Transfusion Medicine

Question 1

describe what blood products are available; including for small animal versus exotics

Answer 1

1. fresh whole blood: for patients with decreased DO2 due to anemia and who need proteins/coag factors
   -main source for large animals, exotics, and local practices
2. pRBCs: for decreased DO2 due to anemia
3. plasma: for coagulopathy, hypoproteinemia, and failure of passive transfer

Question 2

describe blood donor characteristics

Answer 2

1. young
   - <8 year cat/dog/horse
2. fit, healthy: generally utilize sedation for collection (need to be still for a long period of time)
3. friendly/tractable: to make the process easier
4. pre-screened:
   -CBC, chem
   -blood type
   -blood or vector-transmitted pathogens
5. vaccinated, parasite controlled
6. dogs: DEA1 negative
   -cat: need A and B donors
   -horses: Qa (Ca) and Aa negative and donkey factor free
7. never transfused, never pregnant, and there is a preference for male horses

Question 3

describe donation amounts

Answer 3

1. 10% of blood volume normal max to take
2. can take up to 20%: may need fluid supplementation afterwards (bolus)
3. generally wait a month in between donations

Question 4

describe transfusion triggers

Answer 4

1. oxygen delivery is maximized at HCT of 30-40%, in healthy normovolemic animals, O2 delivery is maintained until 18%
   -so can use HCT <18% as a trigger BUT
2. transfuse clinical signs, NOT a number
   -acute blood loss and drop of HCT is associated with much more severe signs than chronic, so more likely to need transfusion in a chronic case
   -obvi def transfuse if PCV or HCT in single digits tho
3. conservative transfusion strategies preferred, patients should demonstrate transfusion triggers:
   -tachycardia, bounding or thready pulses (thin blood easer to push out and flows more quickly)
   -tachypnea
   -increased lactate/hyperlactatemia
   -weakness
   -hypothermia, hypotension (cats especially)
   -may transfuse at a high PCV if animal has concurrent condition affecting O2 utilization or compensation mechanisms (ex. heart failure, don’t want heart working harder to make up for lack of RBCs, or septic patient with increased oxygen demand)

Question 5

describe when to transfuse plasma

Answer 5

1. coagulopathy: esp if clinical bleeding
   -secondary coagulation defect more commonly, but can be for some primary defects (vWF)
   -symptomatic or prophylactic (presurgical)
2. symptomatic hypoproteinemia causing clinical problems
3. failure of passive transfer

Question 6

describe how to determine donor-recipient compatability

Answer 6

1. blood typing
   -RBCs are covered in proteins and carbohydrates; these antigens are different in between species
   -antigens present on the RBCs can vary among individuals of the same species
2. cross match

Question 7

describe dog erythrocyte antigen and other antigens/blood typing

Answer 7

1. 50-60% of dogs are positive; this antigen is associated with the strongest immune response so this is the only one we test for
2. also have DEA 3, 4, 5, 6, 7, 8
3. also have DAL antigen, Kai 1, and Kai 2
4. a true universal donor has no antigen on the RBC at any site
5. if possible, always type a dog prior to a transfusion
   -if not possible, use a DEA negative donor
   -if DEA 1 negative blood, can go to DEA 1+ or negative recipient
   -if DEA 1 positive blood, should only go to DEA 1 positive recipient
   -if animal is periarrest, give what you have

-if it’s the dog’s first transfusion, any type should be fine

Question 8

describe feline blood typing

Answer 8

1. Type A, B, or AB (now called C)
2. cats develop alloantibodies
   -ALL type B cats have STRONG anti-A antibodies
   -up to 50% type A cats have relatively weak anti-B antibodies
3. Mik antigen:
   -Mik-negative cats have alloantibodies against Mik positive bloof
4. NO universal cat donor!
5. a majority of cats are Type A blood but STILL HAVE TO TEST ALL CATS prior to transfusion!!!!!!
6. A gets A
   B gets B
   Type AB (C) gets Type A (relatively fewer and weaker anti-B from Type A blood and there are more Type A donors, will rarely find a Type AB donor)

Question 9

describe horse blood type

Answer 9

1. 7 main blood group systems
   >30 red blood cell factors
2. Qa, Ca, Aa
   -blood type incompatabilities can contribute to neonatal isoerythrolysis if dam is sensitized to the foal’s antigens

Question 10

describe blood typing methods (3)

Answer 10

1. lab
2. point of care
   -card: agglutination is endpoint
   -in areas of card there is anti-antibody on the card, agglutination = antigen has been detected in patient’s blood
   -cannot use method if patient has a condition causing agglutination already (IMHA)
3. immunochromatographic:
   -indicator line is endpoint, like a preg test
   -lateral flow/dipstick/strip test: easier to interpret than card test, less subjective, can also be used in patients who are auto-agglutinating, so is the preferred method
   -want control line!! to show that test is working
   -only available for dog and cat

Question 11

describe cross-matching

Answer 11

1. detects circulating anti-RBC antibodies
   -necessary for any second-time transfusion
2. necessary when using blood products containing RBCs
   -cannot prevent patient sensitization, only detects circulating antigen on the day of testing
3. reaction types:
   -major: donor RBCs, patient plasma
   -minor: donor plasma, patient RBCs
   -looking for agglutination AND hemolysis, rank the type of reaction
4. eval for autoagglutination using a scale
   0 = none
   trace = microscopic
   1+ = small RBC clusters with mostly free RBCs
   2+ few large agglutinates mixed with smaller clumps
   3+ multiple large aggregates
   4+ one large aggregate with no free cells
5. ideally compatible in major and minor
   -major crossmatch takes precedence
6. this test takes time so if in a hurry, just mix the two drops on a slide and if and clumping = not compatible

