Blood bag case study

Red blood cells, used to replace blood loss in surgery, and for certain forms of anaemia  

Whole blood, rarely used except to counteract sudden massive blood 

Platelets, for patients with a low platelet count (leukaemia or after bone marrow transplants)  

Plasma, for processing to extract immvmoglobulin, albiunin (to manage severe shock and burn injuries), and clotting factors, such as factor VIII. 

When a donor initially gives whole blood it is initially stored in a DEHP plasticised PVC bag (see Section 15.3.3 for abbreviation). Usually, blood is centrifuged within 8 h, and separated into red blood cells and plasma. The plasma can be centrifuged further to remove platelets. However, there is an alternative process of apheresis (removal of blood from a donor and reinfusion after components are removed), where platelets are removed continuously in disposable polycarbonate centrifuge luiit. 

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The blood bag case study illustrates the use of polymeric film as a flexible container. It considers the permeability of polymers, plus processes for fabricating plastics film. Plasticised PVC has dominated the market for years, but there could be a changeover to flexible polyolefin films. The case study on replacement joints for implanting in the body illustrates wear and the effects of wear debris. Research continues on improving the wear resistance of the ultra high molecular weight polyethylene (UHMWPE) and mitigating the effects of sterilisation on the implant properties. 

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