Canine Transfusion Reactions and their Management

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TRANSFUSION MEDICINE

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CANINE TRANSFUSION REACTIONS AND THEIR MANAGEMENT Karyn A. Harrell, DVM, and Annemarie T. Kristensen, DVM, PhD

Transfusion of blood products has become an integral component of therapy in veterinary medicine. Although generally considered to be safe in the canine population, transfusions are by no means risk free. Inappropriate or poorly conceived therapy may result in severe and potentially fatal complications. Unfortunately, knowledge regarding incidence, cause, and clinical significance of transfusion reactions in dogs and cats is still limited. The purpose of this article is to discuss these aspects of transfusion medicine, as well as methods used to minimize the frequency of occurrence of these reactions, and the most appropriate means of managing complications when they do occur. HISTORIC OVERVIEW

Experiments involving the transfusion of whole blood were first conducted in the mid-17th century and initially used canine arterial blood that was then transfused into the jugular vein of a second dog. 6• 16 • 17• 32• 50 The knowledge gained from these first successful animal to animal transfusions was soon applied to experimental human medical therapy. The majority of these first attempted therapeutic transfusions used calf or sheep blood given to human patients not to treat hemorrhage or anemia, but as a proposed cure for "maniacal behavior." 16• 17• From the Companion Animal and Special Species Medicine, North Carolina State University, College of Veterinary Medicine, Raleigh, North Carolina (KAH); and Health Care Discovery, Vessel Wall Biology-Pharmacology, Novo Nordisk A/S, Gentofte, Denmark (ATK)

VETERINARY CLINICS OF NORTH AMERICA: SMALL ANIMAL PRACTICE VOLUME 25 • NUMBER 6 • NOVEMBER 1995

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One of these patients, following a second transfusion, experienced pain at the injection site, tachycardia, profuse sweating, nausea, kidney pain, and voiding of black urine. Although not recognized at the time, this description represents the first well-documented transfusion reaction. 16, 17, 32 Progress in the field of transfusion medicine in the 19th and 20th century has been slow and erratic, in large part impeded by the fear of life-threatening complications. 17 However, recent advances in blood typing, donation and administration techniques, appropriate storage, and knowledge of infectious diseases have allowed physicians and veterinarians to better understand the source of transfusion reactions. 16' 17' 32 With this understanding, transfusion therapy can be used with minimal risk. 32, 50

CLINICAL SIGNIFICANCE OF TRANSFUSION REACTIONS

The use of transfusion therapy has become commonplace in veterinary medicine, but little information is available on the side effects of these transfusions in clinical cases, A case report that precisely described an acute hemolytic transfusion reaction due to incompatible DEA 1.1 donor blood was recently published. 21 This report presently is the only documentation of a canine transfusion reaction due to DEA incompatibilities that is published in the veterinary literature. As a result of the lack of publications in this area, the incidence and clinical significance of canine transfusion reactions is not known, The reported prevalence rates of transfusion reactions in human medicine vary widely, ranging from 0.5% to 20%. 4' 6, !3, 36, 39, 40 One study of 131 transfusions conducted at The Animal Medical Center listed 10 dogs (13%) as having some type of transfusion reaction, All of these animals survived, 35 A second retrospective study of canine transfusions given at the University of Minnesota Veterinary Teaching Hospital from September 1, 1988 to December 31, 1991 documented a transfusion reaction prevalence of 2.9% (20 reactions in 680 units given). 28 Of these reactions, 85% (17 of 20) were acute hypersensitivity reactions, 10% (2 of 20) were delayed hemolytic reactions, and 5% (1 of 20) were acute hemolytic reactions. 28 No nonimmunologic reactions were noted. The majority of these reactions were considered mild with vomiting (eight), pyrexia (six), and facial swelling (five) being the most common clinical signs. 28 Two of the reactions were considered severe and consisted of acute hemolysis, pulmonary edema, and pyrexia. 28 These reactions responded well to supportive therapy, which included discontinuation of the transfusion, diphenhydramine, furosemide, dexamethasone, aminophylline, and oxygen, There were no fatalities as a direct result of a transfusion reaction in this study. Research attempting to better document canine transfusion reactions and their clinical significance currently is underway.

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GENERAL CONSIDERATIONS

The incidence of transfusion reactions can be decreased simply by following appropriate guidelines when using blood products. 37• 39• 41 The clinician must first decide whether or not transfusion therapy is truly necessary. This decision should not be based on numbers alone, but on an accurate assessment of the animal's overall condition. 6 One of the most important methods for reducing transfusion reactions is to avoid unnecessary administration of blood products. 6• 37 Once the decision to initiate transfusion therapy has been reached, the specific component needed should be chosen carefully .15• 18• 35• 54 Recent studies in both human and veterinary literature have documented a dramatic decrease in the use of whole blood and a concurrent increase in the use of specific component therapy. 6 • 30• 54 Component therapy allows for more efficient and specific treatment of various disorders. Additionally, proper donor screening, collection, preparation, storage, and administration of blood products is essential in minimizing transfusion reactions. 2• 24• 30• 41 • 61 Specific details regarding these areas are dealt with in other articles in this issue. Overall, with careful patient evaluation and knowledgeable use of blood components, certain transfusion reactions can be avoided, and the benefits of transfusion therapy can be maximized. Transfusion reactions typically are categorized as immune or nonimmune-mediated and further divided by whether they are acute or delayed in nature. 13• 24• 29• 37• 40• 61 An acute transfusion reaction is most often noted minutes to hours after the transfusion is begun; however, it may occur up to 48 hours later.55 Table 1 summarizes this method for characterizing adverse transfusion effects. Table 1. TRANSFUSION REACTIONS Acute

Hemolysis Acute hypersensitivity Platelet sensitivity Leukocyte sensitivity

Immunologic

Delayed Hemolysis Post-transfusion purpura Neonatal isoerythrolysis Immunosuppression

Nonimmunologic Acute Delayed Pretransfusion donor cell hemolysis Infectious disease transmission Circulatory overload Hemosiderosis Bacterial contamination Citrate toxicity Coagulopathy Hyperammonemia Hypothermia Air embolism Pulmonary microembolism Acidosis

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IMMUNE-MEDIATED TRANSFUSION REACTIONS Canine Blood Groups

Specific cell surface antigens are present on all red blood cells (RBCs). 59 Immune-mediated hemolysis occurs as a result of the interaction between these erythrocyte antigens and a patient's circulating antibodies. 6 • 13- 14• 44• 59 Occasionally, a hemolytic reaction may be seen due to antibodies to a recipient's RBCs found in the donor's plasma, but this is a rare occurrence. 13 The final result of the antigen-antibody interaction is decreased donor erythrocyte survival in the recipient's circulation. The degree of severity of a hemolytic reaction, and whether this reaction is intravascular or extravascular in nature, depends on the specific characteristics of both the antigen and the antibody involved. 2, 6, 13, 1s, 44, s9, 61 Antibody-mediated hemolytic transfusion reactions are classified as type II hypersensitivities and are either acute or delayed in nature. These reactions in dogs are caused by incompatibilities in dog erythrocyte antigens (DEA) 1-8. (For a detailed discussion of these antigens, please see the article by Hale, this issue. Typing is routinely conducted for six of these blood groups. 37• 42• 45• 51 • 56 Currently, only DEA 1.1, DEA 1.2, and possibly DEA 7 are believed to be important in producing clinically significant RBC destruction. 24• 37• 42• 45• 51 DEA 1.1 and DEA 1.2 are allelic and do not occur in the same animal.24• 37 Dogs that are DEA 1.1, DEA 1.2, and DEA 7 negative are referred to as universal donors (see article by Hale). Unlike humans and cats, naturally occurring isoantibodies to DEA 1.1 and 1.2 (the most highly antigenic groups) are extremely rare. 12• 15• 21 • 24 • 37• 51 Naturally occurring isoantibodies to DEA 7 have been believed to exist in 50% of the canine population,5 1• 63 but new information suggests this figure may be much lower. 21 Although clinically significant transfusion reactions to DEA 7 incompatible blood have not been documented, it has been shown that chromium-tagged DEA 7 positive erythrocytes are destroyed in 4 to 5 days when given to DEA 7 negative dogs. 51 As this information documents decreased RBC survival, it is suggested that all donors should be screened for DEA 7 in addition to DEA 1.1 and 1.2 and only dogs negative for these antigens be used as donor animals. 29 • 33• 51 ACUTE HEMOLYTIC TRANSFUSION REACTIONS Pathophysiology

A disasterous acute hemolytic crisis is often pictured when the term transfusion reaction is used. Although this is the most feared of all complications, acute hemolytic transfusion reactions (AHTR) are rare in our canine patients because of the low incidence of naturally occurring isoantibodies to DEA 1.1 and DEA 1.2 (A positive). 2 • 12• 15• 24• 61

