Ysis Prescription and Peritoneal Membrane Transport Characteristics on Nutritional Status

These data suggest that dialysis dose is one of the major determinants of protein and energy intake in PD patients and that higher doses of dialysis tend to improve outcome. The data also suggest that with a long time on PD the peritoneal membrane probably has some underlying histological changes that preclude it from optimally responding to injury and may predispose it to irreversible damage. A possible early finding in this case is an increase in peritoneal transport in patients whose transport was initially stable. Peritoneal membrane transport properties are an important determinant of not only dialysis dose, but also nutritional status via both direct and indirect means. It is therefore important to identify the individual patient's peritoneal membrane transport characteristics. These transport characteristics may change over time. High transporters on CAPD represent a unique challenge. They have ultrafiltration problems and a tendency toward protein malnutrition presumably due to increased dialysate protein losses while on CAPD. One must consider that malnutrition in a rapid transporter may be due to the fact that the patient is on the wrong PD therapy. A change to NIPD may rectify some of the biochemical parameters, but these patients may not always improve. Reasons for this occasional lack of improvement are multifactorial, but emphasize our need to look at each patient as an individual and not focus only on laboratory parameters.

Serum Albumin and Other Serum Protein Fractions in Stable Patients on Peritoneal Dialysis

Background

Hypoalbuminemia is common in peritoneal dialysis (PD) patients; but the reduction in serum albumin levels (SAlb) that should be expected in stable PD patients is less clear.

Objectives

To determine prospectively, in a group of stable PD patients without comorbid conditions, the changes in SAlb concentration and in the concentrations of the other serum protein fractions. To investigate the best determinants of a significant decrease in SAlb levels.

Design

Prospective observational study.

Methods

Seventeen PD patients in stable clinical condition, with no signs of systemic inflammatory response, were included in the study. SAlb and the electrophoretic pattern of serum proteins were determined immediately before PD start, and after 6, 9, 12, 15, 18, 21, and 24 months on PD. In each study period, clinical characteristics, adequacy parameters, protein catabolic rate (PNPNA: protein equivalent of non protein nitrogen appearance), and protein losses were determined. Patients were divided into two subgroups according to whether SAlb decreased less than 10%, or 10% or more, from baseline values after 24 months on PD. The main differences between the subgroups were investigated.

Results

Mean SAlb did not decrease significantly after 24 months on PD (from baseline 3.99 ± 0.46 g/dL to 3.80 ± 0.54 g/dL), though percentage SAlb values did (58.36% ± 5.58% vs 55.15% ± 5.42%, p < 0.01). A weak increase in α2-globulin was observed after 18 months on PD (from 10.62% ± 2.53% to 12.96% ± 2.51%, p = 0.001). α1-Globulin showed a sustained increase from a mean baseline value of 3.51% ± 1.09% to 6.83% ± 2.13% after 24 months ( p < 0.0001). Seven patients had a reduction in SAlb greater than 10% after 24 months on PD. Kt/V urea and residual renal function tended to be lower in patients whose SAlb decreased. Mean PNPNA was significantly lower in patients who had a reduction in SAlb (0.76 ± 0.12 g/kg/day vs 0.96 ± 0.12 g/kg/day, p < 0.0001). However, total protein loss was even greater in patients who had no SAlb reduction.

Conclusions

After 24 months on PD, a mean reduction in SAlb of 10% – 15% from baseline values should be expected only in those stable patients whose PNPNA is low.

Effect of Polymeric Diets in Patients on Continuous Ambulatory Peritoneal Dialysis

Objective

To determine if a diet complemented with calcium caseinate is better than a natural high protein diet for increasing serum albumin levels in patients on continuous ambulatory peritoneal dialysis (CAPD).

Patients and Methods

A 4-month clinical trial involving 100 patients older than 18 years was performed. Patients were randomized into two groups: group A, high protein diet (1.4 g natural protein/kg target weight/day and 35 kcal/kg target weight/day); and group B, calcium caseinate (0.7 g calcium caseinate plus 0.7 g natural protein diet/kg target weight/day and 35 kcal/kg target weight/day). Serum levels of albumin, total proteins (TP), BUN, creatinine, glucose, urea, sodium, and potassium, and hematocrit, leukocytes, erythrocytes, and hemoglobin were analyzed at baseline and every 30 days.

