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.

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.

Characterization of chronic and acute ESA hyporesponse: a retrospective cohort study of hemodialysis patients

Background

Some patients with chronic kidney disease do not respond adequately to erythropoiesis-stimulating agent (ESA) treatment; these patients are referred to as ESA hyporesponders. There is no widely accepted contemporary definition for chronic ESA hyporesponse. The study objective was to propose and validate an operational definition for chronic ESA hyporesponse.

Methods

This was a retrospective cohort study using electronic health care records. Participants were anemic hemodialysis patients treated during February 2012 and were followed for 15 months. Patients’ ESA response (responders) or lack of response (chronic and acute hyporesponders) based on longitudinal patterns of ESA dose and hemoglobin level was assessed. Persistence of hyporesponse, longitudinal iron measures, transfusion rates, and mortality rates were analyzed. Frequency of blood transfusions (monthly) and death rates (quarterly) were calculated. Log normalized serum ferritin concentration was analyzed.

Results

Of 97,677 eligible patients, 6632 had acute hyporesponsiveness (ESA responsiveness restituted in ≤ 4 months) and 3086 had chronic hyporesponsiveness (lack of ESA response for > 4 months). Over months 1–4 among chronic hyporesponders, mean serum ferritin (722–785 ng/mL) and transferrin saturation (TSAT; 26.76 %-27.08 %) were constant, while acute hyporesponsive patients experienced increased ferritin (654-760 ng/mL) and TSAT (25.71–30.88 %) levels. Compared to ESA responders (0.19–0.30 %), chronic hyporesponders were transfused 7-times (1.20–2.17 %) more frequently over follow-up. Quarterly mortality was greatest in chronic ESA hyporesponders (2.98–5.48 %), followed by acute ESA hyporesponders (2.17–3.30 %) and ESA responders (1.43–2.49 %). With consistence over the study, chronic hyporesponders died more frequently than patients in the other study cohorts.

Conclusions

Findings indicate that 4 months of continuous ESA hyporesponsiveness can be used to differentiate acute from chronic hyporesponsiveness. This definition of chronic hyporesponsiveness is supported by outcome data showing higher mortality and transfusion rates in chronic hyporesponders compared to acute hyporesponders.

Electronic supplementary material

The online version of this article (doi:10.1186/s12882-015-0138-x) contains supplementary material, which is available to authorized users.

Management of serum calcium reductions among patients on hemodialysis following cinacalcet initiation

PURPOSE

Cinacalcet is indicated for treatment of secondary hyperparathyroidism in patients receiving hemodialysis. Cinacalcet reduces serum calcium concentrations by decreasing parathyroid hormone secretion, but the frequency and degree of calcium reduction following cinacalcet initiation, subsequent physician response, and ultimate calcium recovery in clinical practice are not well described.

METHODS

Patients receiving hemodialysis at a large dialysis organization who enrolled in the organization's prescription benefits service and initiated cinacalcet at serum calcium ≥8.4 mg/dL were studied (N = 13 723). Patients were categorized by whether they experienced a reduction in calcium to <8.4 mg/dL and to what level (<7.5, 7.5-7.9, and 8.0-8.3 mg/dL). Baseline characteristics, frequency of subsequent intervention, and calcium recovery were compared.

RESULTS

Of those who experienced a reduction in calcium to <8.4 mg/dL (n = 6437 [46.9%]), 6.6% had calcium <7.5 mg/dL and 24.5% had calcium 7.5-7.9 mg/dL, while the majority (68.9%) had a level of 8-8.3 mg/dL. Higher baseline parathyroid hormone and alkaline phosphatase were associated with lower resultant calcium. Among patients with calcium reductions, 45.6-63.5% received one or more directed clinical therapeutic responses, including 15.6-28.4% for whom cinacalcet was discontinued; the majority of patients recovered to calcium ≥8.4 mg/dL within 90 days of first detection. Only modest differences in recovery were noted between patients who did and did not receive any therapeutic response and patients who did and did not discontinue cinacalcet.

CONCLUSION

Serum calcium reductions following cinacalcet initiation were common; declines <7.5 mg/dL were infrequent. Calcium recovery occurred in the majority of patients, with or without therapeutic intervention.

