Transfusion/Coagulation Flashcards
What is oxyhemoglobin blood product made up of?
13 g/dl of polymerized bovine hemoglobin in LRS
- Bovine hemoglobin depends on chloride instead of 2-3 DPG to determine oxygen affinity → great oxygen transport ability in the body
What are P50 in dogs and cats?
Dogs: 31.5 mmHg
Cats: 35.6 mmHg
Is oxyhemoglobin isoosmotic or hyperosmotic? hyperoncotic or normooncotic?
Isoosmotic (300 mOsm/L)
Hyperoncotic (COP = 43 mmHg)
What are common complications/side effects for oxyhemoglobin administration? Why?
Hypertension - nitric oxide scanvenging effect leads to vasoconstriction
Volume overload - hyperoncotic & vasoconstriction
Transient Yellow-orange color skin and urine
What is the dose for oxyhemoglobin administration and what is the half-life?
10-30 ml/kg
18-43 hr
What is the formula for albumin deficit?
Albumin deficit (g) = 10 x [Desired albumin - patient albumin] x body weight x 0.3
What are in frozen plasma?
Albumin, fibrinogen, globulin, Factor 2, 7, 9, 10,11, 12
Mainly lacking factor 5, 8
What are in cryoprecipitate?
von Willbrand factor, Factor 8, 13, fibrinogen
What are in cryo-poor plasma?
albumin, vit-K dependent factor, globulin
What is the FFP volume required to raise albumin by 0.5 g/dL
20-25 ml/kg
What is the canine albumin dose required to raise albumin by 0.5 g/dL?
450 mg/kg
True or False: Platelets contains nucleus.
False
List 7 structures in the platelet.
1) Actin
2) Myosin
3) Fibrin-stabilizing factors (fXIII)
4) Prostaglandins
5) Mitochondria → can form ATP and ADP
6) Endoplasmic reticulum
7) Golgi apparatus
8) Growth factors
9) Thrombosthesnin
10) 𝜶 granules
11) Dense granules
12) Lysosomal granules
What are in platelet 𝜶 granules (10) and dense granules (6)?
𝜶 granules:
- Fibrinogen
- von Willbrand factors
- P-selectin
- Factor V, VIII
- Thrombospondin
- Glycoprotein IIb/IIIa
- Platelet factor 4
- Insulin like growth factor
- Platelet derived growth factor
- Vascular endothelium growth factor
Dense granules:
- Ca2+, Mg2+, phosphate
- ATP, ADP
- Histamine
- Serotonin
- Polyphosphate
- Catecholamines
What the structure in the endothelium that store the vWF?
Weibel-Palade bodies
What composes the extrinsic tenase complex?
Tissue factor (fIII), factor VIIa, calcium
What composes the intrinsic tenase complex?
Factor VIIIa, Factor IXa, phospholipid, calcium
What composes the prothrombinase complex?
Factor Xa, Factor Va
What are the 7 G protein-coupled receptors on the platelet and what do them bind to?
ADP (P2Y1, P2Y12)
Thrombin (PAR1, PAR4)
Thromboxane (TP)
Epinephrine (𝜷2 receptors)
Serotonin (5-HT2A)
What are the two integrins receptors and what do they bind to?
Integrin 𝜶2𝜷1 → collagen
Integrin 𝜶II2𝜷3 (GP IIbIIIa) → fibrinogen
- inside-out and outside-in activation
What dose GPIb/IX/V receptors bind to?
vVF, P-selectin, collagen
- a member of the leucine-rich receptor class
What is GPVI activated by?
collagen
- Immunoglobulin superfamily receptors
- activates integrins via inside-out signalling
What is glenzocimab?
Monoclonal antibody against GPVI receptor (experimental)
Where does the thrombopoietin mainly synthesized?
Liver
What is the threshold of platelet count when we can see clinical bleeding?
25000-50000/ul
List 4 tick-borne diseases that can cause thrombocytopenia.
Ehrlichiosis
Babesiosis
Rocky Mountain Spotted Fever (Rickettsia rickettsii)
Anaplasmosis
What are the three proposed mechanisms of drugs causing immune-mediated destruction of platelets and an example for each one of them?
1) hapten-dependent antibody formation: drugs bind covalently with the platelet membrane proteins → antibody production
- Penicillin, cephalosporins
2) drugs induce antibodies to bind to platelet membrane proteins in the presence of drugs (e.g. GPIIbIIIa)
- quinine, vancomycin, sulfonamides, rifampin, fluoroquinolones
3) drugs induce antibodies to bind to platelet membrane proteins without the presence of drugs
- sulfonamides
List 5 drugs that can cause bone narrow suppression.
