Clinical experience with short-time hemodialysis

Hemoglobin Normalization Results in Lower Dialysis Dose, Despite High Dialysate Flow. Single Needle Offers Inadequate Dialysis

Anemia correction by erythropoietin favorably affects dialysis outcome but may also reduce dialysis efficiency increasing morbidity and mortality. Single needle dialysis (SN) and high dialysate flow (DF) are dialysis variations. We studied the effect of hemoglobin (Hb) normalization on dialysis adequacy under high DF. We also compared double needle (DN) and SN dialysis efficiency. Seventeen stable anuric patients (13 M, 4 F), aged 62 (40–90), on hemodialysis for 48 months (8–204), were studied in two, 6 months apart, periods of low (A) and high Hb (B), during a midweek 4 h dialysis with DN and SN. DF was 500 in A and 800ml/min in B. Rebound urea samples, 20 min post dialysis, were used for computer calculated double pool urea kinetics.

Hb levels were 128±8 g/L (B) vs. 119±14 g/L (A), P<0.03. Despite the use of higher DF less dialysis was delivered in B vs. A, under DN or SN (DN: URR 64.8±5.8 vs. 69.7±5.2%, Kt/Vequil. 1.09±0.19 vs. 1.26±0.21, nPCR 1.37±0.29 vs. 1.60±0.36g/kg/day, changes <0.001, SN: URR 49.7±7.5% vs. 52.6±8.8%, Kt/Vequil. 0.74±0.16 vs. 0.82±0.23, nPCR 1.05±0.33 vs. 1.20±0.31, changes NS). SN was found significantly (P<0.001) less efficient than DN in A and B. Serum creatinine drop was significantly (P<0.001) less in both periods with SN vs. DN. Hb (SN in B) correlated inversely to Kt/V (r = –0.5705, P<0.02) and URR (r = –0.6432, P=0.005).

Hb correction to normality is associated with a decrease in dialysis efficiency. The use of high dialysate flow does not compensate for this loss. SN delivers inadequate dialysis independently of dialysate flow or hemoglobin concentration.

Vasopressin and prevention of hypotension during hemodialysis

CONTEXT

The occurrence of intradialytic hypotension (IDH) during hemodialysis (HD) continues to be a main problem in patients with ESRD (end-stage kidney disease). It also negatively affects health-related quality of life. We aimed to determine vasopressin effect in decreasing IDH.

EVIDENCE ACQUISITION

We reviewed clinical and experimental literature in a variety of sources, including PubMed, Current Content, Scopus, Embase, and Iranmedex regarding the possible effect of vasopressin administration in prevention of hypotension during HD to clarify its mechanism, efficacy, and safety.

RESULTS

Although arginine vasopressin is widely recognized for its anti-diuretic properties, it is also a well-recognized vasoconstrictor. It has been shown that the vasopressin release (as it would normally be expected) does not increase in the majority of HD patients with recurrent dialysis hypotension. In addition, it has also been reported that vasopressin secretion (due to the osmotic stimulation) is the most important mechanism in blood pressure control in ESRD patients receiving hypertonic solution for IDH. Therefore, it is suggested that vasopressin administration may improve hemodynamic stability among ESRD patients during HD. There are few clinical trials about this issue, suggesting that administration of exogenous vasopressin may be significantly associated with a decreased incidence of IDH as well as cardiovascular stability in ESRD patients in need of volume removal during HD.

CONCLUSIONS

Vasopressin insufficiency may have an important role in the pathogenesis of hemodynamic instability during HD and administration of exogenous vasopressin is significantly associated with a lower incidence of IDH.

Dialysis time: does it matter? A reappraisal of existing literature

PURPOSE OF REVIEW

The length of time (Td) required for adequate maintenance hemodialysis therapy is perceived as a substantial patient burden. Technological advancements have allowed shortening Td over the past three decades. However, failure to detect improved outcomes with higher dialysis dose has prompted renewed interest in the potential impact of longer Td.

