Red Cell Distribution Width and Mortality in Hemodialysis Patients

BACKGROUND

Red cell distribution width (RDW) is an index of red blood cell volume variability that has historically been used as a marker of iron deficiency anemia. More recently, studies have shown that elevated RDW is associated with higher mortality risk in the general population. However, there is lack of data demonstrating the association between RDW and mortality risk in hemodialysis (HD) patients. We hypothesized that higher RDW is associated with higher mortality in HD patients.

STUDY DESIGN

Retrospective observational study using a large HD patient cohort.

SETTING & PARTICIPANTS

109,675 adult maintenance HD patients treated in a large dialysis organization from January 1, 2007, to December 31, 2011.

PREDICTOR

Baseline and time-varying RDW, grouped into 5 categories: <14.5%, 14.5% to <15.5%, 15.5% to <16.5%, 16.5% to <17.5%, and ≥17.5%. RDW of 15.5% to <16.5% was used as the reference category.

OUTCOME

All-cause mortality.

RESULTS

Mean age of study participants was 63±15 (SD) years and the study cohort was 44% women. In baseline and time-varying analyses, there was a graded association between higher RDW and incrementally higher mortality risk. Receiver operating characteristic, net reclassification analysis, and integrated discrimination improvement analyses demonstrated that RDW is a stronger predictor of mortality as compared with traditional markers of anemia, such as hemoglobin, ferritin, and iron saturation values.

LIMITATIONS

Lack of comprehensive data that may be associated with both RDW and HD patient outcomes, such as blood transfusion data, socioeconomic status, and other unknown confounders; therefore, the possibility of residual confounding could not be excluded. Also, lack of information for cause of death; thus, cardiovascular mortality outcomes could not be examined.

CONCLUSIONS

In HD patients, higher RDW is associated with incrementally higher mortality risk. RDW is also a stronger predictor of mortality than traditional laboratory markers of anemia. Further studies are needed to determine the mechanisms underlying the association between RDW and mortality.

Association between serum resistin level and outcomes in kidney transplant recipients

Resistin is an adipocytokine that is associated with inflammation, coronary artery disease, and other types of cardiovascular disease among patients with normal kidney function. However, little is known about the association of resistin with outcomes in kidney transplant recipients. We collected socio-demographic and clinical parameters, medical and transplant history, and laboratory data from 988 prevalent kidney transplant recipients enrolled in the Malnutrition-Inflammation in Transplant-Hungary Study (MINIT-HU study). Serum resistin levels were measured at baseline. Associations between serum resistin level and death with a functioning graft over a 6-year follow-up period were examined in unadjusted and adjusted models. The mean±SD age of the study population was 51 ± 13 years, among whom 57% were men and 21% were diabetics. Median serum resistin concentrations were significantly higher in patients who died with a functioning graft as compared to those who did not die during the follow-up period (median [IQR]: 22[15-26] vs. 19[14-22] ng/ml, respectively; P < 0.001). Higher serum resistin level was associated with higher mortality risk in both unadjusted and fully adjusted models: HRs (95% CI): 1.33(1.16-1.54) and 1.21(1.01-1.46), respectively. In prevalent kidney transplant recipients, serum resistin was an independent predictor of death with a functioning graft.

Association of Vascular Access Type with Mortality, Hospitalization, and Transfer to In-Center Hemodialysis in Patients Undergoing Home Hemodialysis

BACKGROUND AND OBJECTIVES

In individuals undergoing in-center hemodialysis (HD), use of central venous catheters (CVCs) is associated with worse clinical outcomes compared with use of arteriovenous access. However, it is unclear whether a similar difference in risk by vascular access type is present in patients undergoing home HD.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

Our study examined the associations of vascular access type with all-cause mortality, hospitalization, and transfer to in-center HD in patients who initiated home HD from 2007 to 2011 in 464 facilities in 43 states in the United States. Patients were followed through December 31, 2011. Data were analyzed using competing risks hazards regression, with vascular access type at the start of home HD as the primary exposure in a propensity score-matched cohort (1052 patients; 526 with CVC and 526 with arteriovenous access).

