Predictors of Decline of Residual Renal Function in New Peritoneal Dialysis Patients

♦ Objective

The aim of this study was to prospectively evaluate the risk factors for decline of residual renal function (RRF) in an incident peritoneal dialysis (PD) population.

♦ Design

Prospective observational study of an incident PD cohort at a single center.

♦ Setting

Tertiary-care institutional dialysis center.

♦ Participants

The study included 146 consecutive patients commencing PD at the Princess Alexandra Hospital between 1 August 1995 and 1 July 2001 (mean age 54.8 ± 1.4 years, 42% male, 34% diabetic). Patients with failed renal transplants ( n = 26) were excluded.

♦ Main Measurements

Timed urine collections ( n = 642) were performed initially and at 6-month intervals thereafter to measure RRF. The development of anuria was also prospectively recorded.

♦ Results

The mean (±SD) follow-up period was 20.5 ± 14.8 months. The median slope of RRF decline was –0.05 mL/minute/month/1.73 m2. Using binary logistic regression, it was shown that the 50% of patients with more rapid RRF loss (< –0.05 mL/min/month/1.73 m2) were more likely to have had a higher initial RRF at commencement of PD [adjusted odds ratio (AOR) 1.83, 95% confidence interval (CI) 1.39 – 2.40] and a higher baseline dialysate/plasma creatinine ratio at 4 hours (D/P creat; AOR 44.6, 95% CI 1.05 – 1900). On multivariate Cox proportional hazards model analysis, time from commencement of PD to development of anuria was independently predicted by baseline RRF [adjusted hazard ratio (HR) 0.81, 95% CI 0.60 – 0.81], D/P creat (HR 2.87, 95% CI 2.06 – 82.3), body surface area (HR 6.23, 95% CI 1.53 – 25.5), dietary protein intake (HR 2.87, 95% CI 1.06 – 7.78), and diabetes mellitus (HR 1.65, 95% CI 1.00 – 2.72). Decline of RRF was independent of age, gender, dialysis modality, urgency of initiation of dialysis, smoking, vascular disease, blood pressure, medications (including angiotensin-converting enzyme inhibitors), duration of follow-up, and peritonitis rate.

♦ Conclusions

The results of this study suggest that high baseline RRF and high D/P creat ratio are risk factors for rapid loss of RRF. Moreover, a shorter time to the onset of anuria is independently predicted by low baseline RRF, increased body surface area, high dietary protein intake, and diabetes mellitus. Such at-risk patients should be closely monitored for early signs of inadequate dialysis.

Nutrition Indices in Obese Continuous Peritoneal Dialysis Patients with Inadequate and Adequate Urea Clearance

♦ Objective

To test whether better nutrition is associated more with adequate urea clearance than with inadequate urea clearance in obese patients on continuous peritoneal dialysis (CPD).

♦ Design

Retrospective analysis of clearance and nutrition indices in obese CPD patients. Only obese patients were analyzed. Obesity was defined as a ratio of actual weight to desired weight (W/DW) ≥ 1.2. The dose of dialysis was considered adequate at weekly Kt/V urea ≥ 2.0. Small solute clearances and nutrition indices were compared between patients with weekly Kt/V urea < 2.0 and patients with weekly Kt/V urea ≥ 2.0 at the first clearance study.

♦ Setting

Four university-affiliated and two private dialysis units in Canada and the United States.

♦ Patients

A total of 270 CPD patients with W/DW ≥ 1.2 at the first clearance study.

♦ Results

Among the 270 obese CPD patients, 157 (58.1%) were underdialyzed (weekly Kt/V urea 1.66 ± 0.22) and 113 (41.9%) had adequate dialysis (weekly Kt/V urea 2.51 ± 0.47) at the first clearance study. Creatinine clearance values also differed between the underdialyzed and adequately dialyzed obese groups (55.6 ± 15.2 vs 87.6 ± 29.8 L/1.73 m2 weekly, respectively, p < 0.001). The underdialyzed group contained fewer women (39.5% vs 60.2%, p < 0.001) and more patients with anuria (35.0% vs 8.8%, p < 0.001), and had higher serum urea (20.7 ± 6.9 vs 18.2 ± 5.3 mmol/L, p = 0.001) and serum creatinine (974 ± 283 vs 734 ± 275 μmol/L, p < 0.001), marginally lower serum albumin (35.8 ± 5.2 vs 37.2 ± 6.4 g/L, p = 0.082), lower urea nitrogen excretion (5778 ± 2290 vs 7085 ± 2238 mg/24 hr, p < 0.001) and indices derived from urea nitrogen excretion (protein nitrogen appearance and normalized protein nitrogen appearance), and lower creatinine excretion (1034 ± 349 vs 1217 ± 432 mg/24 hr, p < 0.001) and indices derived from creatinine excretion (lean body mass normalized to actual or desired weight) than the adequately dialyzed group.

