Body weight is a fluctuating parameter in hemodialysis patients

Association of body weight changes with mortality in incident hemodialysis patients

Background

Incident hemodialysis patients may experience rapid weight loss in the first few months of starting dialysis. However, trends in weight changes over time and their associations with survival have not yet been characterized in this population.

Methods

In a large contemporary US cohort of 58 106 patients who initiated hemodialysis during 1 January 2007-31 December 2011 and survived the first year of dialysis, we observed trends in weight changes during the first year of treatment and then examined the association of post-dialysis weight changes with all-cause mortality.

Results

Patients' post-dialysis weights rapidly decreased and reached a nadir at the 5th month of dialysis with an average decline of 2% from baseline, whereas obese patients (body mass index ≥30 kg/m 2 ) did not reach a nadir and lost ∼3.8% of their weight by the 12th month. Compared with the reference group (-2 to 2% changes in weight), the death hazard ratios (HRs) of patients with -6 to -2% and greater than or equal to -6% weight loss during the first 5 months were 1.08 (95% confidence interval, 1.02-1.14) and 1.14 (1.07-1.22), respectively. Moreover, the death HRs with 2-6% and ≥6% weight gain during the 5th to 12th months were 0.91 (0.85-0.97) and 0.92 (0.86-0.99), respectively.

Conclusions

In patients who survive the first year of hemodialysis, a decline in post-dialysis weight is observed and reaches a nadir at the 5th month. An incrementally larger weight loss during the first 12 months is associated with higher death risk, whereas weight gain is associated with greater survival during the 5th to 12th month but not in the first 5 months of dialysis therapy.

Examining the robustness of the obesity paradox in maintenance hemodialysis patients: a marginal structural model analysis

BACKGROUND

The inverse association between body mass index (BMI) and mortality observed in patients treated with maintenance hemodialysis (MHD), also known as the obesity paradox, may be a result of residual confounding. Marginal structural model (MSM) analysis, a technique that accounts for time-varying confounders, may be more appropriate to investigate this association. We hypothesize that after applying MSM, the inverse association between BMI and mortality in MHD patients is attenuated.

METHODS

We examined the associations between BMI and all-cause mortality among 123 624 adult MHD patients treated during 2001-6. We examined baseline and time-varying BMI using Cox proportional hazards models and MSM while considering baseline and time-varying covariates, including demographics, comorbidities and markers of malnutrition and inflammation.

RESULTS

The patients included 45% women and 32% African Americans with a mean age of 61(SD 15) years. In all models, BMI showed a linear incremental inverse association with mortality. Compared with the reference (BMI 25 to <27.5 kg/m(2)), a BMI of <18 kg/m(2) was associated with a 3.2-fold higher death risk [hazard ratio (HR) 3.17 (95% CI 3.05-3.29)], and mortality risks declined with increasing BMI with the greatest survival advantage of 31% lower risk [HR 0.69 (95% CI 0.64-0.75)] observed with a BMI of 40 to <45 kg/m(2).

CONCLUSIONS

The linear inverse relationship between BMI and mortality is robust across models including MSM analyses that more completely account for time-varying confounders and biases.

Serum albumin, body weight and inflammatory parameters in chronic hemodialysis patients: a three-year longitudinal study

BACKGROUNDS AND AIMS

The present study aimed at making prospective longitudinal measurements of nutritional and inflammatory parameters to determine whether nutritional and inflammatory status decline or increase over time in a cohort of prevalent hemodialysis patients, and to evaluate which factors influence eventual changes.

PATIENTS

64 hemodialysis patients were followed at 0, 3, 6, 9, 12, 15, 18, 21, 24, 27, 30, 33, and 36 months. At each follow-up visit, dry body weight, serum albumin, serum total cholesterol, total white blood cells, total lymphocyte count, serum glucose, C-reactive protein, ferritin, fibrinogen, hemoglobin, and weekly erythropoietin dose were assessed.

MAIN OUTCOME MEASURES

Changes in nutritional and inflammatory parameters over time.

