Transfusion medicine is a staple in veterinary emergency medicine that has allowed us to provide a potentially life saving treatment option to our clients and treatment to our patients. Transfusions are a process used to administer blood or blood products to a patient. By providing blood or blood products to a patient we can: treat hypoxemia and hypoxia by increasing oxygen carrying capacity, increase tissue perfusion by increasing circulating volume, improve hemostasis by delivering clotting factors, improve immune system response by delivering antiinflammatory mediators and increase protein levels by delivering protein sources. Component therapy has grown favor over the years in only administering the blood product that the patient is deficient in. This helps to treat the primary problem as well as decrease the risk of transfusion reactions or complications. Whole blood can be broken down into a variety of components: packed red blood cells, plasma, platelet rich plasma and cryoprecipitate to name a few. For the purposes of this lecture we will be focusing our discussion on the uses of whole blood, packed red blood cells and plasma. We will briefly discuss cryoprecipitate and albumin. Whether blood or blood constituents are lost it is important to replace them to regain stability in our emergent patients. Loss of packed red blood cells can be caused by immune mediated diseases like immune mediated hemolytic anemia (IMHA), a decrease in production of red blood cells as seen in chronic kidney disease (CKD), chronic inflammatory diseases like pancreatitis, bone marrow dysfunction as in leukemia or neoplasia. Other causes of red blood cell loss can be from outside sources like infectious agents such as Mycoplasma or toxins such as zinc, garlic or onion ingestion. In these disease processes we are only losing red blood cells so they are the only blood component that we need to replace. Loss of whole blood is commonly seen with trauma’s and toxins like rat bait that contain an anticoagulant (warfarin, hydroxycoumadin, brodifacoum, bromadiolone, diphacinone, etc) and by administering whole blood you can restore oxygen carrying capacity, circulating blood volume, perfusion and hemostasis in one treatment. Loss or impairment of hemostasis secondary to toxins like rat bait, hereditary deficiencies of von willenbrand factor or DIC are typically treated with plasma. These patients do not always require additional red blood cells. Plasma can be further categorized as Fresh Frozen Plasma or Frozen Plasma. Fresh Frozen Plasma contains all viable clotting factors: V, VIII, IX and vWF and can thus be used to treat liver disease, anticoagulant rodenticide toxicity and hereditary diseases. Fresh Frozen Plasma is good for 1 year after it’s collection date. Fresh Frozen plasma becomes Frozen Plasma after that year and can be stored for another 4 years. Frozen plasma still contains all factors and proteins but the following are less viable or active: V, VIII and vWF. Frozen plasma provides antibodies, antiinflammatory agents and proteins and thus can be useful in treating hypoproteinemia, parvo and pancreatitis. Cryoprecipitate and Cryosupernatant are produced by slowly thawing Fresh Frozen Plasma. Cryoprecipitate is a concentrated source of vWF, fibrinogen, factor VIII and fibronectin. It is useful in treating vWF deficient patients. Cryosupernatant is the remainder once the cryoprecipitate is removed. It provides a source for other coagulation factors not including vWF, fibrinogen, factor VIII and fibronectin. It is useful in treating other diseases that affect hemostasis. Regardless of the product that your patient needs the process of setting it up is very similar. Once you have determined which blood component therapy needs to be administered you must find a compatible donor. This is done through blood typing and crossmatching procedures. There are 12 recognized canine blood groups in the U.S with the most known being DEA 1.1, 1.3, 1.4, 1.5 and 1.7. The one that we are most concerned with is DEA 1.1 as it is the most antigenic and will lead to the most transfusion reactions. While canines do not possess naturally occurring antibodies known as alloantibodies to the antigens presented on the red blood cells it is still recommended to blood type every recipient. Felines have blood group classifications similar to humans: A, B and AB. Blood type A is the most common blood type in felines. Unlike canines, felines have naturally occurring alloantibodies to the other blood groups so blood typing is mandatory before transfusing a patient. There are a number of blood typing kits available. In addition to blood typing it is recommended that you perform a crossmatch to determine compatibility between the donor and recipient. Even though they may be the same blood type it does not mean that the recipient’s immune system will not