RESULTS

Over a median follow-up of 312 days, 110 patients died, 604 had at least one hospitalization, and 202 transferred to in-center hemodialysis. Compared with arteriovenous access use, CVC use was associated with higher risk for mortality (hazard ratio, 1.73; 95% confidence interval, 1.18 to 2.54) and hospitalization (hazard ratio, 1.19; 95% confidence interval, 1.02 to 1.39). CVC use was not associated with increased risk for transfer to in-center HD. The results of analyses in the entire unmatched cohort (2481 patients), with vascular access type modeled as a baseline exposure at start of home HD or a time-varying exposure, were similar. Analyses among a propensity score-matched cohort of patients undergoing in-center HD also showed similar risks for death and hospitalization with use of CVCs.

CONCLUSIONS

In a large cohort of patients on home HD, CVC use was associated with higher risk for mortality and hospitalization. Additional studies are needed to identify interventions which may reduce risk associated with use of CVCs among patients undergoing home HD.

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.

What Is Known and Unknown About Twice-Weekly Hemodialysis

BACKGROUND

The 2006 Kidney Disease Outcomes Quality Initiative guidelines suggest twice-weekly or incremental hemodialysis for patients with substantial residual kidney function (RKF). However, in most affluent nations de novo and abrupt transition to thrice-weekly hemodialysis is routinely prescribed for all dialysis-naïve patients regardless of their RKF. We review historical developments in hemodialysis therapy initiation and revisit twice-weekly hemodialysis as an individualized, incremental treatment especially upon first transitioning to hemodialysis therapy.

SUMMARY

In the 1960's, hemodialysis treatment was first offered as a life-sustaining treatment in the form of long sessions (≥10 hours) administered every 5 to 7 days. Twice- and then thrice-weekly treatment regimens were subsequently developed to prevent uremic symptoms on a long-term basis. The thrice-weekly regimen has since become the 'standard of care' despite a lack of comparative studies. Some clinical studies have shown benefits of high hemodialysis dose by more frequent or longer treatment times mainly among patients with limited or no RKF. Conversely, in selected patients with higher levels of RKF and particularly higher urine volume, incremental or twice-weekly hemodialysis may preserve RKF and vascular access longer without compromising clinical outcomes. Proposed criteria for twice-weekly hemodialysis include urine output >500 ml/day, limited interdialytic weight gain, smaller body size relative to RKF, and favorable nutritional status, quality of life, and comorbidity profile.

KEY MESSAGES

Incremental hemodialysis including twice-weekly regimens may be safe and cost-effective treatment regimens that provide better quality of life for incident dialysis patients who have substantial RKF. These proposed criteria may guide incremental hemodialysis frequency and warrant future randomized controlled trials.

Lean Body Mass and Survival in Hemodialysis Patients and the Roles of Race and Ethnicity

BACKGROUND

Lean body mass (LBM) represents the "fat-free" muscle mass in hemodialysis (HD) patients and is an important nutritional measure. Previous studies have found that both higher LBM and body mass index (BMI) were related to greater survival in HD patients. Additional studies have shown differences in survival across racial-ethnic groups of HD patients. However, the association of LBM and mortality across racial-ethnic subgroups has not been examined.

OBJECTIVE

We hypothesize that racial differences in LBM affect the mortality in HD patients.

SETTING AND SUBJECTS

Chronic HD patients from a large dialysis organization in the United States.

PREDICTORS

Estimated LBM (eLBM), self-identified racial subgroups.

MAIN OUTCOME MEASURE

5-year survival.

STUDY DESIGN

We examined the association between baseline eLBM and survival using Cox proportional hazard models adjusted for demographics, comorbidities, and laboratory measures. Associations were examined across subgroups of race-ethnicity (non-Hispanic white, African American, and Hispanic) and BMI.

