General hematology Flashcards
What factors are associated with the development of hospital-acquired anemia?
Cumulative phlebotomy >3% total blood volume
Surgery (OR 10)
Deficiencies in what ATP generation pathway lead to hemolytic anemia in dogs and cat? Why?
Anaerobic glycolysis - RBCs lack a mitochondria and rely on anaerobic glycolysis to produce ATP
What is the role of pyruvate kinase in anaerobic glycolysis?
Catalyzes the conversion of phosphoenolpyruvate to pyruvate, thus generating one ATP molecule
How is pyruvate kinase deficiency inherited?
Autosomal recessive - heterozygous dogs show no clinical signs, homozygous affected
Describe the clinical presentation in dogs with pyruvate kinase deficiency
- Chronic, low grade hemolysis rather an an acute presentation
- Icterus is rare, but will present with signs of anemia
Describe the anemia present in dogs with pyruvate kinase deficiency
- Moderate to severe anemia (median HCT 21%)
- Regenerative (high retic counts - average 500,000 to 1,500,000)
- Macrocytic, hypochromic
Why do dogs with pyruvate kinase deficiency have normal to increased PK activity on testing?
The erythrocytes of affected dogs lack the normal, adult R isozyme of PK but have persistence of the M2 isoform normally found in fetal tissue and precursor cells - causes the total RBC PK activity to seem normal
M2 form NOT found in cats - PK activity will be decreased
Erythrocytes in dogs with pyruvate kinase deficiency have increased concentrations of what molecule?
2,3-diphosphoglycerate (2,3-DPG)
What is the function of 2,3-DPG?
Binds to deoxygemoglobin and facilitates oxygen release from hemoglobin
What is the consequence of increased 2,3-DPG in dogs with pyruvate kinase deficiency?
Lower blood oxygen affinity compared to normal dogs - promotes oxygen delivery to the tissues and helps compensate for anemia (decreases clinical signs)
What other organs are affected by pyruvate kinase deficiency?
Liver - hemosiderosis and fibrosis develop due to progressive iron overload
Bone - myelofirbosis and osteosclerosis also likely due to damage from iron overload or chronic EPO stimulation
What is the expected lifespan of dogs with pyruvate kinase deficiency?
1-5 years, typically die of bone marrow or liver failure
What is the role of phosphofructokinase in glycolysis?
Converts fructose-6-phosphate to fructose 1,6-diphosphate
The PFK isoform found in RBCs is found in what other tissue?
Skeletal muscle (M type PFK)
How is PFK deficiency inherited and what breeds are affected?
Autosomal recessive
Usually spaniels (English Springer, Cocker Spaniels, German Spaniels)
What is the 2,3-DPG concentration in dogs with PFK deficiency?
Low - 2,3-DPG is formed after the PFK reaction
What is the consequence of decreased 2,3-DPG in dogs with PFK deficiency?
Increased oxygen affinity for hemoglobin leads to tissue hypoxia => erythropoiesis and reticulocytosis, even if anemia isn’t present
How do dogs with PFK deficiency present?
- Persistent, low grade, compensated anemia with sporadic episodes of intravascular hemolysis and hemoglobinuria, especially with exercise
- Hyperbilirubinemia (always in males, sometimes in females)
What are the clinical signs of an acute hemolytic crisis from PFK deficiency?
Lethargy, weakness, pale or icteric MM, fever
What other clinicopathologic abnormalities may be seen in dogs with PFK deficiency?
Elevated bilirubin, iron, ferritin, ALP, and CK (twice healthy dogs)
Why does a hemolytic crisis occur in dogs with PFK deficiency?
Secondary to hyperventilation-induced alkalemia - due to a lack of 2,3-DPG (the major anion in RBCs), the RBCs are very alkaline-fragile
What is the prognosis of dogs with PFK deficiency?
Can have normal lifespans - avoid strenuous exercise, excitement or high temps that cause hyperventilation and crisis
What genetic mutation can cause methemoglobinemia in cats and dogs?
Cytochrome B5 reductase
What causes methemoglobinemia?
Hemoglobin with a ferric iron (Fe3+) instead of ferrous iron (Fe2+) - ferric iron cannot carry oxygen
Cyanosis is noted when the methemoglobin fraction of the blood is greater than what percent? What percent is fatal?
Cyanosis: >15%
Fatal: >70%
What is the methemoglobin spot test?