RECENT FINDINGS

Ongoing trials are focused on increasing the frequency of treatments, although the feasibility of having most patients agreeing to more than five treatments per week remain doubtful. Furthermore, survival was better in short daily hemodialysis with Td of 180 vs. 90 min. Within thrice weekly dialysis, several recent epidemiological studies have shown improved survival associated with Td more than 4 h. Improved outcomes for long in-center nocturnal hemodialysis (6-8 h, 3×/week), similar to what has been performed in Tassin for the last 30 years, have also been reported.

SUMMARY

Compelling rationale and recent outcome data support use of longer Td. Improved management of salt and water may be the cause for the dissociation of dialysis time and small molecule clearance. In most industrialized countries, hemodialysis care systems in place have the capacity to accommodate it. Until such time that results from prospective randomized trials are available, we believe that physicians should prescribe and exert all efforts to convince thrice weekly hemodialysis patients to accept 4 h as minimum Td.

Effect of different synthetic membranes on laboratory parameters and survival in chronic haemodialysis patients

Background. A number of studies suggested that the type of dialysis membrane is associated with differences in long-term outcome of patients undergoing haemodialysis, both in terms of morbidity and mortality. In the majority of dialysis units, synthetic membranes are being used. However, no studies are available so far for comparison between different biocompatible membranes. Therefore, we studied the influence of high- and low-flux polysulphone membranes (PS) in comparison with polymethylmethacrylate (PMMA) membranes on mortality and morbidity on the basis of various laboratory parameters. Methods. In a cohort study, data of 260 consecutive haemodialysis patients entering our dialysis unit in the years 2003-07 were collected, comparing 435 PS patient-years and 85 PMMA patient-years. PMMA membranes (n = 33) were used for those patients who did not tolerate (e.g. for pruritus) PS membranes (n = 227). Low-flux dialysers (n = 233) were compared with high-flux (n = 37). Laboratory values were evaluated by unpaired t-test, and mortality was evaluated by log-rank test and Cox regression analysis adjusted for age, diabetes and laboratory parameters. Results. Patients in our dialysis unit had a high cardiovascular risk as demonstrated by a proportion of 63% of peripheral arterial disease. Despite this, cumulative survival was almost 60% after 5 years on dialysis. It was slightly but not significantly higher in patients on PMMA (68%) compared with PS dialysers (54%) and on high-flux (61%) versus low-flux membranes (54%). After accounting for the confounding effect of age and diabetes in the multivariate Cox regression analysis, there was no impact of the membranes used (high- or low-flux, PMMA or PS) on survival. Only age at the onset of dialysis showed a significant influence on survival (P ≤ 0.001). Independent predictors of mortality in all patients in the multivariate Cox regression analysis were age, haemoglobin, leucocytes, C-reactive protein (CRP) and creatinine. Laboratory parameters between the high- and low- flux groups were not different. PS-treated patients showed significantly (P ≤ 0.05) higher values for leucocytes, thrombocytes, ferritin, and CRP and lower values for haemoglobin, transferrin, creatinine, uric acid, creatine kinase (CK), and sodium than PMMA-treated patients. Irrespective of the membrane used, in deceased patients, the following laboratory values were higher than for patients alive: leucocytes, thrombocytes, ferritin and CRP; the following were lower: haemoglobin, iron, total protein, urea, creatinine, uric acid and CK. Conclusions. The data of 260 severely ill haemodialysis patients showed a slightly, but not significantly, reduced mortality in patients treated with PMMA membranes in comparison with PS and with high-flux membranes compared with low-flux. High- or low-flux membranes exhibited no difference in laboratory values. However, in PMMA patients, laboratory data with respect to inflammation, anaemia and nutrition were significantly improved compared with the PS group. A similarly positive laboratory pattern was seen in patients alive compared with patients deceased with both membrane types. The favourable effect of PMMA membranes may be explained by the reduced activation of catabolic components and inflammation, which, in turn, would result in an improved nutrition and better response to recombinant human erythropoietin.

Effect of dialysis flux and membrane material on dyslipidaemia and inflammation in haemodialysis patients

BACKGROUND

Dyslipidaemia, inflammation and oxidative stress are prominent risk factors that potentially cause vascular disease in haemodialysis patients. Dialysis modalities affect uraemic dyslipidaemia, possibly by modifying oxidative stress, but the effects of dialyser flux and membrane material on atherogenic remnant particles and oxidized low-density lipoproteins (LDL) are unknown.