RESULTS

The final cohort included 117,683 HD patients, who were 62 ± 15 (mean ± standard deviation) years old, 43% women and 59% with diabetes mellitus. Higher eLBM was linearly associated with lower mortality. Compared with the reference group (48.4-<50.5 kg), patients with the lowest eLBM (<41.3 kg) had a 1.4-fold higher risk of mortality (hazard ratio: 1.37; 95% confidence interval: 1.30-1.44) in the fully adjusted model. A similar linear association was seen among patients with BMI < 35 kg/m(2) and in non-Hispanic whites and African American subgroups. However, higher eLBM was not associated with improved survival in Hispanic patients or patients with BMI ≥ 35 kg/m(2).

LIMITATION

Potential residual confounding.

CONCLUSIONS

Higher eLBM is associated with a lower mortality risk in HD patients, especially among non-Hispanic white and African American groups. Hispanic patients do not demonstrate a similar inverse relationship. The association between LBM and mortality among different racial groups of HD patients deserves additional study.

Association of Body Mass Index with Clinical Outcomes in Non-Dialysis-Dependent Chronic Kidney Disease: A Systematic Review and Meta-Analysis

BACKGROUND

Previous studies have not shown a consistent link between body mass index (BMI) and outcomes such as mortality and kidney disease progression in non-dialysis-dependent chronic kidney disease (CKD) patients. Therefore, we aimed to complete a systematic review and meta-analysis study on this subject.

METHODS

We searched MEDLINE, EMBASE, Web of Science, Cumulative Index to Nursing and Allied Health Literature (CINAHL), and Cochrane Central Register of Controlled Trials (CENTRAL), and screened 7,123 retrieved studies for inclusion. Two investigators independently selected the studies using predefined criteria and assessed each study's quality using the Newcastle-Ottawa quality assessment scale. We meta-analyzed the results based on the BMI classification system by the WHO.

RESULTS

We included 10 studies (with a total sample size of 484,906) in the systematic review and 4 studies in the meta-analyses. The study results were generally heterogeneous. However, following reanalysis of the largest reported study and our meta-analyses, we observed that in stage 3-5 CKD, being underweight was associated with a higher risk of death while being overweight or obese class I was associated with a lower risk of death; however, obesity classes II and III were not associated with risk of death. In addition, reanalysis of the largest available study showed that a higher BMI was associated with an incrementally higher risk of kidney disease progression; however, this association was attenuated in our pooled results. For earlier stages of CKD, we could not complete meta-analyses as the studies were sparse and had heterogeneous BMI classifications and/or referent BMI groups.

CONCLUSION

Among the group of patients with stage 3-5 CKD, we found a differential association between obesity classes I-III and mortality compared to the general population, indicating an obesity paradox in the CKD population.

Association of Body Mass Index With Mortality in Peritoneal Dialysis Patients: A Systematic Review and Meta-Analysis

♦

BACKGROUND

Although higher body mass index (BMI) is associated with better outcomes in hemodialysis patients, the relationship in peritoneal dialysis (PD) patients is less clear. We aimed to synthesize the results from all large and high-quality studies to examine whether underweight, overweight, or obesity is associated with any significantly different risk of death in peritoneal dialysis patients. ♦

METHODS

We searched MEDLINE, EMBASE, Web of Science, CINAHL, and Cochrane CENTRAL, and screened 7,123 retrieved studies for inclusion. Two investigators independently selected the studies using predefined criteria and assessed each study's quality using the Newcastle-Ottawa Quality Assessment Scale. We meta-analyzed the results of the largest studies with no overlap in their data sources. ♦

RESULTS

We included 9 studies (n = 156,562) in the systematic review and 4 studies in the meta-analyses. When examined without stratifying studies by follow-up duration, the results of the studies were inconsistent. Hence, we pooled the study results stratified based upon their follow-up durations, as suggested by a large study, and observed that being underweight was associated with higher 1-year mortality but had no significant association with 2- and 3- to 5-year mortalities. In contrast, being overweight or obese was associated with lower 1-year mortality but it had no significant association with 2-, and 3- to 5-year mortalities. ♦

CONCLUSION

Over the short-term, being underweight was associated with higher mortality and being overweight or obese was associated with lower mortality. The associations of body mass with mortality were not significant over the long-term.