Dark blood is exposed to air - with methemoglobin, it does not turn red (where it will with other causes of cyanosis)
In the cat, what causes oxygen release from hemoglobin?
Chloride - not 2,3-DPG like in the dog
What are the most common presenting signs in cats with primary erythrocytosis?
Seizures, mentation changes
In cats with lymphocytosis, expansion of B cell and heterogenous phenotypes were more consistent with what diagnosis and presentation?
- Non-neoplastic disease
- Polyclonal antigen receptors
- Younger age
- Lower lymphocyte counts
- Prolonged survival
In cats with lymphocytosis, what were the most common neoplastic lymphocytes on flow cytometry?
CD4+
In cats with lymphocytosis of neoplastic origin, what was the survival of cats with CD4+ vs CD8+ vs double negative lymphocytosis?
CD4+ = prolonged survival 750 days
Double negative = 271 days
CD8+ = 27 days
What is the typical presentation of dogs with sterile, steroid responsive lymphadenopathy?
Young (3 years), female over-represented
Pyrexia, lethargy, and anorexia
How rapidly did dogs with sterile, steroid responsive lymphadenopathy improve with prednisone?
Rapidly - 12 to 48 hours in 96%
What breed is predisposed to idiopathic pyogranulomatous lymphadenitis?
English Springer Spaniel
Aspiration of splenic nodules revealed clinically important results (neoplasia or suppurative inflammation) in what percent of cases?
20%
What ultrasonographic findings were associated with clinically important cytologic findings on splenic ultrasound?
Splenic nodules 1-2cm in diameter, peritoneal fluid, >1 targetoid nodule
NOT associated: echogenicity, margins
What dog breed is more likely to be diagnosed with neoplasia when splenomegaly is observed (vs benign splenic changes)?
Wheatens
Is hemoperitoneum a predictor of splenic malignancy in small breed dogs?
No
Name 3 reasons to perform bone marrow sampling
- Unexplained hemic abnormalities on CBC (cytopenias, elevations in cell numbers, atypical morphology)
- Searching for occult disease/neoplasia (fever of unknown origin, hyperproteinemia, hypercalcemia)
- Cancer staging
What percent of dogs/cats develop complications from bone marrow sampling and what are the most common complications?
14% = pain most common, hematomas can rarely occur
When evaluating bone marrow, how many megakaryocytes should be present in a spicule?
2-7
When evaluating bone marrow, what percent of lymphocytes is normal?
<10% of nucleated cells
What is a normal M:E ratio in dog and cat bone marrow?
Dog: 0.9-1.8 : 1
Cats: 1.2-2.1 : 1
Name 2 causes of a decreased M:E ratio
- Increased erythroid production without concurrent inflammation: hemolytic anemia
- Decreased myeloid production: peripheral consumption of myeloid cells => depletion of maturation and storage pool
Name 2 causes of an increased M:E ratio
- Decreased erythroid production with normal or increased myeloid production: anemia of chronic disease, CKD
- Increased myeloid production with normal erythroid numbers: inflammation
80% of the nucleated erythroid cells in the bone marrow should be what stages of development?
Rubricytes or metarubricytes
80% of the nucleated myeloid cells in the bone marrow should be what stages of development?
Metamyelocytes, bands, or segmented neutrophils
What is ineffective hematopoiesis?
- Death or destruction of hematopoietic cells within the marrow - mature cells are not released into circulation
- Hypercellular marrow with concurrent peripheral cytopenia
What stain is used to assess iron stores in bone marrow?
Prussian Blue - better to directly stain slides, as destaining and then restraining with Prussian Blue underestimates iron stores
What flow cytometry maker identifies monocytes?
CD14, CD172a
What flow cytometry maker identifies B cells?
CD19, CD20, CD79a = all B lymphocytes
CD21 = mature B lymphocytes
What flow cytometry maker identifies hematopoietic stem cells?
CD34
What bone marrow changes may be seen with acute bone marrow injury?
Neutrophilic inflammation, myelonecrosis, hypo-aplasia, or dysmyelopoiesis
Name 2 drugs that cause dose-dependent myelotoxicity
Chemotherapeutics
Cephalosporins
Estrogen
Name 3 drugs that cause idiosyncratic myelotoxicity
Sulfonamides, chloramphenicol, griseofulvin, antiparasitics
What hormone is secreted by Sertoli cell tumors?
Estrogen (70% are functional)
Bone marrow is considered one of the most sensitive tissues to sample for the diagnosis of what infectious agent?
