The advent of high-efficiency
hemodialyzers has afforded improved efficiency of
urea clearance; however, increased clearance of other substances, particularly
antibiotics, also may occur, necessitating changes in clinical practice. Accordingly, we compared the efficiency of
gentamicin removal using two different
hemodialyzers, a conventional saponified
cellulose ester (CD 135) and a high-efficiency
cuprammonium rayon dialyzer (TAF 175L), in eight hospitalized patients undergoing
antibiotic therapy for suspected or proven gram-negative
infection. The rate of dialysis, estimated as the ratio of dialyzer
urea clearance (K) to
urea distribution volume (V) (K/V
urea), and the total elimination rate constant (k) of
gentamicin were measured during 17
hemodialysis treatments. The K/V
urea for the two dialyzers, TAF 175L and CD 135, was 0.390 +/- 0.024 hr-1 and 0.413 +/- 0.129 hr-1 (P = NS), respectively. The TAF 175L
hemodialyzer was almost twice as efficient in removing
gentamicin as the CD 135: TAF 175, k = 0.263 +/- 0.024 hr-1; CD 135, k = 0.132 +/- 0.027 hr-1 (P < 0.001). Moreover, the rate of dialysis (K/V
urea) was correlated with k of
gentamicin for the TAF 175L dialyzer (r2 = 0.50, P < 0.02) but not for the CD 135 dialyzer. We conclude that dialyzer characteristics and the rate of dialysis (K/V
urea) should be taken into consideration when determining the dosage of
gentamicin in patients on
hemodialysis.