Every 2 seconds a blood transfusion is needed in the United States. Let me walk you through what you need to know about how we derive and how we use blood products.
We give transfusions as a way to supplement blood loss, maintain hemostasis and oxygenation in a wide range of scenarios: major blood loss due to trauma, anticoagulation, childbirth and major surgeries. As well as chronic conditions like cancers and sickle cell disease.
5 Blood Products from Whole Blood
From whole blood we can derive:
- Packed Red Blood Cells (PRBC)
- Fresh Frozen Plasma (FFP)
- Platelets
- Cryoprecipitate
- Prothrombin Complex Concentrate (PCC)
How is Donated Blood Processed?
When a donor gives blood, the sample collected is referred to as whole blood. Whole blood is spun in a centrifuge.
A centrifuge will spin blood at a high rate causing it to separate into different blood components.
Red Blood Cells
With the initial spin whole blood will separate into red blood cells and platelet-rich plasma.
The separated red blood cells are referred to as packed red blood cells (PRBCs).
We refer to them as “packed” because each unit of PRBCs has twice the hematocrit (oxygen carrying capacity) as whole blood.
PRBCs will provide oxygen to tissues during a bleed. They can achieve tissue perfusion with less volume than giving whole blood.
Each unit (250ml) will raise hemoglobin by 1-2g/dL.
The recipient and donor blood must be ABO matched for whole blood transfusions. In the blood compatibility unit, I explain three easy steps to match blood recipients and donors.
Plasma
Along with PRBCs, whole blood separates into plasma when centrifuged.
A donor can directly provide plasma via plasmapheresis. A apheresis machine can derived whole blood from the donor, separate the plasma and return red blood cells and platelets back to the patient.
Plasma is the liquid part of blood after removing all cells (red and white blood cells and platelets). It has few cells and contains proteins, mainly clotting factors.
Plasma is then used to create fresh frozen plasma and to isolate platelets.
Fresh Frozen Plasma
Plasma is rapidly frozen to create fresh frozen plasma that will have a shelf life of 1 year from the date collected.
FFP has a lot of clotting factors which is helpful for bleeding when normal blood clotting is affected, such as in warfarin toxicity and severe liver disease.
Administration of FFP requires compatibility between the donor and receiver. Compatibility is not the same between blood groups for red blood cell transfusions and plasma transfusions.
- Patients with type A blood can receive A or AB FFP
- Patients with type B blood can receive B or AB FFP
- Patients with type AB blood can receive AB FFP
- Patients with type O blood can receive A, B, AB, or O FFP
Rhesus (Rh) factor matching is not essential for FFP transfusion but some facilities may require it.
Cryoprecipitate
Fresh frozen plasma can be further separated to create cryoprecipitate. When fresh frozen plasma is thawed, the precipitate from that is cryoprecipitate.
It is concentrated with clotting factor VIII, XIII, fibrinogen and Von Willebrand factor.
Cryoprecipitate has very specific uses because it contains very specific clotting factors.
Patients with:
- hemophilia A (factor VIII deficiency)
- Von Willebrand disease (deficiency in carrier for factor VIII)
- fibrinogen deficiency …
are the usual candidates for cryoprecipitate transfusions
Rh factor compatibility is not required with cryoprecipitate transfusions.
Cryoprecipitate is acellular (like the plasma it is derived from). It has no red blood cells and very little plasma. ABO antigens are found on the cells and in body fluids. So there is very low potential for the presence of antigens that can induce infusion reactions. It is possible, especially with larger volume transfusions but unlikely with typical use of cryoprecipitate.
For this reason, ABO compatibility for cryoprecipitate transfusions are not always performed. It tends to be more of an institution based policy if it is required or not.
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Platelets
Platelet infusions are used in patients who present with bleeding and thrombocytopenia (abnormally low platelet counts ie, platelet count <20,000/μL). Because platelets play a major role in clotting, thrombocytopenia places a patient at risk for bleeding.
Patients on certain chemotherapeutic agents are at risk for thrombocytopenia because these agents attack rapidly dividing cells (like cancers) but also those of the bone marrow which is where platelets are made.
Other drug that can cause thrombocytopenia include linezolid and carbamazepine.
The Problem with Platelet Transfusions and ABO Matching
Every 15 seconds someone is the US needs a platelet transfusion.
Platelets can be specifically extracted from donors (plateletpheresis) or they can be separated from whole blood donations. Once extracted they are stable for only 5 days. Supply is very limited.
If we ABO matched platelets, this would further limit the supply.
We avoid the need for ABO matching, donor plasma (in which platelets are suspended) is replaced with plasma additive solution (PAS).
PAS minimizes the risk of hemolysis between mismatched ABO groups because it reduces the amount of plasma protein including antigens by 65%.
Because of this substitution of plasma with PAS, ABO matching is not required for platelets. Studies show that PAS platelets transfusions have a lower incidence of allergic transfusion reactions compared to 100% plasma.
If we use 100% plasma, the donor should be ABO matched with the recipient’s red blood cells.
Platelets do not expressed Rh antigens, Rh compatibility is not required unless specified by your institution.
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Prothrombin Complex Concentrate
Cryoprecipitate can be further separated into prothrombin complex concentrate (PCC). This is done via ion-exchange chromatography to isolate 3-factor, 4-factors or activated PCC (aPCC). This process creates a product that is 25 times more concentrated in clotting factors that fresh frozen plasma.
Whichever PCC you choose. they will always contain factors II, IX and X.
Factor 4 and PCCa also contain factor VII in an inactive and activated form respectively.
They all contain varying amounts of the naturally occurring anticoagulants protein C and S and well as unfractionated heparin.
PCCs are used for used for reversal of antithrombotic agents in acute major bleeding or when reversal is needed prior to an urgent surgery or invasive procedure.
Compared to donated blood products, PCCs are advantageous because we can get treatment to patients faster:
- Immediate availability: simple reconstitution of PCC rather than thawing blood products and awaiting delivery from lab
- No ABO matching
- Smaller infusion volumes: the faster drug gets to patients the faster it will work
PCCs are also advantages in terms of product longevity:
- Simple Storage: Stored in non-refrigerated vials instead of refrigerated or frozen bags of blood products.
- Long Shelf Life: Some PCCs can last up to 36 months, unlike the shorter lifespan of donated blood products.
PCCs are also advantageous in terms of safety:
- Transfusion Related Lung Injury is not a concern with the administration of PCCs because antibodies are removed from the product
Risk of Blood Product Infusion
Administration of these blood components are not without significant risk. Transfusion reaction is a broad term we use to refer to any number of events that can occur as a direct result of the infusion of blood or its components. Those events can be mild with non specific symptoms like chills, fever, rashes or tachycardia. But they can also be as severe as hemolysis, sepsis or transfusion related lung injury (TRALI).
To further complicate things, these infusion reactions can occur during infusion or days to weeks later. It can be the results of etiologies including immunologic responses to antibodies in donor blood, blood contamination during processing or volume overload from the infusion. Because of these complexities transfusion reactions can be hard to diagnose.
The American Red Cross has a comprehensive resource on practice guidelines for all the infusions we’ve discussed.
If you’ve found this unit helpful I would love to hear from you! Leave a question or comment below.
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