Question 12

describe administration of blood products

Answer 12

1. use a dedicated line ideally
   -can use in line with other stuff just NOT calcium
   -ideally not mixed with other fluid or meds tho
2. filter for RBCs, plasma (NOT platelets)
3. use a gravity or peristaltic pump
   -give slowly, over 4hr (if not periarrest) and monitor for reactions
   -if patient is peri-arrest can bolus

Question 13

describe transfusion reactions

Answer 13

1. 4 major types:
   -acute immunologic
   -delayed immunologic
   -acute non-immunologic
   -delayed non-immunologic
2. TRALI: transfusion related acute lung injury
3. TACO: transfusion associated circulatory overload

Question 14

describe acute immunologic: acute hemolytic transfusion reaction

Answer 14

1. recipient has antibodies against antigens on donor RBCs
2. type II hypersensitivity reaction: antibodies (IgG) and complement
3. clinical signs:
   -urticaria
   -fever
   -hypotension
   -nausea and vomiting
   -icterus
   -diarrhea
   -shock
   -death
   -hemolysis of donor cells: hyperbilirubinemia, hemoglobinemia, bilirubinemia
4. treatment:
   -IV fluids
   -discontinue transfusion
   -vasopressors PRN

Question 15

describe actue immunologic: allergic reaction

Answer 15

1. type I hypersensitivity
   -IgE antibody mediated
   -release of mediators by IgE sensitized mast cells
2. mild: urticaria, pruritis, erythema
3. anaphylaxis:
   -airway swelling/obstruction
   -tachycardia
   -rare
4. treatment: most mild rxns are self limiting
5. anaphylaxis:
   -epinephrine!!
   -diphenhydramine
   -corticosteroids
   -IV fluids

Question 16

describe acute immunologic: non-hemolytic fever

Answer 16

1. most common of acute immunologic reactions
2. primarily due to antibodies against donor WBC and platelets
   -WBC release inflammatory mediators during storage: pyrogens like IL-1, IL-6, IL-8, and TNF alpha
3. the longer the blood is stored, the more likely the recipient is to have a febrile reaction
4. most fevers self-limiting and clinically insignificant
   -if nonhemolytic fever is suspected, stop or slow the transfusion and rule out a more significant reaction
   -if fever is the only problem, restart the transfusion at a slower rate

Question 17

describe acute non-immunologic reactions

Answer 17

most rxns related to storage/handling, administration, or metabolic changes in response to transfusion and are not preventable with crossmatch or blood typing

-storage and warming of RBCs can deplete ATP stores and cause physical damage to RBC membranes, making the cells more fragile

1. acute nonimmunologic hemolysis:
   -can occur secondary to the physical membrane changes
   -animals will have hemoglobinuria and hemoglobinemia in the absence or other systemic signs such as fever
2. blood clots or air embolism: can occur in pulmonary vasculature if products are improperly administered
3. transfusion of blood contaminated by bacteria or other microbes can cause reactions
   -V/D, collapse, shock, death
4. hypocalcemia: may occur in large/multiple transfusions as a result of the citrate anticoagulant in the transfusions complexing with intravascular calcium
   -may manifest as tremors, tetany, seizures, bradycardia, or ventricular arrhythmias, or facial pruritis (cats)
5. hyperkalemia: can occur due to potassium leakage out of stored RBCs into the plasma portion of the transfusiojn
6. volume overload can occur too

Question 18

describe delayed immunologic reactions

Answer 18

1. delayed immune mediated hemolysis:
   -in animals previously sensitized to foreign RBC antigens and have only low levels of circulating antibody; reexposure to antigen triggers memory response and upregulation of antibody production leading to hemolysis up to 2 weeks after transfusion
2. immune mediated thrombocytopenia:
   -can occur 1-2 weeks after exposure to foreign platelet antigens in the transfusion

Question 19

describe delayed nonimmunologic reactions

Answer 19

blood-borne infections like Babesia, Ehrlichia, Leishmania, Mycoplasma haemofelis, FeLV, and FIV cause delayed nonimmunologic reactions

Question 20

describe TRALI

Answer 20

1. development of mild or severe ARDS within 6 hours or less of transfusion; occurs with a two hit

a. neutrophil sequestration and priming in the lung parenchyma due to transfusion factors such as endothelial injury; neutrophils now primed by changing to a state where they will react to an otherwise weak stimulus

b. neutrophil activation by a factor in the blood product; could be antibodies directed against recipient antigens or soluble factors like bioactive lipids; neutrophils release cytokines, reactive oxygen species, and proteases

-products damage pulmonary capillary endothelium, which causes inflammatory (noncardiogenic, nonhydrostatic) pulmonary edema

clinical signs:
-resp distress, tachycardia, hypoxemia
-edema from oral cavity or ET tube
-fever and hypotension
-on rads: pulmonary infiltrates bilaterally with normal heart size

treatment: stop transfusion and supportive care

Question 21

describe TACO

Answer 21

1. manifests as respiratory distress
2. more common in patients with renal insufficiency, a positive fluid balance, compromised cardiac function, or rapid delivery of blood products
3. clinical presentation: more like fluid overload than the inflammatory response of TRALI
   -patient may have jugular venous distension, previous history of CHF, known systolic or diastolic dysfunction
   -rads consistent with hydrostatic pulmonary edema