recognize the transfused cells as foreign and destroy them. Crossmatching tests help to ensure that the recipient is going to be able to get the most benefit from the transfusion. Crossmatching tests are subcategorized as major and minor. A major crossmatch tests the recipients blood to determine if it has antibodies against the antigens on the donor’s red blood cells. A minor crossmatch tests the donors blood to determine if it has antibodies against the antigens on the recipient's red blood cells. Both tests provide important information but since we are primarily concerned with how the recipient is going to react to the donor’s cells, a major crossmatch is the minimum recommendation. A crossmatch should most definitely be performed if the blood type of the recipient is unknown, the recipient has received a blood transfusion in the past or more than 4 days ago. There are crossmatching kits sold that make the process more efficient and user friendly. If access to these kits is not possible then you can perform either the slide method or the cell washing method of a manual crossmatch. The slide method is quicker but not as sensitive. The cell washing method is a little more specific. By washing the cells and using a concentrated population of red blood cells we can minimize false incompatible test results due to the presence of excess potassium, cytokines and allergen proteins. Interpretation of the results is dependent upon looking for the presence of hemolysis and agglutination. If these exist in the recipient prior to performing the crossmatch then our results are unreliable. Sometimes by performing the cell washing method you can reduce the agglutination aspect in the sample and still be able to perform a reliable test. However if hemolysis is present then results are not reliable. In feline patients you can identify incompatible matches due to the anti-MIK alloantibody even if they are of the same blood type. Procedure for Major crossmatch using the slide method: 1. Place 2 drops of the recipient’s plasma on a slide 2. Add 1 drop of the donor’s EDTA whole blood to the plasma on the slide 3. Gently mix by swirling the two samples together 4. Observe for agglutination 5. If agglutination is present than the donor and recipient are incompatible Procedure for Minor crossmatch using the slide method: 1. Place 2 drops of the donor’s plasma on a slide 2. Add 1 drop of the recipient’s EDTA whole blood to the plasma on the slide 3. Gently mix by swirling the two samples together 4. Observe for agglutination 5. If agglutination is present than the donor and recipient are incompatible Procedure for crossmatch using the cell washing method: 1. Obtain blood in a lavendar top tube and serum separator for both the recipient and donor. 2. Centrifuge the lavendar top tube and pipette off the plasma. Discard plasma 3. Add 2ml of 0.9% saline to the lavendar top tube, Mix and centrifuge. This step is called washing the red blood cells. 4. Repeat this process 2 more times 5. Add 0.2ml of the washed red blood cells to 4.8ml of 0.9% Saline (this is your red blood cell suspension) a. Major = Place 2 drops of the recipients serum and 1 drop of the donor’s red blood cell suspension into a plain red top tube. b. Minor = Place 2 drops of the donor’s serum and 1 drop of the recipient’s red blood cell suspension into a plain red top tube 6. Incubate by mixing gently on a rocker for 10min 7. Centrifuge the red top tube for 15s. Note the serum’s color for hemolysis. Resuspend the cells and place a drop on a slide with a coverslip over it. Examine under the microscope for autoagglutination which represents incompatibility There are a variety of ways to determine the amount of product needed to be transfused. Some DVM’s like to use calculations which can be more specific in predicting what the packed cell volume (PCV) of the recipient will be post the transfusion while others like to use a general rule of thumb as outlined in the chart below. Here are a few calculations related to determining the volume of whole blood or packed red blood cells to transfuse based on the desired PCV goal. Products like cryoprecipitate and platelet concentrate are administered at a dose of 1 unit per 10kg of body weight. Canines: 1. VT (ml) = Body weight (kg) x Blood volume (90ml/kg) x [(desired PCV - recipient PCV) / donor PCV] 2. For pRBC’s with PCV’s >60%: VT (ml) = 1.5 x desired rise in PCV x BW (kg) Felines: VT (ml) = Body weight (kg) x Blood volume (70ml/kg) x [(desired PCV - recipient PCV) / donor PCV] Albumin: (ml) of 5% Albumin = 90ml/kg x BW in kg x [target albumin - patient albumin / 5g/dL] Species Whole Blood Packed Red Blood Plasma Cells Canine 10 to 20ml/kg 10ml/kg 10 to 20ml/kg Feline 5 to 10ml/kg 5ml/kg 5 to 10ml/kg Transfusion time frames vary and are dependent upon the patient’s stability and ability to handle the product being transfused.