Pre-dialysis serum sodium and mortality in a national incident hemodialysis cohort

BACKGROUND

A consistent association between low serum sodium measured at a single-point-in-time (baseline sodium) and higher mortality has been observed in hemodialysis patients. We hypothesized that both low and high time-varying sodium levels (sodium levels updated at quarterly intervals as a proxy of short-term exposure) are independently associated with higher death risk in hemodialysis patients.

METHODS

We examined the association of baseline and time-varying pre-dialysis serum sodium levels with all-cause mortality among adult incident hemodialysis patients receiving care from a large national dialysis organization during January 2007-December 2011. Hazard ratios were estimated using multivariable Cox models accounting for case-mix+laboratory covariates and incrementally adjusted for inter-dialytic weight gain, blood urea nitrogen and glucose.

RESULTS

Among 27 180 patients, a total of 7562 deaths were observed during 46 194 patient-years of follow-up. Median (IQR) at-risk time was 1.4 (0.6, 2.5) years. In baseline analyses adjusted for case-mix+laboratory results, sodium levels <138 mEq/L were associated with incrementally higher mortality risk, while the association of sodium levels ≥140 mEq/L with lower mortality reached statistical significance only for the highest level of pre-dialysis sodium (reference: 138-<140 mEq/L). In time-varying analyses, we observed a U-shaped association between sodium and mortality such that sodium levels <138 and ≥144 mEq/L were associated with higher mortality risk. Similar patterns were observed in models incrementally adjusted for inter-dialytic weight gain, blood urea nitrogen and glucose.

CONCLUSIONS

We observed a U-shaped association of time-varying pre-dialysis serum sodium and all-cause mortality in hemodialysis patients, suggesting that both hypo- and hypernatremia carry short-term risk in this population.

Serum phosphorus and association with anemia among a large diverse population with and without chronic kidney disease

BACKGROUND

We hypothesized that phosphorus has an effect on anemia in both normal kidney function and early chronic kidney disease (CKD). We sought to determine whether higher phosphorus levels are associated with anemia in a large diverse population without CKD and early CKD.

METHODS

This study is a historical population-based study within the Kaiser Permanente Southern California health system (1 January 1998 to 31 December 2013) among individuals aged 18 years and older with estimated glomerular filtration rate >30 mL/min/1.73 m(2) and measurements of serum phosphorus, creatinine and hemoglobin. Individuals were excluded if they had secondary causes of anemia. Odds ratio (OR) estimated for moderate anemia defined as hemoglobin <11 g/dL for both sexes. Mild anemia was defined as <12 g/dL (females) and <13 g/dL (males).

RESULTS

Among 155 974 individuals, 4.1% had moderate anemia and 12.9% had mild anemia. Serum phosphorus levels ≥3.5 mg/dL were associated with both mild and moderate anemia. Moderate anemia OR (95% confidence interval) was 1.16 (1.04-1.29) for every 0.5 mg/dL phosphorus increase and 1.26 (1.07-1.48) in the highest versus middle phosphorus tertile. Additional independent anemia risk factors, including female sex, Asian race, diabetes, low albumin and low iron saturation, were observed, but did not alter the anemia-phosphorus association.

CONCLUSIONS

Higher phosphorus levels were associated with a greater likelihood for anemia in a population with early CKD and normal kidney function. Phosphorus may be a biomarker for anemia and may affect aspects of hematopoiesis.

Hypomagnesemia and Mortality in Incident Hemodialysis Patients

BACKGROUND

In the general population, low serum magnesium levels are associated with poor outcomes and death. While limited data suggest that low baseline magnesium levels may be associated with higher mortality in hemodialysis (HD) patients, the impact of changes in magnesium levels over time is unknown.

STUDY DESIGN

We examined the association of time-varying serum magnesium levels with all-cause mortality using multivariable time-varying survival models adjusted for clinical characteristics and other time-varying laboratory measures.