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When AHTR do occur, they are usually the result of antibodies formed as a result of a previous transfusion or pregnancy. 9 • 15• 20• 30 With a random, nontyped first-time transfusion, there is a 25% chance of giving A-positive blood to an A-negative dog. This translates into a 15% chance of a hemolytic transfusion reaction with a second random transfusion. 24• 56• 61 Compatible transfused canine erythrocytes have a half-life of approximately 21 days, whereas DEA 1.1, and DEA 1.2 incompatible cells have a half-life of only 12 hours. 10 A rather gruesome study conducted in the late 1940s involving the purposeful infusion of incompatible RBCs to a group of dogs showed a destruction rate of 84% within 10 minutes. 30 Additional studies estimate RBC destruction to occur within 30 to 90 minutes. 30 An understanding of the pathophysiology of AHTRs is necessary to rationally determine appropriate therapy when reactions are encountered. The severity of an AHTR depends on a variety of factors. The antibody class involved (lgG or IgM), the temperature at which these antibodies bind to RBCs, the extent of complement fixation, and the presence of a binding site for phagocytic cell types are all important parameters in determining the extent of a reactionY· 59 Complement activation plays a crucial role in the pathogenesis of these reactions. 6• 13 A single IgM antibody is capable of binding to complement (C1)Y· 59 Thus, IgM class antibodies are very efficient at complement fixation and have a great potential for cell lysis that can lead to severe hemolysis.B· 49 IgG antibodies must be present in relatively high concentrations to activate the complement system and consequently have intermediate hemolytic capabilities. 13 IgG antibodies that coat the RBC surface but are unable to activate complement lead to RBC destruction due to Fe receptors for these opsonized erythrocytes on phagocytic cellsY· 49• 59 This enhanced phagocytosis leads to extravascular hemolysis (EVH) that usually is delayed in nature.B· 39• 44 Delayed hemolytic transfusion reactions (DHTR) will be discussed at a later point in this article. IgG antibodies also may activate complement but terminate at the level of C3. 13 Erythrocytes in this case are coated with both antibodies and C3b. This type of complement fixation results in EVH, which may have an acute or delayed time course.B· 44 These reactions generally are mild, even when occurring acutely. The activation of the complement cascade to the terminal C5-C9 steps results in RBC membrane penetration, lysis, and release of anaphlylatoxins C3a and C5a. 13 The consequence of this interaction is rapid intravascular hemolysis with the potential for extremely severe transfusion reactions. 13• 39• 43• 61 Any combination of the previously mentioned reactions may occur in the same patient. See Figure 1 for a schematic summary of the interaction between the antigen-antibody complex and complement in AHTR. The two main mechanisms responsible for the severity of intravascular HTR are the activation of the hemostatic system and the release of vasoactive substances leading to significant hemodynamic alterq_tions. 6• 22• 39 It is well documented that the combination of these two mechanisms

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Intravascular Hemolysis

Extravascular Hemolysis

RBC antigen + lgG or lgM

RBC antigen + lgG

,...,__1-.1- - C1- C4 _ __._I_----I..~C4b2b

C4b2b ....

C3 _ ___._l_---1.,~ C3b+C3a (anaphylatoxin) C5

C3 _ ___._1_----1.,~ C3b (enhanced phagocytosis)

I

± C~

-----'------1.,~ C3b5b+C5a

(anaphylatoxin) C6-C9 ,.

ICell membrane lysis

Figure 1. A summary of the interaction of the antigen-antibody complex with complement fixation in acute hemolytic transfusion reactions. Extravascular hemolysis occurs when the complement is activated to the C3 stage. Phagocytosis is enhanced due to C3 receptors on phagocytic cells. Intravascular hemolysis secondary to cell lysis is seen when the complement system is completely activated. C3a and C5a are important anaphylatoxins and contribute to the severity of the transfusion reaction.

are capable of producing DIC, shock, and, possibly, acute renal failure. 13• 22· 25· 27· 39• 44• 63 A summary of the major mediators of these conditions is given in Table 2. 15•

Hemostatic System Activation

Intravascular hemolysis leads to immediate hemostatic abnormalities.25 A variety of factors are responsible for these abnormalities. Antigen-antibody complex stimulates activation of Hageman Factor, which Table 2. MAJOR COMPONENTS CONTRIBUTING TO SHOCK, DIG, AND ACUTE RENAL FAILURE IN AHTRS Factors Contributing to DIC

1. Hageman factor 2. 3. 4. 5.

Vasoactive Mediators Contributing to Shock

Factors Contributing to Acute Renal Failure

1. Complement system 1. Vasomotor alterations anaphylatoxins (C3a and (shock) C5a) Complement system 2. Release of serotonin and 2. Fibrin thrombi in renal histamine from mast cells microcirculation (DIG) and platelets Leukocyte thromboplastic 3. Bradykinin 3. Ischemia material Platelet factor 3 4. Catecholamines 4. RBC stroma antigenantibody complexes RBC membrane phospholipid

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in tum activates the intrinsic clotting system. 6 • 13· 22 As previously discussed, the complement system is also activated. 6• 13· 39· 44 Thromboplastic substances from both white blood cells and platelets are released. 6• 13· 22 Additionally, erythrocytin, a phospholipid material with procoagulant activity contributes to the induction of DIC. 6 • 13• 22 • 49 It has been documented, however, that DIC does not occur as a result of hemolysis alone without the associated interactions of antigen-antibody complexes. 6• 22• 39· 49 The liberation of freely circulating RBC stroma-antibody complexes also is believed to play a role in the development of DIC. 6• 13• 22 • 49 Various cytokines such as 11-1 and TNF are also released from monocytes in an AHTR. 49 These factors also promote clotting and microvascular thrombosis.49 The final results of these interactions are the generation of fibrin with systemic formation of microthrombi, a consumption of platelets and coagulation factors, fibrinolysis, and, ultimately, uncontrolled bleeding. 6 Bloody diarrhea frequently is seen secondary to thrombosis of intestinal capillaries and hemorrhagic mucosal necrosis.B· 25 Necropsy studies also have confirmed the presence of fibrin thrombi throughout the lungs, kidney, and intestine. 13• 25 Rapid injection of incompatible blood has been shown to result in much more severe forms of DIC with subsequent pulmonary thrombi, hypotension, and cor pulmonale. 13• 25 Development of Shock

The generation and release of numerous vasoactive substances during an AHTR lead to severe vasomotor alterations that, in tum, result in shock. 6 • 13• 22 The activation of the complement system produces C3a and C5a, powerful anaphylatoxins that stimulate the release of serotonin and histamine from mast cells. 6• 13· 22 Platelets also release serotonin and histamine secondary to antigen-antibody activation. 6• 13· 22 Bradykinin is produced by the interaction of activated Hageman factor with kallikrein. 6• 13 The net result of the release of these vasoactive substances is arteriolar dilatation and capillary permeability which lead to systemic hypotension. 6• 13• 22 In response to this hypotension and as a direct result of antigen-antibody complex interaction, catecholamines such as norepinephrine are produced by the sympathetic nervous system and released from the adrenal medulla. 6 • 13• 22 These catecholamines preferentially cause vasoconstriction of the renal, intestinal, pulmonary, and cutaneous blood vessels. 6 Thrombus formation in the lungs secondary to DIC also leads to poor hemodynamic stability. 6• 13 Cytokines such as TNF also have been implicated in the development of shock. 49 The end result if these mechanisms are left unchecked is shock and potential end organ damage.13, 22 Special attention should be given to anesthetized patients receiving transfusions. Early signs of an AHTR often are masked by the anesthesia. 6• 15 Diffuse oozing or inappropriately low blood pressure may be the first sign of a transfusion reaction. 6 Hemoglobinuria may also be noted. 6 If these signs are not recognized as a transfusion reaction, addi-

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tiortal incompatible blood may be given and appropriate treatment of the reaction will be delayed. 6 Acute Renal Failure

There has been a great deal of debate over the factors involved in the pathogenesis of acute renai failure resulting from AHTR in both dogs and humans. 22• 49· 63 Free circulating hemoglobin by itself has a questionable role in the development of renal fa.ilure.l3, 15· 25· 63 However, even small amounts of RBC stroma-antibody complex plays a significant role in the pathophysiology of acute renal failure. 13• 15· 44 Renal ischemia and hypoperfusion is believed to occur as a result of the combined effects of DIC and l.ts associated renal vasculature fibrin deposition, systemic hypotension, and renal vasoconstriction. 6· 13· 22• 49 The severity and duration of the renal ischemia determine whether renal failure will be transient, temporary, or permanent. 6· 13· 22 Clinical Signs

The clinical signs associated with an AHTR are variable and depend on the amount of blood transfused, previous sensitization, and specific type of antibody involved. 13· 25• 39 These signs may include pyrexia, tachycardia, restlessness, salivation, tremors, weakness, vomiting, dyspnea, acute collapse, hypotension and convulsions. 6· 15· 30· 39· 41· 59· 61 None of these signs are pathognomonic for an AHTR and also may be seen with a variety of other types of transfusion reactions or primary disease processes. 39 Depending on the mechanism of action, the hemolysis may be intravascular or extravascular in nature. 2· 6· 15· 44• 61 Intravascular reactions are characterized by hemoglobinemia and hemoglobinuria secondary to RBC membrane lysis within the vasculature and usually occur within minutes of the start of the transfusion. 2· 39· 61 These reactions tend to be more severe and may lead to DIC and shock with the possibility of subsequent renal damage (as discussed in the preceding section). 6· 39· 49 EVH as a result of the destruction of antibody coated erythrocytes by the monocyte-macrophage system in the liver and spleen. 6· 13· 59 This type of destruction leads to hyperbilirubinemia and bilirubinuria and may be acute or delayed in nature. 6· 13· 61 Clinical signs resulting from EVH are usually more mild than those seen with intravascular hemolysis (IVH).6, 13,49 Recognition and Treatment of a Hemolytic Transfusion Aeaction Monitoring