A retrospective, longitudinal study estimating the association between interdialytic weight gain and cardiovascular events and death in hemodialysis patients

BACKGROUND

Greater interdialytic weight gain (IDWG) is associated with risk of all-cause mortality and hospitalization. Dialysis patients are also at greater risk of cardiovascular (CV) events than patients without kidney disease. This retrospective study examined the potential association between IDWG and specific types of CV events.

METHODS

Data were obtained from United States Renal Data System claims and the electronic health records of Medicare patients who initiated hemodialysis between 01 January 2007 and 31 December 2008 at a large dialysis organization. Absolute IDWG was defined as predialysis weight minus postdialysis weight from the prior treatment, and relative IDWG was calculated as percentage of postdialysis weight with mean values for each, calculated over dialysis days 91 to 180. Patient outcomes were considered beginning on day 181, continuing until death, discontinuation of care, censoring, or study end (31 December 2009). Outcomes included all-cause mortality, CV mortality, hospitalization for nonfatal heart failure/volume overload, hospitalization for nonfatal myocardial infarction, MACE (a composite measure of nonfatal myocardial infarction, nonfatal ischemic stroke, or CV death), and MACE+ (events comprising MACE as well as arrhythmia, nonfatal hemorrhagic stroke, or hospitalization for heart failure). Associations between IDWG and outcomes over the exposure period were estimated using proportional hazards regression and adjusted for baseline characteristics.

RESULTS

39,256 patients qualified for analysis. In general, associations of relative IDWG with outcomes were more potent, consistent, and monotonic than those for absolute IDWG. Relative IDWG > 3.5 % body weight was independently associated with all outcomes studied: point estimates ranged from 1.18 (myocardial infarction) to 1.26 (CV mortality) and were consistent among patients with and without diabetes, and with and without baseline heart failure. Absolute IDWG > 3 kg was associated with outcomes other than myocardial infarction: point estimates ranged from 1.11 (MACE) to 1.20 (heart failure).

CONCLUSIONS

Greater IDWG is associated with an increased risk of CV morbid events. Strategies that mitigate IDWG may improve CV health and survival among hemodialysis patients.

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.

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.

Associations of Posthemodialysis Weights above and below Target Weight with All-Cause and Cardiovascular Mortality

BACKGROUND AND OBJECTIVES

Fluid removal via ultrafiltration is a primary function of hemodialysis, and inadequate volume control is associated with significant morbidity and mortality among chronic dialysis patients. Treatment-to-treatment fluid removal goals are typically calculated on the basis of interdialytic weight gain and prescribed target weight. The clinical effect of frequent missed target weights is unclear. This study was designed to evaluate the associations of postdialysis weights above and below the prescribed target weight (separately) and outcomes.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

Data were taken from a national cohort of 10,785 prevalent, thrice-weekly, in-center hemodialysis patients dialyzing from 2005 to 2008 (median time at risk, 2.1 [25th percentile, 75th percentile] years) at a single dialysis organization. Patients were characterized as having an above target weight miss if their postdialysis weight was >2 kg above target weight in at least 30% of baseline treatments (14.6% of cohort), or they were characterized as control otherwise. Below target weight miss characterization was analogous for patients with postdialysis weight >2 kg below target weight (6.6% of cohort). Coprimary endpoints were all-cause and cardiovascular mortality.

RESULTS

Above target weight miss in at least 30% of treatments (versus not) was associated with greater all-cause mortality (adjusted hazard ratio, 1.28; 95% confidence interval, 1.15 to 1.43); and below target weight miss in at least 30% of treatments (versus not) was associated with greater all-cause mortality (adjusted hazard ratio, 1.22; 95% confidence interval, 1.05 to 1.40). Both above and below target weight misses were also significantly associated with greater cardiovascular mortality. Secondary analyses demonstrated dose-response relationships between target weight misses and mortality. Results from sensitivity analyses considering the difference in postdialysis and target weights as a proportion of body weight were analogous to the primary results.

CONCLUSIONS

Postdialysis weights >2 kg above and below target weight are associated with higher all-cause and cardiovascular mortality. Consistent target weight achievement is a viable target for improving fluid management.

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.

End-stage renal disease in autosomal dominant polycystic kidney disease: a comparison of dialysis-related utilization and costs with other chronic kidney diseases

BACKGROUND

Autosomal dominant polycystic kidney disease (ADPKD) is the leading inheritable cause of end-stage renal disease (ESRD) and one of the leading causes of ESRD overall. ADPKD patients differ from the overall dialysis population; however, there is little published data regarding health care costs for ADPKD patients on dialysis.