Leishmania
What histopathologic changes can be seen with chronic bone marrow injury?
Chronic inflammation, myelofibrosis, osteosclerosis, and/or gelatinous transformation
What is the most common cell type noted in the bone marrow of cats with chronic inflammation? In dogs?
Cats: Benign lymphocytosis - usually aggregates of B cells
Dogs: Plasmacytosis
Bone marrow plasmacytosis has been noted with what two infectious diseases in dogs?
Ehrlich canis, Leishmania
What is the definition of myelofibrosis?
Proliferation of fibroblasts, collagen, or reticulin fibers in the hematopoietic space
What causes primary myelofibrosis?
Clonal myeloproliferative neoplasms - in humans, often secondary to mutations in JAK2, CALR, or MPL
What causes secondary myelofibrosis?
Likely a reactive change secondary to bone marrow injury and cytokine stimulation of fibroblasts
Associated with myelonecrosis, neoplasia, drugs, IMHA, irradiation, PK deficiency (dogs), FIP, CKD (cats)
What causes gelatinous transformation (aka serous atrophy of fat)?
Prolonged starvation or anorexia
What is myelodysplasia or dysmyelopoiesis?
Heterogenous group of bone marrow disorders characterized by abnormalities in precursor cell maturation => dysplastic changes and ineffective hematopoiesis
What is found on bone marrow histopathology on cases of myelodysplasia?
- Peripheral cytopenia with hyper cellular marrow
- Evidence of dysplastic changes to one or more cell lines
What causes primary myelodysplastic syndrome?
Clonal expansion of a defective pluripotent hematopoietic stem cell
What causes secondary myelodysplastic syndrome?
Still a clonal disorder but caused by exposure to gamma radiation, FeLV infection, or drug exposure
What causes cyclic hematopoiesis?
Impaired intracellular trafficking and misdirection of proteins to the membrane rather than granules => cyclic neutropenia with granulocytic hypoplasia in the bone marrow
What causes secondary dysmyelopoiesis?
- NOT clonal (unlikely myelodysplasia)
- Drug associated (vincristine, chloramphenicol, phenobarbital, estrogen, lead)
- Disease associated (lymphoma, myeloma, IMHA, ITP, etc)
- Iron or cobalamin associated
Where is the majority of the total body iron located?
Hemoglobin and myoglobin
Where can iron be stored in the body?
Within hepatocytes, within macrophages of the spleen, liver and bone marrow
What is hemosiderin?
Partially degraded ferritin (less soluble)
What transporter is located on the apical surface of enterocytes and allows iron absorption from the gut?
DMT1
What regulates proteosomal-degredation of DMT1 and ferroportin?
Hepcidin - so when hepcidin concentrations are high, DMT1 and ferroportin are degraded and less iron is absorbed
What transporter is located on the basolateral membrane of enterocytes and allow iron to be absorbed from the enterocyte into the blood?
Ferroportin
What other cells express ferroportin? What is the effect of hepcidin on these cells?
- Hepatocytes and macrophages - allows storage of iron
- Hepcidin also causes decreased ferroportin on these cells => sequestration of iron
What factors cause increased hepcidin transcription (leading to decreased iron absorption and increased sequestration)?
High iron stores/plasma iron
Inflammation
What factors cause decreased hepcidin transcription (leading to increased iron absorption and decreased sequestration)?
Anemia, hypoxia, iron deficiency
Ferritin is usually considered an indicator of total body iron. However, what can increase ferritin levels?
Inflammation - acute phase protein
So iron deficient animals with significant inflammation may have “normal” ferritin
Do cats store iron in their bone marrow?
No - lack of hemosiderin staining is normal
What blood product could be used instead of fresh frozen plasma to treat vitamin K deficient/rodenticide?
Cryopoor plasma
What causes hemophilia A?
Factor VIII deficiency
Hemophilia A will result in prolongation of what clotting test?
aPTT
NOT PT
In dogs with heatstroke, what coagulation parameters were associated with outcome?
Prolonged PT, aPTT, total protein C activity, and low fibrinogen at 12-24 hours
In a clinical trial comparing lyophilized platelets vs cryopreserved platelets, which treatment had improved bleeding scores 1 hour after administration? At 24 hour?
Lyophilized platelets - improved DOGiBAT score at 1 hour
Both groups similar at 24 hours
What effect did twice daily Yunnan Baiyao have on TEG parameters in healthy dogs after one week?
