ELSEVIER PI1 SOl42-9612(96)00018-X zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIH Eiomateriols 17 (1996) 1995-2002 0 1996 Elsevier Science Limited Printed in Great Britain. All rights reserved 014%9612/96/$15.00 Influence of wall shear rate on parameters of blood compatibility of intravascular catheters zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPO N.P. Rhodes*, T.V. Kumar$ and D.F. Williams* *Department of Clinical Engineering, University of Liverpool, PO Box 147, Liverpool L69 3BX, UK; +Sree Chitra Tirunal institute for Medical Sciences & Technology, Biomedical Technology Wing, Satelmond Pa/ace Campus, Poojappura Trivandrum-695010, India Three polymeric materials (silicone, PVC and nylon) were compared in an in vitro perfusion model, whereby 5 ml whole blood were perfused along 1 m lengths of polymeric tubing of 1 mm internal diameter at wall shear rates of up to lOOOs_‘. Perfusion took place at 37°C for 30 min. The polymers were investigated for platelet activation, granulocyte secretion, complement activation and contact phase activation. These parameters were also analysed in static contact for comparison. All the parameters measured displayed a dependence on wall shear rate. In all the materials studied, platelet adhesion and platelet activation increased with increasing flow rate. Granulocyte elastase release increased slightly with increasing flow rate up to 300~~‘. Complement activation was greatest for PVC at lOOOs_‘, greatest for nylon at lOOs_‘, but there was no measurable difference at either rate for silicone. All samples caused an increase in clotting time with increasing wall shear rate. PVC was the most platelet compatible material, nylon the worst. Silicone caused least contact phase activation, PVC and nylon the most. 0 1996 Elsevier Science Limited. Keywords: Wall shear rate, blood compatibility, intravascular catheters Received 10 April 1995; accepted 7 February 1996 Among the most common types of medical device that comes into contact with blood are intravascular catheters. These are made from one of several varieties of polymer and are used in several different situations of both diagnostic and therapeutic character. It is widely recognized that the placement of such catheters within the vascular system carries the attendant risk of thrombus formation1-3. A considerable amount is known about the mechanisms of the interactions between blood and polymers and a certain amount of information is available concerning variations in blood compatibility between various materials. There is still, however, a considerable uncertainty as to how different materials will perform under given clinical conditions, where variables of the host may be as important as variables of the catheter. Amongst the most important of these variables are the characteris- tics of blood flow. This should not be too surprising since the interactions between a solid surface and components of a complex fluid flowing over that surface should be dependent upon the characteristics of transport of the critical components in that fluid. It is well known that the formation of a thrombus is dependent upon either or both the behaviour of platelets at or near the surface and on the protein-based Correspondence to Dr N.P. Rhodes. coagulation cascade4-6. The haemodynamic characteris- tics that control platelet movement and protein transport near the surface are therefore likely to be of considerable significance in controlling events. Naturally it should be expected that there will be considerable differences in behaviour between conditions of turbulent and laminar flow and, even under laminar flow conditions it should be anticipated, and indeed it is observed, that variations in wall shear rates will have an influence on behaviour7. In the experiments reported in this study, a number of parameters of blood compatibility have been assessed, under in vitro conditions, with respect to wall shear rate. A multiparametric approach has been taken and the influence of wall shear rate assessed in each case. The major biochemical and cellular pathways generally regarded as important in material haemocompatibility have been studied, namely platelet adhesion, platelet activation, contact activation, neutrophil activation and complement activation. Platelet adhesion is important as a first stage in the generation of a thrombus and it was this parameter which was previously regarded as the most important indicator of the unwanted reactivity of a material to bloodsSg. Kush” , Experiments by Feuerstein and however, in which platelets have been observed flowing over a material surface by 1995 Biomaterials 1996, Vol. 17 No. 20