Blood component issues for technicians: component selection, storage, handling, and administration (Proceedings)

This discussion will focus on blood components commonly available and how to choose the appropriate blood component for the patient. Literally volumes of information have been written on transfusion medicine. In the essence of time allotted, this discussion will cover whole blood, packed red blood cells, and plasma. Storage of these blood components, proper handling, transfusion guidelines, and transfusion reactions will also be covered.

The bygone days of routine whole blood therapy

Gone are the days of hastily collecting blood from the clinic's resident cat or dog and then transfusing whole blood to treat every need. The need is clear to make the most of valuable resources, which are the donor and the blood itself. To be efficient the blood must be separated into components and each utilized according to proper indications. There may still be select few times when the use of whole blood best fits the patient's needs. However, there are inherent risks to blood transfusion and it is best for the patient to receive only the component(s) truly necessary. A more judicious use of your hospital blood bank and a possible decrease in owner's costs are additional reasons to use components wisely.

Whole blood (WBD)

Considered a full unit 400-450mls blood from a dog, or 55mls from a cat, is collected using an anticoagulant of CPDA-1 or ACD-A. This product will contain the red cells and all plasma components, but will not preserve platelets or white blood cells after aging for more than 4 hours.

Indications and matching. Whole blood contains red blood cells, plasma proteins, coagulation factors, white cells, and platelets. When administered fresh, it may be appropriate for treatment of hemorrhage with concurrent coagulopathies, although there may not be a clinically significant amount of platelets transferred. It is the author's opinion that whole blood is most appropriately used when the changes that occur during packed red blood cell storage are undesirable or when stored blood is not available. Canine matching: Blood from a universal donor (referred to as 1.1negative) should be used unless the recipient has been identified by card test (DMS Labs, KS) or laboratory method as 1.1positive. If the patient is typed as 1.1positive then blood from a 1.1,4 donor is utilized. Full cross matching should be performed if the recipient has been previously transfused. A Coombs test should be performed for any suspected IMHA patient. Feline matching: All recipients must be typed using a card test or lab method. Blood would then be chosen from a corresponding A or B donor. Full cross matching should be performed if the recipient has been previously transfused.

Contraindications. Or better expressed as reasons not to choose whole blood-

• Most expensive transfusion. Dedicates entire donor usage to treating only one patient.

• Anemia may be tolerated in many cases or treated by promotion of erythropoesis (Epogen).

• Hypovolemia should be treated with other volume expanders (crystalloids, colloids); hypoxemia may be treated with packed red blood cells and oxygen supplementation.

• In cases of coagulopathies- other components (fresh frozen plasma) will provide coag factors, platelet release may be encouraged pharmacologically (vincristine).

• Administration of white blood cells can lead to a fever response.

• Stored whole blood may build up of potassium which may lead to hyperkalemia in certain canine breeds-Akitas, Sheba Inus.

Administration. Transfuse whole blood slowly for the first 15 minutes and monitor for anaphylaxis. Body temperature, heart rate, respiratory rate, and patient demeanor should monitored at 0, 2, 5, 10, and 15 minutes. The rate may then be increased as quickly as tolerated by the patient. Additional monitoring at every half hour and hour mark should be taken until the unit is finished. Cardiac patients may not tolerate sudden volume expansion. The complete blood transfusion should be finished within 4 hours to provide viable platelets and to avoid bacterial growth. A blood administration set with in-line blood filter (170-260 microns) should be used to avoid fibrin clots.

Storage, handling and expiration. Donor PCV will vary according to cat or dog blood. 1-6 degrees Celsius; room temperature if platelets are desired. Platelets are not viable after 4 hours or upon refrigeration. Coagulation factors are not viable after 8 hours of collection. Red blood cells are viable for 21 days storage. Stored units of whole blood should be warmed to 37 degrees if time allows before administration.

Side effects. Immunologic hemolytic transfusion reaction: Red blood cell antigen mismatch can lead to acute or delayed transfusion reactions. In the dog, DEA 1.1 mismatches lead to acute reactions; and other DEA mismatches lead to delayed transfusion reactions. In the cat, acute reactions occur with mismatches between Type A and Type B blood. Acute reactions may be fatal and occur immediately or up to 24hrs. Signs may include shock, fever, dyspnea, DIC, hemoglobinuria, hemoglobinemia, hyperbilirubinemia, renal failure, chills, pain. Delayed reactions are not typically fatal and may occur 4-14 days later. Signs may include continued anemia, fever, hemoglobinuria, and hyper-bilirubinemia.

Non-immunologic hemolytic transfusion reaction: The signs are the same as noted above but may be caused by-bacterial contamination, processes within IMHA recipients, concurrent administration of hypotonic fluids with blood, or other mechanical lysis.

Allergic reactions: Urticaria, wheezing, angioedematous reactions, broncho spasm, dyspnea, and pulmonary edema. Four types of allergic reactions are recognized; with type 1 described above being the most commonly seen.