It is of crucial importance to carefully monitor transfusions; early reaction recognition may prevent disaster. The form used for appropriate

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monitoring at the North Carolina School of Veterinary Medicine is included as Appendix I. Special caution always should be taken in the first 30 minutes of a transfusion and if previous transfusions have been given. Diagnosis

If an AHTR is suspected, certain laboratory tests may help verify this reaction. Additionally, history of a prior transfusion (given more than 5-7 days before the second transfusion) or pregnancy should be documented. The clinician should then verify that the correct unit of blood was given. 6• 13 The presence of recipient hemolysis should be confirmed. 6 • 13• 61 The donor blood also should be rechecked for hemolysis. Mechanical and thermal damage should be ruled out. 6 • 13• 61 A Coombs test, recrossmatching and blood typing may be considered. 13• 30• 39 A Gram stain with or without cultures performed on the unused portion of blood also may help to rule out bacterial contamination. Treatment

If an AHTR is suspected, the transfusion should be stopped immediately and aggressive fluid administration to address hypotension and renal hypoperfusion should be begun. 6 • 13• 61 It is imperative, however, to avoid overhydration with excessive fluid administration. 6 Monitoring central venous pressure (CVP), heart rate, and lung auscultation are important aids to appropriate monitoring. 6• 13• 30 Shock doses of glucocorticoids are advocated by some clinicians. 30 The administration of lowdose furosemide starting at 1 to 2 mg/kg will improve renal cortical perfusion. 6 Furosemide therapy is not without risk and should be monitored carefully. 6 Therapy with low-dose dopamine (< 5 ~-tg/kg/min) also may improve renal perfusion and also should be considered if ARF is suspected. 6• 13 Higher doses of dopamine are vasoconstrictive and, consequently, are contraindicated because they decrease renal perfusion.6 Mannitol has lost favor as a treatment for acute renal failure (ARF) resulting from a hemolytic transfusion reaction. 6• 13• 22• 39 Therapy for DIC is a controversial topic. 6· 13• 22 Most sources advocate the use of heparin early in the course of DIC, but the clinician is cautioned to use heparin only in severe hemolytic transfusion reactions when DIC is likely. 6· 13• 22• 39 A standard canine dose of heparin is not well documented, but 50 to 100 U /kg subcutaneously three times a day is a frequently suggested dose. Fresh frozen plasma (FFP) or cryoprecipitate (CP) also may be used to treat DIC; however, they may exacerbate the hemolysis. 6• 13• 39 In addition to monitoring CVP and heart rate, temperature, mucous membranes, capillary refill time (CRT), and general attitude should be monitored closely. The placement of a urinary catheter also should be considered.B A urine output of at least 3 mL/kg should be maintained. Complete blood cell (CBC) count, activated clotting time or coagulation profiles, urinalysis, blood urea nitrogen (BUN), creatinine, and electro-

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lytes should be monitored carefullyY· 30 Although rare in canine patients, AHTR is severe and warrants quick recognition and rapid institution of appropriate treatment.

DELA YEO HEMOLYTIC TRANSFUSION REACTIONS

DHTRs are a result of EVH that can be seen 3 to 21 days after transfusion. 13• 30• 41 • 45 Infrequently, intravascular hemolysis has been seen. As previously discussed, EVH results from IgG antibody opsonization of foreign erythrocytes with subsequent destruction of these cells in the liver and/ or spleen. 6, 13, 44, 45, s9 DHTRs are seen when the transfused cells possess an antigen for which the recipient has already been sensitized by previous transfusion or pregnancy. 6 • 13• 15• 30• 44• 46 Crossmatching may not detect incompatibilities due to low levels of circulating antibodiesY· 15• 44 On administration of the transfusion, an anamnestic response is triggered and antibodies increase to levels sufficient to cause varying degrees of RBC destruction. 6, 13, 1s. 44, 46

Clinical Signs

Generally the consequences of DHTRs vary from subclinical to mildY· 15 Occasional reports of more severe and even fatal reactions have been documented in the human literature. 6• 46 With multiple transfusions, DHTRs are believed to be more common than AHTR. 6• 61 Fever is one of the most common presenting complaints documented with a DHTRs. 6• 46• 61 Anorexia and jaundice also have been noted by owners. 61 Documentation of a DHTR is based on the finding of hyperbilirubinemia and bilirubinuria with a concurrent, and otherwise unexpected, decrease in PCV. 15• 30• 61 A positive direct antiglobulin test (Coomb's) is seen as strong supportive evidence of a DHTR. 6• 13• 15 It is difficult to document this type of a reaction in patients with immune-mediated hemolytic anemia (IMHA) as the primary disease process masks the reaction. 15

Treatment

Because DHTRs tend to be mild, specific treatment is often not necessary. 6• 15• 44 Symptomatic treatment may be necessary for fever and anorexia. Severe hemolytic reactions should be managed as an AHTR. The most important effect of a DHTR is an exacerbation of a pre-existing anemia. 6• 13• 15 Additional use of blood products may be necessary, but they do carry the risk of further reaction. 13

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PREVENTION OF HEMOLYTIC TRANSFUSION REACTIONS Donors

Use of DEA 1.1, DEA 1.2, or DEA 7 positive donors increases the risk of a variety of HTRs. These reactions include shortened donor cell survival due to the formation of antibodies against the donor's RBCs, sensitization of the recipient to subsequent nonuniversal transfusions, risk of immediate hemolytic reactions in a sensitized animal, and hemolytic disease in newborn puppies. 23· 45 Because of theses risks, universal donors should be used whenever possible. Crossmatching

A crossmatch will detect pre-existing antibodies in donor or recipient blood and is an excellent screening test to document incompatibilities that may lead to HTRs. 2· 15· 42· 61 This screening is especially important in dogs that have received previous transfusions because antibody production and subsequent sensitization can occur in as little as 4 days. 2 • 15· 42• 61 In addition, because all antigenic groups have not been fully characterized in dogs, it may be advisable to perform a crossmatch even when using universal blood types and with first-time transfusions. A major and minor crossmatch may be performed. 2• 15· 61 The major crossmatch tests the reaction of the recipient's serum or plasma to the donor's erythrocytes, and the minor crossmatch tests the recipient's RBCs to the donor's serum (a summary of these reactions is presented in Table 3). 2• 15· 41 Additionally, auto controls testing recipient cells to its own serum and donor cells to its own serum are performed. Incompatibilties are seen as hemolysis or agglutination either grossly or microscopically.53 Because reactions can be temperature dependent, the crossmatch is performed at 37°C, 25°C, and 4°C. 2 The major crossmatch always should be compatible at 37°C and 25°C. The minor crossmatch is rarely useful in dogs. 15 This test may be considered if large amounts of plasma are to be given. Crossmatching is a simple technique that can be performed with the use of standard laboratory equipment. In a recent study of 25 animal Table 3. THE CROSSMATCH

Major Minor Compatible

Donor

Recipient

Cells Serum/plasma

Serum/plasma Cells

1. No agglutination or hemolysis at 4°C, room temperature 3rC 2. No agglutination or hemolysis when Coomb's antiglobulin reagent added

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clinics, it was found that only 10 of 25 performed crossmatches before transfusions. 33 Five of the 10 clinics that did perform crossmatches did so in less than 50% of the cases. 33 For details on the crossmatching procedure see article by Feldman and Kristensen. It is important to note that a compatible crossmatch means only that no detectable antibodies presently exist and does not prevent sensitization from occurring after the transfusion is given. 2' 15• 61 A dog that has had a compatible crossmatch and transfusion 4 to 5 days earlier will not necessarily again be compatible with the same donor. It is advisable to repeat a crossmatch. Occasionally, antibodies may be present at levels too low to detect on a crossmatch and a mild hemolytic reaction may occur. Finally, note that a crossmatch tests only for antibodies to RBCs and not to white blood cells or platelets. 10 Antibodies to these components may cause mild-to-severe nonhemolytic transfusion reactions. s, 36• 58

Other Pretransfusion Considerations

HTRs have not been shown to be suppressed by the use of steroids or antihistamines. 15 The administration of these drugs before transfusion may lead to a false sense of security and must not be used as a substitute for appropriate screening methods. In one study conducted in the mid1950s, the administration of cortisone as a pretreatment before the administration of incompatible blood resulted in more severe clinical signs than in those dogs not given similar prophylactic treatment.2 5 Clerical errors such as mislabeling, incorrect patient identification, and failure to verify labels are the most common causes of HTR in human medicine. 6 • 13' 39' 44 Although the incidence of these types of errors in veterinary medicine are not known and may be less likely due to a lower volume of blood products used, it is important to institute appropriate safeguards to avoid these very preventable but potentially dangerous errors. In summary, the most effective means to prevent HTRs rests not in the administration of prophylactic drugs, but in the appropriate use of crossmatching, donor selectin, and careful record keeping.