Results

The final mean albumin value was, for group A, 3.04 ± 0.39 g/dL, and for group B, 3.1±2 0.41 g/dL ( p < 0.05); TP for group A, 6.29 ± 0.47 g/dL, and for group B, 6.49 ± 0.51 g/dL ( p < 0.05); leukocytes for group A, 688 ± 8 1282/mm3, for group B, 7288 ± 1878/mm3 ( p = 0.05); BUN for group A, 47 ± 11 mg/dL, for group B, 50 ± 16 mg/dL ( p = 0.05). Regression analysis showed a treatment effect in serum albumin and TP levels from the third month in both groups. In group B, a constant elevation of serum albumin of 0.19 mg/dL and TP of 0.27 mg/dL was observed in every month of treatment with calcium caseinate. In the regression analysis of group A we observed a smaller increase in serum albumin, 0.06 mg/dL, and in TP, 0.11 mg/dL, in each month of treatment with the high protein diet. Both differences are significant ( p < 0.05).

Conclusion

Calcium caseinate used in CAPD patients suffering from malnutrition increases serum albumin levels.

Arterial pulse wave velocity and peritoneal transport characteristics independently predict hospitalization in Chinese peritoneal dialysis patients

OBJECTIVE

Cardiovascular disease (CVD) is the most common cause of mortality in chronic peritoneal dialysis (PD) patients. Increased arterial stiffness may be related to a high peritoneal permeability resulting in fluid overload in PD patients. We studied the relations between arterial stiffness, peritoneal transport, and radiographic parameters of systemic fluid overload in a cohort of Chinese PD patients.

DESIGN

Prospective cohort study.

SETTING

University referral center.

PATIENTS

We studied 107 PD patients. Vascular pedicle width and cardiothoracic ratio were measured from a plain postero-anterior chest radiograph. Pulse wave velocity (PWV) was determined at carotid-femoral (C-F) and carotid-radial sites. Peritoneal transport was determined by the dialysate-to-plasma ratio (D/P) of creatinine at 4 hours of dwell. Patients were followed for 9.4 +/- 4.6 months.

OUTCOME MEASURES

Duration of hospitalization; actuarial and technique survival.

RESULTS

There were no relationships between radiographic measures, arterial PWV, and D/P creatinine. However, both C-F PWV and D/P creatinine were independent predictors of the number of hospitalizations for CVD. None of the parameters correlated with mortality in this study.

CONCLUSIONS

There were no relationships between radiological parameters of fluid overload, peritoneal transport characteristics, and arterial PWV. Both C-F PWV and D/P creatinine were independent predictors of the number of hospitalizations for CVD. Our result suggests that arterial stiffness and high peritoneal transport each contribute to the development of CVD in this group of patients.

NUTRITIONALMANAGEMENT OFMAINTENANCEDIALYSISPATIENTS: Why Aren't We Doing Better?

About 40% of patients undergoing maintenance dialysis suffer from varying degrees of protein-energy malnutrition. This is a problem of substantial importance because many measures of nutritional status correlate with the risk of morbidity and mortality. There are many causes of protein-energy malnutrition in maintenance dialysis patients. Evidence indicates that nutritional decline begins even when the reduction in glomerular filtration rate is modest, and it is likely that the observed decrease in dietary protein and energy intake plays an important role. The nutrient intake of patients receiving maintenance dialysis also is often inadequate, and several lines of evidence suggest that toxins that accumulate with renal failure suppress appetite and contribute to nutritional decline once patients are on maintenance dialysis. Recent epidemiologic studies have suggested that both increased serum levels of leptin and inflammation may reduce nutrient intake and contribute to the development of protein-energy malnutrition. It is likely that associated illnesses, which are highly prevalent, contribute to malnutrition in maintenance dialysis patients. Recent data from the United States Renal Data System registry suggest that in the United States, the mortality rate of dialysis patients is improving. However, it remains high. We offer suggestions for predialysis and dialysis care of these patients that can result in improvement in their nutritional status. Whether this improvement will result in a decrease in patient morbidity and mortality is unknown.

Children with hypoalbuminemia on continuous peritoneal dialysis are at risk for technique failure

BACKGROUND

Few data are available on the clinical significance of hypoalbuminemia [serum albumin (SA) <35 g/L] in children with end-stage renal disease (ESRD) on continuous peritoneal dialysis (CPD). This study was conducted to analyze the prevalence of hypoalbuminemia, its predictive factors, and its clinical impact in these children.

METHODS

A retrospective analysis was done of 180 patients on CPD over the last 22 years. Patients were excluded from the study if they were on CPD for less than four months or had nephrotic syndrome. Demographic, clinical, and biochemical variables were studied. Children continued on CPD until they received a transplant or were transferred to an adult unit or to hemodialysis as a result of technique failure. The subjects were divided into two groups based on SA levels at last follow-up.

