High bicarbonate dialysate in haemodialysis patients: effects on acidosis and nutritional status.

BACKGROUND: Metabolic acidosis adversely affects both protein and bone metabolism in patients with chronic renal failure, and could also affect morbidity and mortality. This trial aimed to investigate the effects of different dialysate bicarbonate concentrations on control of acid base balance, and nutritional status. METHODS: Forty-six stable haemodialysis patients were dialysed using LowBic. (30 mmol/l) or HighBic. (40 mmol/l) bicarbonate dialysate in a single blind double crossover trial, of two consecutive six-month periods. Blood gas analysis, anthropometric indices and dialysis dose were measured, in addition to biochemical indices. RESULTS: Predialysis 'arterial' plasma pH values were significantly higher when using the HighBic. dialysate (LowBic. 7.38 +/- 0.05, HighBic. 7.43 +/- 0.04, P < 0.001), as was predialysis serum total CO2 at all times during the study (P < 0.01). Kt/V, (LowBic. 1.27 +/- 0.19, HighBic. 1.27 +/- 0.25), urea generation rates (UGR) (LowBic. 1.99 +/- 0.77, HighBic. 1.92 +/- 0.77 mmol/min), and normalized protein catabolic rate (NPCR) (LowBic. 1.04 +/- 0.26, HighBic. 0.99 +/- 0.28 g/kg/day) did not differ, and values of parathroid hormone (PTH) were comparable. Triceps skinfold thickness (TSF) showed a significant change (LowBic. 14.8 +/- 6.9-11.8 +/- 5.5, HighBic. 14.9 +/- 6.3-15.8 +/- 6.4 mm, P < 0.05) which was reversed following dialysate change (HighBic. 11.8 +/- 5.5-13.3 +/- 7.2, LowBic. 15.8 +/- 6.4-13.8 +/- 6.7 mm, P < 0.05). No differences in mid upper arm circumference were found. CONCLUSIONS: Bicarbonate dialysate concentrations of 40 mmol/l were safe, well tolerated, and produced better control of acidosis, with an increase in TSF, compared to a bicarbonate concentration of 30 mmol/l.