Mass Transfer Characteristics of Hollow‐Fiber Dialyzers and Hemoperfusion Devices

Abstract

Clearance versus time tests were carried out on three charcoal-based hemoperfusion devices (Sandev, Becton-Dickinson and Gambro) using solutions of 1 gm/L sodium salicylate in a pH 7.4 buffer and in bovine blood at flow rates of 200 rnl/min. Similar tests were performed on a Cordis Dow 2.5 m2 hollowfiber dialyzer at a tube side flow rate (QB) of 200 ml/min. Buffer was pumped through the dialysate side at a flow rate (QD) of 400 ml/min. Two dialyzers were run in series at QB = 200 ml/min and QD = 500 or 1000 ml/min. Mass transfer resistances were computed from the test results. These values are useful in that they constitute an index of the intrinsic initial kinetics of solute transfer in each device. However, the clearance versus time curves indicate that these initial kinetics decrease at different rates for each hemoperfusion unit as sorption capacity begins to be depleted. In contrast, the initial clearances for the dialyzers remain at their initial values. These data reveal much about the relative mass transfer characteristics of these devices. mass transfer, hemoperfusion, dialyzers, clearances, kinetics Nomenclature A C fluid phase concentration K overall mass transfer coefficient Q volumetric flow rate RT total mass transfer resistance S W total solute transfer rate z axial length B blood or buffer D dialysate total external area for mass transfer external surface area per unit length of column Subscripts

Skin Allograft and Vascularized Composite Allograft

“…[42][43][44][45] The indirect pathway also results in the production of allospecific antibodies by B-cells, leading to a delayed type graft rejection. [46][47][48] Auchincloss et al showed that skin grafts from MHC knockout mice (DCs lacking MHC-II) were rejected despite the direct pathway inhibition (eg, lack of MHC-II on DCs), suggesting that the indirect pathway is sufficient to cause allograft rejection. [49][50][51] Experimental techniques to modify the immunogenic response to allogeneic grafts have been trialed with some success in experimental animal studies.…”