METHODS

We performed a randomized crossover study in 36 patients on haemodialysis to analyse the effect of dialyser flux and membrane material on plasma lipids, apolipoproteins and markers of inflammation and oxidative stress. Stable patients on low-flux dialysis with polysulphone for >/=6 weeks were assigned to high-flux polysulphone or high-flux modified cellulose with similar dialyser surface area and permeability characteristics and crossed over twice every 6 weeks.

RESULTS

Thirty patients completed the study per protocol. Treatments with high-flux polysulphone and modified cellulose lowered serum triglyceride (by 20% and 10%, respectively; P<0.05) and remnant-like particle cholesterol by 32% (P<0.001) and 11% (NS) after the first 6 weeks of treatment. Oxidized LDL decreased significantly with high-flux polysulphone, but not with modified cellulose. Apolipoproteins CII and CIII were reduced, whereas the ratio CII/CIII was increased (all P<0.05). Acute-phase proteins and LDL and high-density lipoprotein cholesterol remained unaffected.

CONCLUSIONS

This randomized crossover study demonstrates a potent effect of high-flux haemodialysis on uraemic dyslipidaemia. Polysulphone membrane material showed superiority on oxidatively modified LDL, an indicator of oxidative stress in haemodialysis patients.

Best Method for Estimating Urea Volume of Distribution: Comparison of Single Pool Variable Volume Kinetic Modeling Measurements with Bioimpedance and Anthropometric Methods

The urea volume of distribution (Vurea) is a key component of the Kt/V parameter calculated during urea kinetic modeling. The Vurea parameter has been approximated empirically using total body water (TBW) estimates derived from anthropometric formulas or measured by bioelectric impedance analysis (BIA). The author compared TBW values derived using various anthropometric formulas (Watson, Hume, Randall, Tzamaloukas, Chertow) and BIA to the Vurea parameter calculated using three point variable volume single pool urea kinetic modeling. A total of 127 chronic hemodialysis patients were studied (mean age 66 +/- 13 years; 42% female; 37% black; 47% diabetic). Agreement between anthropometric formulas, BIA, and Vurea values was assessed by linear regression and Bland Altman analyses. The closest correlations were obtained with the BIA (r = 0.972), Chertow (r = 0.917), and Tzamaloukas (r = 0.905) methods. When compared with Vurea, 95% confidence intervals by Bland Altman analysis were lowest with BIA (4L) and highest with the Watson method (8L). These results indicate that BIA best approximates Vurea in dialysis patients.

In search of ideal hemodialysis: is prolonged frequent dialysis the answer?

Advances in technology have made it possible to deliver a high Kt/V in a shorter time. The realization that duration of dialysis may be an important predictor of survival independent of dialysis dose has resulted in the popularity of prolonged slow dialysis (PHD). The longer duration and increased frequency of dialysis achieve excellent small- and middle-molecular weight solute clearance and also attenuate the peak concentration of uremic toxins. The slow dialysis process enables the equilibration of tissue and vascular compartments, resulting in better clearance and decreased postdialysis rebound increase in solutes. Gentle, persistent ultrafiltration allows the control of hypertension with minimal antihypertensive use. The intense and more frequent dialysis improves appetite and permits liberalization of diet. This greater dietary protein intake results in a progressive increase in serum albumin level and dry weight. Nocturnal hemodialysis achieves control of hyperphosphatemia without phosphate binders and a significant reduction in serum beta(2)-microglobulin levels. Normalization of extracellular volume, better clearance of uremic toxins, and improved nutrition result in a significant improvement in survival. The flexible time schedule with home hemodialysis and improvement of sleep and neurocognitive function allow better rehabilitation. The available evidence indicates PHD may be closer to the concept of an ideal dialysis, but there is lingering uncertainty about the consequence of prolonged immune stimulation, catabolism, and loss of essential solutes with these therapies.