SETTING & PARTICIPANTS

9,359 maintenance HD patients treated in a large dialysis organization between 2007 and 2011.

PREDICTOR

Time-varying serum magnesium levels across 5 magnesium increments (<1.8, 1.8-<2.0, 2.0-<2.2, 2.2-<2.4, and ≥2.4mg/dL).

OUTCOME

All-cause mortality.

RESULTS

2,636 individuals died over 5 years. Time-varying serum magnesium levels < 2.0mg/dL were associated with higher mortality after adjustment for demographics and comorbid conditions, including hypertension, diabetes, and malignancies (reference: magnesium, 2.2-<2.4mg/dL): adjusted HRs for serum magnesium level < 1.8 and 1.8 to <2.0mg/dL were 1.39 (95% CI, 1.23-1.58; P<0.001) and 1.20 (95% CI, 1.06-1.36; P=0.004), respectively. Some associations were attenuated to the null after incremental adjustment for laboratory test results, particularly serum albumin. However, among patients with serum albumin measurements, low albumin level (<3.5g/dL) and magnesium level < 2.0mg/dL were associated with an additional death risk (adjusted HR, 1.17; 95% CI, 1.05-1.31; P=0.004), whereas patients with high serum albumin levels (≥3.5g/dL) exhibited low death risk (adjusted HRs of 0.53 and 0.53 [P≤0.001] for magnesium < 2.0 and ≥2.0mg/dL, respectively; reference: albumin < 3.5g/dL and magnesium ≥ 2.0mg/dL).

LIMITATIONS

Causality cannot be determined, and residual confounding cannot be excluded given the observational study design.

CONCLUSIONS

Lower serum magnesium levels are associated with higher mortality in HD patients, including those with hypoalbuminemia. Interventional studies are warranted to examine whether correction of hypomagnesemia ameliorates adverse outcomes in this population.

Changes in pulse pressure during hemodialysis treatment and survival in maintenance dialysis patients

BACKGROUND AND OBJECTIVES

Pulse pressure has been shown as a risk factor for mortality in patients on maintenance hemodialysis (MHD). However, the effect of change in pulse pressure during hemodialysis on survival in a large cohort of patients on MHD has not been sufficiently investigated.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

This study examined the association between time-varying Δ pulse pressure (postdialysis minus predialysis pulse pressure) and mortality in a cohort of 98,577 patients on MHD (July 2001-June 2006) using Cox proportional hazard models with restricted cubic splines.

RESULTS

The average patient age was 62 years old; among the patients, 33% were black and 59% had diabetes. During 134,814 patient-years of at-risk time, 16,054 (16%) patients died, with 6827 (43%) of the deaths caused by cardiovascular causes. In the models including adjustment for either predialysis systolic BP or mean arterial BP, there was a U-shaped association between change in pulse pressure during hemodialysis and all-cause mortality. In the systolic BP plus case mix plus malnutrition-inflammation complex syndrome-adjusted model, large declines in pulse pressure (>-25 mmHg) and increases in pulse pressure >5 mmHg were associated with higher all-cause mortality (reference: ≥-5 to <5 mmHg): hazard ratios (95% confidence intervals [95% CIs]) for change pulse pressures of <-25, ≥-25 to <-15, ≥-15 to <-5, 5 to <15, 15 to <25, and ≥25 mmHg were 1.21 (95% CI, 1.14 to 1.29), 1.03 (95% CI, 0.97 to 1.10), 1.01 (95% CI, 0.96 to 1.06), 1.06 (95% CI, 1.01 to 1.11), 1.17 (95% CI, 1.11 to 1.24), and 1.15 (95% CI, 1.08 to 1.23), respectively. The U-shaped association was observed with cardiovascular death.

CONCLUSIONS

Modest reductions in pulse pressure after hemodialysis are associated with the greatest survival, whereas large declines or rises in pulse pressure are related to higher mortality. Trials determining how to modify pulse pressure response to improve survival in the hemodialysis population are indicated.