1) Chemotherapeutic drug
2) Methimazole
3) Phenobarbitals
4) Penicillins
5) Azathioprine
6) Estrogen
What is the MOA of using vincristine to treat ITP?
1) stimulate thrombopoiesis
2) accelerate fragmentation of megakaryocytes
3) impairment of the phagocytosis of platelets by macrophages
4) interference with antiplatelet antibody formation and binding
True or False: lyophilized platelets have shorter half-life than PRP.
True
Define platelet concentrate
Plt concentrates are derived from centrifugation of whole blood or by apheresis. They are stored at room temperature with constant mixing and they last 5-7 days.
If they are refrigerated they can last for 14 days, but they have lower survival post transfusion while maintaining good haemostatic function.
How long can lyophylised or cryopreserved platelets be kept for?
3y
According to the European guidelines, when is prophylactic transfusion of platelets indicated?
Prophylactic transfusions are indicated by the European guidelines by plt count thresholds of 10 x109 in critically ill patients
Are platelet transfusions indicated for the reversal of anti-platelet agents?
No evidence supporting improved outcomes
Findings of PROPPR trial regarding platelet transfusion
PROPPR trial showed that early (<6h) platelet administration was associated with improved hemostasis and decreased mortality.
What is the max platelet increase when giving one unit of fresh whole blood derived PRP (80K/uL)/10kg ?
40K/uL
True or False: Extrinsic thrombocytopathies are more common than intrinsic thrombocytopathies in small animals.
False
Intrinsic is more common!
Side effects of platelet transfusions
SIDE EFFECTS:
* Thrombosis (especially in thrombotic thrombocytopennic purpura and other microvascular thrombotic disorders)
* Infection (TRIM)
* Pulmonary events (TRALI, TACO)
* Impaired neurological recovery (in brain haemorrhage)
What is the most common extrinsic thrombocytopathy?
von Willebrand’s disease
List 3 places where von Willebrand factors are stored.
1) Platelet 𝜶 granules
2) Weibel-Palade bodies in the endothelial cells (richest!)
3) plasma (bind with fVIII)
Describe three types of VWD in dogs
Type I: quantitative reduction of von Willebrand factors
Type II: qualitative reduction of von Willebrand factors
Type III: absolute lack of von Willebrand factors
What is normal BMBT in dogs and cats?
< 3 min
List 4 differential for prolonged BMBT.
1) vWD
2) Thrombocytopenia
3) Thrombocytopathia
4) Vascular wall abnormalities
List two treatments for vWD.
1) Cryoprecipitate (1 unit/10kg)
2) DDAVP (Desmopressin acetate)
What is the MOA of DDAVP administration in vWD?
Stimulate endothelial V2 receptors to release intracellular von Willebrand factors.
- Type I has the best response compared to Type II and Type III
For vWD patient that needs surgery, when should you give DDAVP, the dose and how long does it last?
Give 1 ug/kg SC/IV 30min - 1hr before surgery
Last about 2 hours
How to perform clot retraction assay? What does it used for?
Clot retraction is determined by the placement of 5 ml of whole blood into a sterile glass tube (without any anticoagulant). A wooden applicator is inserted into the tube and blood. The tube then is sealed with plastic paraffin film before incubation at 37°C. The assessment of clot formation and clot retraction is noted over 8 to 24 hours. Within 2 to 4 hours a normal clot retracts markedly.
* Used in patient with normal platelet count
Abnormal result → thrombocytopathia, low fibrinogen or coagulopathy
What is the breed that can have idiopathic asymptomatic macrothrombocytopenia?
Cavalier King Charles Spaniels (CKCS)
- mutation in β1-tubulin
List 3 causes of acquired vWD.
1) Immune-mediated disease
2) Hypothyroidism
3) Hydroxyethyl starch administration
4) High shear stress (e.g. mitral regurgitation, aortic stenosis)
What is the proposed major cause of uremia causing bleeding?
*defects in vWD structure (sort of acquired type II vWd)
*defective intracellular Ca++ mobilisation –> defective plt degranulation
* storage pool deficiency in dense and alpha granules
What is Virchow’s triad?
It describes the three factors that predispose a patient to vascular thormbosis.
Endothelial injury
Hypercoagulability
Blood stasis
How many deoxygenated Hb need to be present in the vessels for the cyanosis to be clinically appreciable?
5 g/dL
“Serious bleeding concerns arise when there are ___ platelets or less per high-power field.”
What is the number in the blank?
3
What are the two heavy metal that can induce hemolysis?
Zinc, copper
List 5 substances that can cause methemoglobinemia.