NONHEMOLYTIC IMMUNE-MEDIATED REACTIONS Acute Hypersensitivity Pathophysiology

Acute hypersensitivity reactions may be considered anaphylactic or anaphylactoid in nature. 23, 49, 61 Anaphylactic or allergic reactions are classified as type I hypersensitivities and are mediated by IgE antibodies.23· 44, 49 , 60 • 61 These IgE antibodies have the ability to activate mast cells

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to release or produce a variety of vasoactive substances.5 • 23 • 44 • 49 Preformed substances that are released include histamine, serotonin, kallikreins, and proteases; these substances are capable of activating the complement system to form the potent anaphylatoxins C3a and C5a. 23 • 34• 60 Substances produced from the phospholipid membrane of mast cells include leukotrienes, prostaglandins, and platelet activating factor. 23 • 49• 60 The combination of the previously mentioned mediators are capable of producing hypotension, increased vascular permeability, and bronchoconstriction in addition to urticaria and pruritis. Anaphylactoid, or immediate generalized reactions (IGR), are reactions that closely resemble allergic type responses, but are not mediated by IgE-mast cell interaction. 2 • 23• 49• 61 The exact mechanism of this reaction is unclear. 23 • 49 The presence of plasma contact factors that activate the kinin system leading to production of vasoactive amines may play a role in the immediate generalized reactions. 2• 61 The possibility of transfusion reactions associated with plasma and plasma products is sometimes overlooked. 34 The complexity and heterogeneity of plasma products suggest a wide range of possible reactions, and it is believed that plasma reactions are more common than previously recognized. 34• 28 Plasma products frequently have been associated with acute hypersensitivity type reactions. 12• 14• 23 • 34• 44 These reactions may occur as a result of transfusion of allergens (such as antibiotics or chemicals used in blood preparation), alloantigens (albumin, C4, and other proteins), or, less frequently, as a result of the transfusion of IgE antibodies from the donor to the recipients. 15• 23 • 34• 39• 49 Acute hypersensitivity reactions secondary to transfusion of IgA antibodies to IgA-deficient patients who possess anti-IgA antibodies is also of major concern in human medicine, but it has not been documented in the canine population.23. 39• 44• 49 Breeds with IgA deficiencies may be at higher risk for these reactions. In addition, atopic patients and patients who have received multiple transfusions are at higher risks for developing acute hypersensitivity reactions. 5 • 34• 44 Clinical Signs

The clinical signs of acute hypersensitivity reactions result from release of vasoactive amines and vary widely from minor skin reactions to cardiopulmonary arrest. 2• 15• 34• 39• 49 Onset of a reaction is rapid, usually occurring from 1 to 45 minutes from the start of the transfusion. 23 • 34• 49 Urticaria is the classic sign of an allergic reaction in the dog. 2• 12• 14• 15• 30 Other possible signs include pruritius, erythema, angioneurotic edema, emesis, dyspnea, hypotension, bronchoconstriction, and severe shock. 23 Treatment

As with all suspected transfusion reactions, stopping the transfusion is the first step in management.l5 • 23• 30• 34• 49• 61 Most mild reactions (urticaria, pruritus, erythemia) respond well to the intramuscular (IM) ad-

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ministration of diphenhydramine at 2 mg/kg. 2· 14· 29· 59 The administration of steroids is also advocated in some situations. 15· 34· 60 An anti-inflammatory dose of dexamethasone IV or IM (0.5-1.0 mg/kg) can be used in a mild transfusion reactionY Severe signs such as shock, bronchoconstriction, angioneurotic edema or other life-threatening situations warrant use of high-dose IV dexamethasone (4-6 mg/kg IV). 15· 34· 47 Intravenous epinephrine at a dose of 0.01 mg/kg (1:1000) also should be used with severe reactions. 15· 34· 39· 49· 60· 61 Appropriate resuscitation with ventilatory assistance, oxygen therapy, and colloids also may be required if a severe reaction occurs. 34 Prevention

Administration of diphenhydramine at a dose of 2 to 4 mg/kg SC or IM 15 to 20 minutes before transfusion has been shown to decrease the occurrence of acute hypersensitivity type reactions. 5 Intravenous administration of diphenhydramine should be avoided due to the possibility of hypotension. 61 Close monitoring (see Appendix I) and the appropriate use of component therapy also are important steps in preventing severe anaphylactic or IGR.

Leukocyte/Platelet Sensitivity Reactions

Definition and Pathophysiology

Febrile non-HTRs (FNHTR) are the most common complications seen in human medicine. 30· 36· 39· 46 These reactions are suspected when a temperature increase of at least 1oc is documented and no other cause for the fever is found. 8• 20· 52 The majority of these FNHTR have been documented to be caused by white blood cell antigen/ antibody reactions.8· 30· 49· 58· 61 Platelet antigen/ antibody interaction also has been shown to cause febrile reactions. 8• 39· 44· 49· 58· 61 The incidence of these white blood cell or platelet antibody I antigen reactions is unknown in dogs. 30 The exact mechanism of fever induction secondary to leukocyte or platelet antibody-antigen interaction is not completely understood, but release of endogenous pyrogens such as IL-l from granulocytes, macrophages, monocytes, or lymphocytes is thought to be important. 30· 52 Additionally, the binding of antibodies to white blood cells will activate the complement system leading to the production of C3a and C5a. 8· 49 This interaction can cause not only fever, but also neutrophil accumulation in the lungs that in turn may be responsible for more severe respiratory signs and shock. 49 In humans, white blood cell or platelet sensitivity reactions are more common in multiparous women and patients who have received frequent transfusions. 8• 39· 52 However, these reactions also have been documented to occur during a first transfusion.36

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Clinical Signs

Mild and transient fever is by far the most common sign observed with leukocyte or platelet incompatibility reactions.s, 14, 15, zo, 3o, 36, 39, 44, 52, 61 This fever usually occurs within the first 30 minutes and may continue to increase for up to 8 hours after transfusion and persist for 12 additional hours. 8 • 39 Vomiting and tremors also may be seen. 52 Transfusion related lung injury and shock also have been reported. 39• 49• 52 Severe lung injury may lead to adult respiratory distress syndrome manifested by noncardiogenic pulmonary edema, dyspnea, and hypoxemia. 39• 44• 49 These pulmonary hypersensitivity reactions are relatively rare but should be recognized early because of their severity. 39• 44• 49 Monitoring/Documentation

Close monitoring usually will show a fairly rapid increase in the patient's temperature. 8• 20• 39• 52 Respiratory signs such as tachypnea or dyspnea also tend to occur early in the transfusion. 49 • 52 It is important to rule out a hemolytic reaction or a reaction due to the infusion of contaminated blood. 20• 38 In addition, worsening of the primary disease should be considered. 20• 52 In humans, patient serum may be tested for specific white blood cell or platelet antibodies. 8 • 36• 49 • 58 This currently is not feasible in the canine patient. Recognition of a leukocyte or platelet sensitivity reaction is usually based on clinical signs. Specific evidence implicating white blood cell or platelet antibodies as the cause of a transfusion reaction in dogs is difficult to obtain. As numerous causes for fever during transfusion exist, the diagnosis of these types of transfusion reactions generally are based on exclusion of other documented causes. 36• 39• 52 Treatment

Because white blood cell/platelet sensitivity reactions are dose dependent, the transfusion should be immediately stopped. 44• 49 • 52 Treatment then is determined by monitoring the severity of the reaction. Most of these reactions are mild and transient. 14• 15• 44• 52• 61 Often the transfusion may be started again (after a 10-15 minute break to monitor for more severe signs) at a slower rate without further complication. 15• 61 Antipyretics such as aspirin (10 mg/kg orally) or dexamethasone SP (1 mg/kg IV or IM) may be given if the fever is more severe. 44• 52• 61 Severe pulmonary signs and ARDS must be treated aggressively. 49 Ventilatory assistance may be indicated. 39• 49 High-dose dexamethasone SP (4-6 mg/ kg IV) is controversial, but it may suppress neutrophil activation. 49 Pulmonary edema should be treated with furosemide (2-4 mg/kg) IV initially and repeated if necessaryY With appropriate monitoring and supportive care, most patients

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who are not severely compromised recover from these transfusion reactions within 24 hours. 15• 39· 52 Prevention

If white blood cell or platelet sensitivity reactions are suspected to have occurred with previous transfusions, the administration of aspirin (10 mg/kg orally) or low-dose dexamethasone SP (1 mg/kg IV or IM) may help prevent additional febrile reaction from occurring. 30· 52 Routine use of pretreatment with these drugs is not encouraged. 30· 52 Leukocytedepleted blood products are sometimes given to humans who have exhibited febrile reactions. 39· 44• 49· 52. ss

DELA YEO IMMUNE-MEDIATED TRANSFUSION REACTIONS Post-transfusion Purpura

An acute thrombocytopenia occurring 1 week post-trahsfusion has been seen as a rare complication in humans. 38· 39· 44 The pathophysiology is believed to be anamnestic in nature and due to the development of circulating platelet specific antibodies that destroy not only the transfused platelets, but also attack the patient's autologous platelets.38· 39· 44 The exact mechanism of this attack is unknown, but it is postulated to be due to adsorption of antigen-antibody complexes. 39 Thrombocytopenia may persist for 10 days to 2 months. 44 The incidence of posttransfusion purpura in the canine population is not known. Monitoring and Documentation

Serial platelet counts along with clihical signs of thrombocytopenia (petechia, scleral and aural hemorrhage, hematuria) are suggestive of posttransfusion purpura. Identification of a specific platelet antibody can be documented in human patients. 38· 39· 44 It is important to rule out other causes of thrombocytopenia related to the primary disease process or drug reactions. Treatment

Post-transfusion purpura generally is a self-limiting disease. 44 Therapy has not been thoroughly evaluated because this is a rare complication.44 Platelet transfusion may be ineffective due to rapid destruction and may result in febrile reactions. 38· 39· 44 Standard therapy for immunemediated thrombocytopenia may be indicated.

