor to calculate the PRR for intervals preceding and during IDH. RESULTS: Prior to IDH the PRR was 1360+/-550 ml/h; which was less than the UFR of 1471+/-602 ml/h and was associated with a 4.4% rise in haematocrit. However, during IDH the PRR was dramatically lower (P<0.001): only 242+/-151 ml/h. The PRR was not correlated (P>0.05) with the absolute, per cent change or rate of rise in haematocrit, UFR, ultrafiltration goal or heart rate. CONCLUSIONS: On-line haematocrit monitoring allows for the calculation of plasma volume changes, UFR and PRR, and the mismatch in those rates helps explain the physiology of hypotension episodes. The precipitous fall in PRR during sudden IDH supports activation of the cardiodepressor Bezold-Jarisch reflex. As both the UFR and PRR variables can change during a single dialysis session, this supports the use of devices with automated continuous adjustments of the UFR and suggests additional profiling methodologies.     

Mineral metabolism and cardiovascular morbidity and mortality risk: peritoneal dialysis patients compared with haemodialysis patients.

BACKGROUND: The K/DOQI guideline for bone metabolism and disease in chronic kidney disease is predominantly based on studies in haemodialysis (HD) patients. However, in clinical practice, this guideline is also applied to peritoneal dialysis (PD) patients. To validate the implementation of this guideline in PD patients, we evaluated the associations between plasma concentrations outside the K/DOQI-targets and the risk of cardiovascular morbidity and mortality in incident PD patients compared with HD patients. METHODS: In a large prospective multicentre study in the Netherlands (The Netherlands Cooperative Study on the Adequacy of Dialysis, NECOSAD), we included patients starting PD or HD between 1997 and 2004. Relative risk of cardiovascular morbidity and mortality were estimated using time-dependent Cox regression modelling. RESULTS: We included 586 PD patients with mean age 52 +/- 15 years (66% males) and 1043 HD patients with mean age 63 +/- 14 years (58% males). Cardiovascular disease (CVD) was the reason for hospitalization in 102 PD and 271 HD patients. In HD patients, the relative risk of CVD-related hospitalization increased with elevated plasma calcium concentrations (hazard ratio: 1.4; 95% CI: 1.1-1.9). Cardiovascular mortality was significantly higher for phosphorus concentrations above the K/DOQI-threshold in PD (2.4; 95% CI: 1.3-4.2) and HD patients (1.5; 95% CI: 1.1-2.1), and for elevated Ca x P in PD (2.2; 95% CI: 1.3-3.8) and HD patients (1.5; 95% CI: 1.1-2.1). CONCLUSIONS: Plasma calcium concentrations above the K/DOQI-threshold increase the relative risk of CVD-related hospitalization in HD patients. Associations with cardiovascular mortality were more pronounced. Both in PD and HD patients with elevated plasma phosphorus and Ca x P concentrations, the cardiovascular mortality risk is increased. Therefore, it seems appropriate to adopt the current guideline in PD patients.     

Which targets in clinical practice guidelines are associated with improved survival in a large dialysis organization?

Professional organizations have developed practice guidelines in the hope of improving clinical outcomes. The National Kidney Foundation's Kidney Disease Outcomes Quality Initiative (KDOQI) has set targets for dialysis dosage (single-pool Kt/V), hematocrit, serum albumin, calcium, phosphorus, parathyroid hormone, and BP for hemodialysis (HD) patients. Several guidelines are largely based on results from observational studies. In contrast to other parameters, BP values within the KDOQI guidelines have been associated with increased mortality. Therefore, it was postulated that having multiple parameters that satisfy the current guidelines, except those for BP, is associated with improved survival among HD patients. A retrospective analysis was conducted of incident HD patients who were treated at facilities operated by Dialysis Clinic Inc., a not-for-profit dialysis provider, between January 1, 1998, and December 31, 2004 (n = 13,792). Cox proportional hazards models were used to assess the association between satisfying guidelines and mortality. Values within guidelines for single-pool Kt/V, hematocrit, serum albumin, calcium, phosphorus, and parathyroid hormone were associated with decreased mortality (P < or = 0.0001). The largest survival benefit was found for serum albumin (hazard ratio [HR] 0.27; 95% confidence interval [CI] 0.24 to 0.31). Satisfying these six guidelines simultaneously was associated with an 89% reduction in mortality (HR 0.11; 95% CI 0.06 to 0.19]). Conversely, BP values satisfying the guideline were associated with increased mortality (HR 1.90; 95% CI 1.73 to 2.10). Because this target was largely extrapolated from the general population, a randomized, controlled trial is needed to identify the optimal BP for HD patients.     

