Association of Changes in Vector Length with Changes in Left Ventricular Mass Among Patients on Maintenance Hemodialysis: A Secondary Analysis of the Frequent Hemodialysis Network Daily Trial.

BACKGROUND: Hypervolemia is thought to be a major contributor to higher left ventricular mass (LVM), a potent predictor for cardiovascular mortality among patients on maintenance hemodialysis. We hypothesized that a decrease in vector length (a bioimpedance proxy of hypervolemia) would be associated with an increase in LVM. METHODS: Using data from the Frequent Hemodialysis Network Daily Trial (n=160) we used linear regression to assess the association of changes in vector length from baseline to month 12 with changes in magnetic resonance imaging (MRI) measures of LVM and other cardiac parameters. We adjusted models for the randomized group, baseline vector length, age, sex, race, body mass index, vascular access, dialysis vintage, history of hypertension, heart failure, and diabetes, residual kidney function, pre-dialysis systolic blood pressure (BP), ultrafiltration rate, serum-dialysate sodium gradient, hemoglobin, phosphate, angiotensin-converting enzyme inhibitor or angiotensin receptor blocker use, erythropoietin dose, and equilibrated Kt/V. RESULTS: The mean age was 50 ±13 years; 35% were female. In the fully adjusted models, a decline in vector length (per 50 Ω/m; i.e., increase in volume) was associated with a 6.8 g (95%CI -0.1, 13.7) and 2.6 g/m2 (95%CI -1.2, 6.3) increase in LVM and LVM index, respectively; and an increase of 15.0 mL (95%CI 7.5, 22.4), 7.3 mL (95%CI 3.0, 12.7), 7.8 mL (95%CI 3.0, 12.7), and -0.9 % (95%CI -3.1, 1.3) in left ventricular (LV) end-diastolic volume (LVEDV), end-systolic volume (LVESV), stroke volume (LVSV), and ejection fraction (LVEF), respectively. The lowest tertile of change in vector length (i.e., greater increase in volume) was associated with greater increases in LVEDV and LVSV, versus the highest tertile. There was no evidence of heterogeneity by randomized group. CONCLUSIONS: Change in vector length, a bioimpedance-derived proxy of volume status, was inversely associated with indices of left ventricular mass and volume measured by cardiac MRI in patients randomized to conventional or frequent hemodialysis over 12 months.

Association of Bioimpedance Parameters with Increases in Blood Pressure during Hemodialysis.

BACKGROUND: Intradialytic hypertension, defined as an increase in BP from pre- to post-hemodialysis (HD), affects 5%-15% of patients receiving maintenance HD and is associated with cardiovascular and all-cause mortality. Hypervolemia is believed to be a major etiological factor, yet the association of more objective biomarkers of volume status with intradialytic hypertension is not well described. METHODS: In a post hoc analysis of the Frequent Hemodialysis Network Daily Trial ( n =234), using data from baseline, 1-, 4-, and 12-month visits ( n =800), we used random-effects regression to assess the association of bioimpedance estimates of volume (vector length) with post-HD systolic BP (continuous) and any increase in systolic BP (categorical) from pre- to post-HD. We adjusted models for randomized group; age; sex; self-reported race; Quételet (body mass) index; vascular access; HD vintage; hypertension; history of heart failure; diabetes; residual kidney function (urea clearance); pre-HD systolic BP; ultrafiltration rate; serum-dialysate sodium gradient; and baseline values of hemoglobin, phosphate, and equilibrated Kt/V urea. RESULTS: The mean age of participants was 50±14 years, 39% were female, and 43% were Black. In adjusted models, shorter vector length (per 50 Ω/m) was associated with higher post-HD systolic BP (2.9 mm Hg; 95% confidence interval [CI], 1.6 to 4.3) and higher odds of intradialytic hypertension (odds ratio 1.66; 95% CI, 1.07 to 2.55). Similar patterns of association were noted with a more stringent definition of intradialytic hypertension (>10 mm Hg increase from pre- to post-HD systolic BP), where shorter vector length (per 50 Ω/m) was associated with a higher odds of intradialytic hypertension (odds ratio 2.17; 95% CI, 0.88 to 5.36). CONCLUSIONS: Shorter vector length, a bioimpedance-derived proxy of hypervolemia, was independently associated with higher post-HD systolic BP and risk of intradialytic hypertension.

The Association of Ejection Fraction With Hospital-Associated Cardiac Arrest and Heart Failure Hospitalization Differs According to Baseline Estimated GFR.