METHODS

This retrospective observational cohort study was designed to quantify health care utilization and costs for ADPKD patients with ESRD who received initial services at a single large dialysis organization between January 1, 2007 and December 31, 2009. Parallel results and baseline patient characteristics for control patients with ESRD etiologies other than ADPKD were performed for reference. Dialysis-related utilization and health care costs for patients with ADPKD in ESRD overall and during time horizons that correspond to Medicare-eligibility benchmarks were analyzed. Baseline patient characteristics were described for all patients and included demographics, comorbid illnesses, and clinical characteristics. Dialysis-related utilization, hospitalization rates, and health care costs were considered longitudinally.

RESULTS

Total health care costs for ADPKD patients were high at US$51,048 per patient-year based on the overall analysis. Total health care costs were lower for ADPKD patients than for control patients on dialysis. Patients with ADPKD were generally younger, had a lower Charlson Comorbidity Index, and had lower rates of comorbid conditions, which may have contributed to the lower overall costs seen for patients with ADPKD.

CONCLUSION

Health care resource utilization and costs for patients with ADPKD in ESRD requiring dialysis were high, and therapeutic interventions that can prevent or delay the progression to ESRD may increase dialysis-free life for patients with ADPKD.

Intradialytic hypotension and risk of cardiovascular disease

BACKGROUND AND OBJECTIVES

Patients undergoing hemodialysis have an elevated risk of cardiovascular disease-related morbidity and mortality compared with the general population. Intradialytic hypotension (IDH) is estimated to occur during 20%-30% of hemodialysis sessions. To date, no large studies have examined whether IDH is associated with cardiovascular outcomes. This study determined the prevalence of IDH according to interdialytic weight gain (IDWG) and studied the association between IDH and outcomes for cardiovascular events and mortality to better understand its role.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

This study retrospectively examined records of 39,497 hemodialysis patients during 2007 and 2008. US Renal Data System claims and dialysis provider data were used to determine outcomes. IDH was defined by current Kidney Disease Outcomes Quality Initiative guidelines (≥20 mmHg fall in systolic BP from predialysis to nadir intradialytic levels plus ≥2 responsive measures [dialysis stopped, saline administered, etc.]). IDWG was measured absolutely (in kilograms) and relatively (in percentages).

RESULTS

IDH occurred in 31.1% of patients during the 90-day exposure assessment period. At baseline, the higher the IDWG (relative or absolute), the greater the frequency of IDH (P<0.001). For all-cause mortality, the median follow-up was 398 days (interquartile range, 231-602 days). Compared with patients without IDH, IDH was associated with all-cause mortality (7646 events; adjusted hazard ratio, 1.07 [95% confidence interval, 1.01 to 1.14]), myocardial infarction (2396 events; 1.20 [1.10 to 1.31]), hospitalization for heart failure/volume overload (8896 events; 1.13 [1.08 to 1.18]), composite hospitalization for heart failure/volume overload or cardiovascular mortality (10,805 events; 1.12 [1.08 to 1.17]), major adverse cardiac events (MACEs; myocardial infarction, stroke, cardiovascular mortality) (4994 events, 1.10 [1.03 to 1.17]), and MACEs+ (MACEs plus arrhythmia or hospitalization for heart failure/volume overload) (12,221 events; 1.14 [1.09 to 1.19]).

CONCLUSIONS

IDH was potently associated with cardiovascular morbidity and mortality. Clinical trials to ascertain causality are needed and should consider reduction in IDWG as a potential means to reduce IDH.