Thyroid functional disease: an under-recognized cardiovascular risk factor in kidney disease patients

Thyroid functional disease, and in particular hypothyroidism, is highly prevalent among chronic kidney disease (CKD) and end-stage renal disease (ESRD) patients. In the general population, hypothyroidism is associated with impaired cardiac contractility, endothelial dysfunction, atherosclerosis and possibly higher cardiovascular mortality. It has been hypothesized that hypothyroidism is an under-recognized, modifiable risk factor for the enormous burden of cardiovascular disease and death in CKD and ESRD, but this has been difficult to test due to the challenge of accurate thyroid functional assessment in uremia. Low thyroid hormone levels (i.e. triiodothyronine) have been associated with adverse cardiovascular sequelae in CKD and ESRD patients, but these metrics are confounded by malnutrition, inflammation and comorbid states, and hence may signify nonthyroidal illness (i.e. thyroid functional test derangements associated with underlying ill health in the absence of thyroid pathology). Thyrotropin is considered a sensitive and specific thyroid function measure that may more accurately classify hypothyroidism, but few studies have examined the clinical significance of thyrotropin-defined hypothyroidism in CKD and ESRD. Of even greater uncertainty are the risks and benefits of thyroid hormone replacement, which bear a narrow therapeutic-to-toxic window and are frequently prescribed to CKD and ESRD patients. In this review, we discuss mechanisms by which hypothyroidism adversely affects cardiovascular health; examine the prognostic implications of hypothyroidism, thyroid hormone alterations and exogenous thyroid hormone replacement in CKD and ESRD; and identify areas of uncertainty related to the interplay between hypothyroidism, cardiovascular disease and kidney disease requiring further investigation.

Association of thyroid functional disease with mortality in a national cohort of incident hemodialysis patients

CONTEXT

Hypothyroidism is a common condition that disproportionately affects hemodialysis patients. In the general population, hypothyroidism is associated with higher mortality, particularly in populations with underlying cardiovascular risk. Despite their heightened cardiovascular mortality, the impact of hypothyroidism on the survival of hemodialysis patients remains uncertain.

OBJECTIVE

To examine whether hypothyroidism is independently associated with higher mortality in hemodialysis patients.

DESIGN, SETTING, AND PATIENTS

Among 8840 incident hemodialysis patients receiving care from a large national dialysis provider from January 2007 to December 2011, we examined the association of hypothyroidism (TSH >5.0 mIU/L) with mortality.

MAIN OUTCOME MEASURES

Associations between baseline and time-dependent hypothyroidism with all-cause mortality were determined using case-mix adjusted Cox models. In secondary analyses, we examined the impact of low-normal, upper-normal, subclinical range, and overt range TSH levels (TSH ≥ 0.5-3.0, >3.0-5.0, >5.0-10.0, and >10.0 mIU/L, respectively) on mortality risk.

RESULTS

The study population consisted of 1928 (22%) hypothyroid and 6912 (78%) euthyroid patients. Baseline and time-dependent hypothyroidism were associated with higher mortality: adjusted hazard ratios (95% confidence intervals) were 1.47 (1.34-1.61) and 1.62 (1.45-1.80), respectively. Compared to low-normal TSH, upper-normal, subclinical hypothyroid, and overt hypothyroid TSH levels were associated with incrementally higher adjusted death risk in baseline and time-dependent analyses. In time-dependent analyses, the hypothyroidism-mortality association was increasingly stronger across higher body mass index strata.

CONCLUSIONS

Hypothyroidism as well as upper-normal TSH levels are associated with higher mortality in hemodialysis patients. Further studies are needed to determine whether restoration of TSH to low-normal levels with thyroid hormone replacement therapy ameliorates adverse outcomes in hemodialysis patients.

Association of Adiponectin With Body Composition and Mortality in Hemodialysis Patients

BACKGROUND

In the general population, circulating adiponectin is associated with a favorable cardiovascular risk profile (eg, lower triglycerides and body fat) and decreased mortality. Hemodialysis (HD) patients have comparatively higher adiponectin concentrations, but prior studies examining the adiponectin-mortality association in this population have not accounted for body composition or shown a consistent relationship.

