Blood and blood products are used for transfusion in various situations in medicine. Blood products are also called blood based products.
Here, it is pertinent to mention the term blood substitute which is a substance used to mimic and fulfill some functions of biological blood. It aims to provide an alternative to blood transfusion.
Blood transfusion is often required as part of treatment to treat the deficiency of whole blood, blood components, anemia, hereditary hematological diseases and to compensate blood loss.
Indications of Blood or Blood Products Transfusion
- Traumatic severe blood loss
- Hemorrhage from pathological lesions, for example from the gastrointestinal tract.
- During major operative procedures where a certain amount of blood loss is inevitable.
- Following severe burns where, despite initial fluid and protein replacement, there may be associated hemolysis.
- To arrest hemorrhage or as a prophylactic measure prior to surgery, in a patient with a hemorrhagic state such as thrombocytopenia, hemophilia or liver disease
- To supplement a deficient blood component
How Blood is Collected from Donors?
Before donation, the donors are screened for the diseases which could be transferred, in particular hepatitis B and C viruses, and HIV.
For blood donation, the donor lies on a couch, a sphygmomanometer cuff is applied to the upper arm and inflated to a pressure of 70-80 mmHg.
After introducing 0.5 ml of local anesthetic, a 15G needle is introduced into the median cubital vein at the elbow and 410 ml of blood allowed to run into the bag containing 75 ml of citrate potassium dextrose anticoagulant solution.
During collection, the blood is constantly mixed with the anticoagulant to prevent clotting, and at the end of the procedure the tube is clamped and the needle removed. Specimens for use in blood grouping and cross-matching procedures may be obtained by clamping off small sections of the plastic tubing containing the donor blood.
All blood for transfusion must be stored in special blood bank refrigerators controlled at 1-6 degrees centigrade. The shelf life is 35-42 days
The red blood cells, or erythrocytes, suffer a temporary reduction (24—72 hours) in their ability to release oxygen to the tissues of the recipient, so if a patient requires an urgent and massive transfusion it is wise to give 1 or 2 units of blood which are less than 7 days old.
White blood cells are rapidly destroyed in stored blood.
The survival of platelets is considerably reduced, and few are functionally useful after 24 hours. Platelets which are separated (see below) show good survival even after 72 hours.
Like platelets, clotting factors VIII and V are labile and their levels fall quickly.
Blood products are classified as
- Blood components
- Red cells
- Fresh frozen plasma
- Plasma derivatives [manufactured from pooled plasma donations in plasma fractionation]
- Coagulation factors
Whole blood is now rarely used as as most patients require a specific element of blood, such as red cells or platelets, and the dose can then be optimised. Whole blood may be divided into various fractions. This is not only more economical of blood donors, but certain fractions are more appropriate than whole blood transfusion for certain clinical conditions. Fractionation procedures are relatively safe and simple, using sealed sterile plastic bag units.
Each component is stored under ideal conditions (e.g. red cells must be refrigerated, platelets must not) and the use of precious blood donations becomes more efficient.
Packed red blood Cells
Red cells are used to restore oxygen carrying capacity and are especially advisable in patients with chronic anaemia where alternative treatments are ineffective or inappropriate. They are specifically indicated in the elderly, in small children and in patients in whom introduction of large volumes of fluid may cause cardiac failure.
Packed red cells are suitable for most forms of transfusion therapy, including major surgery, especially in association with clear fluids.
They must be ABO compatible with the recipient
Red cells in additive solution
In red cells in additive solution the majority of plasma is removed and replaced by 100 mL saline, adenine, glucose and mannitol additive solution (SAG-M).
They are stored at a temperature 2-6 degrees. Shelf life is up to 35 days.
Irradiated red cells
Gamma or X-rays irradiated red cells are indicated for patients at risk of transfusion-associated graft-versus-host disease. The component must be irradiated by within 14 days of donation. The shelf life is 14 days from irradiation.
Washed red cells
Washed red cells are indicated for patients with
- Recurrent or severe allergic or febrile reactions to red cells
- Severe IgA deficiency in patients with anti-IgA antibodies
Washed red cells are produced either manually or by a closed, automated system.
Former has a shelf life of 24 hours where as latter has a shelf life of 14 hours.
Platelet transfusion is indicated for the treatment or prevention of bleeding in patients with a low platelet count (thrombocytopenia) or platelet dysfunction
Platelets have ABO antigens on their surface and may have reduced survival if transfused to an ABO-incompatible recipient, though this is not usually clinically significant.
Platlets are usually only available in groups O, A or B. AB platelets produced in lesser quantities.
Anti-A or anti-B antibodies in the plasma of platelet components may rarely cause haemolysis of the recipient’s red cells, especially in babies and small children.
Group O platelets should ideally only be given to group O recipients.
Rh negative patients especially to Rh negative women of child-bearing potential should receive Rh negative platelet concentrates.
Platelets are produced in two ways
- Whole blood donations are centrifuged and the buffy coats (between the red cell and plasma layers) from four donations are pooled in the plasma of one of the donors [male, to reduce the risk of transfusion-related acute lung injury]
- An adult therapeutic dose of platelets is obtained from a single donor by apheresis. A single donor may give two or three adult therapeutic dose at a single session).
