Influence of dialysate composition on cardiovascular function in isovolaemic haemodialysis

Haemodynamic studies were made in eight patients before and during isovolaemic dialysis with five different dialysis solutions which varied with regard to concentration of sodium, acetate, bicarbonate and urea. Low sodium (133mmol/L) in the dialysate induced a fall in blood pressure both with and without urea removal, but no significant fall in peripheral vascular resistance. Acetate in the dialysate at higher sodium concentration (140mmol/L) resulted in peripheral vasodilation but no fall in blood pressure due to a compensatory increase in heart rate and cardiac output. We conclude that a fall in plasma tonicity (sodium) is the most important pathogenetic factor in dialysis associated hypotension; fall in total osmolality (mainly urea) is of no importance and acetate vasodilation can be compensated for haemodynamically provided that tonicity is kept stable.