STUDY DESIGN

Prospective cohort study.

SETTINGS & PARTICIPANTS

We examined baseline serum adiponectin concentrations in 501 HD patients across 13 dialysis centers from the prospective MADRAD (Malnutrition, Diet, and Racial Disparities in Chronic Kidney Disease) cohort (entry period, October 2011 to February 2013; follow-up through August 2013).

PREDICTOR

Serum adiponectin concentration in tertiles (tertiles 1, 2, and 3 defined as ≤16.1, >16.1-<30.1, and ≥30.1-100.0 μg/mL, respectively). Adjustment variables included case-mix and laboratory test results (age, sex, race, ethnicity, vintage, diabetes, serum albumin, total iron-binding capacity, serum creatinine, white blood cell count, phosphate, hemoglobin, and normalized protein catabolic rate), body composition surrogates (subcutaneous, visceral, and total-body fat and lean body mass), and serum lipid levels (cholesterol, high-density lipoprotein cholesterol, and triglycerides).

OUTCOMES

All-cause mortality using survival (Cox) models incrementally adjusted for case-mix and laboratory test results.

RESULTS

Among 501 HD patients, 50 deaths were observed during 631.1 person-years of follow-up. In case-mix- and laboratory-adjusted Cox analyses, the highest adiponectin tertile was associated with increased mortality versus the lowest tertile (HR, 3.35; 95% CI, 1.50-7.47). These associations were robust in analyses that additionally accounted for body composition (HR, 3.18; 95% CI, 1.61-8.24) and lipid levels (HR, 3.64; 95% CI, 1.34-7.58).

LIMITATIONS

Residual confounding cannot be excluded.

CONCLUSIONS

Higher adiponectin level is associated with a 3-fold higher death risk in HD patients independent of body composition and lipid levels. Future studies are needed to elucidate underlying mechanisms and determine therapeutic targets associated with improved outcomes in HD patients.

Dietary restrictions in dialysis patients: is there anything left to eat?

A significant number of dietary restrictions are imposed traditionally and uniformly on maintenance dialysis patients, whereas there is very little data to support their benefits. Recent studies indicate that dietary restrictions of phosphorus may lead to worse survival and poorer nutritional status. Restricting dietary potassium may deprive dialysis patients of heart-healthy diets and lead to intake of more atherogenic diets. There is little data about the survival benefits of dietary sodium restriction, and limiting fluid intake may inherently lead to lower protein and calorie consumption, when in fact dialysis patients often need higher protein intake to prevent and correct protein-energy wasting. Restricting dietary carbohydrates in diabetic dialysis patients may not be beneficial in those with burnt-out diabetes. Dietary fat including omega-3 fatty acids may be important caloric sources and should not be restricted. Data to justify other dietary restrictions related to calcium, vitamins, and trace elements are scarce and often contradictory. The restriction of eating during hemodialysis treatment is likely another incorrect practice that may worsen hemodialysis induced hypoglycemia and nutritional derangements. We suggest careful relaxation of most dietary restrictions and adoption of a more balanced and individualized approach, thereby easing some of these overzealous restrictions that have not been proven to offer major advantages to patients and their outcomes and which may in fact worsen patients' quality of life and satisfaction. This manuscript critically reviews the current paradigms and practices of recommended dietary regimens in dialysis patients including those related to dietary protein, carbohydrate, fat, phosphorus, potassium, sodium, and calcium, and discusses the feasibility and implications of adherence to ardent dietary restrictions and future research.

A review: Radiographic iodinated contrast media-induced thyroid dysfunction

CONTEXT

Thyroid hormone production is dependent on adequate iodine intake. Excess iodine is generally well-tolerated, but thyroid dysfunction can occur in susceptible individuals after excess iodine exposure. Radiological iodinated contrast media represent an increasingly common source of excess iodine.