Alloimmunization (sensitization) of recipient: Red blood cell antigens promote the strongest immunogenic response. Mismatches lead to antibody production and to sensitization of the patient to future transfusions. Careful blood typing and cross matching will help to avoid sensitization to antibodies.

Circulatory overload: May occur with cardiac patients or fluid challenged patients. Evaluate fluid load carefully and monitor central venous pressure.

Pulmonary thromboembolism: Signs may include very rapid respirations, dyspnea, cyanosis, pulmonary edema, pleural effusion. An in-line blood filter should always be used during administration.

Infectious disease transmission: Thorough screening of donor pool must be employed to avoid FIV, FeLV, Babesia, Ehrlichia, Leishmaniasis, Mycoplasma, and microfilaria transmission.

Bacterial contamination: Aseptic collection and processing of blood is crucial.

Citrate toxicity: Transfusion of multiple units or liver disease may lead to citrate toxicity. Citrate binds with calcium which can lead to hypocalcemia. Signs may include tremors, seizures, and arrhythmias.

Packed red blood cells (PRBC)

Red blood cells are processed after obtaining a full unit of whole blood. The red cells, along with a very small percentage of plasma, are separated from the body of plasma after the unit has been centrifuged under refrigeration. A nutrient solution is also added to stabilize the blood cells during storage. Typical unit volumes after processing are 290mls for canine and 25mls for feline PRBC's.

Indications & matching. During hemorrhage and hypovolemic shock PRBC's along with IV fluids (a crystalloid/colloid combination) provide volume expansion while increasing oxygen carrying capacity. Patients with chronic anemia or hemolytic anemia, where plasma proteins are not deficient, will benefit from the decreased volume of transfusion. A smaller volume is also crucial for cardiac patients. Post surgical blood loss is a great indication for PRBC usage. Typing and matching considerations are the same as whole blood usage.

Contraindications. Contraindications for PRBC usage would be limited to incompatible cross matched samples and patients with hepatoencephalopathy that could not tolerate rising ammonia concentrations from prolonged storage of blood. Selecting units with the shortest storage time would be appropriate for liver failure patients.

Administration. Transfusion procedures are the same as for whole blood units with the exception of adding 100ml of warmed 0.9% NaCL for a canine unit and 10ml 0.9% NaCL for a feline unit of PRBC's. Adding saline to the unit promotes passage of the blood through the filter but is not essential to administering PRBC's. The formula for determining volume needed is:

Donor PCV will vary from cat normal to dog normal. A commonly used rule of thumb is 10ml/kg will raise PCV by 10%. Monitoring should be performed the same as with whole blood administration.

Storage, handling, & expiration. 1-6 degrees Celsius. The units should be agitated and turned once daily to ensure mixing of cells with the nutrient solution. Red cells are stable for 35 days if combined with nutrient solution. Units should be warmed to 37 degrees if time allows before administration.

Side effects. Transfusion reactions due to administration of PRBC's are the same as for whole blood. There may be less incidence of volume overload due to the smaller volumes during transfusion.

Fresh frozen plasma (FFP)

A unit of fresh frozen plasma is the clear portion of a full unit of anticoagulated whole blood that is separated off after centrifugation. FFP is technically termed "fresh frozen plasma" if the unit has been separated within 6 hours of collection and is completely frozen within 8 hours in order to retain the labile coag factors. Beyond that length of time during processing the plasma is termed "frozen plasma" and will only retain the stabile coagulation factors. FFP should be clear in color and free of red cells. To help ensure this about 10% of the plasma is left to remain with the PRBC's during processing in order to avoid the red blood cells and their antigenic properties. FFP contains all of the coagulation factors, plasma proteins, immunoglobulins, lipids, and electrolytes. A full unit for canine FFP will contain 210mls; and for cats will contain 22mls.

Indications and matching. FFP is appropriate for use in mild and severe coagulopathies. It may also be combined with PRBC's for patients with anemias and coagulopathies. Plasma proteins will benefit patients with hypoalbuminemia although a clinically significant rise in serum albumin levels will not be observed with typical plasma transfusions. For dogs, cross matching to plasma units is not routinely performed due to the fact that the plasma unit should not contain red blood cells when separated correctly. Cats possess naturally occurring antibody to the opposite type of blood within their plasma so type specific plasma should always be administered. Dosage range 10-20ml/kg; often repeated during severe coagulopathies.

Contraindications. FFP is not a singular treatment for hypoproteinemia or volume expansion. Cats should not receive unknown blood type plasma.

Administration. Begin plasma transfusions slowly as with red cell products and monitor for reaction. Blood filter administration sets are used and transfusion should be completed within 4 hours.

Storage, handling, and expiration. Manual defrost freezers at less than –18degrees Celsius are recommended.

After one year of storage the coagulation factors will be affected and the product is now classified as frozen plasma and will last four years. Units are thawed in a water bath between 30-37degrees Celsius inside a water tight bag.

Side effects. Side effects are less common but may be caused by the same factors as other components. Transfusion reactions may be caused by erythrocyte antigen reaction, allergic reaction, and volume overload.