♦ Conclusion

Nutrition indices derived from urea nitrogen and creatinine excretion are worse in underdialyzed than in adequately dialyzed obese CPD patients. This finding may have clinical importance, despite the mathematical coupling between small solute clearances and excretion rates in cross-sectional studies, because of evidence from other studies that small solute excretion rate in cross-sectional studies is a robust independent predictor of outcome in CPD.

High rates of protein intake are associated with an accelerated rate of decline of residual kidney function in incident peritoneal dialysis patients

BACKGROUND

Preservation of residual kidney function (RKF) is a relevant objective in peritoneal dialysis (PD) patients. The influence of dietary protein intake (PI) on this variable has not been adequately investigated.

METHODS

Following an observational design, we studied 336 patients incident on PD, with a minimum follow-up of 6 months. The main study variable was the mean PI [normalized rate of protein nitrogen appearance (nPNA)] during the first 4 months on PD. The main outcome variables were the absolute rate of decline of RKF and the proportion of patients presenting a >50% decay of their RKF during the first year of follow-up. We applied univariate and multivariate strategies of analysis, taking into consideration the main control variables bearing a correlation with nPNA and/or RKF.

RESULTS

Mean nPNA (first 4 months) was 1.23 ± 0.33 g/kg/day, while the overall rate of decline of RKF was -0.13 ± 0.29 mL/min/month; 69 patients (25.1%) had lost >50% of their initial RKF by the end of the first year. Univariate analysis disclosed consistent associations between the main study variable on one hand and baseline RKF (r = 0.32, P < 0.0005) and its rate of decline (r = -0.23, P < 0.0005) on the other. The latter two variables were also significantly correlated (r = -0.36, P < 0.0005). Multivariate analysis identified mean nPNA as an independent predictor of the rate of decline of RKF [odds ratio 1.09 per 0.10 g/kg/day, 95% confidence interval (CI) 0.99-1.19, P = 0.058] and, in particular, of the probability of losing >50% of the baseline RKF during the first year of treatment (odds ratio 1.15 per 0.10 g/kg/day, 95% CI 1.04-1.27, P = 0.006).

CONCLUSION

Higher rates of PI during the first months of therapy are associated with a faster decline of RKF among patients incident on PD. Our results underline the convenience of keeping an adequate balance between sufficient protein ingestion, to prevent malnutrition and wasting, and sensible restriction in stable, adequately nourished individuals with rates of intake in the higher range or above-recommended allowances.

Pathophysiological and clinical aspects of malnutrition in chronic renal failure

Kidney diseases are the ninth leading cause of death in the USA. In these patients cardiovascular mortality is greater than in the general population. This observation, not completely explained by the so-called 'traditional' cardiovascular risk factors, lead the authors to postulate other 'emerging' ones found in chronic renal failure patients. Among these new findings, nutritional status, considered as the balance existing between nutrient requirements and intakes, plays an important role for the development of cardiovascular diseases. In fact several nutritional parameters are widely known as pathophysiological determinants of cardiovascular disturbances, which are based on accelerated atherosclerosis, due especially to enhanced oxidative stress and endothelial dysfunction. Chronic renal failure is a clinical condition that from many points of view seems to be a chronic inflammatory state, and many studies confirm this observation. This influences nutritional status especially in dialysis patients. Malnutrition is related in turn to accelerated atherosclerosis thus leading to a postulated 'malnutrition, inflammation, atherosclerosis' (MIA) syndrome in which malnutrition, inflammation and atherosclerosis contribute to an elevated cardiovascular mortality rate. The present review explores this issue, first by describing epidemiological aspects of malnutrition in chronic renal failure patients and then by analysing the specific biochemical and metabolic features of these patients.