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Neonatal lsoerythrolysis Definition and Pathogenesis

Hemolytic disease of newborn puppies occurs as a result of sensitization of breeding bitches due to prior transfusion of incompatible RBCs. DEA 1.1 and 1.2 negative bitches, when given DEA 1.1 or 1.2 positive blood, will develop antibodies to these blood types. DEA 1.1- or 1.2positive puppies born to this bitch (bred to a DEA 1.1- or 1.2-positive male) will consume large quantities of anti-DEA 1.1 or 1.2 antibodies in colostrum in the first 24 hours of the pup's life. These antibodies have the ability to cause severe hemolysis. Clinical Signs

Weakness, failure to thrive, and hemoglobinuria may be the first signs noted by owners of these puppies. Laboratory work shows hemoglobinemia, spherocytosis, and possibly a positive Coomb's test. Puppies may die in 2 to 3 days if the disease cannot be controlled. Monitoring and Documentation

Clinical and laboratory signs of hemolysis, a positive Coomb's test, and a history of the bitch receiving a prior transfusion lead to the diagnosis of neonatal isoerythrolysis. Typing of affected puppies may help to confirm a diagnosis because only DEA 1.1- or 1.2-positive puppies experience neonatal isoerythrolysis. Toxic and infectious causes of hemolysis should also be ruled out. Prevention and Treatment

Neonatal isoerythrolysis is a preventable complication of transfusion. Breeding bitches should receive only typed or universal blood when being transfused. If a bitch is suspected to have alloantibodies resulting from a previous transfusion or a prior litter exhibiting neonatal isoerythrolysis, the pups should not be allowed access to her for up to 72 hours. Affected pups may exhibit mild to severe clinical signs of hemolysis. If a RBC transfusion is indicated, universal blood should be used. Intramedullary infusion through the femur or humerus may be necessary. Please refer to the section on HTRs for further therapy. Immunosuppression

Renal allografts in both dogs and humans have been documented to survive longer in patients who have received transfusion therapy than in those patients not requiring similar transfusions. 15, 30, 44 Addition-

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ally, human patients who have received transfusions during tumor resection have been shown to have shorter survival times than similar patients who were not transfused. 15, 30 An additional study noted an increase in postoperative infections in transfused patients. 30 The mechanism of immunosuppression is not fully understood, but it has been suggested that plasma may contain immunoregulatory substances leading to this immunosuppression. 15, 44 NONIMMUNE-MEDIATED TRANSFUSION REACTIONS Acute Reactions Hemolysis

Significant lysis of erythrocytes may occur in the absence of immune-mediated mechanisms. 6' 13, 14, 15 This destruction of transfused RBCs may produce clinical and laboratory signs and needs to be distinguished from immune-mediated hemolysis. 6' 13 Etiologies of nonimmune-mediated hemolysis include contamination of the blood product, inappropriate administration, mishandling before administration, and use of outdated products, 6' 13' 14' 15 Contaminated Blood. Bacterial contamination of blood units frequently cause a color change or hemolysis in the unit itself. 6 Hemolysis is a relatively minor complication in comparison to the more severe consequences seen when a contaminated unit is transfused. 6 A discussion of the reactions seen with the use of contaminated blood will be found later in this article. Mechanical Hemolysis. Mechanical trauma secondary to infusion technique may lead to RBC lysis. 6 ' 13, 14, 15 Small needle or catheter size, twisted lines, plugged filters, and rapid infusion have all been documented to result in hemolysis. 6 ' 14' 15 Optimally, the largest bore needle and slowest practical rate of infusion will produce the least hemolysis. Outdated RBC products also may be hemolyzed within the unit, are much more fragile than fresh erythrocytes, and should not be used intentionally, 6 , 13 A recent study evaluated the use of three peristaltic pumps used to administer whole blood. Two of these pumps, the Animed Flowset 100 (San Diego, CA) and the IVAC 560 (San Diego, CA), were found to cause excessive or intermediate hemolysis, respectively, whereas the IVAC 530 (San Diego, CA) was able to administer blood at rates of up to 200 mL/h without hemolysis. 30 Thermal Hemolysis. Overheating or freezing RBC products results in sufficient damage to cause hemolysis before transfusion. 6' 13, 15 Blood should not be cooled to less than -3°C or heated to more than 37°C. 6 Irreversible damage to erythrocytes occurs at 50°C, and this blood is cleared rapidly from the recipient's circulation, 6 Even focal overheating

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of a portion of a unit may result in significant hemolysis. 6 These reactions can be minimized by use of carefully monitored refrigerators and appropriate warming of blood products. 6' 13, 15 Osmotic Hemolysis. RBCs should be diluted only with isotonic saline (0.9%). 6' 13, 14 Lysis of erythrocytes occurs with hypotonic solutions such as 5% dextrose in water and hypotonic saline. 6' 13, 15 Prevention and Treatment. All units should be inspected grossly for color change and a sample spun down to check for hemolysis. 6 The presence or absence of contamination or immune-mediated hemolysis must be documented to institute appropriate therapy. 6' 13 Expiration dates should be checked, and appropriate storage and administration should be confirmed. Hemolyzed blood should never be given intentionallyY If hemolysis is noted during transfusion, the transfusion should be stopped and the reason for hemolysis ascertained. Except in the case of bacterial contamination, nonimmune hemolysis has a fairly benign clinical course and usually requires no special treatment other than monitoring.13 It is, however, important to note that increased destruction of transfused RBCs decreases the efficacy of transfusion. Circulatory Overload

Pathophysiology

Circulatory overload is a state of hypervolemia induced by overly aggressive administration of blood products. 20, 24' 52 Rapid transfusion of large amounts of blood given to normovolemic patients is one of the most common mechanisms that may lead to circulatory overload. 15, 20, 24, 41 Patients with underlying cardiac disease are at a higher risk of developing hypervolemia with standard transfusion rates. 2' 15, 52 In addition, dogs with chronic anemia are at risk of developing circulatory overload secondary to rapid replacement of erythrocytes. 15, 39 In this case, cardiac compensatory mechanisms such as increased cardiac output and cardiac hypertrophy are present due to the primary anemia. 15 Large amounts of blood or rapid infusions may decompensate an already stressed cardiovascular balance. 15 This may lead to congestive heart failure and pulmonary edema. 15 Circulatory overload is one of the more common transfusion reactions in small animals. 15, 24 Clinical Signs

Most of the symptoms of circulatory overload are cardiovascular in nature. These include cough, tachypnea, dyspnea, and tachycardia. 2' 15' 30, 41 In severe cases, pulmonary edema and congestive heart failure may develop. 39' 52' 61 Vomiting and urticaria also may be seen. 24

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Monitoring and Diagnosis

Clinical signs will be suggestive of circulatory overload. Routine monitoring may show tachypnea and tachycardia. 2 • 24• 3° Central venous pressure (CVP) should be monitored in patients at risk of developing hypervolemia. 2• 39• 61 Evidence of congestive heart failure and pulmonary edema may be seen if thoracic radiographs are made. Acute hemolysis, sepsis, and anaphylaxis should be ruled out. Prevention and Treatment

The use of appropriate component therapy decreases the risk of development of fluid overload. 2• 14• 15• 30• 39• 52 A well thought out dosage and rate of transfusion also will help prevent hypervolemia. 14• 30• 52 A rapid transfusion rate in a patient that is not hemorrhaging may do more harm than good. 52 Extreme care should be used when transfusing patients with underlying cardiac disease. 15• 24 • 52 A rate of 1 mL/kg/hr for these patients has been suggested. 24• 52 If circulatory overload is suspected, the transfusion should be slowed or stopped. 15• 52• 61 Furosemide (2-8 mL/kg IV) is effective at alleviating pulmonary edema. 15• 39• 47• 52• 61 Supplemental oxygen also may be needed. 15• 52 With prompt recognition and treatment, the prognosis for recovery from circulatory overload is good. Bacterial Contamination Pathophysiology

Blood is an excellent substrate for the growth of bacteria. 49 Gramnegative organisms such as Pseudomonas, Citrobacter, Yersinia, and various coliforms have the ability to grow at low temperatures and are able to use citrate as a major source of carbon. 6• 13• 31 • 39• 49 • 61 Contamination with these bacteria may be a result of the entrance of contaminated air into the blood-collecting apparatus, donor skin contamination, or the existence of a subclinical bacteremia in the donor. 31 • 39• 49• 63 Yersinia infection and contaminated platelet concentrates (stored at 20°C-24°C) have been of special concern in recent human literature. 4• 31 • 49 Fortunately, because of aseptic techniques, disposable plastic products, and appropriate donor screening and storage methods, bacterial contamination is a rare occurrence. 4• 6 • 13• 15• 31 Clinical Signs