Increased the strength of the clot - increased G, A30 and A60. Decreased LY30 and LY60
On a TEG, what is the R values and what does it correspond to?
Initiation phase of a clot - reflects activity of factors 12, 11, 9, and 8
On a TEG, what is the K value and what does it correspond to?
Amplification phase of a clot, clot formation time - influenced by factors II, VIII, platelet number, thrombin formation, fibrin concentrations
On a TEG, what is the MA and what does it correspond to? What is the G value?
MA: Final clot strength - influenced by fibrin, fibrinogen concentrations, platelet numbers/function, thrombin, factor XIII
G: log derivative of MA
In a clinical trial evaluating the use of Yunnan Baiyao on healthy cats, what effect did the drug have on TEG parameters?
None
What were the side effects of Yunnan Baiyao in cats?
18% of cats - vomiting
Significant reduction in HCT and RBC count
Compared to dogs receiving clopidogrel alone, dogs receiving clopidogrel and prednisone had what response?
Increased platelet dysfunction - over controlled based on AUC in aggregometry
- 11 times more likely to have an excessive response
In a study comparing clopidogrel vs aspiring for dogs with PLN, what differences were noted on aggregometry?
Clopidogrel: aggregometry differed at all time points after ADP stimulation of platelets but not arachidonic acid stimulation (may be able to overcome ADP inhibition and activate platelets by other mechanisms)
Aspirin: no difference at any time point
Low dose aspirin inhibits cyclosporine-induced synthesis of what platelet factor?
Thromboxane
Does the use of cyclosporine alter the anti-platelet effects of aspirin?
No
When given to cats, when is the peak effect of rivaroxaban?
3 hours post-administration
In cats, plasma rivaroxaban concentration correlated with what coagulation parameters?
Prothrombin time and aXa
In cats, how long did it take coagulation parameters to return to normal after stopping rivaroxaban therapy?
24 hours
In dogs treated with rivaroxaban, what coagulation test correlated well with anti-Xa activity?
PT (r = 0.915 in one study, 0.82 in another) - may be a second line monitoring option if anti-Xa is not available
aPTT was ok (r = 0.77)
In dogs treated with rivaroxaban, what coagulation test did not correlated well with anti-Xa activity?
Rapid TEG performed with strong activators in one study, but in another study R value did correlate
In 4 patients with thrombosis (2 PTE and 2 systemic) treated with rivaroxaban, what happened to clot size?
Decreased thrombus size
Did administering rivaroxaban with food, sucralfate, or omeprazole inhibit drug absorption?
Technically, rivaroxaban alone resulted in higher anti-Xa activity 36 hours after administration. But clinically, no difference
What prolongation in PT is required to achieve therapeutic anti-Xa concentrations of rivaroxaban in healthy dogs?
1.5-1.9x delay in PT
When diagnosing overt DIC in dogs, what DIC score yields a 73% sensitivity and 80% specificity for mortality and was accurate in 78% of cases?
A score of 3/6: increase PT, aPTT, or D dimers; decreased antithrombin, fibrinogen, and platelet count
In cats, >90% of aortic thromboembolism are secondary to what?
Cardiac disease
In dogs, what are the most common causes of aortic thromboembolism?
A wide variety of disease can cause it
- PLN most consistently diagnosed: 10-35%
- Cardiac disease 0-38%
- Neoplasia 0-33%
What are the advantages of low molecular weight heparin over unfractionated heparin?
- More reliable activity
- Increased anti-Xa activity
- Decreased binding to thrombin
What is the mechanism of action of warfarin?
Inhibition of vitamin K epoxide reductase
At low shear rates (as in venous flow), what is platelet adhesion to the vessel wall dependent on? At high shear rates (as in arterial flow)?
Low shear: dependent on fibrinogen
High shear: dependent on vWF
Compare arterial and venous thrombi
Arterial: platelet rich
Venous: small numbers of platelets, large numbers of RBCs, WBC, and fibrin
What are the clinical signs of dogs presenting for aortic thrombus?
Hind limb weakness most common (exercise intolerance to complete paraplegia)
Hind limb pain, decreased femoral pulses, decreased CP
Unlike cats, cold extremities and cyanosis uncommon
Often chronic signs rather than acute
What is the mechanism of action of tissue plasminogen activator (TPA)?
Converts plasminogen to plasmin => fibrin degradation
More specific for fibrin-bound plasminogen and less likely to lead to systemic lytic states
What does a shortened PT or aPTT correlate with?