RESULTS

A total of 135 children was included. After a mean duration of CPD of 573 +/- 437 (120 to 2960) days, 54 children (40%) were observed to have hypoalbuminemia. Four patients (2.9%) died, 7 (5.2%) continued on continuous cyclic peritoneal dialysis, and 13 (9.6%) were transferred to an adult unit for continuation of CPD. Ninety-five (70.3%) were transplanted, and 16 (11.8%) were transferred to hemodialysis because of technique failure. Children in group I (N = 54, SA <35 g/L), compared with group II (N = 81, SA > or =35 g/L), were younger at initiation of PD, more likely to have hypoalbuminemia at one month and six months after initiation of PD, and have more episodes of peritonitis. No differences were seen between the groups in gender, modality of CPD, body surface area, initial body mass index, and presence of hypertension or acidosis. The only factors predictive of hypoalbuminemia on follow-up were low SA at one month after PD and recurrent peritonitis using multiple logistic regression analysis. Evaluating the clinical impact of hypoalbuminemia, we observed a higher incidence of failed PD in children who had hypoalbuminemia.

CONCLUSION

Low SA at one month after PD and recurrent peritonitis are predictive of hypoalbuminemia in children on CPD, which is associated with an increased incidence of CPD failure.

Pathogenic effects of a high peritoneal transport rate

Recent studies have shown that patients with high peritoneal transport characteristics have substantially increased morbidity and mortality. This finding is counter-intuitive, since HTs will a priori achieve higher clearances. There are many possible causes: increased protein losses with consequent hypoalbuminemia; poor ultrafiltration capacity causing fluid retention, ventricular hypertrophy and hypertension; increased glucose absorption leading to anorexia, hyperinsulinism, and local AGE formation; and the development of an atherogenic lipid profile. While common pathogenic causes of high peritoneal transport and atherosclerosis have been hypothesized, it is more likely that CAPD as currently practiced is unsuitable for HTs, who should be switched to HD or NIPD. Renal and peritoneal clearances have different clinical effects and should be assessed separately. Current measures of dialysis adequacy, such as total Kt/V, do not therefore describe the patient's clinical situation accurately and are insufficient.

Morbidity and mortality in redefining adequacy of peritoneal dialysis: a step beyond the National Kidney Foundation Dialysis Outcomes Quality Initiative

The National Kidney Foundation Dialysis Outcomes Quality Initiative (NKF-DOQI) Peritoneal Dialysis (PD) Adequacy Work Group intentionally limited the scope of its work to address adequacy in terms of small-solute removal. This decision was based on the need for rigorous evidence and that mortality is the most objective parameter in the literature. This review attempts to more broadly redefine the concept of the adequacy of PD, particularly as it relates to the most common general medical problems that PD patients experience; namely, cardiovascular disease and malnutrition. Whereas we are sensitive to the developmental process of the NKF-DOQI, we are critical that the definition of adequacy may be too narrow, leading clinicians to overlook other important morbidities. We have reiterated the evidence that suggests a weekly solute clearance (Kt/Vurea) of 1.7 or greater is associated with better patient survival. The arguments to target a greater Kt/Vurea of 2.0 are challenged, yet the concept is ultimately supported. Because cardiovascular disease is the cause of death in half of all patients with end-stage renal disease, dialysis adequacy must be defined, in part, by the potential of that therapy to diminish cardiovascular maladies. Blood pressure, volume, left ventricular hypertrophy, and dyslipidemias are discussed in this context. Lastly, assumptions that increasing total solute clearance leads to improved nutrition in PD patients are challenged. We have attempted to expand on what the NKF-DOQI did not include, and we urge the dialysis community to seek the answers to the many controversies that remain. We need to redefine the adequacy of PD in a holistic manner and find outcome parameters that are not as final as death.

The importance of monitoring dialysis adequacy in chronic peritoneal dialysis

The case of a patient who was noted to be malnourished but improved after his dialysis dose was increased is presented. This case and the discussion that follows emphasize the importance of proactively monitoring peritoneal dialysis adequacy and nutritional intake, supporting the notion that the dose of peritoneal dialysis is a major determinant of appetite and, consequently, of nutritional status. In the clinical setting, this influence is best indicated by changes in the serum albumin level and ultimately in long-term patient survival. The case discussion reviews the major principles and supporting literature, describing how we target peritoneal dialysis delivery and optimize nutritional status in an effort to reduce morbidity and mortality.

Why are dialysis patients malnourished?

There are multiple causes of protein-energy malnutrition in maintenance dialysis patients. The requirements of protein in dialysis patients are higher than in healthy individuals, and the intake of protein and energy in relation to the requirements is frequently low. Anorexia may be caused by uremia and underdialysis. There is experimental evidence that dialyzable uremic toxins accumulate in renal failure and suppress the appetite. In addition there are several psychosocial and comorbidity factors that may hamper adequate nutrition. There are also several factors in dialysis patients that may enhance protein catabolism and increase protein requirements, such as low energy intake, metabolic acidosis, dialytic loss of glucose, protein and amino acids and other catabolic effects of the dialytic procedures, as well as effects of infections and other comorbidity factors. The relative importance of the various factors that cause anorexia and stimulate protein catabolism is still not well understood.