Sources of variation in estimates of lean body mass by creatinine kinetics and by methods based on body water or body mass index in patients on continuous peritoneal dialysis

OBJECTIVE

We identified factors that account for differences between lean body mass computed from creatinine kinetics (LBM(cr)) and from either body water (LBM(V)) or body mass index (LBM(BMI)) in patients on continuous peritoneal dialysis (CPD).

DESIGN

We compared the LBM(cr) and LBM(V) or LBM(BMI) in hypothetical subjects and actual CPD patients.

PATIENTS

We studied 439 CPD patients in Albuquerque, Pittsburgh, and Toronto, with 925 clearance studies.

INTERVENTION

Creatinine production was estimated using formulas derived in CPD patients. Body water (V) was estimated from anthropometric formulas. We calculated LBM(BMI) from a formula that estimates body composition based on body mass index. In hypothetical subjects, LBM values were calculated by varying the determinants of body composition (gender, diabetic status, age, weight, and height) one at a time, while the other determinants were kept constant. In actual CPD patients, multiple linear regression and logistic regression were used to identify factors associated with differences in the estimates of LBM (LBM(cr)<LBM(V), or LBM(cr)<LBM(BMI)).

MAIN OUTCOME MEASURE

We sought predictors of the differences LBM(V) - LBM(cr) and LBM(BMI) - LBM(cr).

RESULTS

Both LBM(V) (regardless of formula used to estimate V) and LBM(BMI) exceeded LBM(cr) in hypothetical subjects with average body compositions. The sources of differences between LBM estimates in this group involved differences in the coefficients assigned to gender, age, height, weight, presence or absence of diabetes, and serum creatinine concentration. In CPD patients, mean LBM(V) or LBM(BMI) exceeded mean LBM(cr) by 6.2 to 6.9 kg. For example, the LBM(V) obtained from one anthropometric formula was 50.4+/-10.4 kg and the LBM(cr) was 44.1+/-13.6 kg (P < .001), whereas among the 925 clearance studies, only 216 (23.3%) had LBM(cr)>LBM(V). The differences in determinants of body composition between groups with high versus low LBM(cr) were similar in hypothetical and actual CPD patients. Multivariate analysis in actual CPD patients identified serum creatinine, height, age, gender, weight, and body mass index as predictors of the differences LBM(V)-LBM(cr) and LBM(BMI)-LBM(cr).

CONCLUSIONS

Overhydration is not the sole factor accounting for the differences between LBM(cr) and either LBM(V) or LBM(BMI) in CPD patients. These differences also stem from the coefficients assigned to major determinants of body composition by the formulas estimating LBM.

Malnutrition–Inflammation–Atherosclerosis (MIA) Syndrome Components in Hemodialysis and Peritoneal Dialysis Patients

BACKGROUND

Malnutrition, inflammation, and atherosclerosis (MIA syndrome) are common in end-stage renal disease (ESRD) patients. Each component of MIA syndrome is the predictor of outcomes in ESRD patients. In this cross-sectional study, we aimed to compare both dialysis modalities for MIA syndrome components.

MATERIAL AND METHODS

Thirty hemodialysis (HD) (mean age 44 +/- 11 years, 14 male and 16 female, mean time on dialysis: 31.0 +/- 19.0 months) and 30 continuous ambulatory peritoneal dialysis (CAPD) patients (41 +/- 9 years, 12 male and 18 female, mean time on dialysis: 25.5 +/- 21.5 months) were included. In order to determine malnutrition in ESRD patients, serum albumin level and anthropometric measurements were used. For inflammation, serum C-reactive protein level, erythrocyte sedimentation rate, and fibrinogen levels were measured. Mean-carotid artery intima media thickness (m-CIMT), presence of carotid plaque and serum homocysteine level were used to determine atherosclerosis.

RESULTS

Five CAPD patients (16%) and one HD patient (3%) was hypoalbuminemic. HD and CAPD groups were similar for inflammation. Mean-CIMT and serum homocysteine level were higher in HD patients than CAPD patients. There was a positive correlation between homocysteine and m-CIMT.

CONCLUSION

Before choosing renal replacement therapy, malnutrition, inflammation, and atherosclerosis parameters must be investigated in ESRD patients. Hemodialysis seems to be more advantageous for malnutrition components than CAPD. Both dialysis modalities seem to be similar for inflammation, and CAPD modality has superiority for atherosclerosis. Before choosing the type of renal replacement therapy, assessment of MIA syndrome components could be useful for individualization of the decision on which dialytic modality is appropriate in ESRD patients.

