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 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 that the patient is deficient in. This helps to treat the primary problem as well as decrease the risk of transfusion reactions or complications. can be broken down into a variety of components: , plasma, rich plasma and 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 (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 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 (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 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 , antiinflammatory agents and proteins and thus can be useful in treating hypoproteinemia, parvo and pancreatitis. Cryoprecipitate and are produced by slowly thawing Fresh Frozen Plasma. Cryoprecipitate is a concentrated source of vWF, , 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 presented on the red blood cells it is still recommended to 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 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 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% 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 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. Most products can be administered as a bolus or over 2 to 4 hours with initial rates being ¼ to ½ the hourly rate. If a product is administered as a bolus, it is important to monitor that patient closely for any signs of reactions. Slower administration times lower the risk of transfusion reactions and volume overload. In general, whole blood and plasma transfusions are administered over 2 - 4 hours as long as the patient can tolerate the volume being delivered each hour without increasing the risk of volume overload. Packed red blood cells are generally administered over 2 hours because of the lower volume being administered and thus decreased risk for volume overload. Albumin transfusions are typically administered over a longer period of time such as 4 - 8 hours because albumin is a large protein that has effects on oncotic pressure and water shifting in the body. Slower transfusion times are required to assist in preventing volume overload.

Now that we know what product and volume of product we would like to administer to our patient we need to gather supplies to perform the transfusion with. All blood products should be administered through some type of filter to collect clots and small particulates. There are transfusion administration sets that contain filters in them or you can use a Hemonate filter. The transfusion administration sets are typically used for administering greater than 60ml of product to a patient. Hemonate filters are used for transfusions that are less than 50 - 60ml in volume because that is the maximum volume that they are able to filter effectively. While some products can be administered using a fluid pump some cannot because of the risk of damaging the cells. Due to the mechanical motion that most pumps use to move fluid through them and into the patient, pumps are not recommended to be used when administering whole blood or packed red blood cells. The mechanical motion increases the risk of lysing red blood cells which will decrease the benefit of the product for the recipient. Thus, for whole blood and packed red blood cell administrations you must calculate a drip rate. However, because plasma does not contain viable red blood cells, you can administer plasma through a pump. Exceptions to this rule would be with low volume whole blood and packed red blood cell transfusions as seen in small dogs or felines. For these smaller patients the blood is drawn from the collection bag into a syringe and administered using a syringe pump. The cells are not going through a pump but they are still undergoing some stress by being pushed through a line. This still puts the cells at some risk of being lysed but has been shown to be lower than traditional pumps. An alternative method for small dogs is setting up the transfusion with a transfusion administration set, calculating a drip rate and weighing the bag at the beginning and intermittently during the transfusion. Weighing the bag before beginning gives you the starting weight. Determine your goal weight using the desired volume to be transfused. General rule is that 1ml = 1 gram. So if you start out with a bag that weighs 125g and you want to administer 90ml then your goal weight would be 35g.

Transfusion monitoring of patients is the same no matter which product is being administered. If we have typed and crossmatched the donor and recipient then our risk for a transfusion reaction is low and our main concern would be monitoring for signs of volume overload. All vital signs should be monitored including temperature, heart rate, respiratory rate and blood pressure. This is done every 5 min for the first 15 minutes of the transfusion which should be running at either ¼ to ½ the hourly rate. If vitals are stable then the rate of transfusion can be increased to the hourly rate and vitals reassessed in 15 minutes. If the patient is still doing well then continue monitoring vitals every 30 minutes until the transfusion is complete. Once the transfusion is completed, vitals are monitored every 30 min for an additional 2 hours for signs of any delayed reactions.

There are two classifications for transfusion reactions: Immunological and Non-immunological. Immunological transfusion reactions involve the recipients immune system reacting to the transfused product. It is further categorized as hypersensitivity reactions, febrile non-hemolytic transfusion reaction or transfusion related acute lung injury. Hypersensitivity reactions are further classified as type I, type II or type III reactions. Type I hypersensitivity reactions are true allergic reactions mediated by IgE which causes a release of inflammatory mediators like histamine, serotonin, prostaglandins and leukotrienes. Symptoms of these reactions include hives (urticaria), pruritis (itching), erythema (reddening of the skin), facial swelling, vomiting, diarrhea, fever and worst case scenario . This type of reaction is usually seen within the first 30 min of the transfusion and is treated with benadryl. Type II hypersensitivity reactions are cytotoxic and caused by the recipients antibodies recognizing the glycoproteins and glycolipids on the donor’s red blood cells as foreign and initiating phagocytosis. This leads to hemolysis. This can be due in canine’s to the DEA 3, 4 or 7 being present in the donor’s blood. Symptoms include fever, hemoglobinemia, hemoglobinuria, hypotension, bradycardia and in worst cases disseminated intravascular coagulation (DIC). This type of transfusion can be seen immediately or can have a delayed onset of occurrence of up to 3 weeks post the transfusion. It is treated symptomatically. Type III hypersensitivity reactions are known as and due to a failure of the recipient's body to phagocytize the antigen - complexes formed in type II reactions. These complexes build up on blood vessel walls leading to vasculitis, arteritis, glomerulonephritis and synovitis. It typically affects areas with high blood flow. Symptoms of type III reactions include fever, erythema, urticaria, neutropenia (below normal neutrophil count), enlarged lymph nodes, joint swelling and proteinuria. Signs can be seen up to 3 weeks post transfusion.

Other immunological reactions include febrile non-hemolytic transfusion reactions (FNHTR) and transfusion related acute lung injury (TRALI) which are thought to be caused by an immune response to the leukocyte antigens from the donor in the transfused blood. Symptoms of FNHTR generally include fever and vomiting and are treated symptomatically. Symptoms of TRALI include fever, hypotension, tachypnea, dyspnea, hypoxemia and pulmonary edema not related to circulatory overload. Treatment of this type of reaction is also supportive and usually requires oxygen.

Non-immunological reactions or complications to transfusions include transfusion associated circulatory overload (TACO), transmitted bacterial , hypothermia (below normal body temperature), citrate toxicity and hyperammonemia. TACO is caused by intravascular volume overload with symptoms including tachypnea, dyspnea and hypotension. It is treated symptomatically with furosemide and sometimes requires oxygen therapy. Symptoms of bacterial infections include fever, leukopenia or leukocytosis and are treated with antibiotics. Hypothermia is typically transient and can be countered with active warming. Citrate toxicity occurs when the recipient’s liver is unable to metabolize the citrate found in the anticoagulant into bicarbonate. Citrate chelates (bonds to) calcium causing hypocalcemia. Symptoms of citrate toxicity include tremors, vomiting and ventricular arrhythmias. It is treated by slowing down the transfusion or in severe cases administering an infusion of calcium gluconate. Hyperammonemia is an increase in ammonia in the blood and is typically seen when transfusing older cells. Erythrocytes (red blood cells) store ammonia and as they die during blood storage that ammonia is released. In most patients, the liver metabolizes ammonia. However, this is typically only seen in patients with liver disease.

Transfusion of blood products can be a life saving tool in veterinary medicine. However, much like all other aspects of a patient’s treatment plan we must weigh the risks against the benefits of this therapy and take steps to minimize adverse reactions. Remember 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. We can help in decreasing the risk of transfusion reactions by typing and crossmatching donors and recipients blood. By using component therapy we can decrease the risk of non-immunological reactions like TACO. And with careful monitoring we can react to concerns sooner and minimize effects. Good luck!