RESULTS

43 patients completed the study at 36 months. Mean serum albumin levels (g/dl) improved significantly between baseline (3.76 +/- 0.24) and 36 months (3.93 +/- 0.27) (F = 4.005; p = 0.0009). Dialytic age was significantly associated with changes of serum albumin (F = 2.797; p = 0.028). The mean dry weight slightly remained stable over time (F = 1.473; p = 1.0) as well as the level of total cholesterol (p = 0.77) and lymphocyte count (F = 1.539; p = 0.186). Over time, the levels of C-reactive protein tended to decrease, although the differences were not statistically significant (F = 1.332; p = 0.19). Over time, the serum level of fibrinogen (F = 0.422; p = 0.17) and ferritin (F = 0.314; p = 0.52) remained stable. The number of white blood cells significantly decreased over time (F = 4.691; p = 0.0079) and dialytic age (F = 3.214; p = 0.015) was the variable significantly associated with such decline. The hemoglobin levels (F = 1.423; p = 0.14) and the weekly erythropoietin dose did not change significantly during the study (F = 1.019; p = 0.61), nor did the serum glucose levels (F = 1.231; p = 0.10).

CONCLUSION

These results support the hypothesis that end-stage renal disease and HD are not necessarily associated with deterioration of the nutritional status over time.

Inflammatory syndrome in patients on hemodialysis

Mortality is markedly elevated in hemodialysis (HD) patients. Between 30 and 50% of prevalent patients have elevated serum levels of inflammatory markers such as C-reactive protein and IL-6. The presence of inflammation, chronic or episodic, has been found to be associated with increased mortality risk. The causes of inflammation are multifactorial and include patient-related factors, such as underlying disease, comorbidity, oxidative stress, infections, obesity, and genetic or immunologic factors, or on the other side, HD-related factors, mainly depending on the membrane biocompatibility and dialysate quality. The adequate knowledge of these causes and their prevention or treatment if possible may contribute to improving the inflammatory state of patients who are on HD and possibly their mortality.

The effect of dialysis membrane flux on amino acid loss in hemodialysis patients

We examined whether high flux membranes (HF) may induce a greater loss of amino acids compared to low flux membranes (LF). Ten hemodialysis patients participated in this study. Pre- and post-hemodialysis plasma amino acid profiles were measured by reverse-phase high pressure liquid chromatography for both HF and LF. We measured the dialysate amino acid losses during hemodialysis. The reduction difference for plasma total amino acid (TAA), essential amino acid (EAA), and branch chained amino acid (BCAA) was not significantly different in comparisons between the two membranes. (HF vs. LF; TAA 66.85 +/- 30.56 vs. 53.78 +/- 41.28, p=0.12; EAA 14.79 +/-17.16 vs. 17.97 +/- 28.69, p=0.12; BCAA 2.21 +/- 6.08 vs. 4.16 +/- 10.98 mg/L, p=0.13). For the HF, the reduction in plasma amino acid levels for TAA and EAA were statistically significant. Although it was not statistically significant, the dialysate losses of BCAA were greater than the reduction in plasma (plasma reduction vs. dialysate loss; HF 2.21 +/- 6.08 vs. 6.58 +/- 4.32, LF 4.16 +/- 10.98 vs. 7.96 +/- 3.25 mg/L). HF with large pores and a sieving coefficient do not influence dialysate amino acid losses. Hemodialysis itself may influence the dialysate amino acid losses and may have an effect on protein metabolism.

UNRESOLVED ISSUES IN DIALYSIS: Adiposity in Dialysis: Good or Bad?

There exists in the general population a complex and mostly positive relationship between adiposity and mortality risk. Because the dialysis population has a high prevalence of excess adiposity, in addition to a strikingly elevated mortality rate, the effects of obesity are of potential clinical importance. In contrast to the general population, the preponderance of data in dialysis, particularly hemodialysis patients, suggest that adiposity has a neutral or even protective association with mortality. Although methodological concerns exist with regards to confounding and survival bias, among others, the major limitation of this body of literature is its inability to establish causality. Thus, although obese dialysis patients, with certain exceptions, appear to live longer, there is no evidence to suggest that intentional weight loss adversely affects patient outcomes. In light of these limitations and the substantial body of literature implicating obesity as a pathophysiological state, it is currently premature to advocate for excess adiposity as being beneficial or intentional weight loss as dangerous. Decisions regarding optimal weight should be made by clinicians on an individual basis and with close supervision and follow-up. Efforts should be made to preserve lean mass during weight loss regimens by encouraging exercise and recommending sufficient protein consumption. Future research efforts in this area should focus on interventional trials designed to manipulate weight and measure outcomes, identifying potentially beneficial secretory products of adipose tissue, and documenting obesity's effects on quality of life and resource utilization in the dialysis setting.

Multiple Factors Affect Renal Dietitians’ Use of the NKF-K/DOQI Adult Nutrition Guidelines

OBJECTIVE

We investigated the components of the National Kidney Foundation-Kidney Disease Outcomes Quality Initiative Nutrition Guidelines that are implemented by renal dietitians and the types of resources and support available to assist in implementing these guidelines.