Current and future modalities for functional renal replacement

Approximately 310,000 Americans suffer from end-stage renal disease, with more than 70,000 new cases reported each year. Advances in immunosuppressive therapy for transplanted patients, in addition to the refined care of patients who are dependent on dialysis, have led to an improved survival for patients with renal failure. Structural, molecular, and pharmacologic developments continue to enhance the efficacy and safety of dialysis in the future. In addition, progressive improvements in the past 2 decades in organ transplantation, a greater insight into the immunobiology of graft rejection, and better surgical and medical management have resulted in improved outcomes. Although renal xenotransplantation is still in its early stages of development, additional research is leading this technology forward. Recent successes in harvesting and expanding renal cells in vitro and the development of biologically active synthetic materials allow for the creation of three-dimensional functioning renal units, which, in the future, may be applied ex vivo or in vivo for partial or full replacement of kidney function.

Reduction of plasma apolipoprotein-B by effective removal of circulating glycation derivatives in uremia

Patients with diabetes and renal insufficiency (Db/ESRD), a group subject to accelerated atherosclerosis exhibit marked increases in the levels of circulating, glycation-derived reactive substances, termed advanced glycation endoproducts (AGEs). These products have been previously shown to react covalently with apoliprotein B (ApoB) to form AGE-ApoB, a modification that results in delayed low density lipoprotein (LDL) clearance and possibly to dyslipidemia. Because the effect of hemodialysis on AGE removal was shown to be unsatisfactory, based on single intradialytic studies, we examined the effect of long-term hemodialysis therapy on serum AGE-ApoB levels, as well as on total serum ApoB of 25 Db/ESRD patients treated by two types of hemodialysis filters, the Fresenius Inc. F8, as the low flux (LF), or high-flux polysulfone AN69 (HF) for two months using an AGE-specific ELISA. At the end of eight weeks, circulating AGE-ApoB levels were reduced significantly (by 35%) from baseline (P = 0.039) in patients treated by HF compared to a modest 16% reduction noted in patients treated by LF (P = 0.05) N = 12, P = 0.047). Of note, total plasma ApoB was reduced by 27% from baseline (P = 0.02) in patients treated by HF compared to a 6% reduction noted in those treated with LF (P = 0.8). In vitro comparison of AGE mass balance, and mass adsorption by the different filters revealed that the higher efficiency of HF filter was due to greater adsorption. The association of reduced AGE-ApoB levels with a decrease in total circulating ApoB by HF and not by LF dialysis suggests: (1) a causal link between AGE clearance and dyslipidemia in diabetic ESRD, and, (2) that more efficient modes of renal replacement treatment and AGE removal could significantly benefit clinical outcome.

Mortality, hospital admissions, and medical costs of end-stage renal disease in the United States and Manitoba, Canada

OBJECTIVES

National registry data suggest that mortality rates among patients with end-stage renal disease are lower in Canada than in the United States. Casemix and treatment variables, although limited in such instances, do not explain this difference. Using a more complete set of casemix and treatment variables from clinical databases, this study assesses mortality, hospital admission, and the cost of medical care for patients with end-stage renal disease treated in Manitoba, Canada and the United States.

METHODS

Mortality rates were compared in patients with end-stage renal disease treated in the Province of Manitoba and a random sample of US patients enrolled in the US Renal Data System Casemix Severity Study. Hospital admission rates and costs of care were compared in Manitoba patients and in patients with end-stage renal disease in a large health care organization in Detroit, Michigan.

RESULTS

Levels of serum creatinine, urea, and estimated glomerular filtration rate indicated more severe renal impairment at the outset of treatment in Manitoba than in the United States. Manitoba patients were more than twice as likely to receive kidney transplants as US Renal Data System patients. No patients in Manitoba used reprocessed dialyzers, compared with 57% of US Renal Data System patients. After adjustment for all casemix and treatment variables, the mortality rate was 47% higher in the United States. The hospital admission rate in Detroit was 41% lower than the hospital admission rate in Manitoba, which primarily reflects the doubled rate of transplantation in Manitoba. Adjusted total monthly costs were $503 higher in Detroit than in Manitoba.