Impact of dialysis duration and glucose absorption on nutritional indices in stable continuous ambulatory peritoneal dialysis patients

OBJECTIVE

The presence of comorbidity is a risk factor for both poor nutrition and poor outcome in continuous ambulatory peritoneal dialysis (CAPD) patients. In CAPD specifically, peritoneal glucose load is associated with a possible suppression of appetite, contributing to protein malnutrition. This study sought to explore the factors associated with malnutrition indices in stable peritoneal dialysis patients without significant comorbidity, and to assess the impact of peritoneal glucose absorption on nutrition parameters.

DESIGN

This was a cross-sectional observational study.

SETTING

This study took place in the peritoneal dialysis department of a university hospital, and involved outpatients.

PATIENTS

There were 23 stable, comorbidity-free CAPD patients (9 women), aged 54 +/- 12 years, with a CAPD duration of 28 +/- 25 months (values are mean +/- SD unless otherwise noted).

METHODS

Nutritional status was evaluated by means of anthropometric and serum measurements. A peritoneal equilibration test was performed, and daily glucose absorption was measured. Lean body mass (LBM) was assessed through creatinine kinetics.

RESULTS

A significant impact of CAPD duration was found. Patients in the upper quartile of CAPD duration had worse nutritional parameters compared with the rest of the group: their mid-upper-arm surface area and fat surface area were lower (65 +/- 9 cm(2) vs. 78 +/- 6.2 cm(2) and 16 +/- 5.3 cm(2) vs. 26 +/- 9.5 cm(2), respectively, P < .05), their albumin concentration was lower (36 +/- 0.5 g/L vs. 42 +/- 4 g/L, P < .05), and their cholesterol and triglycerides were lower (3.5 +/- 0.5 vs. 5.2 +/- 1 mmol/L and 1.3 +/- 0.6 vs. 2.3 +/- 1.1 mmol/L, respectively, P < .05). No significant correlations between peritoneal glucose absorption and these indices were found.

CONCLUSION

The duration of dialysis treatment, but not peritoneal glucose absorption, is a predictor of malnutrition in stable, comorbidity-free CAPD patients.

Hypoalbuminemia is Also a Marker of Fluid Excess Determined by Bioelectrical Impedance Parameters in Dialysis Patients

Hypoalbuminemia may be secondary to volume expansion conditions and an independent risk factor for cardiovascular disease. Bioelectrical impedance analysis (BIA) is an accurate, non-invasive method to measure body composition, especially the water compartments in humans. The aim of this cross-sectional study is to evaluate the relationship between serum albumin concentration (SA) and hydration state measured by whole BIA. The study investigated 108 non-selected patients (73 on hemodialysis, 35 on peritoneal dialysis) with a mean age of 61.4 +/- 15.6 years, 42.7% of whom were female. The patients were allotted to groups according to their SA: Group 1, < or = 3.5 g/dL; Group 2, 3.6-4.0 g/dL; and Group 3, >4.0 g/dL. The BIA parameters used included: total body water, intracellular water (ICW), extracellular water (ECW), phase angle (PA), body cell mass (BCM), ICW/ECW ratio and ICW/ECW ratio patients/controls (fluid index). Seventy-five healthy volunteers formed the control group. A strong positive correlation was found between the PA and fluid index (r (2) = 0.993, P < 0.001), as well as between the PA and SA (r = 0.386, P < 0.001), and the ICW/ECW ratio and SA (r = 0.227, P < 0.001). The ECW was negatively correlated with SA (r = -0.330, P < 0.001). Every 0.1 g/dL decrease in SA was associated with a 0.33 L increase in ECW. Group 1 patients had lower reactance (P = 0.006), PA (P < 0.001), BCM (P = 0.012), fluid index (P < 0.001) and ICW/ECW ratio (P = 0.015), and an increased ECW (NS) than groups 2 and 3. We conclude that hypoalbuminemia is also a marker of fluid excess. The SA is associated to the fluid index and the PA allows assessment of the dry weight and its variations in an individualized manner in dialysis patients.

