The change from conventional HDF to on-line HDF results in increased convective removal and fluid replacement (18 l/session). During on-line HDF treatment, dialysis dose was increased for both small and large molecules with a decrease in uraemic toxicity level (TAC). On-line HDF provided a better correction of anaemia with lower dosages of erythropoietin. Finally, blood pressure was easily controlled.

An American National Study shows that survival benefits from higher dialysis doses appear to be present up to a Kt/V level of 1.3 or a urea reduction ratio (URR) of 70%. The effect of increasing dialysis efficiency magnified urea rebound and the error in URR determinations. Several formulas have been developed to calculate URR considering the urea rebound (URRr). Smye and coworkers have proposed a method whereby the equilibrated blood urea nitrogen is predicted by additional intradialytic urea sample. Maduell and colleagues, based on analysis of postdialysis urea rebound, have proposed a method whereby the urea rebound is predicted. To compare measured URRr to estimated by Smye and Maduell formulas, 384 patients were studied, 211 males and 173 females, who received a dialysis session with their habitual parameters. Measurements of plasma urea concentration were obtained at the beginning, 90–100 min following the start of dialysis, at the end, and 45 min after dialysis. The postdialysis urea rebound was 22.4 ± 9.7%. The urea kinetic model Kt/V was 1.365 ± 0.26, and Kt/Vr was 1.14 ± 0.23. URR was 68.7 ± 6.6%, and when it was calculated with urea rebound, it decreased to 61.9 ± 7.4%. The URRr correlated with calculations by Smye and Maduell formulas: 60.7 ± 8.4 (r = 0.722, p < 0.001) and 61.8 ± 6.6 (r = 0.933, p < 0.001), respectively. The precision of estimated limits of agreement and percentage of error by Bland and Altman analysis show that URRr estimated Maduell formula could be used in place of the URRr. Otherwise, the degree of agreement of the Smye method was not clinically acceptable. In conclusion, our results led us to suggest that in actual dialysis, the use of URR is not adequate for delivered hemodialysis dose, and URRr should be used. URRr estimated by Maduell formula could be a simple and accurate method for use in clinical practice. The recommended dialysis dose by the American National Study of URR of 70% could correspond, considering urea rebound, to Kt/Vr 1.18 or URRr of 64%.

Eight patients undergoing acetate-free biofiltration (AFB) suffered aluminum intoxication. The source of this outbreak was parenteral exposition to high concentrations of aluminum in sodium bicarbonate solutions. The manufacturer of bicarbonate solutions used in AFB was substituted in May 1994 and the solutions were stored in glass containers. At the peak of intoxication (July 1994) serum aluminum determination revealed an average value of 147.3 ± 21 µg/l. Aluminum levels in bicarbonate solutions were 400 µg/l. Serum ferritin rose from 307.4 ± 161 to 735.6 ± 206 ng/ml, whereas MCV decreased significantly from 98.4 ± 9 to 90.1 ± 10 fl. No significant changes were found in hemoglobin, neither in plasma iron, nor in iron transferrin saturation. The doses of recombinant human erythropoietin showed a considerable increase. The replacement solutions were changed and a new solution, stored in plastic containers and with aluminum levels lower than 10 µg/l, was used. The biochemical parameters were normalized. This outbreak demonstrates the need for a stringent control of aluminum-containing replacement fluids.