CONCLUSIONS

The higher mortality rates in the United States cannot be fully explained by adjustments for observable casemix or treatment variables. Further research is needed to identify factors that explain how Manitoba achieves a lower mortality rate while paying less for end-stage renal disease care than the United States.

The outcomes of ESRD and its treatment

In recent years, the notion that studying outcomes is a distinct form of clinical research has gained currency. This article offers a conceptual framework for thinking about outcomes research in end-stage renal disease and examines one issue in detail. Although the meaning of the term "outcome" is often assumed, it is currently used in two ways. In the broader sense, outcomes are the results of health care. These may include survival and the presence or absence of symptoms and clinical signs of disease. As it has recently been used in the medical literature, however, the term outcomes frequently connotes outcomes with respect to patient function and experience. Patient experience comprises functional status, general well-being, and satisfaction with care. The principle that the outcomes of end-stage renal disease should be studied has been established. A substantial body of knowledge has accumulated regarding characteristics of the patient population, of the treatments administered, and of the consequences with respect to survival. Whether the investigation and practice of renal replacement therapy should encompass the measurement of patient experience has been a subject of controversy. Reasons to perform such measurements are enumerated, and countervailing arguments are examined critically. The technological prerequisites for success in the widespread measurement of patient experience are set forth.

Role of dialysis dose on morbidity and mortality in maintenance hemodialysis patients

The United States dialysis population has an excessive mortality rate that cannot be fully explained by comorbid conditions or demographic factors. The quantity of dialysis has been suggested to be insufficient. This report reviews the several dialysis-related factors that impact on mortality. Since the National Cooperative Dialysis Study in 1983, there have been no controlled trials. However, numerous retrospective and two recent larger prospective studies indicate that increasing the quantity of dialysis by 40% to 50% of that traditionally provided in the United States will significantly improve survival. This is equivalent to a Kt/V of less than 1.2 and possibly less than 1.4 using single pool urea kinetics. It is estimated that this would save an additional 8,000 to 16,000 lives per year.

The decline in serum albumin after conversion to high flux, high efficiency dialysis

Hypoalbuminemia among chronic hemodialysis patients is recognized as a poor prognostic sign. We observed that many of our chronic patients had a progressive decrease in their plasma albumin concentrations after they were converted to high flux, high efficiency dialysis from conventional dialysis mode. This change occurred in the absence of changes in the KT/V and protein catabolic rate (pcr) normalized to body mass. When nitrogen losses were measured, we found no difference in the dialysate concentrations of urea, alpha amino nitrogen, uric acid, or total nitrogen when high flux polysulfone was compared with high efficiency Cuprophan. While urea was the predominant nitrogen solute in all dialysate samples, there were some with a large gap between total and urea nitrogen. Alpha amino nitrogen losses, expressed as leucine equivalents, were substantial, ranging from 8.4 to 9.8 g/3.5 h dialysis treatment. We believe that the increased losses of nitrogen experienced by patients after their conversion to a more efficient method of dialysis and not compensated for by a spontaneous increased intake of protein led to the observed fall in plasma albumin. Both urea and amino acid nitrogen losses need to be accounted for when achievement of higher KT/V dialysis is pursued.

Lipoprotein metabolism in normal and uremic patients

Abnormalities in circulating lipoprotein concentrations are a characteristic finding both in patients with uremia and in patients undergoing dialysis. These patients tend to have elevated triglyceride (TG) concentrations and low concentrations of high-density lipoprotein (HDL) cholesterol. Elevations of low-density lipoprotein (LDL) are not usually observed unless the patients have undergone renal transplantation and are receiving therapy with immune suppressive medications. Hypertriglyceridemia and low HDL may be the consequence of decreased actions of lipoprotein lipase (LPL), the endothelial cell-bound enzyme that degrades circulating lipoprotein triglyceride. A poorly characterized circulating inhibitor to this enzyme is found in uremic plasma. Preliminary data suggest that high-flux dialysis with polysulfone (PS) membranes improves the lipoprotein abnormalities and decreases circulating LPL inhibitors. Whether such therapy will alter the incidence of coronary morbidity and mortality in patients with end-stage renal failure remains to be tested.