Disentangling the Ultrafiltration Rate–Mortality Association

Abstract

SummaryBackground and objectives Rapid ultrafiltration rate is associated with increased mortality among hemodialysis patients. Ultrafiltration rates are determined by interdialytic weight gain and session length. Although both interdialytic weight gain and session length have been linked to mortality, the relationship of each to mortality, independent of the other, is not adequately defined. This study was designed to evaluate whether shorter session length independent of weight gain and larger weight gain independent of session length are associated with increased mortality.Design, setting, participants, & measurements Data were taken from a national cohort of 14,643 prevalent, thriceweekly, in-center hemodialysis patients dialyzing from 2005 to 2009 (median survival time, 25 months) at a single dialysis organization. Patients with adequate urea clearance and delivered dialysis session $240 and ,240 minutes were pair-matched on interdialytic weight gain (n=1794), and patients with weight gain #3 and .3 kg were pair-matched on session length (n=2114); mortality associations were estimated separately.Results Compared with delivered session length $240, session length ,240 minutes was associated with increased all-cause mortality (adjusted hazard ratio [95% confidence interval], 1.32 [1.03 to 1.69]). Compared with weight gain #3, weight gain .3 kg was associated with increased mortality (1.29 [1.01 to 1.65]). The associations were consistent across strata of age, sex, weight, and weight gain and session length. Secondary analyses demonstrated dose-response relationships between both and mortality.Conclusions Among patients with adequate urea clearance, shorter dialysis session length and greater interdialytic weight gain are associated with increased mortality; thus, both are viable targets for directed intervention.

Intradialytic Hypotension and Risk of Cardiovascular Disease

“…These findings could have widespread implications in the treatment of patients with ESRD undergoing HD, considering that IDH is estimated to occur in 20%-30% of all dialysis treatments (depending on the definition used for IDH) (4), and that IDWG has been shown to increase the risk of CV events and mortality (10,11).…”

“…It is likely that longer dialysis treatments provide enhanced solute clearance beyond what is reflected by clearance of urea. It is also possible that prolonged dialysis sessions allow ultrafiltration to proceed slowly and in a manner that improves BP control and allows for consistent dry weight achievement (11).…”

Pre-Dialysis Serum Sodium and Mortality in a National Incident Hemodialysis Cohort

“…left ventricular hypertrophy and fibrosis) [17,19,20]; and (iv) higher ultrafiltration volumes/rates leading to intra-dialytic hypotension, myocardial stunning and cardiac remodeling [16,19,42]. However, our observed dysnatremia-mortality association persisted in multivariable-adjusted analyses that accounted for many of these confounders, suggesting that altered serum sodium may be directly harmful in hemodialysis patients.…”

“…For example, in past studies there has been variable consideration of risk factors for dysnatremia (e.g. large inter-dialytic weight gain (IDWG) [16][17][18][19][20], poor nutritional status and low solute intake [21][22][23], comorbidities predisposing to excess thirst [11,24]) that are in and of themselves associated with death risk. Interpretation of prior data are also made difficult due to focus upon prevalent hemodialysis patients whose characteristics may be confounded by survivor bias [6-8, 10, 11], and examination of select study populations (i.e.…”

Oh! What a Tangled Web We Weave

“…Most of the study's limitations were acknowledged by Flythe et al (1). Matching was desirable, although a relatively low fraction of the source cohort was successfully matched in both parallel analyses, and the matched population was not representative of the overall population with respect to body size.…”