Completed notes of the course

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Biomachines – Prof. Costantino A.Y. 2017/2018 Author: Guido Nannini 1 Coagulation When blood gets in contact with non-biological surfaces, coagulation occurs. Coagulation is a phenomenon which develops cascaded: platelets get stuck each other and activate fibrinogens, a protein component of blood, which transforms into fibrine, a protein, that together with platelets form a clot of new tissue over a wound site. Coagulation can be controlled over non-biological surface by using two kinds of drugs: anticoagulant and antiaggregant. Anticoagulants impede the transformation of fibrinogens into fibrine, so the clot is not formed. The platelets try to react to unknown surfaces, but they can’t aggregate, so we manage to avoid the formation of small masses that may flow in the circulatory system and occlude small vessels (it can happen that capillaries in the brain get occluded, so brain is not well perfused). To impede the formation of these small masses we basically transform blood into a non-reactive fluid with respect to non-biological surfaces. Every time that we introduce a biomedical device that is in contact with blood we have to use anticoagulant. Antiaggregant agents have a less massive effect on blood: platelets are inhibited to stuck on non-biological surfaces. The advantage in using antiaggregant agents instead of anticoagulants, lies in the fact that the patient doesn’t become haemophiliac. Haemophilia is the incapacity of creating coagulation, haemophiliac individuals risk to die by haemorrhage, because they can’t repair wounds. When a patient is prescribed with anticoagulants he becomes temporarily haemophiliac, so when we deal with permanent prosthesis (like heart-valves) we have to use antiaggregant agents. No material is completely compatible with blood when…