Estimates of body water, fat-free mass, and body fat in patients on peritoneal dialysis by anthropometric formulas

BACKGROUND

Anthropometric formulas that are used to estimate body water in peritoneal dialysis patients can also be used to estimate fat-free mass and body fat. Evaluation of body composition by the anthropometric formulas rests on two assumptions: (1) fat contains no water, and (2) the water content of the fat-free mass is constant (72%).

METHODS

We compared estimates of body water, fat-free mass, and body fat by anthropometric formulas to estimates employing dilution of tracer substances to measure body water and standard methods to analyze body composition in studies performed on peritoneal dialysis patients. We also analyzed the potential errors of the estimates of body composition by the formulas.

RESULTS

Estimates of the average body composition provided by the anthropometric formulas agreed with estimates provided by the standard methods. However, these formulas have the potential of introducing large errors when estimating body composition in individuals differing from the average subject, either because the anthropometric formulas do not account for major determinants of body composition, such as physical exercise, nutrition, and catabolic illness, or because these formulas systematically overestimate body water in subjects who are obese or experiencing volume excess.

CONCLUSION

Anthropometric formulas currently in existence can provide only approximations of body composition and may be the sources of large errors in evaluating body composition in peritoneal dialysis patients. The potential errors include estimates of body water. These errors may alter the interpretation of urea kinetic studies in certain categories of peritoneal dialysis patients (e.g., obese subjects).

Hypoalbuminemia is a marker of overhydration in chronic maintenance patients on dialysis

Hypoalbuminemia is an important risk factor for increased morbidity and mortality in patients on dialysis. Hypoalbuminemia is usually attributed to malnutrition or a state of chronic inflammation. However, hypoalbuminemia could result from hemodilution caused by chronic volume expansion. We prospectively evaluated 142 patients on chronic dialysis for 12 consecutive months (mean age: 62 +/- 14 years; 41% women, 37% African American, 43% diabetic, 27% peritoneal dialysis). Intracellular (ICW) and extracellular (ECW) water content was estimated using single frequency bioelectrical impedance. Values in each albumin grouping (group 1, < 3.5 g/dl; group 2, 3.5-4.0 g/dl; group 3, > 4.1 g/dl) are expressed as annual mean +/- SEM. Group 1 patients had lower body weight, body mass index, blood urea nitrogen, serum creatinine, dietary protein intake, and ICW content than those in groups 2 and 3. ECW was significantly increased in group 1 when compared with groups 2 and 3 (p < 0.001). A significant correlation was found between ECW and serum albumin concentration (R = 0.2230; p < 0.0001). Resistance and reactance were decreased in group 1 when compared with groups 2 and 3 (p < 0.05 and 0.001, respectively), causing the resultant bioimpedance vector to move away from the normal population range into the overhydration boundaries. We conclude that, in addition to malnutrition and chronic inflammation, overhydration is a contributor to hypoalbuminemia in patients on chronic dialysis.

Body composition analysis by bioelectrical impedance in chronic maintenance dialysis patients: comparisons to the National Health and Nutrition Examination Survey III

OBJECTIVE

To compare bioelectrical impedance analysis derived parameters in chronic maintenance dialysis patients to those obtained in National Health and Nutrition Examination Survey (NHANES) III.

DESIGN

Cross-sectional nutritional surveillance study.

SETTING

Hospital-based, not-for-profit chronic maintenance dialysis center.

PATIENTS

A total of 913 chronic maintenance dialysis patients and a subset of 10,263 subjects from NHANES III who underwent bioelectrical impedance analysis. Independent (Predictor) Variables: Bioelectrical impedance parameters including resistance, reactance, phase angle, and total body capacitance.

MAIN OUTCOME MEASURES

Total body water, intracellular and extracellular water, body cell mass, fat free mass, fat mass.

RESULTS

Relative to NHANES III, end-stage renal disease patients have lower resistance (3%), reactance (26%), phase angle (28%); and intracellular water (9%) values, whereas extracellular water content is 17% higher (P < .001). In addition, body cell mass, fat free mass, and fat mass were lower in end-stage renal disease patients when compared with NHANES III subjects (9%, 3%, and 12%, respectively; P < .001).

CONCLUSIONS

End-stage renal disease patients have a lower tissue mass than the general population and remain in a state of overhydration while on chronic maintenance dialysis therapy.