Increased D dimer concentration, more thrombus formation, increased suspicion of PTE compared to dogs with normal PT and aPTT
May be indicative of a hypercoagulable state
81% of dogs undergoing splenectomy developed thrombocytosis post-operatively. When did this occur?
Platelet count peaked at day 7 post-operatively (715K) and had decreased slightly by day 14 (580K)
In dogs post-op for splenectomy, higher platelet counts correlated with what other coagulation test?
Thromboelastography - 89% of dogs were hypercoagulable on TEG at day 7
In dogs with aortic thrombosis, what physical exam finding correlated with survival to discharge?
Ambulation status - non-ambulatory dogs less likely to survive
What is the prognosis of dogs with aortic thrombus in Lynch’s JVIM study?
57% survived to discharge, but only 16% were alive at 180 days :(
Studies evaluating dogs with acute pancreatitis have identified these dogs as hypercoagulable. What changes in coagulation have been noted?
- Decreased thrombomodulin expression
- Decreased antithrombin activity
- Decreased fibrinolysis
What form of pancreatitis may be more associated with thrombosis?
Acute necrotizing pancreatitis - consider anti-thrombotic for this population
What effect does prednisone have on hemostasis in healthy dogs?
- Increased coagulation factors and fibrinogen
- Increased platelet aggregation
- Increased clot strength
- Increased thrombin generation
- Reduced antithrombin
What form of cancer is more associated with hypercoagulability in several studies?
Carcinoma
In the CURATIVE guidelines, what diseases are considered high risk for thrombosis and should be treated with anti-thrombotics?
- Dogs with IMHA, PLN
- Cats with cardiomyopathy and left atrial dilation, spontaneous echo contrast, or reduced LA appendage flow rate
- Dogs or cats with >1 disease/risk factor for thrombosis, including: pancreatitis, sepsis, hyperadrenocorticism, cancer, glucocorticoid administration
In the CURATIVE guidelines, what conditions are considered low/moderate risk for thrombosis?
- Dogs/cats with a single risk factor or disease
- Dogs/cats with a known risk factor condition that, with treatment, is likely to resolve in days to weeks
In cats with ATE, is treatment with aspirin or clopidogrel superior?
Clopidogrel - significantly prolonged survival time and time to a subsequent thrombotic event (75% recurrence of ATE with aspirin vs 36% with clopidogrel)
What new anti-platelet agent blocks alphaIIb-beta3 integrin?
Abciximab, lotrafiban
What is the mechanism of action of clopidogrel?
Irreversibly binds to the platelet ADP receptor, P2Y12 - reduces activation of the platelets by ADP, inhibits full activation of the GPIIb/IIIa complex
The CURATIVE guidelines suggest that aspirin may be effective in what disease state? It is not recommended for what disease state?
- May be effective in canine ATE
- No evidence for or against canine venous thrombi
- NOT recommended as a sole agent for feline ATE
In patients receiving unfractionated heparin, what should the anti-Xa target be? For low molecular weight heparin?
Unfractionated: 0.35-0.7 U/mL
LMW: 0.5-1.0 U/mL 2-4 hours post dose
Do unfractionated heparin, low molecular weight heparin, or oral anti-Xa agents need to be tapered prior to discontinuation? Why?
Unfractionated and oral anti-Xa - yes
LMW - no
Abrupt discontinuation can lead to “rebound hypercoagulability” caused by increased thrombin production
What are eicosanoids?
Signaling molecules derived from oxidation of fatty acids
What fatty acid is esterified in membrane phospholipids? This fatty acid is released from the membrane under inflammatory stimuli via what enzyme?
Arachiadonic acid
Released by phospholipase A2
Arachidonic acid is then turned into what substances by COX1 and COX2 enzymes?
Prostanoids - prostaglandins, prostacyclins, and thromboxane
Arachidonic acid is then turned into what substances by LOX enzymes?
Leukotrienes and lipoxins
What drug blocks the actions of phospholipase A2, thus inhibiting the release of arachidonic acid from membranes in inflammation?
Corticosteroids
How long does clopidogrel take to inhibit platelet activation? How long does inhibition last after stopping the drug?
- Inhibition within 24 hours, consistent inhibition after 3 days
- Persists for 5-10 days (irreversibly binds, so must generate new platelets that can be activated)
What is the function of tissue factor pathway inhibitor?