Association of mortality risk with various definitions of intradialytic hypotension

Intradialytic hypotension is a serious and frequent complication of hemodialysis; however, there is no evidence-based consensus definition of intradialytic hypotension. As a result, coherent evaluation of the effects of intradialytic hypotension is difficult. We analyzed data from 1409 patients in the HEMO Study and 10,392 patients from a single large dialysis organization to investigate the associations of commonly used intradialytic hypotension definitions and mortality. Intradialytic hypotension definitions were selected a priori on the basis of literature review. For each definition, patients were characterized as having intradialytic hypotension if they met the corresponding definition in at least 30% of baseline exposure period treatments or characterized as control otherwise. Overall and within subgroups of patients with predialysis systolic BP<120 or 120-159 mmHg, an absolute nadir systolic BP<90 mmHg was most potently associated with mortality. Within the subgroup of patients with predialysis BP≥160 mmHg, nadir BP<100 mmHg was most potently associated with mortality. Intradialytic hypotension definitions that considered symptoms, interventions, and decreases in BP during dialysis were not associated with outcome, and when added to nadir BP, symptom and intervention criteria did not accentuate associations with mortality. Our results suggest that nadir-based definitions best capture the association between intradialytic hypotension and mortality.

Confounders of mortality and hospitalization rate calculations for profit and nonprofit dialysis facilities: analytic augmentation

BACKGROUND

Patient outcomes have been compared on the basis of the profit status of the dialysis provider (for-profit [FP] and not-for-profit [NFP]). In its annual report, United States Renal Data System (USRDS) provides dialysis provider level death and hospitalization rates adjusted by age, race, sex, and dialysis vintage; however, recent analyses have suggested that other variables impact these outcomes. Our current analysis of hospitalization and mortality rates of hemodialysis patients included adjustments for those used by the USRDS plus other potential confounders: facility geography (end-stage renal disease network), length of facility ownership, vascular access at first dialysis session, and pre-dialysis nephrology care.

METHODS

We performed a provider level, retrospective analysis of 2010 hospitalization and mortality rates among US hemodialysis patients exclusively using USRDS sources. Crude and adjusted incidence rate ratios (IRRs) were calculated using the 4 standard USRDS patient factors plus the 4 potential confounders noted above.

RESULTS

The analysis included 366,011 and 34,029 patients treated at FP and NFP facilities, respectively. There were statistical differences between the cohorts in geography, facility length of ownership, vascular access, and pre-dialysis nephrology care (p < 0.001), as well as age (p < 0.01), race (p < 0.001), and vintage (p < 0.001), but not sex (p = 0.12). When using standard USRDS adjustments, hospitalization and mortality rates for FP and NFP facilities were most disparate, favoring the NFP facilities. Rates were most similar between providers when adjustments were made for each of the 8 factors. With the FP IRR as the referent (1.0), the hospitalization IRR for NFP facilities was 1.00 (95% confidence interval [CI] 0.97-1.02; p = 0.69), while the NFP mortality IRR was 1.01 (95% CI 0.97-1.05; p = 0.64).

CONCLUSIONS

These data suggest there is no difference in mortality and hospitalization rates between FP and NFP dialysis clinics when appropriate statistical adjustments are made.

Patient-stated preferences regarding volume-related risk mitigation strategies for hemodialysis

BACKGROUND AND OBJECTIVES

Larger weight gain and higher ultrafiltration rates have been associated with poorer outcomes among patients on dialysis. Dietary restrictions reduce fluid-related risk; however, adherence is challenging. Alternative fluid mitigation strategies include treatment time extension, more frequent dialysis, adjunct peritoneal dialysis, and wearable ultrafiltration devices. No data regarding patient preferences for fluid management exist. A survey was designed, tested, and administered to assess patient-stated preferences regarding fluid mitigation.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

A written survey concerning fluid-related symptoms, patient and treatment characteristics, and fluid management preferences was developed. The cross-sectional survey was completed by 600 patients on hemodialysis at 18 geographically diverse ambulatory facilities. Comparisons of patient willingness to engage in volume mitigation strategies across fluid symptom burden, dietary restriction experience, and patient characteristics were performed.

RESULTS

Final analyses included 588 surveys. Overall, if allowed to liberalize fluid intake, 44.6% of patients were willing to extend treatment time by 15 minutes. Willingness to extend treatment time was incrementally less for longer treatment extensions; 12.2% of patients were willing to add a fourth weekly treatment session, and 13.5% of patients were willing to participate in nocturnal dialysis three nights per week. Patients more bothered by their fluid restrictions (versus less bothered) were more willing to engage in fluid mitigation strategies. Demographic characteristics and symptoms, such as cramping and dyspnea, were not consistently associated with willingness to engage in the proposed strategies. More than 25% of patients were unsure of their dry weights and typical interdialytic weight gains.