Effects of postdialysis urea rebound on the quantification of pediatric hemodialysis

Urea rebound (UR) causes single pool urea kinetic modeling (UKM), which is based on end-dialysis urea instead of its equilibrated value (Ceq), to erroneously quantify hemodialysis (HD) treatment. We estimated the impact of postdialysis UR on the results of formal variable volume single pool (VVSP) UKM [Kt/V, urea distribution volume (V), urea generation rate (G), normalized protein catabolic rate (nPCR), and urea reduction ratio (URR)] in children on chronic HD. Thirty-eight standard pediatric HD sessions in 15 stable patients (9 female, 6 male) aged 14.5 +/- (SD) 3.28 years were investigated. The HD sessions lasted 3.75 +/- 0.43 h. The single pool urea clearance was 4.84 +/- 1.25 ml/min/kg. All HD sessions were evaluated by VVSP and URR (%) with postdialysis urea taken at the end of HD and with Ceq taken 60 min after the end of HD, incorporating double pool effects and representing true double pool values. The anthropometric V was calculated by Cheek and Mellits formulae for children. VVSP significantly overestimated Kt/V by 0.26 +/- 0.18 U (1.68 +/- 0.36 vs. 1.42 +/- 0.30, p < 0.0001), i.e., 19. 05 +/- 13.07%, G/V (0.20 +/- 0.04 vs. 0.18 +/- 0.04, p < 0.0001), nPCR (1.26 +/- 0.23 vs. 1.18 +/- 0.22 g/kg/day, p < 0.0001), and URR (73.92 +/- 6.49 vs. 69.22 +/- 7.06, p < 0.0001). VVSP significantly underestimated kinetic V in comparison to anthropometric V (18.74 +/- 4.04 vs. 20.76 +/- 4.43 liters or expressed as V/body weight: 58 +/- 8 vs. 65 +/- 9%, p < 0.05), while double pool kinetic V was more accurate (21.45 +/- 4.34 liters, V/body weight: 64 +/- 6%, p > 0.05). We conclude that UR has a significant effect on all results of UKM even after standard pediatric HD, and the degree of this efffect is documented. We suggest an increase of the minimum required prescribed single pool Kt/V in children and reduction of any delivered single pool Kt/V by approxiamtely 0.26 Kt/V U. Overestimation of nPCR by approximately 0.08 g/kg/day and underestimation of V by 8.5% should be kept in mind.     

Increasing blood flow increases kt/V(urea) and potassium removal but fails to improve phosphate removal

BACKGROUND: Hyperphosphatemia and hyperkalemia are major determinants of morbidity and mortality in hemodialysis patients. Half of the dialysis population suffers from hyperphosphatemia which is now recognized as an important cardiovascular disease risk factor. It is, therefore, necessary to improve the removal of these molecules. In this study, we investigated the effect of enhancing blood flow on Kt/V for urea (Kt/Vu), potassium and phosphate removal. METHODS: Thirteen patients were investigated in a randomized, cross-over, prospective study using 3 blood flows (Qb) of 200,250 and 300 ml/min which gave 39 standardized high-flux hemodialysis treatments. Effective blood flows were measured by ultrasonic flow meter. Quantification of delivered dialysis dose was performed by partial dialysate and ultrafiltrate collection for the determination of potassium and phosphate removal and by blood urea concentrations for determination of Kt/Vu. RESULTS: Kt/Vu rose significantly from 1.10 +/- 0.14 to 1.22 +/- 0.14 and finally to 1.39 +/- 0.16 (p = 0.0001) with increasing Qb similar to the increase in potassium removal from 53.0 +/- 2.4 to 63.4 +/- 2.6 and to 74.2 +/- 3.8 mMol (p = 0.01). Phosphate removal only improved from 28.1 +/- 1.3 to 31.4 +/- 1.5 (p = 0.050) when Qb was increased from 200 to 250 ml/min but remained unchanged at 31.2 +/- 1.5 mMol (NS compared to phosphate removal at Qb = 250 ml/min) when Qb was increased to 300 ml/min. CONCLUSIONS: Increasing delivered Kt/Vu and potassium removal with higher Qb fails to produce the same desired effect with phosphate removal during high-flux hemodialysis.     

