Dialysis dose and intradialytic hypotension: results from the HEMO study

Abstract

Background: Intradialytic hypotension (IDH) is common and is associated with increased morbidity and mortality in chronic hemodialysis patients. A higher dialysis 'dose' may generate transient intradialytic osmotic gradients, predisposing to intracellular fluid shifts and resulting in hypotension.

Study design: We performed a post hoc analysis of the HEMO study, a multicenter trial that randomized chronic hemodialysis patients to high versus standard Kt/V and higher versus lower membrane flux. In order to achieve dose targets, per protocol, adjustments were made in membrane efficiency, blood flow or dialysate flow before changing session length. Detailed hemodynamic and urea kinetic modeling data were abstracted from 1,825 individuals. The primary outcome was the occurrence of hypotensive events necessitating clinical intervention (saline infusion, lowering of ultrafiltration rate or reduced blood flow).

Results: Intradialytic hypotensive events occurred more frequently in the higher-Kt/V group (18.3 vs. 16.8%; p < 0.001). Participants randomized to higher-target Kt/V had a greater adjusted risk of IDH than those randomized to standard Kt/V [odds ratio (OR) 1.12; 95% confidence interval (CI) 1.01-1.25]. Higher vs. lower dialyzer mass transfer-area coefficient for urea and rate of urea removal were associated with greater adjusted odds of IDH (OR 1.15; 95% CI 1.04-1.27 and OR 1.05; 95% CI 1.04-1.06 per mg/dl/h, respectively).

Conclusions: Higher dialysis dose, at relatively constrained treatment times, may associate with an increased risk of IDH. These findings support the possibility that rapidity of intradialytic reductions in plasma osmolality may play an important role in mediating hemodynamic instability during dialysis.

Figure 1. The association between quartiles of rate of decline in plasma BUN and intra-dialytic hypotension

Associations between quartiles (Q; referent Q1) of rate of decline in plasma BUN and intra-dialytic hypotension (IDH) are presented as odds ratios (95% confidence intervals). Estimates were calculated using generalized linear models and adjusted for HEMO study flux assignment (higher vs lower), session length (≤180, >180, ≥210, ≥240 mins), blood flow (≤250, 250–349, 350–449, ≥450 mL/min), dialysate flow (0–500, 501–800, >800 mL/min), age, race (black, non-black), sex, post-dialysis weight, sex-by-weight cross-product terms, access, pre-dialysis SBP, height, ischemic heart disease, congestive heart failure (none, mild, moderate/severe), peripheral vascular disease, diabetes mellitus, arrhythmia, serum sodium, creatinine, albumin, phosphorus, bicarbonate and ultrafiltration requirement.