Forms a complex with factors VIIa and Xa to inhibit these factors; expressed by the endothelium
At rest, platelet membranes express neutral phospholipids on the outer surface (phosphatidylcholine). What enzyme maintains this?
Floppase (ATP dependent)
At rest, procoagulant phospholipids are maintained on the inner surface of platelets (phosphatidylserine). What enzyme maintains this?
Flippase (ATP dependent)
During coagulation and platelet activation, what enzyme results in expression of pro-coagulant phospholipids (phosphatidylserine) on the OUTER surface of the membrane?
Scramblase
Name 3 pro-thrombotic effects of thrombin?
- Strong activator of platelets
- Catalyzes the conversion of fibrinogen to fibrin
- Activates factor XIII, which is needed for cross linking fibrin in clots
What are the 3 stages of coagulation in the cell based model?
Initiation, amplification, propagation
What occurs in the initiation stage of coagulation?
Tissue factor bearing cells initiate thrombin production (similar to the extrinsic pathway)
What occurs in the amplification stage of coagulation?
Platelet activation - membrane flipping, shape change, release of granules
What occurs in the propagation stage of coagulation?
Similar to the intrinsic pathway - ongoing of production of thrombin and fibrin
What is the most common presenting complaint of young male dogs with hemophilia A?
- Lameness from hemarthrosis most common
- Bleeding from vaccines, while teething, or at neuter also observed
What clotting factor is deficient in hemophilia B?
Factor IX
In both hemophilia A and B, what clotting tests will be prolonged?
aPTT and ACT - intrinsic pathway defect
What blood products can be given to hemophilia patients to provide clotting factors?
- Both - fresh frozen plasma
- Known hemophilia A - can also use cryoprecipitate
- Known hemophilia B - can also use frozen plasma or cry-poor plasma
What disorders can be treated with fresh frozen plasma?
- All hereditary or acquired coagulation factor deficiencies and vWF
- Coagulopathy of trauma
What disorders can be treated with cryoprecipitate?
- Hemophilia A
- vWD
- Hypofibrinogenemia
What disorders can be treated with cryo-poor precipitate?
- Hemophilia B and deficiencies of II, VII, X, and XI
- Vitamin K deficiency/antagonism
What is a normal measurement of vWF:Ag? What is abnormal?
Normal: >70%
Abnormal: <49%
Grey zone in between
What is Glanzmann thrombasthenia? What breeds does it occur in?
- Absence or deficiency of the fibrinogen receptor GPIIb-IIIa
- Otterhounds, Great Pyrenees
What platelet disorder is present in up to 60% of Greater Swiss Mountain Dogs?
P2Y12 receptor disorder => impaired binding of ADP to the receptor
What is Scott syndrome and what breed does it affect?
Impaired platelet membrane phosphatidylserine externalization and decreased prothrombinase activity
German Shepherds
Do dogs have naturally occurring alloantibodies to blood types? Which blood types?
Yes
DEA 3 - 20%
DEA 5 - 10%
DEA 7 - 0-38%
Are the naturally occurring alloantibodies to blood types in dogs clinically relevant?
- Do not cause acute hemolytic transfusion reactions
- May result in premature removal of transfused RBCs (delayed hemolytic reaction, 3-5 days post-transfusion)
What 3 factors in a transfusion recipient influence the severity of an alloimmune hemolytic transfusion reaction?
- Alloantibody titer (higher = more severe reaction)
- Alloantibody type (hemolytic reactions mediated by IgM, where IgG tends to cause agglutination)
- Alloantibody binding affinity
What 2 factors in a transfusion donor influence the severity of an alloimmune hemolytic transfusion reaction?
- Antigen expression on RBC surface (more expression = more severe reactions)
- Transfusion volume (higher dose of antigen = more severe)
2 Dal negative dogs were transfused with Dal positive blood in a 2017 study. When did anti-Dal antibodies develop post-transfusion? When was the highest agglutination titer reached?
- IgG detected on day 4 in one dog and day 21 in the other
- Highest titers at 4 weeks and 8 weeks
In general, the canine population is 50/50 DEA positive vs negative. What breed is primarily DEA negative, however?
Greyhounds - also tend to be DEA 3+ and 5+
What breeds are more commonly Dal negative?
Dalmatians, Dobermans, Shih Tzu, Beagle
What breeds were found to be 100% Dal positive?
Greyhounds, Labs, Goldens
What situation could cause neonatal isoerythrolysis in cats?
