Optimization of dialysate bicarbonate in patients treated with online haemodiafiltration

Abstract

Background Metabolic acidosis is a common problem in haemodialysis patients, but acidosis overcorrection has been associated with higher mortality. There is no clear definition of the optimal serum bicarbonate target or dialysate bicarbonate. This study analysed the impact of reducing dialysate bicarbonate from 35 to 32 mEq/L on plasma bicarbonate levels in a cohort of patients treated with online haemodiafiltration (OL-HDF). Methods We performed a prospective cohort study with patients in a stable chronic OL-HDF programme for at least 12 months in the Hospital Clinic of Barcelona. We analysed pre- and post-dialysis total carbon dioxide(TCO2) before and after dialysate bicarbonate reduction from 35 to 32 mEq/L, as well as the number of patients with a pre- and post-dialysis TCO2 within 19–25 and ≤29 mEq/L, respectively, after the bicarbonate modification. Changes in serum sodium, potassium, calcium, phosphorous and parathyroid hormone (PTH) were also assessed. Results We included 84 patients with a 6-month follow-up. At 6 months, pre- and post-dialysis TCO2 significantly decreased (26.78 ± 1.26 at baseline to 23.69 ± 1.92 mEq/L and 31.91 ± 0.91 to 27.58 ± 1.36 mEq/L, respectively). The number of patients with a pre-dialysis TCO2 >25 mEq/L was significantly reduced from 80 (90.5%) to 17 (20.2%) and for post-dialysis TCO2 >29 mEq/L this number was reduced from 83 (98.8%) to 9 (10.7%). PTH significantly decreased from 226.09 (range 172–296) to 182.50 (125–239) pg/mL at 6 months (P < 0.05) and post-dialysis potassium decreased from 3.16 ± 0.30 to 2.95 ± 0.48 mEq/L at 6 months (P < 0.05). Sodium, pre-dialysis potassium, calcium and phosphorous did not change significantly. Conclusions Reducing dialysate bicarbonate concentration by 3 mEq/L significantly and safely decreased pre- and post-dialysis TCO2, avoiding acidosis overcorrection and improving secondary hyperparathyroidism control. An individualized bicarbonate prescription (a key factor in the adequate control of acidosis) according to pre-dialysis TCO2 is suggested based on these results.

Collection of data to contribute to finding specific biochemical ranges in pre- post-hemodialysis in patients with chronic renal failure.

“…Our results were consistent with those of numerous studies demonstrating biological disorders in the blood induced by continuous decrease in renal clearance or GFR [6][7][8][9][10][11][12]. Despite the effectiveness of dialysis in filtering and purifying the blood, we found that some analytes remained at very high levels and an interpretation of the result using the existing RIs was meaningless.…”

Prescription of online hemodiafiltration (ol‐HDF)

“…In a recent study assessing sodium mass balance in HD and online post‐dilution HDF, it has been shown that sodium mass removed was nearly identical, provided dialysate sodium prescription was lower than the predialysis plasma sodium concentration 42 . Usually, no specific adaptation is required for most electrolytes when compared with stable patients on maintenance high‐flux HD 43 . However, in particular cases, dialysate electrolytes prescription must be probed to patient results: particularly with more frequent or longer HDF treatment schedules and when larger convective volumes are delivered as with pre‐dilution HDF, especially when treating vulnerable populations (elderly and children), and specific conditions (parathyroid disorders, calcimimetics, and alkalotic patients).…”

Basic prerequisites for on‐line, high‐volume hemodiafiltration

“…The levels of electrolytes in the dialysis fluid used for high‐volume HDF might need to be adjusted from those used in conventional hemodialysis to avoid electrolyte imbalances. For example, it may be necessary to reduce the bicarbonate concentration in the dialysis fluid to avoid over‐correction of the metabolic acidosis seen in hemodialysis patients 7 . It might also be necessary to adjust the dialysis fluid sodium concentration.…”

“…For example, it may be necessary to reduce the bicarbonate concentration in the dialysis fluid to avoid over-correction of the metabolic acidosis seen in hemodialysis patients. 7 It might also be necessary to adjust the dialysis fluid sodium concentration. The Gibbs-Donnan effect causes ultrafiltrate to have a lower sodium concentration than the plasma water from which it is derived, leading to an increase in plasma water sodium concentration along the length of the dialyzer.…”