Platelet prepared by apheresis reduce the exposure of patients to multiple donors and also reduces risk of Cruetzfelt Jacob disease.
Platelets are stored in temperature-controlled incubators (20–24°C) and the usual shelf life is 5 days. Automated bacterial screening extends shelf life from 5 to 7 days after donation.
Platelets may be irradiated to prevent transfusion associated graft versus host disease in susceptible patients. They retain their normal shelf life.
Platelets in additive solution
Most of the plasma is washed and the platelets are resuspended in 200 mL of platelet additive solution (PAS).
Platelets in additive solution are indicated for patients with recurrent severe allergic or febrile reactions to standard platelet transfusions. The shelf life is reduced to 24 hours.
Human leucocyte antigen (HLA)-selected platelets
These are indicated for patients refractory to random platelet components due to the development of HLA antibodies after previous transfusions.
A panel of HLA-typed platelet is made by blood bank from whom platelets are prepared by apheresis.
Human platelet antigen (HPA)-selected platelets
HPA-1a/5b negative platelets are used for babies with neonatal alloimmune thrombocytopenia. They are available in selected centers only.
Fresh Frozen Plasma
Plasma is obtained from whole blood donations or component donation by apheresis. Only male donors are used to reduce the risk of TRALI.
Plasma components of the same ABO group should be transfused to patients wherever possible.
Plasma components do not need to be matched for Rh group as they contain no red cells or red cell stroma. They do not cause transfusion associated graft versus host disease and irradiation is not required.
Plasma is frozen soon after collection to maintain the activity of blood-clotting factors. It can be stored for up to 36 months at –25°C or below.
Thawed units of FFP can be stored for up to 24 hours at 4°C before transfusion. Clotting factor levels vary widely between normal healthy donors and this variability is reflected in the concentrations found in individual packs of FFP.
Fresh frozen plasma is indicated for the treatment
- Bleeding due to multiple clotting factor deficiencies
- Disseminated intravascular coagulation
- Inherited clotting factor deficiencies (e.g. Factor V deficiency)
Fresh frozen plasmacarries a significant risk of severe allergic reactions.
Pathogen-inactivated Fresh Frozen Plasma
Solvent detergent treated fresh frozen plasma prepared from pools [maximum of 1520 donors pooled].
Solvent detergent process inactivates bacteria and most encapsulated viruses, including hepatitis B and C and HIV.
It contains anticoagulant sodium citrate and is stored at –18°C. It has a shelf life of 4 years but should be transfused immediately after thawing
Trteatment with methylene blue also results in pathogen inactivation but also reduces activity of fibrinogen and Factor VIII.
Cryoprecipitate is made by thawing fresh frozen plasma 4°C, producing a cryoglobulin rich in fibrinogen, Factor VIII and von Willebrand factor.
Cryoprecipitate was developed as a treatment for haemophilia but now Factor VIII concentrate is preferred.
Cryoprecipitate is mainly used as a more concentrated source of fibrinogen than FFP.
It is prepared as single-donor packs or as pools of five donations.
Transfusion of granulocytes (neutrophils – phagocytic white blood cells) may be indicated in patients with life-threatening soft tissue or organ infection with bacteria or fungi with severe, prolonged neutropenia. The use is controversial though.
There are two main granulocyte-rich components available
- Granulocytes developed from buffy coats [individual or pooled]
- Granulocytes collected by apheresis from individual donors.
Human albumin solution
Human albumin solution (HAS) contains no clotting factors or blood group antibodies and crossmatching is not required. The clinical indications for HAS are controversial.
HAS is available in two forms:
Isotonic solutions (4.5 and 5.0%)
Often used to replace subacute plasma volume loss caused by burns, pancreatitis or trauma, and as a replacement fluid in plasma exchange.
Concentrated solutions (20%)
Indications may include
- Initiating diuresis in hypoalbuminaemic patients with liver cirrhosis
- Nephrotic syndrome
- Removal of large volumes of ascites in patients with portal hypertension
- Exchange transfusion in the newborn (unconjugated bilirubin binds to albumin).
Clotting Factor Concentrates
Single-factor concentrates are available for the treatment of most inherited coagulation deficiencies except Factor V and Factor II (prothrombin).
Fibrinogen concentrate (Factor I) for the treatment of congenital hypofibrinogenaemia
Prothrombin complex concentrate contains Factors II, VII, IX and X and is used for rapid reversal of warfarin overdose, with elevated international normalised ratio (INR) and severe bleeding.
These are manufactured from large pools of donor plasma:
These contains antibodies to viruses that are common in the population. These may used to protect susceptible contacts against hepatitis A, measles or rubella.
High-dose intravenous immunoglobulin is used as replacement therapy in patients with severe immunoglobulin deficiency and in the treatment of autoimmune diseases such as idiopathic thrombocytopenic purpura.
These immunoglobulins are made from selected donors with high antibody levels to the target of treatment. Examples include tetanus, hepatitis B and rabies immunoglobulins as well as anti-D immunoglobulin .