Introduction: Chronic kidney disease (CKD) and left ventricular (LV) dysfunction are risk factors for cardiovascular events. We explore whether the association of LV ejection fraction (LVEF) with cardiac arrest, heart failure hospitalization, and all-cause mortality differs across stages of kidney impairment. Methods: We performed an observational cohort study of 19,032 patients from 2004 to 2014 with estimated glomerular filtration rate (eGFR) ≤90 ml/min per 1.73 m2 and without end-stage kidney disease (ESKD). Cox regression models, incorporating an interaction term for eGFR and LVEF, were fit and adjusted for relevant covariates. Results: Mean age of the patients was 67 ± 14 years, and 51% were male. The mean eGFR was 64 ± 19 ml/min per 1.73 m2 and LVEF was 54 ± 13%. Over a median follow-up of 3.0 (0.7-6.0) years there were 504 cardiac arrests, 4181 heart failure hospitalizations, and 6989 deaths. The association of LVEF with cardiac arrest and heart failure hospitalization differed according to continuous eGFR (P-interaction <0.01 for both outcomes). The association of LVEF with cardiac arrest in the lowest quartile was attenuated (adjusted hazard ration [aHR] per 5% higher LVEF 0.92; 95% confidence interval [CI] 0.88-0.96) compared to the highest eGFR quartile (aHR per 5% higher LVEF 0.85; 95% CI 0.78-0.91). The association of LVEF with heart failure hospitalization was similarly attenuated in the lowest eGFR quartile. There was no effect modification of LVEF by continuous eGFR for all-cause mortality (P-interaction 0.26). Conclusion: Among non-ESKD patients with eGFR ≤90 ml/min per 1.73 m2, the association of LVEF with cardiac arrest and heart failure hospitalization is attenuated at lower levels of kidney function. Further research is required to elucidate what factors beyond LVEF drive these observations.

Temporal Changes in Electrolytes, Acid-Base, QTc Duration, and Point-of-Care Ultrasound during Inpatient Hemodialysis Sessions.

Background: Of the more than 550,000 patients receiving maintenance hemodialysis (HD) in the United States, each has an average of 1.6 admissions annually (>880,000 inpatient HD sessions). Little is known about the temporal changes in laboratory values, ECGs, and intravascular and extravascular volume during inpatient HD sessions. Methods: In this prospective cohort study of hospitalized HD patients, we assessed intradialytic laboratory values (metabolic panels, blood gases, ionized calcium levels), ECGs, and sonographic measures of volume status. Results: Among 30 participants undergoing HD (mean age 62 years; 53% men, 43% Black) laboratory values had the largest changes in the first hour of HD. There was no significant change in ionized calcium levels pre- to post-HD (change: -0.01±0.07, P=0.24); 12 of 30 and 17 of 30 patients had levels below the lower reference limit at the beginning and end of HD, respectively. The mean pH increased pre- to post-HD (change: 0.06±0.04, P<0.001); 21 of 30 had a pH above the upper reference limit post-HD. There was a trend toward longer median QTc duration from pre- to post-HD (change: 7.5 msec [-5 msec, 19 msec], P=0.07). The sum of B lines on lung ultrasound decreased from pre- to post-HD (median decrease: 3 [1, 7], P<0.01). The collapsibility index of the inferior vena cava increased pre- to post-HD (median increase: 4.8% [1.5%, 13.4%], P=0.01), whereas internal jugular vein diameter did not change (P=0.24). Conclusions: Among hospitalized patients undergoing HD, we found dynamic changes in laboratory values, QTc duration, and volume status. Further research is required to assess whether HD prescriptions can be tailored to alter these variations to potentially improve patient outcomes.

Risk of Intradialytic Hypotension by Day of the Week in Maintenance Hemodialysis.

Intradialytic hypotension (IDH) is a common complication of hemodialysis (HD) and is associated with a higher risk of cardiovascular (CV) events and mortality. CV events are more common on the days of HD, especially following the longer interdialytic interval. We investigated the risk of IDH according to day of HD in adults undergoing in-center, thrice-weekly HD in the Hemodialysis (HEMO) Study (N = 1,837 patients; n = 64,474 sessions), and the DaVita Clinical Research biorepository [BioReG]) (N = 952 patients; n = 61,197 sessions). Random effects logistic regression models assessed the risk of IDH (defined as nadir intra-HD systolic blood pressure [SBP] <90 mm Hg if pre-HD SBP <160 mm Hg, or <100 mm Hg if pre-HD SBP ≥160 mm Hg [Nadir90/100 definition]) according to HD day (Mon/Tue [HD1]; Wed/Thu [HD2]; Fri/Sat [HD3]). Alternative definitions of IDH were explored. Nadir90/100 occurred in 14% of HEMO and 18% of BioReG sessions. A monotonic increase in the risk of IDH was observed for HD2 and HD3, compared with HD1, for all IDH definitions in both cohorts. Compared with HD1, HD2 was associated with a 10% higher risk of Nadir90/100 (adjusted odds ratio, 1.10; 95% CI, 1.03-1.17) and HD3 was associated with a 31% higher risk (adjusted odds ratio, 1.31; 95% CI, 1.19-1.45) in HEMO, with consistent results in BioReG. We observed a monotonic increased risk of IDH with later days of the dialytic week in two separate cohorts. Further research to determine the underlying mechanisms is necessary to guide strategies for IDH prevention.

