RESUMEN

The ultrafiltration characteristics of a commercial dialyzer were examined by measuring the sieving coefficient (s.c.) for three proteins, i.e., cytochrome c, chymotrypsinogen, and albumin, in a bovine blood system. Test blood was passed through a filter at a blood flow rate of 200 ml/min and filtrate was collected at an ultrafiltration flow rate of 10 ml/min from a port located near the blood inlet. The s.c. for cytochrome c and chymotrypsinogen in bovine blood sharply increased at the beginning of the experiment and reached a steady value that was about 60% of that obtained in an aqueous solution system. This may have been caused by the masking effect of the erythrocytes. The s.c. for albumin at steady state in bovine blood that contained added albumin only was almost the same as that obtained in the aqueous solution system. When all three proteins were added to bovine blood, however, the s.c. for albumin showed a steady value (after a slight decrease at the beginning of the experiment) the absolute value of which was higher than that found in the aqueous solution system. This phenomenon may have been caused by the stirring effect of erythrocytes that would disturb the concentration polarization of albumin formed near the membrane.

Asunto(s)

RESUMEN

BACKGROUND: Many synthetic polymeric membranes have been widely used for blood purification therapies for removing larger solutes and for better blood compatibility. METHODS: Five different filters with polyester polymer alloy (PEPA) membrane (Nikkiso) that included polyvinylpyrrolidone (PVP), that is, standard-pore-size FLX (PEPA with PVP(-)), standard-pore-size FDX (PEPA with PVP(+)), new FDX (PEPA with PVP(++)), larger-pore-size FDY (PEPA with PVP(+)), and new FDY (PEPA with PVP(++)), were evaluated in terms of in vivo blood compatibility and aqueous in vitro sieving coefficient (s.c.) for albumin. RESULTS: FDY showed excellent small changes in C3a concentration during the treatment right after switching from polysulfone membrane, leaving no significant changes in other blood-compatible indices. New FDY, in contrast, showed less biocompatible characteristics in terms of C3a, which may be caused by increased use of PVP. FLX (no PVP) showed the highest s.c. for albumin. With a hydrophilic agent (PVP), the s.c. was greatly reduced in FDX. By enlarging the pore diameter in FDY, the s.c. increased in accordance with the enlargement. Generally speaking, polysulfone filters with PVP(+++) reach the peak s.c. value approximately 10 min after starting the experiment. The s.c. of the PEPA membrane with no or small amount of PVP, which showed excellent blood compatibility, never showed peaks, whereas the peak s.c. values were found in new PEPA with increased amount of PVP that showed higher C3a changes. CONCLUSIONS: The separation characteristics of aqueous albumin may be related to its blood compatibility.