OBJECTIVE

This review will discuss the thyroidal response after acute exposure to excess iodine; contrast iodine-induced thyroid dysfunction; risks of iodine-induced thyroid dysfunction in vulnerable populations, such as the fetus, neonate, and patients with impaired renal function; and recommendations for the assessment and treatment of contrast iodine-induced thyroid dysfunction.

METHODS

Data for this review were identified by searching PubMed, Google Scholar, and references from relevant articles from 1948 to 2014.

CONCLUSIONS

With the increase in the use of computed tomography scans in the United States, there is increasing risk of contrast-induced thyroid dysfunction. Patients at risk of developing iodine-induced thyroid dysfunction should be closely monitored after receiving iodinated contrast media and should be treated as needed.

Protein-energy wasting and uremic failure to thrive in children with chronic kidney disease: they are not small adults

Protein-energy wasting (PEW), a condition of decreased body protein and fat mass, is highly prevalent in patients with chronic kidney disease (CKD) and a potent predictor of mortality in this population. In adults with CKD, PEW has typically been defined on the basis of (1) deranged biochemical parameters, (2) reduced body mass, (3) reduced muscle mass, and (4) decreased dietary protein intake. Emerging data suggest that PEW may also commonly afflict children with CKD and have a negative impact on growth and development ("uremic failure to thrive"), yet it remains comparatively understudied and less well characterized in these patients. Given the challenges of applying adult-defined PEW criteria to the pediatric population, the authors of a recent study entitled "Protein energy wasting in children with chronic kidney disease" [Abraham et al. (2014) Pediatr Nephrol 29:1231-1238] have sought to develop a scoring system and three alterative definitions for this condition using a combination of biochemical markers, clinical measurements, and subjective reporting in children in the CKiD cohort: (1) minimal PEW definition (≥2 adult-defined PEW criteria); (2) standard PEW definition (≥3 adult-defined PEW criteria); (3) modified PEW definition (≥3 adult-defined PEW criteria, plus short stature or poor growth). These authors observed that meeting the modified PEW definition was associated with a significantly increased risk of hospitalization in unadjusted analyses, i.e., a 2.2-fold higher risk, and trended towards increased risk in multivariable adjusted analyses, i.e., 2.0-fold higher risk. At the present time, future studies validating these findings and developing further refined definitions and/or scoring systems for the detection and management of PEW in children and uremic failure to thrive are urgently needed.

Body mass index and mortality in kidney transplant recipients: a systematic review and meta-analysis

BACKGROUND

A higher body mass index (BMI) seems to be linked to survival advantage in maintenance hemodialysis patients. However, it is uncertain if this 'obesity survival paradox' is also observed in kidney transplant recipients. Hence, we systematically reviewed the literature on the impact of pre-transplantation BMI on all-cause mortality in this population.

METHODS

We searched MEDLINE, EMBASE, Web of Science, CINAHL, and Cochrane CENTRAL for relevant studies up to July 2013. Two investigators independently selected the studies using predefined criteria, abstracted the data from the included studies, and independently assessed each study's quality using the Newcastle-Ottawa Quality Assessment Scale. In addition to the qualitative synthesis, we quantitatively pooled the results of the studies with clinical, methodological, and statistical homogeneity.

RESULTS

We screened 7,123 records, from which we included 11 studies (with a total of 305,392 participants) in this systematic review and 4 studies in the meta-analyses. In the only study that included children, obesity was linked to higher mortality in children of 6-12 years old. For adults, our meta-analyses indicated that compared to normal BMI, underweight [Hazard Ratio (HR): 1.09; 95% Confidence Interval (CI): 1.02-1.20], overweight (HR: 1.07; 95% CI: 1.04-1.12), and obese (HR: 1.20; 95% CI: 1.14-1.23) levels of BMI were associated with higher mortality.

CONCLUSION

The presence of the obesity survival paradox is unlikely in kidney transplant recipients since both extremes of pre-transplantation BMI are linked to higher mortality in this population.