Type B queen (strong alloantibodies against type A) mated with a Type A tom => giving birth to a type A or AB kitten
What cat breeds are more commonly type B?
Turkish Angora, Devon Rex, British shorthair, Cornish Rex, Exotic shorthair, Birman, Somali, Sphinx
Apart from type A or B, what alloantigens are recognized in cats?
- Mik antigen
- 5 new feline erythrocyte antigens (FEA) - although one is likely Mik
Why crossmatching is needed
Cats developed alloantigens against blood antigens (other than AB) how many days post-transfusion?
- 2 days in the 2017 JFMS study
- 25% of cats developed alloantibodies against antigens outside the AB system
In the 2017 JFMS study, were positive cross matches identified in transfusion naive cats?
No - likely do not need to cross match the first transfusion
Point of care blood typing is available for what antigens in dogs?
DEA 1, 4, 5 and Dal
Name 3 point of care assays that can be used for blood typing
- Card agglutination (if agglutination occurs, animal is positive for that blood type)
- Immunochromatographic cartridge (useful for patients with autoagglutination)
- Gel tube test
What does the major cross match test for?
Alloantibodies in the recipient’s plasma against donor cells
What does the minor cross match test for?
- Alloantibodies in the donor’s plasma against the recipient cells
- Rarely used
What is considered the “gold standard” method for veterinary cross matching, although Mus hates it?
Laboratory tube agglutination assay - not standardized, subjective
What cross matching method is used in human medicine and how is it interpreted?
Gel tube agglutination - agglutinated RBCs form a line at the top of the gel (incompatible) whereas non-agglutinated RBCs pass to the bottom (compatible)
Cross matching predicts what type of transfusion reaction?
Acute, hemolytic reactions - does not necessarily predict delayed hemolysis or other types of reactions
What is the most common adverse event associated with transfusion in dogs/cats?
Fever
What defines febrile, non-hemolytic transfusion reaction?
Temperature >102.5F AND increase in temperature >1.8F during or within 4 hours of the transfusion (without other cause)
What causes febrile, non-hemolytic transfusion reactions?
Donor WBC or platelet antigen-antibody reactions or transfer of proinflammatory mediators in stored blood products
What is transfusion associated circulatory overload?
- Acute, non-immunologic reaction secondary to an increase in blood volume from transfusion
- Characterized by acute respiratory distress and hydrostatic pulmonary edema
- Occurs during or within 6 hours of transfusion
What is transfusion related acute lung injury (TRALI)?
- Acute, immunologic reaction secondary to antigen-antibody interactions in the lungs
- Acute hypoxemia with evidence of non-cardiogenic pulmonary edema
- Occurs during or within 6 hours of transfusion
In humans, what blood products carry the highest risk of TRALI and allergic transfusion reaction?
Plasma and platelet products
What defines and allergic transfusion reaction?
- Acute, immunologic reaction - type 1 hypersensitivity to an antigen in the blood product
- Dogs: Erythema, urticaria, pruritus, facial/extremity angiodema, V/D, hemoabdomen
- Cats: upper respiratory tract edema, bronchoconstriction, GI signs
- Occurs during or within 4 hours of transfusion
Blood type incompatibilities cause what type of transfusion reaction?
Acute, immunologic, hemolytic reaction - caused by type II hypersensitivity
How are acute hemolytic transfusion reactions diagnosed?
- New onset evidence of hemolysis within 24 hours of transfusion (hyperbilirubinemia, hemoglobinemia/uria, spherocytes, ghosts)
- AND inadequate increase in PCV post-transfusion
What causes delayed hemolytic transfusion reactions and when to they occur?
- Caused by a secondary immune response to the donor RBCs (the recipient possesses low levels of antibodies not detected on crossmatching - new antibody production is stimulated by transfusion)
- Occur 24 hours to 28 days after transfusion
Transfusion of type A blood into a type B cat results in what type of reaction?
Acute hemolytic reaction - B cats have HIGH type A antibodies that rapidly destroy the transfused blood
Transfusion of type B blood into a type A cat results in what type of reaction?
Delayed hemolytic reaction - type A cats have LOW antibody titers against B blood - results in delayed reactions in ~2 days
What blood product has the highest level of citrate and is most at risk of causing citrate toxicity?
Fresh frozen plasma
What are the clinical signs of citrate toxicity in dogs?
- Nausea, vomiting
- Tachycardia, QT prolongation, T wave inversion
- Reddening of the pinnae, facial swelling, salivation
What blood collection systems can be used in feline donors?
