Is there a difference in dialysis sessional calcium balance between haemodiafiltration and highflux haemodialysis...

The number of kidney dialysis patients treated by haemodiafiltration continues to increase. Previous studies have suggested that more calcium is removed during haemodiafiltration (HDF) sessions than haemodialysis (HD), particularly with pre-dilution haemodiafiltration (pre-HDF). So, we investigated whether there were differences between post-haemodiafiltration (post-HDF), pre-HDF and high flux HD treatments.

We collected a continuous aliquot of effluent dialysate during dialysis sessions, and calculated dialysis calcium mass balance by the difference between the amount of calcium delivered in fresh dialysate and that lost in effluent dialysate.

Effluent dialysate was collected during 244 dialysis sessions (post-HDF (70.9%), HD (20.1%), pre-HDF (9.0%)) from 154 patients, 99 male (64.3%) median dialysis vintage of 21.4 (11.0-55.3) months. Although the total amount of calcium delivered was significantly greater with pre-HDF (168.9 (150.1-203.9) versus post-HDF (141.9 (127.2-165.1) versus HD (125.7 (119.4-127.2) mmol), as was calcium in the effluent dialysate, so the over-all sessional calcium balances were similar (pre-HDF 5.5 (-4.3 to 14), post-HDF (5.6 (-1.1 to 11.9) and HD 6.1 (-3.5 to 11.2) mmol. Calcium balance was predominantly dependent on dialysate calcium concentration (rho 0.59, p < 0.001), and in a multivariable model higher dialysate calcium concentration (odds ratio: 35,509, 95% CI: 280-4.5 × 10⁶, p < 0.001), whereas ultrafiltration lowered calcium balance (odds ratio: 0.35, 95% CI: 0.18-0.67, p = 0.002).

We found no difference in dialysis sessional calcium balance between the different modes. When switching patients from HD to HDF, the choice of dialysate calcium should be individualised according to bone-mineral health rather than the dialysis modality.