Infusion of a significant amount of gram-negative bacteria will result in rapid and severe consequencesY· 15• 30• 61 Endotoxin-mediated

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septic shock is a severe and complex syndrome caused by aberrations of oxygen transport, myocardial function, peripheral perfusion, and metabolism along with complement, kinin, and coagulation system activation.6' 2&--27, 39, 48 Clinical signs consist of fever, severe hypotension, hemolysis, vomiting, diarrhea, and DIC. 6, 14, 39, 49,61 Monitoring and Diagnosis

Contaminated blood is often darkly discolored and may contain air bubbles, particulate matter, and clots (due to bacteria use of the citrate anticoagulant). 2 ' 24, 30, 31 , 39, 61 Because clinical signs develop rapidly, close monitoring of temperature, pulse, and respiration as previously discussed will often be the first sign of a reaction. Acute hemolysis should be ruled out. 61 Although Gram stains and cultures recently have been shown to be insensitive documentation of contaminated blood, these tests still should be performed. 4 ' 6, 15, 30, 4 9,61 Prevention and Treatment

Appropriate, aseptic collection and administration techniques are the most important aspects in controlling bacterial contamination. 2' 6' 14' 24, 39 Blood that is discolored or has evidence of particulate matter should be tested for contamination and discarded. 4 ' 31 , 49 Once a unit has been warmed or opened (by the introduction of needles), it should be used within 24 hours or discarded. 2' 6 The administration of a transfusion should not exceed 4 hours. Rapid diagnosis of contamination and institution of appropriate therapy is essential for the successful treatment of septic shock. 15, 39 The transfusion must be stopped immediately. 14' 15, 30 Supportive care and broad-spectrum antibiotic coverage should be instituted. 14, 15, 39, 49 , 61 A complete discussion on the management of septic shock is beyond the scope of this review and can be found elsewhere. 26, 27, 48 Even with heroic measures, the fatality rate for these reactions is high. 39' 49 Prevention of bacterial contamination to avoid severe endotoxic shock must be emphasized. Citrate Toxicity Pathophysiology

Citrate in blood products is capable of chelating calcium leading to a decrease in the amount of circulating ionized calcium. 2' 14, 29, 52, 61 A normally functioning liver, however, is efficient at rapidly metabolizing citrate to bicarbonate; thus, hypocalcemia is a rare complication. 14, 15, 29 ' 52, 61 There are two situations that place patients at a higher risk of

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developing hypocalcemia. When the liver is compromised as with portosystemic shunts or liver failure, citrate cannot be metabolized as quickly and hypocalcemia may occur. 2 • 14• 15• 52• 61 Additionally, rapid transfusion of large amounts of blood products may overwhelm the ability of the liver to metabolize citrate. 2• 30• 39 • 52• 61 FFP, platelet-rich plasma, and whole blood have the highest amounts of citrate presenU 5 Hypomagnesemia also has been reported (also due to citrate chelation) to occur, but its significance is unknown. 52 Clinical Signs

Tremors may be the first clinical sign noted. 2• 15• 61 Tetany may be seen in severe cases. 52 Electrocardiogram (ECG) findings include prolongation of the Q-T interval, depression of P and T waves, and ventricular arrhythmias. 14• 15• 52• 61 Vomiting has also been noted. 14 Diagnosis and Monitoring

Diagnosis usually is made by clinical signs, as well as an appropriate history of liver disease or rapid infusion. Ionized calcium may be measured for confirmation. Physical monitoring for tremors and ECG recordings are useful for documentation and follow-up reactions. 15, 52, 61 Prevention and Treatment

Although hypocalcemia is a rare complication, caution should be exercised when transfusing patients with liver disease. Appropriate administration rates should be followed. 30 If rapid infusion is necessary, an ECG can be recorded. Hypocalcemia is transient and rapidly reversible. 14• 15 The transfusion should be stopped until signs resolve and restarted at a slower rate. 2• 14• 15• 52 Infusion of 10% calcium gluconate rarely is necessary, but it can be given at 50 to 150 mg/kg slowly to effecU· 15• 29 • 30• 47• 61 ECG monitoring should be continued during infusion because ventricular arrhythmias and arrest can occur with calcium infusion. 52 MISCELLANEOUS ACUTE REACTIONS Coagulopathy

Massive transfusion of stored blood that is deficient in platelets, fibrinogen, and coagulation factors (especially V, VIII, IX) may result in a dilutional coagulopathy. 2• 40• 41 Replacements of these constituents with platelet-rich plasma, FFP, or CP may be necessary to control bleeding.

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Diluting RBCs with calcium-containing solutions such as lactated Ringer's will recalcify the anticoagulant and may lead to coagulation. 61 Only isotonic saline should be used to dilute packed RBCs. 61 Hyperammonemia

Ammonia levels increase in stored blood and may cause ammonia toxicity. 15· 52 This complication is rare and thought to be a problem only in patients with significant liver disease who are unable to metabolize and excrete ammonia properly. 15· 52 Careful monitoring and use of blood that has not been stored for long periods is suggested when transfusing patients with liver disease. Some clinicians advocate the use of washed RBCs when transfusing patients with liver failure. 52 Hypothermia

Infusion of chilled blood may cause clinically significant hypothermia in young and small animals. 2 Massive transfusion of cold blood products also may lead to hypothermia in adult animals. 52 Severe hypothermia may cause cardiac arrhythmias and sudden death. 52 Warming of blood products with monitored electric warmers (without overheating) is useful to alleviate this complication. 52 Air Embolism

Air embolism is now a rare complication of transfusion as a result of the use of closed system infusion. 39 Transmission of a large volume of air, not just a few bubbles, is necessary to cause clinical signs. This may occur when venting glass bottles during transfusion. 61 Cough and acute dyspnea are the most common clinical signs. 39 Treatment consists of stopping the transfusion and placing the dog on its left side with its head down. 39 Pulmonary Microembolism

Microaggregates of platelets, white blood cells, and fibrin form in blood stored for more than 7 days. 2• 15· 52 These microaggregates range in size from 20 to 120 J.Lm and thus cannot be removed by the standard 170 to 230 J.Lm filters. 39 • 52 The clinical significance of these particles in causing pulmonary microembolism has been the subject of much debate.15· 39• 52 Human clinicians in the 1960s advocated the use of microfil-

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ters (20-40 fLm) for massive transfusions and cardiac surgery. 52 Although much controversy still exists, most of the more recent research has shown no significant benefit associated with the use of microfilters. 15' 52 Use of these smaller filters currently is not advocated for routine transfusions. 15, 52 In addition, microfilter use in massive transfusion may be detrimental due to delayed infusion of needed blood. 15, 52 Acidosis

Stored blood undergoes a number of biochemical changes leading to a decrease in pH. 53, 62 The use of glucose leads to the production of lactic and pyruvic acid which is responsible for this decrease in pH. 62 Massive transfusion has the theoretical potential to result in a clinically significant acidosis. In reality, posttransfusion acidosis is rarely seen. 15' 53 In patients with a normally functioning liver, both citrate and lactic acid are converted to bicarbonate within several hours of the transfusion. 15' 53 Any prior acidosis is thus offset by this metabolism. 15 DELA YEO NONIMMUNE-MEDIATED TRANSFUSION REACTIONS Disease Transmission

The most common cause of transfusion-related fatality in human medicine is the transmission of infectious disease. 15 The AIDS crisis and the impact it has had on transfusion medicine has heightened the awareness of not only clinicians but laypeople to the dangers of transfusion transmitted disease. Although no retroviral agent has yet been identified in the canine population, a variety of other blood-borne infections have the potential to transmit serious disease to recipient dogs. 9' 15 ' 30 A recent survey studying transfusion practices found that 36% of the participating clinics did not screen for the presence of infectious disease in their donors. 33 Infectious agents carrying the highest risk of transmission have long incubation periods, are stable in stored blood, and have the ability to persist subclinically in healthy dogs for prolonged periods. 15 It currently is recommended that donor dogs be screened for disease based on the specific geographic prevalence of infectious diseases. 9 , 15' 61 Heartworm tests should be conducted on most animals. Ehrlichia and Babesia are more common in the southern states_?, 57 In addition, racing Greyhounds have been documented to have a high incidence of seropositivity to Babesia canis?, 57' 19 Direct smears should be examined and immunofluorescent antibody titers run to screen donors for babesiosis_?, 19, 57 Even

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with these tests, it is sometimes difficult to confirm or rule out this disease?· 19 The use of splenectomy to enhance the ability to diagnose babesiosis is controversiaF Borrelia spirochetes have been shown to survive in packed RBC at 4°C centigrade and FFP at -l8°C 3 This fact suggests the risk of transmission of Lyme disease through contaminated blood products. Because there currently is no test that is considered accurate for the confirmation of subclinicallyme disease, routine screening is not recommended. 1• 3 Because blood-borne diseases may have serious and even fatal consequences in a recipient dog, it is essential to screen donor dogs appropriately for the presence of infectious disease.