A thrice weekly in-center nocturnal hemodialysis program

The mortality associated with hemodialysis (HD) remains high. Recent studies have found that a session time of 4 to 4.5 hours and an ultrafiltration rate of less than 10 cc/h/kg were each independently associated with a decreased mortality among HD patients. We started a thrice-weekly nocturnal HD program in May 2005 and have since enrolled a total of 16 patients. The Kt/V urea (2.6 +/- 0.65 vs. 1.2 +/- 0.16, mean +/- SD, P < .05) and serum phosphorus (4.4 +/- 1.1 v 5.3 +/-1.3 mg/dL, P =.049) values obtained 6 months after enrollment in the nocturnal HD program were significantly better than the baseline values obtained before the initiation of the nocturnal HD program. The ultrafiltration rate was 5.9 +/- 1.7 mL/h/kg 6 months after patients participated in the nocturnal HD program, whereas the rates for these same patients at baseline was 10.3 +/- 4.5 mL/h/kg. Psychosocial assessments were performed at baseline and again at 6 months. No difference was seen in the results of these assessments. We conclude that patients receiving long, in-center thrice-weekly nocturnal HD have a decrease in serum phosphate, an improvement in urea clearance, and a reduction in ultrafiltration rate to less than 10 mL/h/kg. This therapy appears to have no negative impacts on a variety of quality of life measures.     

The contribution of residual renal function to overall nutritional status in chronic haemodialysis patients.

BACKGROUND: The benefits of residual renal function (RRF) in peritoneal dialysis patients have been described frequently. However, previous reports have shown that RRF diminished faster in haemodialysis (HD) patients than in peritoneal dialysis patients, and in most of the studies in HD patients, RRF was ignored. In this study, the RRF in chronic HD patients was studied to assess its impact on patients' nutritional status. METHODS: In 41 chronic HD patients with at least a 2-year history of HD treatment, RRF was determined by a urine collection for 7 consecutive days. Nutritional parameters, such as percentage body fat, fat-free mass index, serum albumin concentration and normalized protein catabolic rate, were also measured. RESULTS: In all 41 patients, mean weekly total Kt/V urea was 4.88 and renal Kt/V urea was 0.65. RRF was well correlated with serum albumin concentration, but dialysis Kt/V urea was not. One year after the start of this study, RRF and nutritional indices were re-examined and patients were classified into two groups: with RRF, preserved residual renal diuresis over 200 ml/day (mean, 720 ml; range, 230-1640 ml), N=23; and without RRF, persistent anuria (mean, 51 ml; range, 0-190 ml), N=18. At the start of this study, the mean serum albumin concentration and mean normalized protein catabolic rate in patients with RRF were 3.84 g/dl and 1.16 g/kg/day, respectively, which were significantly higher than those in patients without RRF (P=0.02 and P=0.0002, respectively), despite total (renal+dialysis) Kt/V urea being equal in both groups. During the 1-year study period, there was no significant change in total Kt/V urea in either group. Mean serum albumin concentration increased to 4.05 g/dl in patients with RRF, but did not change significantly (from 3.66 to 3.62 g/dl) in patients without RRF. The same trend was observed in all other parameters. CONCLUSION: Over half of our HD patients had sufficient RRF. RRF itself may have a beneficial effect on nutritional parameters, and it is important to determine RRF over time, even in chronic HD patients.     

Effect of age on protein catabolic rate, morbidity, and mortality in uraemic patients with adequate dialysis

To test the validity of the assumption that the protein catabolicrate (PCRn g/kg/day) is dependent on the normalized dose ofdialysis (Kt/V urea), and to try to define the charactensticsof the patients in the undefined domain A of the mechanisticmap of the National Cooperative Dialysis Study (NCDS), whichshould include patients with adequate amount of dialysis butinadequate PCRn, urea kinetic model ling was performed over12 months on 85 patients undergoing haemodialysis All the patientswere man aged to maintain a Kt/V urea 0.9. During the entireperiod of study the total number of hospitalizations and thenumber of days of hospitalization were recorded. Total serumproteins and serum albumin concentrations were measured at thestart and at the end of the study. The results of the studyshow that there was no correlation between Kt/V and PCRn norbetween Kt/V and patient's age, but there was a strong inversecorrelation between age and PCRn (r=0.578; P <0.0001). Furtherdivision of the patients into four groups according to age showedthat the lowest values of PCRn were for the group of patients75 years old. Twelve patients with PCRn0.8 and Kt/V0.9 wereincluded in domain A of the mechanistic map. Eleven (92%) ofthese 12 patients were years old. No correlations were foundbetween the total number of hospitalizations, the total daysof hospitalization, Kt/V, time on HD, body weight and PCRn bymultiple regression analysis, while the inverse correlationbetween PCRn and age was confirmed. Body weight, total serumproteins and serum albumin concentration remained stable throughoutthe study. However, the basal serum albumin was less in thegroup of patients 75 years old. We conclude that if an adequateamount of dialysis is delivered, the protein intake becomesindependent of the quantity of dialysis and dependent on otherfactors not yet known. In this situation, the age of the patientsexerts a great negative influence on PCRn, particularly in patients75 years old. In the 12 patients from the whole group with Kt/V0.9 and PCRn 0.8g/kg/day (domain A of the mechanistic map),we could find no differences in death, hospitalization rate,or duration of hospitaliza flon compared to the others. Thereduced PCRn in the oldest patients does not affect body weight,total serum protein, and serum albumin concentrations over time.This suggests that these patients might do well even with lessprotein intake.     

