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Blood Components
Why blood components and not whole blood?

Fresh, whole blood is a vestige of transfusion practice when technology did not allow us to separate the individual components of this precious resource.

When whole blood is stored at 2o to 6o Centigrade, 80 – 90 per cent of platelets become non-functional and 30 – 40 per cent of labile coagulation factors are lost.

The processing of donor blood, which includes screening for infectious diseases, is rarely completed within 24 hours. The whole blood that remains at the end of 24 hours is valuable only for its red cells.

Therefore, it is advisable to use components as per requirement.

Components are separated from whole blood within 4 to 6 hours and stored in special conditions required for each component. The conditions are:
  • Red cells at 2o to 6o Centigrade
  • Platelets on an agitator at 20o to 24o Centigrade
  • Fresh frozen plasma at -30o to – 70o Centigrade
  • Cryoprecipitate at -30o Centigrade
Transfusing specific components reduces the risk of side-effects. It also allows several patients to benefit from one unit of whole blood.

COMMON BLOOD COMPONENTS
Packed Red Cells
What are packed cells: Packed red cells are prepared by removing most of the plasma from a unit of whole blood. Typically, one unit of whole blood (450 ml) yields around 220 ml of RBCs.

Who needs packed cells: Packed red cells are usually transfused to correct low haemoglobin levels and increase red cell mass in anaemic patients. Transfusion with packed cells reduces the risk of circulatory overload due to lower volume of anti-coagulant and plasma. It also reduces the severity and incidence of allergic reactions associated with plasma proteins.

One unit of packed cells in an adult patient raises the haematocrit by 3 per cent and haemoglobin by 1g/dl.

Fresh Frozen Plasma
What is fresh frozen plasma: Fresh frozen plasma is plasma that is frozen within 6 to 8 hours after donation to preserve its clotting factors. And, yes, it needs to be thawed before it is transfused. FFP contains plasma proteins and all coagulation factors including labile coagulation factors V to VIII. It is usually administered in the dose of 10-15 ml/kg of body weight.

Who needs fresh frozen plasma: It is mainly transfused into patients with certain bleeding disorders, where the missing clotting factor is unknown or when the specific clotting factor is not available. Plasma also is used when bleeding is caused by insufficient production of all or many of the different clotting factors as a result of liver failure or severe infection.

Platelet Concentrate
What are platelets: Platelets are also called thrombocytes whose most important function is the clotting of blood.

Units of platelets are prepared by using a centrifuge to separate the platelet-rich plasma from a unit of whole blood. The platelet-rich plasma is then centrifuged again to further concentrate the platelets.

Platelets may also be obtained from a donor by a process known as apheresis or platelet pheresis. Here, blood is drawn from the donor into an apheresis instrument, which uses centrifugation to separate blood from its components. While retaining the platelets, the instrument returns the remaining blood to the donor.

The process produces a component that contains six times as many platelets as a unit of platelets obtained from whole blood by conventional means.

Who Needs Platelets: Platelets are used to treat a condition called thrombocytopenia (shortage of platelets) and in patients with abnormal platelet function. One unit of random donor platelets per 10 kg body weight is the usual recommended dose. 1 unit of RDP increases recipient platelet by 5,000 to 7,000/mm3 in an adult, 20,000/mm3 in a child of 18 kg body weight and 75,000/mm3 to 100,000/mm3 in an infant.

Cryoprecipitated Antihaemophilic Factor or Cryoprecipitated AHF What is Cryoprecipitated AHF: These are precipitated proteins that are separated from blood plasma. It is rich in clotting factors, including Factor VIII, fibrinogen, von Willebrand factor and Factor XIII.

Who needs Cryoprecipitated AHF: This blood component is used to prevent or control bleeding in individuals with haemophilia and von Willebrand’s disease, which are major coagulation abnormalities. It is also used for patients with congenital or acquired fibrinogen deficiency. Cryoprecipitated AHF may also be used as a haemostatic preparation of fibrin sealant or fibrin glue during surgery.

Saline Washed Packed Cells
What are Saline Washed Packed Cells: This is a unit of concentrated red blood cells (packed cells) that have been washed two or three times with sterile solution (normal saline). They are then re-suspended in the saline solution. Washed red blood cells are free of almost all traces of plasma.

Who needs saline washed packed cells: This specially treated blood component is transfused into patients (instead of just packed cells) who are hypersensitive to plasma proteins or when multiple transfusions are anticipated.
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