Any - closed, semi-closed, or open
Human closed systems may be impractical for cats due to small size. Studies show no change in bacterial contamination with the methods used
Why might leukoreduction before blood storage be beneficial?
Stored WBC can produce inflammatory cytokines - in human medicine, leukoreduction reduces the risk of febrile transfusion reactions. Not enough evidence in vet med though
What factor increased in vivo hemolysis of RBC transfusions?
Age of the RBC - increased in vivo hemolysis with stored vs fresh RBCs in dogs
Fresher RBC transfusion products should be considered in dogs with what conditions?
Hemolytic anemia, sepsis
In patients at risk of hyperammonemia (liver dysfunction, etc), transfused blood should be how old to reduce ammonia formation in storage?
Whole blood <24 hours
pRBC <7 days
RBC units should be checked for hemolysis prior to administration. Units with what percent hemolysis should not be used? Why?
> 1%
- Increased risk of transfusion reactions
- Free hemoglobin can cause proximal renal tubular damage and redox injury of the endothelium
Any dog that has been transfused more than ___ days prior should be crossmatched
> 4 days
Type AB cats should receive what type of transfusion if AB blood is not available?
Type A blood
Should transfusion naive cats be crossmatched? When should crossmatching be performed after transfusion?
Yes - type naive cats and then if they were transfused >2 days prior
Should type specific plasma be given? Should crossmatching be performed prior to plasma administration?
Dogs: not recommended
Cats: yes, give typed plasma but no need to crossmatch
What substance can be added to gel column and tube crossmatching techniques to improve accuracy?
Antiglobulin
If canine blood is administered to a cat, what is the lifespan of the canine RBCs?
3 days (delayed hemolytic reactions common)
If a second canine xenotransfusion is given to cats >6 days after the initial one, what can occur?
Significant risk of severe anaphylaxis and death
What types of infusion pumps should be avoided when giving a transfusion?
Peristaltic or rotary pumps - can increase hemolysis
Name 4 vector borne diseases that should be tested for (PCR and serology) in all canine blood donors?
- Anaplasma phagocytophilum and platys
- Babesia canis and gibsoni (especially Greyhounds, Pitbulls)
- Bartonella
- Ehrlichia canis
- Mycoplasma hemocanis
Name 4 vector borne diseases that should be tested for (PCR and serology) in canine blood donors in endemic areas?
- Ehrlichia chaffeensis and ewingii
- Hepatozoon canis/americanum
- Leishmania
- Trypanosoma cruzi
- Brucella canis is intact or exposed dogs
Name 4 diseases that should be tested for (PCR and serology) in all feline blood donors?
- Anaplasma phagocytophilum
- Bartonella
- Mycoplasma haemofelis
- FeLV/FIV
In endemic areas, finding a PCR negative, seronegative donor may be difficult for some diseases. When is using a seropositive donor ok?
- Anaplasma in dogs and cats
- Bartonella in cats
- DO NOT use Ehrlichia seropositive dogs - significant pathogen
Can dogs infected with Dirofilaria pass the organism to another dog during transfusion?
No - microfilaria from an infected donor cannot lead to heartworm disease in the recipient. BUT donors should be screened for it - transfused blood could cause the recipient to test positive or infect mosquitos. Collection of large amounts of blood from the donor may not be safe
In a group of 149 transfusion naive dogs, what percent were incompatible with at least one potential donor on cross match?
17%
In a group of 149 transfusion naive dogs, did the results of cross matching affect the change in HCT after transfusion?
Yes - dogs that had crossmatching performed and were given compatible blood had a median change of 12.5% hematocrit vs 9.0% in dogs not crossmatched
Are dogs most commonly positive or negative for Kai 1 and 2 blood types?
94% are Kai 1+ / Kai 2 -
No dogs were positive for both
Concentrations of what proinflammatory eicosanoids increased in pRBC units during storage and transfusion?
PGF2alpha, 6-keto-PGF1alpha, and leukotriene B2
What inflammatory substance is implicated in the development of TRALI in humans?
Neutrophil NETs
Are NETs found in canine blood products?
Yes - increase during RBC storage and are higher in non-leukoreduced units on day 42
Are FFP transfusions beneficial in cats?
Yes - significantly less likely to be coagulopathic afterward
What percent of cats experience acute transfusion reactions after receiving FFP?
14-16%, depending on the study
- Most commonly increased temp, followed by respiratory signs