Effect of dialysis dose on nutritional status of children on chronic hemodialysis.

It had been suggested that larger hemodialysis (HD) doses in children could result in better appetite, higher protein intake, better nutritional status and better growth. We investigated how different HD doses affect protein intake and nutritional status of children on chronic HD. Indices of nutritional status used were normalized protein catabolic rate (nPCR) calculated by formal 3-sample urea kinetic modeling and serum albumin level. Data of 38 HD sessions in 15 stable patients (6 males, 9 females) aged 14.5 +/- 3.28 years (mean +/- SD) were analyzed. HD sessions were divided into three groups based on delivered Kt/V: group 1 (n = 5), inadequate (Kt/V < 1.3, mean 1.05 +/- 0.14); group 2 (n = 12), adequate (Kt/V = 1.3-1.6, mean 1.50 +/- 0.07) and group 3 (n = 21), high (Kt/V >1.6, mean 1.94 +/- 0.22). Mean nPCR and Kt/V per patient during the studied week were estimated for 11 patients in whom 3 HD sessions were available within the 38 sessions analyzed. Serum albumin level was adequate in all patients (43.77 +/- 2.28 g/l). Mean overall Kt/V and nPCR were 1.68 +/- 0.36 and 1.26 +/- 0.23, respectively, r = 0.430. Average nPCR differed between groups depending on Kt/V. It was lowest in group 1 (1.01 +/- 0.12 g/kg/day) where the highest correlation between nPCR and Kt/V was found (r = 0.648). nPCR was higher and similar in groups 2 (1.27 +/- 0.23 g/kg/day) and 3 (1.31 +/- 0.22 g/kg/day), with low correlation coefficients between nPCR and Kt/V in both groups (r = 0.275 and r = 0.197, respectively). A weak positive correlation (r = 0.249) between nPCR and Kt/V was found when average weekly values per patient (n = 11) were analyzed. Results of groups 1 and 2 confirm, what is already well established in adults, that adequate dialysis needs to be achieved in order to insure good protein intake. However, our data clearly show that nPCR did not increase with a further increase in delivered HD dose, i.e. Kt/V >1.6. Our results show that the nutritional status of children on chronic HD does not seem to benefit from very high HD doses (Kt/V >1.6).     

Acute-phase response predicts erythropoietin resistance in hemodialysis and peritoneal dialysis patients

We defined erythropoietin (EPO) resistance by the ratio of the weekly EPO dose to hematocrit (Hct), yielding a continuously distributed variable (EPO/Hct). EPO resistance is usually attributed to iron or vitamin deficiency, hyperparathyroidism, aluminum toxicity, or inflammation. Activation of the acute-phase response, assessed by the level of the acute-phase C-reactive protein (CRP), correlates strongly with hypoalbuminemia and mortality in both hemodialysis (HD) and peritoneal dialysis (PD) patients. In this cross-sectional study of 92 HD and 36 PD patients, we examined the contribution of parathyroid hormone (PTH) levels, iron indices, aluminum levels, nutritional parameters (normalized protein catabolic rate [PCRn]), dialysis adequacy (Kt/V), and CRP to EPO/Hct. Albumin level serves as a measure of both nutrition and inflammation and was used as another independent variable. Serum albumin level (deltaR2 = 0.129; P < 0.001) and age (deltaR2 = 0.040; P = 0.040) were the best predictors of EPO/Hct in HD patients, and serum albumin (deltaR2 = 0.205; P = 0.002) and ferritin levels (deltaR2 = 0.132; P = 0.015) in PD patients. When albumin was excluded from the analysis, the best predictors of EPO/Hct were CRP (deltaR2 = 0.105; P = 0.003) and ferritin levels (deltaR2 = 0.051; P = 0.023) in HD patients and CRP level (deltaR2 = 0.141; P = 0.024) in PD patients. When both albumin and CRP were excluded from analysis in HD patients, low transferrin levels predicted high EPO/Hct (deltaR2 = 0.070; P = 0.011). EPO/Hct was independent of PTH and aluminum levels, PCRn, and Kt/V. High EPO/Hct occurred in the context of high ferritin and low transferrin levels, the pattern expected in the acute-phase response, not in iron deficiency. In well-dialyzed patients who were iron replete, the acute-phase response was the most important predictor of EPO resistance.     

