As you might very well know blood contains following substances:
- Plasma proteins (albumin, globulin, fibrinogen etc.)
- Clotting factors
All these are essential for body homeostasis. Human body can suffer from the lack of any of these substances.
Lack of plasma proteins results to swelling of the feet (fluid escapes blood vessels) and ascites (intra-abdominal fluid) due to low colloid osmotic pressure. They are many albumin products available which can be used to substitute the lack of albumin in blood.
They are not that many indications to give frozen plasma to patients (Medscape, British Committee for standards in haematology). The main indication to frozen plasma is the treat the lack of clotting factors. Clotting factors cannot be synthesized compared other substances in the plasma and therefore frozen plasma is manufactured and given to patients.
Common reason for lack of clotting factors is major bleeding (trauma etc.) Therefore frozen plasma is routinely given to patients with major trauma and subsequent bleeding. Patients with haemophilia or coagulation factor deficiency and treated with frozen plasma. Third common indication for frozen plasma transfusion is any kind of liver disease. Liver is responsible for manufacturing coagulation factors and therefore patients suffering fro severe liver disease do not have normal levels of clotting factors in their blood.
Of course there many other indications for frozen plasma transfusion but I think those cover the most important one and give some insight.