DESIGN AND PARTICIPANTS

A 49-item survey was mailed to 1694 dietitians in the United States. who were members of the National Kidney Foundation Council on Renal Nutrition in June 2003. The survey included sections on clinical practice, tools available to perform nutrition assessments, daily activities of the dietitian, and demographic and professional questions.

RESULTS

Of the 1694 surveys mailed, 951 were returned (56% response rate); 848 were useable (89%). The primary employer was for-profit dialysis units (67%) and the mean (+/- SD) number of patients per dietitian was 104.9 +/- 48.3. Virtually all of the dietitians were aware of the nutrition guidelines (97%); 58% read all of the guidelines, whereas only 41% read some of the guidelines. Ninety-two percent of respondents implemented at least one guideline in their clinical practice; 72% and 55% had implemented 5 and 10 guidelines, respectively; but only 5% implemented all of the guidelines. Several barriers to implementation included lack of tools such as computers, calipers, and food models (57%); inadequate time including high dietitian-to-patient ratios (40%); and lack of administrative support from the dialysis unit (29%).

CONCLUSIONS

There are multiple barriers that prevent the adequate assessment of the nutritional status of dialysis patients. Only after these resources are provided will it be possible to determine the impact of the nutrition guidelines on patient outcomes.

Are nutritional status indicators associated with mortality in the Hemodialysis (HEMO) Study?

BACKGROUND

The purpose of this study was to determine if indicators of nutritional status were associated with subsequent mortality in hemodialysis patients.

METHODS

Twelve selected nutrition indicators were measured prior to randomization in the Mortality and Morbidity in Hemodialysis (HEMO) Study. Relative risks (RR) of mortality were assessed at <6 months and >6 months of follow-up using Cox regression after controlling for case mix, comorbidity, and treatment assignment (high vs. standard Kt/V and high vs. low membrane flux).

RESULTS

Low values of most nutritional status indicators were associated with increased RR of mortality. RRs were greatest over the short term (<6 months) and diminished with increasing follow-up (>6 months). Increases in body mass index (BMI) at lower levels (e.g., < or =25 kg/m(2)) and increases in serum albumin at any level were associated with reduced short-term RR, even after adjusting for case mix, treatment assignment, and for the joint effects of equilibrated normalized protein catabolic rate, total cholesterol, and serum creatinine. For >6 months' follow-up, increases in values among those with lower levels of BMI and serum albumin (< or =3.635 g/dL) and increases in all serum creatinine levels were associated with lower RR.

CONCLUSION

Nutrition indicators are associated with subsequent mortality in a time-dependent manner, with greatest effects at <6 months of follow-up. The RR for these indicators may also vary within different ranges of values.

The effect of dialysis dose and membrane flux on nutritional parameters in hemodialysis patients: Results of the HEMO Study

BACKGROUND

The effect of standard or high dialysis dose and low or high dialysis flux on nutritional status was ascertained in 1846 maintenance hemodialysis patients enrolled in the HEMO Study.

METHODS

Serum albumin levels, equilibrated protein catabolic rate, and postdialysis weight were obtained monthly, while adjusted protein and energy intake, self-reported appetite assessment, upper arm circumference, and calf circumference were obtained yearly. To account for patient attrition due to death or transfer, three statistical models were used to test the effects of the study interventions on longitudinal changes in nutritional parameters.

RESULTS

During the first 3 years of follow-up, neither mean serum albumin levels, which declined by 0.21 g/dL, nor mean postdialysis weight, which declined by 2.7 kg, were significantly affected by either study intervention. Mean levels of all anthropometric measures declined during follow-up. For years 1, 2, and 3, the mean +/- SE declines in upper arm and calf circumferences were 0.35 +/- 0.16 cm (P= 0.031) and 0.31 +/- 0.13 (P= 0.015) cm less, respectively, in the high flux compared to the low flux group. Appetite scores and mean equilibrated protein catabolic rate also declined in all randomized groups; however, the average decline in equilibrated protein catabolic rate during years 1, 2, and 3 was 0.019 +/- 0.007 g/kg/day less in the high dose than the standard dose group (P= 0.007). There was no significant change in either mean energy or protein intake from diet records over time, and neither parameter was affected by the study interventions.

CONCLUSION

Although the dose and flux interventions may subtly influence certain nutritional parameters, neither intervention prevented deterioration in nutritional status over time.