Intradialytic glucose infusion increases polysulphone membrane permeability and post-dilutional haemodiafiltration performances.

INTRODUCTION: During real-time monitoring of the ultrafiltration coefficient (Kuf) in haemodiafiltration (HDF), it was noticed that the ultrafiltration performance of polysulphone membrane dialysers increased when hypertonic glucose (D50%) was administered through the venous blood return. METHODS: This observation was explored in six non-diabetic chronic dialysis patients during 48 HDF sessions using 1.8 m(2) polysulphone membrane dialysers. In all six patients, 24 sessions were performed with glucose supplementation (as a continuous D50% (500 g/l) infusion at 40 ml/h) and 24 sessions without supplementation. RESULTS: Glucose supplementation led to a marked increase in Kuf from 22.8+/-2.2 (without D50%, n=24) to 32. 1+/-3.9 ml/h/mmHg (with D50%, n=24) (P<0.0001). An increase in percentage reduction ratios for urea and creatinine were also consistently observed during the sessions with glucose administration (from respective mean values of 75+/-5 and 68+/-4% to 79+/-4 and 74+/-10%). Mean double-pool Kt/V, calculated from serum urea concentrations, rose from 1.65+/-0.24 (n=24) to 1.86+/-0.24 (n=24) (P<0.005). Similar results were observed in a subgroup of 18 HDF sessions (nine with glucose and nine without) monitored with an on-line urea sensor of spent dialysate. No detrimental effects were induced at any time. CONCLUSIONS: We conclude that intravenous glucose administration during high-flux HDF using polysulphone membranes increases significantly both ultrafiltration capacity and dialysis dose delivery.     

Improved clearance of iohexol with longer haemodialysis despite similar Kt/V for urea.

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<0.01), but increased after HD, and more so after the short dialysis, reaching 46% of the predialysis mass 24 h after 3 h HD vs. 36% after 6 h HD (P<0.05). The removed mass of iohexol was 920+/-110 mg with 6h HD and 700+/-81 mg with 3h HD, (P<0.01). Thus, the longer dialysis removed 32% more iohexol despite similar blood Kt/V for urea. CONCLUSION: The treatment time per se affects solute removal despite similar blood Kt/V for urea. This is particularly true for an intermediate-size molecule like iohexol.     

Evaluation of hemodialysis adequacy using online Kt/V and single-pool variable-volume urea Kt/V

OBJECTIVE: The hemodialysis (HD) team should deliver single-pool variable-volume (SPVV) urea Kt/V>or=1.2. At present dialysis machines provide online assessment of Kt/V. The aim of our study is to assess if online Kt/V and SPVV urea Kt/V yield similar values and if it may be replaced in evaluation of HD adequacy. PATIENTS AND METHODS: Studies were carried out two times (evaluation I and evaluation II) in 40 patients dialyzed using machines with online Kt/V monitoring by the conductivity method. During the middle HD session in the week, SPVV Kt/V was estimated from urea measurements in serum at the beginning and at the end of the HD session using the second generation formula of Daugirdas. Values of SPVV urea Kt/V and simultaneously obtained online Kt/V were compared. RESULTS: In I, SPVV Kt/V was 1.37+/-0.16, and online Kt/V was 1.16+/-0.14 (P=0.000), r=0.559 (P=0.000); a regression equation indicated SPVV Kt/V as 0.62457+0.64048 * online Kt/V. In II, estimated SPVV Kt/V was 1.37+/-0.20, online Kt/V-1.16+/-0.15 (P=0.000), r=0.493 (P=0.001), and calculated SPVV Kt/V was 1.37+/-0.10. In I, SPVV urea Kt/V>1.20 was shown in 87.5% of patients, whereas online Kt/V>1.20 was observed in 37.5% of cases (P=0.000). In II, respective values were 82.5% and 40.0% of patients (P=0.000). CONCLUSIONS: SPVV urea Kt/V indicates a more adequate HD session than online Kt/V. This difference has to be considered when applying Kt/V to clinical practice.