A comparison of solute clearance during continuous hemofiltration, hemodiafiltration, and hemodialysis using a polysulfone hemofilter.

The clearance of urea, creatinine, amino acids, vancomycin, and phenytoin was measured in vivo in a small animal model during continuous venovenous (CVV) hemofiltration, CVV hemodiafiltration, and CVV hemodialysis using a 0.25 m2 polysulfone hemofilter. Six domestic piglets (weighing 6-11.8 kg) each received 1 hr of all three techniques in random order. Blood flow was 50 ml/min. During CVV hemofiltration, filtrate production was 500 ml/hr and dialysate flow was zero. During CVV hemodiafiltration, filtrate production was 250 ml/hr and dialysate flow was 250 ml/hr. During CVV hemodialysis, net filtrate production was zero and dialysate flow was 500 ml/hr. The ratio of concentration of solute in filter effluent to concentration in whole plasma was derived for each solute during each of the three techniques. Mean (SD) effluent:plasma ratio for urea during CVV hemofiltration was 0.957 (0.038), CVV hemodiafiltration 0.876 (0.109), and CVV hemodialysis 0.754 (0.123); creatinine 0.942 (0.05), 0.934 (0.056), and 0.814 (0.057); amino acids 0.996 (0.344), 0.904 (0.196), and 0.778 (0.18). For small unbound solutes, there is a decrease in clearance of 6% from CVV hemofiltration to CVV hemodiafiltration and a further decrease of 14% from hemodiafiltration to hemodialysis. The effluent:plasma ratio for vancomycin during CVV hemofiltration was 0.739 (0.082), CVV hemodiafiltration 0.643(0.063), and CVV hemodialysis 0.509 (0.081), corresponding to a decrease of 30% from CVV hemofiltration to CVV hemodialysis. The effluent:plasma ratio for phenytoin was 0.302 (0.028) during CVV hemofiltration and was not significantly different during CVV hemodiafiltration or CVV hemodialysis.(ABSTRACT TRUNCATED AT 250 WORDS)