Predialysis serum phosphate and intradialytic hypotension.

INTRODUCTION: Intradialytic hypotension (IDH) is a common complication of hemodialysis (HD) and is associated with excess morbidity and mortality. Higher serum phosphate is associated with adverse cardiovascular outcomes in maintenance HD patients; however, its association with IDH has not previously been assessed. METHODS: This is an analysis of a prospective cohort of 969 HD patients (80,968 HD sessions) receiving HD at a large dialysis organization (LDO) and a post-hoc analysis of 1838 HD patients (10,594 HD sessions) in the Hemodialysis study (HEMO), a multicenter randomized controlled trial that examined standard or high-dose HD and low-flux or high-flux membranes. Unadjusted and adjusted mixed effects regression models were fit to determine the association of pre-HD serum phosphate with IDH, defined as a nadir intra-HD systolic blood pressure (SBP) <90 mmHg. FINDINGS: In the LDO cohort, baseline mean pre-HD serum phosphate was 5.2 ± 1.7 mg/dl. IDH occurred in 15.6% of HD sessions. In the adjusted model, higher pre-HD serum phosphate (per 1 mg/dl) was associated with a 12% increased risk of IDH (aOR 1.12, 95% CI 1.10-1.13, p <0.001). In exploratory models where pre-HD laboratory values were available, the effect estimate was attenuated but remained statistically significant (aOR 1.05; 95% CI 1.02-1.08; p <0.01). Participants in the highest (compared with the lowest) quartile of pre-HD serum phosphate had a 56% greater risk of IDH in the adjusted model (aOR Q4:Q1 1.56; 95% CI 1.44-1.68, p <0.001). The association of higher phosphate with IDH was consistent in the HEMO data. DISCUSSION: Higher pre-HD serum phosphate is independently associated with an increased risk of IDH. As HD may cause an acute decline in serum phosphate, future studies to investigate the mechanisms of this association are warranted.

A randomized controlled trial of two dialysate sodium concentrations in hospitalized hemodialysis patients.

BACKGROUND: Several large dialysis organizations have lowered the dialysate sodium concentration (DNa) in an effort to ameliorate hypervolemia. The implications of lower DNa on intra-dialytic hypotension (IDH) during hospitalizations of hemodialysis (HD) patients is unclear. METHODS: In this double-blind, single center, randomized controlled trial (RCT), hospitalized maintenance HD patients were randomized to receive higher (142 mmol/L) or lower (138 mmol/L) DNa for up to six sessions. Blood pressure (BP) was measured in a standardized fashion pre-HD, post-HD and every 15 min during HD. The endpoints were: (i) the average decline in systolic BP (pre-HD minus lowest intra-HD, primary endpoint) and (ii) the proportion of total sessions complicated by IDH (drop of ≥20 mmHg from the pre-HD systolic BP, secondary endpoint). RESULTS: A total of 139 patients completed the trial, contributing 311 study visits. There were no significant differences in the average systolic blood pressure (SBP) decline between the higher and lower DNa groups (23 ± 16 versus 26 ± 16 mmHg; P = 0.57). The proportion of total sessions complicated by IDH was similar in the higher DNa group, compared with the lower DNa group [54% versus 59%; odds ratio 0.72; 95% confidence interval (95% CI) 0.36-1.44; P = 0.35]. In post hoc analyses adjusting for imbalances in baseline characteristics, higher DNa was associated with 8 mmHg (95% CI 2-13 mmHg) less decline in SBP, compared with lower DNa. Patient symptoms and adverse events were similar between the groups. CONCLUSIONS: In this RCT for hospitalized maintenance of HD patients, we found no difference in the absolute SBP decline between those who received higher versus lower DNa in intention-to-treat analyses. Post hoc adjusted analyses suggested a lower risk of IDH with higher DNa; thus, larger, multi-center studies to confirm these findings are warranted.