VANCOMYCIN MASS-TRANSFER CHARACTERISTICS OF HIGH-FLUX CELLULOSIC DIALYZERS

Background. In comparison to conventional haemodialysis membranes, hig hly permeable membranes allow a broader spectrum of solute removal, in cluding enhanced elimination of vancomycin (1448 Daltons). However, th e mass transfer characteristics of vancomycin removal by highly permea ble membranes have not been adequately assessed. An understanding of v ancomycin's predominant dialytic mass transfer mechanism under a given set of operating conditions, including dialyser type and flow rates, may permit more accurate dosing of the drug. Methods. We performed a m ass transfer analysis of vancomycin removal by a high-flux dialyser, c ellulose triacetate (CT). In a cross-over fashion with a 3-week washou t between treatments, eight subjects received vancomycin 1000 mg (1) d uring the last hour of CT haemodialysis; or (2) after dialysis. Serial urea and vancomycin serum concentrations were used to assess dialytic removal. Results. Dialysis removed 26.2% (mean; range 16-44%) of the administered vancomycin dose. While vancomycin removal and (Kt/V)(urea ) were directly correlated (r = 0.88; P < 0.005), no correlation was o bserved between vancomycin removal and weight-normalized ultrafiltrati on rate. Conclusions. These findings suggest that for the CT dialyser and dialysis operating conditions employed in this study, vancomycin c learance was primarily mediated by diffusion. As such, these data chal lenge the general concept that convection is primarily responsible for the removal of solutes in the same molecular weight class as vancomyc in during high-flux dialysis.