Hemosiderosis

A rare complication of iron overload can occur when multiple transfusions are given to a patient who is not bleeding. 15• 39• 52 Excess iron is initially bound to transferrin. 15 When transferrin is saturated, additional iron is stored in the liver and may result in hepatic damage. 15Appropriate component therapy will reduce the risk of hemosiderosis. Additionally, iron should not be routinely supplemented unless an iron deficiency has been documented. 15

SUMMARY

There is a wide range of mechanisms by which transfusion reactions may occur. These reactions typically are categorized as immune- or nonimmune-mediated and also as to whether they are acute or delayed in nature. The type and severity of clinical signs vary according to the specific reaction present. Many reactions can be prevented with the use of standard and appropriate transfusion medicine procedures. These methods include careful collection and storage of blood products, adequate screening and blood typing of donor dogs, crossmatching donor and recipient blood, use of component therapy, correct administration of blood products, and the use of pretransfusion prophylaxis when appropriate. Because many reactions are dose dependent, careful monitoring of transfusions cannot be overemphasized. Rapid recognition of a transfusion reaction and immediate discontinuation of the transfusion, along with appropriate supportive therapy, is essential for the successful treatment of transfusion reactions. A summary of transfusion reactions including clinical signs, diagnosis, and basic treatment protocols is given in Table 4. When used appropriately, transfusion of blood products can be a highly beneficial, low-risk form of therapy.

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Table 4. DIAGNOSIS AND TREATMENT OF TRANSFUSION REACTIONS Clinical Signs

Fever

Rule outs

Leukocyte/platelet sensitivity Acute hypersensitivity HTR

Other clinical signs/ diagnostics

Facial swelling pruritus

Positive hemolysis + /- Gram stain/culture of donor blood

Treatment

Stop transfusion If mild fever without more severe clinical signs, may be able to restart transfusion at a slower rate in 10-15 minutes Monitor temperature +1- antipyretics Dexamethasone SP (1 mg/kg IV) Aspirin (1 0 mg/kg orally) + /- external cooling If HTR ·························· If acute hypersensitivity If bacterial contamination treat for sepsis

Hemolysis

Pruritis/Facial Swelling

Respiratory Distress

Circulatory overload HTR Severe acute hypersensitivity Bacterial contamination Severe leukocyte/platelet reaction

AHTR Improper storage or administration Bacterial contamination

Acute hypersensitivity

Examine donor blood for hemolysis or other color change Review history for prior transfusions or pregnancy Crossmatch + /- typing donor and recipient

Monitor for more severe clinical signs

Stop transfusion Monitor temperature Monitor for shock, DIC, renal failure Fluid diuresis (0.9% NaCI) +1- Dexamethasone SP (4-6 mg/kg IV) +1- Furosemide (1-2 mg/kg IV) +1- Dopamine (<5 fl-g/kg/min IV) + 1- Heparin (1 00 U/kg SQ) or (or more aggressive dosage if confirmed DIC) + 1- treatment for sepsis

Stop or slow transfusion Stop transfusion Furosemide (2-8 mg/kg IV) Diphenhydramine (2 mg/kg IM) + /- Dexamethasone (0.5-1.0 mg/kg IV) +1- Oxygen + /- Assisted ventilation If severe signs: If contamination, treat for Dexamethasone (4-6 mg/kg IV) sepsis Epinephrine (0.0)1 mg/kg IV)

··· ················ ···· Positive hemolysis ···················· Pruritus/facial swelling Prior history of cardiac disease Auscultation (chest) + /thoracic radiographs + /- Gram stain/culture of donor blood

<··············· ·················· If pruritis/facial swelling ·· ·················· ·· ·················· ··· · If hemolysis

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References 1. Aoiki SK, Holland PV: Lyme disease-Another transfusion risk? Transfusion 29:646, 1989 2. Authement JM, Wolfsheimer KJ, Catchings S: Canine blood component therapy: Product preparation, storage, and administration. J Am Anim Hosp Assoc 23:483, 1986 3. Badon SJ, Fister RD, Cable RG: Survival of Borrelia burgdorferi in blood products. Transfusion 29:581, 1989 4. Barrett BB, Andersen JW, Anderson KC: Strategies for the avoidance of bacterial contamination of blood products. Transfusion 33:228, 1993 5. Bliss JQ, Johns DG, Burgen SV: Transfusion reactions due to plasma incompatibility in dogs. Circ Res 7:79, 1959 6. Brecher ME, Taswell HF: Hemolytic transfusion reactions. In Rossi CE, Simon TL, Moss GS (eds): Principles of Transfusion Medicine. Baltimore, Williams & Wilkins, 1991, p 619 7. Breitschwerdt EB, Malone JB, MacWilliams P, et al: Babesiosis in the greyhound. J Am Vet Med Assoc 182:978, 1983 8. Brubaker DB: Clinical significance of white cell antibodies in febrile nonhemolytic transfusion reactions. Transfusion 30:733, 1990 9. Bucheler J, Cotter SM: Outpatient blood donor program. Probl Vet Med 4:572, 1992 10. Bull RW: Antigens, graft rejections, and transfusions. J Am Vet Med Assoc 181:1115, 1982 11. Busand R, Lindsetmo R, Balteskard L, et al: Repeated plasma therapy induces fatal shock in experimental septicemia. Circ Shock 40:268, 1993 12. Byars TO, Divers TJ: Clinical use of blood transfusions. California Vet 1:14, 1981 13. Capon SM, Sacher RA: Hemolytic transfusion reactions: A review of mechanisms, sequelae, and management. J Intensive Care Med 4:100, 1989 14. Cotter SM: Blood banking-Indications and side effects. In Proceedings of the Sixth Annual Members Meetings, American College of Veterinary Internal Medicine Forum, Washington, DC, 1988, p 48 15. Cotter SM: Clinical transfusion medicine. In Cotter SM (ed): Comparative Transfusion Medicine. Advances in Veterinary Science and Comparative Medicine, vol 36. San Diego, CA, Academic Press, 1991, p. 188 16. Cotter SM: History of transfusion medicine. In Cotter SM (ed): Comparative Transfusion Medicine. Advances in Veterinary Science and Comparative Medicine, vol36. San Diego, CA, Academic Press, 1991, p. 1 17. Diamond LK: A history of blood transfusion. In Wintrobe MM (ed): Blood, Pure and Eloquent. New York, McGraw Hill, 1980, p. 659 18. Dodds JW: Medical, ethical concerns paramount for blood donors. DVM January:4, 1993 19. Freeman MJ, Kirby BM, Panciera DL, et al: Hypotensive shock syndrome associated with Babesia canis infection in a dog. JAm Vet Med Assoc 204:94, 1994 20. Giger U: Feline transfusion medicine. Probl Vet :Med 4:600, 1992 21. Giger U, Galens CJ, Callan MB, et al: An acute hemolytic transfusion reaction caused by dog erythrocyte antigen 1.1 incompatability in a previously sensitized dog. J Am Vet Med Assoc 206:9, 1995 22. Goldfinger 0: Acute hemolytic transfusion reactions-A fresh look at pathogenesis and considerations regarding therapy. Transfusion 17:85, 1977 23. Greenberger P A: Plasma anaphylaxis and immediate type reactions. In Rossi CE, Simon TL, Moss GS (ed): Principles of Transfusion Medicine. Baltimore, Williams & Wilkins, 1991, p. 635 24. Greene RT: Blood banking and transfusion therapy. Compend Contin Educ Pract Vet 6:134, 1985 25. Hardaway RM, McKay DG, Wahle GH, et al: Pathologic study of intravascular coagulation following incompatible blood transfusion in dogs. Am J Surg 91:24, 1956 26. Hardie EM, Krase-Elliot K: Endotoxic shock part II: A review of treatment. J Vet Intern Med 4:306, 1990