CONCLUSIONS

Patients were generally averse to treatment time extension>15 minutes. Patients more bothered (versus less bothered) by their prescribed fluid restrictions were more willing to engage in volume mitigation strategies. Additional study of patient-stated preferences in hemodialysis treatment practices is needed to guide patient care and identify deficiencies in patient treatment and disease-related knowledge.

Dose of hemodialysis and survival: a marginal structural model analysis

BACKGROUND

Observational studies have consistently demonstrated the survival benefits of a greater dialysis dose in maintenance hemodialysis (MHD) patients, whereas randomized controlled trials have shown conflicting results. The possible causal impact of dialysis dose on mortality needs to be investigated using rich cohort data analyzed with novel statistical methods such as marginal structural models (MSMs) that account for time-varying confounding and exposure.

METHODS

We quantified the effect of delivered dose of hemodialysis (HD) [single-pool Kt/V (spKt/V)] on mortality risk in a contemporary cohort of 68,110 patients undergoing HD 3 times weekly (7/2001- 9/2005). We compared conventional Cox proportional hazard and MSM survival analyses, accounting for time-varying confounding by applying longitudinally modeled inverse-probability-of-dialysis-dose weights to each observation.

RESULTS

In conventional Cox models, baseline spKt/V showed a weak negative association with mortality, while higher time-averaged spKt/V was strongly associated with lower mortality risk. In MSM analyses, compared to a spKt/V range of 1.2 - <1.4, a spKt/V range of <1.2 was associated with a higher risk of mortality [HR (95% CI) 1.67 (1.54 - 1.80)], whereas mortality risks were significantly lower with higher spKt/V [HRs (95% CI): 0.74 (0.70-0.78), 0.63 (0.59-0.66), 0.56 (0.52-0.60), and 0.56 (0.52-0.61) for spKt/V ranges of 1.4 - <1.6, 1.6-<1.8, 1.8 - <2.0, and ≥2.0, respectively]. Thus, MSM analyses showed that the greatest survival advantage of a higher dialysis dose was observed for a spKt/V range of 1.8-<2.0, and the dialysis dose-mortality relationship was robust in almost all subgroups of patients.

CONCLUSIONS

Higher HD doses were robustly associated with greater survival in MSM analyses that more fully and appropriately accounted for time-varying confounding.

Use of the Tego needlefree connector is associated with reduced incidence of catheter-related bloodstream infections in hemodialysis patients

BACKGROUND AND OBJECTIVES

Catheter-related bloodstream infections (CRBSIs) are common in hemodialysis patients using central venous catheters, and catheter occlusion also occurs frequently. The Tego needlefree connector was developed to reduce the incidence of these complications; however, existing studies of its effectiveness and safety are limited.

MATERIALS AND METHODS

This retrospective analysis compared outcomes among patients of a large dialysis organization receiving in-center hemodialysis using a central venous catheter with either the Tego connector or standard catheter caps between October 1 and June 30, 2013. Incidence rates for intravenous (IV) antibiotic starts, receipt of an IV antibiotic course, positive blood cultures, mortality, and missed dialysis treatments were calculated, and incidence-rate ratios (IRRs) were estimated using Poisson regression models. Utilization of erythropoiesis-stimulating agents (ESAs) and thrombolytics was described for each patient-month and compared using mixed linear models. Models were run without adjustment, adjusted for covariates that were imbalanced between cohorts, or fully adjusted for all potential confounders.

RESULTS

The analysis comprised 10,652 Tego patients and 6,493 controls. Tego use was independently associated with decreased risk of CRBSI, defined by initiation of IV antibiotics (adjusted IRR 0.92, 95% confidence interval [CI] 0.87-0.97) or initiation of IV antibiotic course (adjusted IRR 0.89, 95% CI 0.84-0.95). Tego use was independently associated with decreased rate of missed dialysis treatments (adjusted IRR 0.98, 95% CI 0.97-1.00); no significant difference between Tego and control cohorts was observed with respect to mortality. Tego use was associated with decreased likelihood of thrombolytic use (adjusted per-month probability of 5.6% versus 6.2% for controls) and lower utilization of ESAs in study months 7-9.

CONCLUSION

Use of the Tego connector may reduce the risk of CRBSI and result in lower utilization of thrombolytics, antibiotics, and ESAs, as well as fewer missed dialysis treatments.