Bicarbonate versus acetate dialysate in long term haemodialysis: impact on acid-base status, delivered Kt/V and protein nutritional status. A prospective crossover study

ABSTRACT

We selected 40 cases of chronic renal failure [CRF] [25 males and 15 females] on thrice weekly haemodialysis [HD] using acetate for at least 1 year before study onset. All cases were allowed unrestricted protein intake starting one month before they were randomly divided into 2 groups matched for age, gender, body weight [BW] and socioeconomic status, Group 1 were shifted to bicarbonate dialysis while Group 2 patients were kept on acetate dialysis for 3 months then cross over was done for the following 3 months. Both biocarnonate and acetate were used at a fixed concentration of 36 mmol/L. Prescribed Kt/V was kept constant throughout the 6 months. Pre and post dialysis [Dx] blood pH and serum bicarbonate [Sbic].predialysis serum prealbumin [Spalb], and transferring [Stf], triceps skin fold thickness [TSF], mid arm muscle circumference [MAMC] as well as protein catabolic rate [PCR and nPCR] and urea reduction ratio [URR] were estimated at the onset and at the end of each 3 month period. Delivered kt/V was estimated from URR. Pre Dx Sbic and pH were significantly higher during bicarbonate dialysis compared to acetate dialysis [p<0.001]. Spalb increased significantly in Group 1 during bicarbonate and decreased significantly during acetate dialysis [p<0.00011 and 0.06,respectively] while in Group 2 it increased significantly in both periods [p<0.05 and 0.004.respectively]. Stf didn't show any significant change throughout the study. TSF, MAC and MAMC increased significantly in Group 1 during bicarhonate dialysis and decreased significantly during acetate dialysis [p<0.001,0.02.0.001,0.05,0.004 and 0.03,respectively for TSF, MAC and MAMC at 0,3 months and MAMC at 0,3 months and 6 months] while in Group 2 they did not change during acetate dialysis and increased significantly during bicarbonate dialysis [p<0.05,<0.002.>0.05, <0.03, >0.05 and <0.05, respectively]. nPCR increased significantly in Group 1 during bicarbonate dialysis and did not change during acetate dialysis [p<0.001 and >0.05, respectively] while in Group 2 nPCR did not change during acetate dialysis and increased significantly during bicarbonate dialysis [p>0.05 and >0.05, respectively]. Although prescribed Kt/V did not change throughout the study, delivered Kt/V increased significantly in Group 1 during bicarbonate dialysis and decreased significantly during acetate dialysis [p<0.001 and < 0.02, respectively]. In Group 2 delivered Kt/V did not change during acetate dialysis and increased significantly during bicarbonate dialysis [p>0.5 and <0.0001, respectively]. Conclusions: 1. Bicarbonate dialysis offers better blood pH and Sbic levels 2. Optimized serum pH and bicarbonate offers improvement in protein intake evidenced by increased nPCR associated with improved protein anabolism as evidenced by increased Spalb, TSF, MAC and MAMC. 3. Increased delivered Kt/V is likely due to better patient compliance during bicarbonate haemodialysis