Phosphorus kinetics during haemodialysis and haemofiltration.

Phosphorus excretion during haemodialysis positively correlates with the plasma inorganic phosphorus (Pi) concentration and the dialyser Pi clearance. Therefore, by using highly efficient dialysers or haemofilters, disciplined patients may achieve a well regulated P-balance. The plasma Pi concentration time curve during haemodialysis or haemofiltration must be seen as the result of passive diffusion combined with an active mobilisation of Pi from a rapidly exchangeable P-pool. The plasma Pi concentration hardly falls below the normal range in dialysis patients, regardless of the quantity of Pi removed by haemodialysis or haemofiltration. The stability of plasma Pi demonstrates the existence of a mechanism for phosphate regulation in body fluids, independent of the calcium homeostasis.