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27. Hardie EM, Rawlings CA: Septic shock. Part II Prevention, recognition and, treatment. Compend Cantin Educ Pract Vet 5:483, 1983 28. Harrell KA, Kristensen AT, Klausner JS, eta!: Prevalence, type and outcome of canine transfusion reactions: A retrospective study of 680 transfusions. In Programs and Abstracts of the Critical Care Meetings, San Antonio, TX, 1992 29. Hohenhaus AE: Transfusions, infusions and other solutions. In Proceedings of the 12th Annual Members Meeting, American College of Veterinary Internal Medicine Forum, San Francisco, CA, 1994, p. 158 30. Hohenhaus AE: Canine blood transfusions. Probl Vet Med 4:612, 1992 31. Hoppe PA: Interim measures for the detection of bacterially contaminated red cell components (editorial). Transfusion 32:199, 1992 32. Hosgood G: Blood transfusion: A historical review. JAm Vet Med Assoc 197:998, 1990 33. Howard A, Callan B, Sweeney M, et al: Transfusion practices and costs in dogs. J Am Vet Med Assoc 201:1697, 1992 34. Isbister JP: Adverse reactions to plasma and plasma components. Anesth Intensive Care 21:31, 1993 35. Kerl ME, Hohenhaus AE: Packed red cell transfusions in dogs: 131 cases (1989). JAm Vet Med Assoc 202:1495, 1993 36. Kevy SV, Schmidt PJ, McGinniss MH, et al: Febrile, nonhemolytic transfusion reactions and the limited role of leukoagglutinins in their etiology. Transfusion 2:7, 1962 37. Killingsworth CR: Use of blood and blood components for feline and canine patients. JAm Vet Med Assoc 185:1452, 1984 38. Lau P, Sholtis CP, Aster RH: Post-transfusion purpura: An enigma of alloimmunization. Am J Hematol 9:331, 1980 39. Masouredis SP: Preservation and clinical use of blood components. In Williams WJ, Beutler E, Ersler AJ, et al (eds): Haematology, vol 2. New York, McGraw Hill, 1977, p. 1530 40. Myhre BA, Wortham W: Untoward responses to blood transfusion. Lab Med 9:29, 1978 41. Oakley DA, Shaffran N: Blood transfusions: Part II. Collection, storage, and administration. Compend Cantin Educ Vet Tech 8:189, 1987 42. O'Neill S: Blood transfusions. Part I the blood donor colony. Compend Cantin Educ Vet Tech 8:87, 1987 43. Paradis MR: Neonatal transfusion medicine. In Cotter SM (ed): Comparative Transfusion Medicine. Advances in Veterinary Science and Comparative Medicine, vol36. San Diego, CA, Academic Press, 1991, p. 225 44. Pearl TCY, Toy MD, Girish NV: Blood transfusion reactions. In Engelfriet CP, van Loghem JJ, von dem Borne AEGK (eds): Immunohaematology. Amsterdam, Elsevier Science Publishers, 1984, p. 119 45. Pichler ME, Turnwald GH: Blood transfusion in the dog and cat Part I. Physiology, collection, storage, and indications for whole blood therapy. Compend Cantin Educ Pract Vet 7:64, 1985 46. Pineda AA, Taswell HF, Brzica Jr SM: Delayed hemolytic transfusion reaction: An immunologic hazard of blood transfusion. Transfusion 18:1, 1978 47. Plumb DC: Veterinary Drug Handbook. M:!nneapolis, PharmaVet Publishers, 1991 48. Rackow EC, Astiz ME: Pathophysiology and treatment of septic shock. J Am Med Assoc 266:548, 1991 49. Ramsey G: The pathophysiology and organ-specific consequences of severe transfusion reactions. New Horizons 2:575, 1994 50. Rossi CE, Simon TL, Moss GS: Transfusion in transition. In Rossi CE, Simon TL, Moss GS (eds): Principles of Transfusion Medicine. Baltimore, MD, Williams & Wilkins, 1991, p. 1 51. Smith CA: Transfusion medicine: The challenge of practical use. JAm Vet Med Assoc 198:747, 1991 52. Snyder EL, Stack G: Febrile and nonimmune transfusion reactions. In Rossi CE, Simon TL, Moss GS (eds): Principles of Transfusion Medicine. Baltimore, MD, Williams & Wilkins, 1991, p. 641 53. Steinbronn K, Huestis DW: Rationale for blood component therapy. In Blitt CD, Gieske

CANINE TRANSFUSION REACTIONS AND THEIR MANAGEMENT

54. 55. 56. 57. 58. 59. 60. 61. 62. 63.

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RH (eds): Contemporary Anaesthesia Practice, vol 6. Philadelphia, FA Davis, 1983, p. 151 Stone E, Badner D, Cotter SM: Trends in transfusion medicine in dogs at a veterinary school clinic: 315 cases (1986-1989). JAm Vet Med Assoc 200:1000, 1992 Stone MS, Cotter SM: Practical guidelines for transfusion therapy. In Kirk RW, Bonagura JD (eds): Current Veterinary Therapy, XI. Philadelphia, WB Saunders, 1992, p. 475 Stormont CJ: Blood groups in animals. JAm Vet Med Assoc 181:1120, 1982 Taboada J, Harvey JW, Levy MG, et al: Seroprevalence of Babesia. JAm Vet Med Assoc 200:47, 1992 Thulstrup H: The influence of leukocyte and thrombocyte incompatibility on nonhaemolytic transfusion reactions. Vox Sang 21:233, 1971 Tizard I: Erythrocyte antigens and type II hypersensitivity. In Veterinary Immunology: An Introduction, ed 4. Philadelphia, WB Saunders, 1992, p. 351 Tizard I: Type I hypersensitivity. In Veterinary Immunology: An Introduction, ed 4. Philadelphia, WB Saunders, 1992, p. 335 Turnwald GH, Pichler ME: Blood transfusion in dogs and cats part II. Administration, adverse effects, and component therapy. Compend Cantin Educ Pract Vet 7:115, 1985 Wardrop KJ, Owen TJ, Meyers KM: Evaluation of an additive solution for the preservation of canine red blood cells. J Vet Intern Med 8:253, 1994 Yuile CL, VanZandt TF, Ervin DM, et al: Hemolytic reactions produced in dogs by transfusion of incompatible dog blood and plasma. Blood 4:1232, 1949

Address reprint requests to Karyn A. Harrell, DVM North Carolina State University College of Veterinary Medicine 4700 Hillsborough Street Raleigh, NC 27606

Patient Information:

DATE:

AM PM

TIME:

FEE·

Cage!StaUNo. _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ __ Clinician _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ __

StudenU Technician:

Problem list

1) _ _ _ _ _ _ _ _ _ 2) _ _ _ _ _ _ __ 3) 4) _ _ _ _ _ _ __

Y _ N __ Date(s) _ _ __ Y_N_

Previous transfusions? Previous pregnancies?

Weight~--·- KG

Packed red blood cells Fresh frozen plasma Whole blood Special request

Reason for transfusion _ _ _ _ _ _ _ __ Blood component(s) needed _ _ _ _ _ _ __ Amount single unit _ _ _ _ double umt Y _ _ N _ _ Dose _ _ _ _ _ __ Heparin added to plasma? Blood type (if known) _ _ _ _ _ _ _ _ __ y __ N Vomiting prior to Transfusion?

(PRBC) (FFP) (WB)

Cross match Donors Compatible? (Results) _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ __ Donor used Premedication(s) + dose(s) - - - - - - - - - - - - - - - - - - - - - - - - - - Administration rate(s) - - - - - - - - - - - - - - - - - - - - - - - - - - - -

To be filled in during transfusion by ICU/Anesthesia. Monitoring:

Time

T

p

R

PCV

TPP (FFP)

ACT (WB)

Plt.ct.

_

Pre 15 min. 30 min. 1 hour 1 hour post 12 hour post 24hourpost

Transfusion start time _ _

Stopped _ _ __

Transfusion reaction(s) (include blood pressure readings if available)

Signature of person preparing components VH-
Clinician Signature

MEDICAL RECORD

Appendix I. Form used for the appropriate monitoring of blood transfusion. (Courtesy of the North Carolina State University, Veterinary Teaching Hospital, Raleigh, North Carolina.)

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CANINE TRANSFUSION REACTIONS AND THEIR MANAGEMENT

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Appendix II CROSS MATCH MAJOR ONLY Principle of Procedure

A test for incompatibility between donor and recipient blood performed before transfusion to avoid potentially lethal hemolytic reactions between the donors RBCs and antibodies in the recipients plasma. Incompatibility is indicated by clumping of the RBCs or hemolysis and contraindicates use of the donors blood. Equipment and Supplies

Isotonic saline Guinea pig complement 10 X 75 disposable glass tubes 12 X 75 disposable glass tubes Serofuge 37°C incubator (heat block) Pasteur pipets Timer Microscope slides Reagent Storage and Stability

Guinea pig complement stored at - 70oC Sample Requirements

Donor cells (pigtail) Recipient clot tube (serum) Recipient edetic acid (EDTA) tube (cells) Procedure 1. Allow red top tube to clot, spin and separate the serum into 12

X 75 mm glass tubes and label. 2. Make approximately 5% cell suspension of recipient and donor cells respectively (100 J..LL of cells and three-fourth tube of saline in a 12 X 75 mm glass tube) wash cells three times (spin for 1 minute in serofuge, decant, and resuspend in saline). After final

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HARRELL & KRISTENSEN

wash decant, shake and resuspend cells to approximately a 4% suspension in saline (cherry kool-aid color). 3. For a major only cross match label 6 (10 X 75 mm glass tubes) for the first donor as follows: tube no. 2 and no. 3, 4°C + ID; tube no. 2 and no. 3, 25°C + ID; tube no. 2 and no. 3 37°C + ID. For additional donors label three tubes each no. 3, 4°C + ID; tube no. 3, 25°C + ID; tube no. 3, 37°C + ID (tube no. 2 is the patient auto and only needs to be set up once). 4. Add serum and cells as follows: Donor cells Recipient cells Recipient serum Guinea pig C'

Tube 2 2 drops 2 drops 2 drops

Tube 3 2 drops 2 drops 2 drops

5. Mix gently-spin 25°C tubes immediately 1 minute in serofuge and read for hemolysis and agglutination. Incubate tubes at appropriate temperature (4.25, 37°C) for 30 minutes. 6. After 30 minutes, spin tubes for 1 minute and read for hemolysis and agglutination. If tube 2 (patient auto) has agglutination present, tube 3 should be read knowing the patient has an autoagglutinin. 7. Hemolysis or agglutination in tube 3 denotes incompatibility. 8. Read all 37°C tubes and other questionably positive tubes microscopically for agglutination. 9. Gradation of agglutination (macroscopic): Hem = hemolysis 4+ one solid aggregate 2+ medium-size aggregates, clear background 1+ Small aggregates, turbid reddish background +I microscopic aggregates eg = no agglutination or hemolysis