A prospective comparison of bicarbonate dialysis, hemodiafiltration, and acetate-free biofiltration in the elderly.

Hemodiafiltration (HDF) and more recently acetate-free biofiltration (AFB) have shown good blood purification and cardiovascular stability in young and middle-aged hemodialysis patients. It is not clear if this is also valid for elderly patients. Twelve patients aged more than 70 years (mean age +/- SD, 76 +/- 4 years) on regular dialysis for at least 5 months were treated with bicarbonate dialysis (BD), HDF, or AFB in a randomized sequence and prospectively followed for 6 months (72 dialysis sessions/patient) for each procedure. The dialysis solution (containing bicarbonate), blood flow rate, and dialysate flow rate were the same with all the methods. During HDF and AFB solutions containing bicarbonate at a concentration of 27 to 30 mEq/L and 145 mEq/L, respectively, were infused postdilution at a rate of 66 +/- 7 mL/min and 2.81 +/- 0.12 L/hr, respectively. During the period of observation we evaluated the number of intradialytic hypotensions, the episodes of nausea, vomiting, headache (dialysis intolerance), body weight, the interdialysis weight gain, the duration of the dialysis session, the number of hospitalizations/patient, and the length of hospitalization/patient. At the end of each observation period we determined: Kt/V, protein catabolic rate, acid base balance, serum creatinine, serum calcium, serum phosphorus, alkaline phosphatases, and serum intact parathyroid hormone. After the switch from BD to either HDF or AFB, the results have shown a significant reduction of dialysis hypotension episodes (18 percent on BD, 14 percent on HDF, and 13 percent on AFB; BD v HDF, P = 0.001; BD v AFB, P = 0.0001; and HDF v AFB, P = NS) and of dialysis intolerance (3.3 percent on BD, 1.3 percent on HDF, and 1.1 percent on AFB; BD v HDF, P = 0.021; BD v AFB, P = 0.019; and HDF v AFB, P = NS). Kt/V improved significantly after the switch from BD to either HDF or AFB (1.17 +/- 0.06 on BD, 1.32 +/- 0.12 on HDF, and 1.32 +/- 0.13 on AFB; BD v HDF, P = 0.021; BD v AFB, P = 0.003; HDF v AFB, P = NS). Protein catabolic rate also improved in HDF and AFB compared with BD (0.90 +/- 0.12 on BD, 1.03 +/- 0.15 on HDF, and 1.04 +/- 0.14 on AFB; BD v HDF, P = 0.001; BD v AFB, P = 0.009; and HDF v AFB, P = NS). AFB showed a better correction of acidosis compared either with BD or HDF (serum bicarbonate, 20.3 +/- 1.1 mEq/L on BD, 20.8 +/- 2.2 mEqL on HDF, and 22.2 +/- 2.4 mEq/L on AFB; BD v HDF, P = NS; BD v AFB, P = 0.01; and HDF v AFB, P = 0.030). The other parameters observed did not differ. In conclusion HDF and AFB show a better dialysis efficiency and a better hemodynamic tolerance compared with BD. This fact is associated with an improvement in protein intake as assessed by kinetic criteria. Acetate-free biofiltration has the further advantage of a better control of the acid-base balance compared with BD and HDF. HDF and AFB are useful dialytic options to traditional BD hemodialysis even in patients older than 70 years.