1) Acetaminophen
2) Nitrates
3) Skunk musk
4) Nitrites
5) topical benzocaine formulations
6) hydroxycarbamide
7) phenazopyridine
List 5 RBC’s self-protective mechanisms for oxidative injury.
1) superoxide dismutase
2) catalase
3) glutathion peroxidase
4) glutathion
5) metHb reductase
Why is feline Hb more susceptible to oxidative injury?
Because feline Hb has 8 SH-group (sulfhydryl) on the globin part; dogs’ only have 4.
True or False: Heinz bodies can be seen in normal feline erythrocytes.
True
What are the three major components of glutathione?
Glutamic acid
Cysteine
Glycine
What is the process of vitamin K dependent coagulation factors systhesis called?
𝛄-carboxylation (vitamin K is the cofactor)
There are two ADP receptors on the platelets, what are their functions?
P2Y1: platelet shape change and mild aggregation
P2Y12: activation of intergrin and platelet granule release, induction of thromboxane production
** Both ADP receptors need to be activated for full ADP-induced platelet aggregation
True or False: Clopidogrel is a prodrug and require hepatic cytochrome p450 system transformation to be effective.
True
True or False: Is clopidogrel irreversible or reversible antagonist when it binds to P2Y12 ADP receptors?
Irreversible antagonist
What is the MOA of aspirin in anti-platelet aggregation?
It irreversibly blocks COX-1 in the platelets → inhibit thromboxane (TXA2) production → inhibit TXA2 induced platelet aggregation
What is the MOA of Abciximab?
Non-competitive GPIIbIIIa inhibitor → inhibit fibrinogen induced platelet aggregation
What is extrinsic factor pathway also called? What about intrinsic factor pathway?
Extrinsic factor pathway: tissue factor pathway
Intrinsic factor pathway: contact activation pathway
Where are the tissue factor located?
Extravascular cells
Monocytes, macrophages, neoplastic cells, microparticles released from endothelial cells, platelets
List 10 functions of thrombin.
1) Platelet activation
2) Convert fibrinogen to fibrin
3) Activate FXI & FV (11 & 5)
4) Release FVIII from von Willebrand factors
5) Activate FVIII (8)
5) Activate thrombin-activatable fibrinolysis inhibitor (TAFI)
6) Induce inflammation
7) Combine with thrombomodulin → activate protein C
8) Increase endothelial cell microparticle release
9) Activate fXIII (13)
10) Activate protein C (alone, slow)
What is INR and what is it used for?
It is an abbreviation of International Normalized Ratio. It is a type of calculation based on PT result, and is used to monitor patients’ on anticoagulant.
INR = [Patient PT/Control PT]^ISI
*ISI = international sensitivity index; the relative strength of the thromboplastin reagent
Why is the benefit of INR compared to PT test result? What is normal INR?
INR takes into account of the variation of different machines, different reagents used and sensitivity difference in the TF activators.
Normal INR: ≤ 1.1
Why at the beginning of warfarin treatment, patient may be in hypercoagulable state instead of hypocoagulable state?
Because warfarin also inhibit the activation of protein C and protein S, both of which are anticoagulant.
- Sometimes patients can be treated with heparin at the first few days of warfarin therapy
When a patient is on vitamin K anticoagulant, what is the therapeutic range for INR?
2.0 - 4.0
What coagulation factors can unfractionated heparin inhibit?
Factor II, X
Factor IX, XI, XII
Which one is highly protein bound, UFH or LMWH?
UFH
Which one can bind to endothelial cells and possible platelets or other plasma proteins, UFH or LMWH?
UFH
What are the elimination of UFH and LMWH, respectively?
UFH
- saturable pathway: cleared by reticuloendothelial system and endothelial cells
- non-saturable pathway: excreted via kidneys
LMWH
- mainly excreted via kidneys
What are the half-life of UFH and LMWH, respectively?
UFH: 60-90 min
LMWH: 3-6 hours
Which test do you used to monitor UFH? PT or aPTT?
aPTT
Why are old clots more resistant to thrombolysis?
Because of more extensive fibrin polymerization
Where is the urokinase or urokinase plasminogen activator produced?
renal tubular epithelium
What is the most common complication from thrombolytic therapy in cats?
Reperfusion injury
What is the MOA of EACA and TXA?
Both drugs **reversibly **bind to lysine-binding site on the plasminogen → inhibit plasminogen to bind to fibrin → inhibit plasminogen activation → inhibit fibrinolysis
What does plasmin bind to?
Fibrin
Fibrinogen
TPA
True or False: Is estrogen prothrombotic or antithrombotic?
Prothrombotic
Which one is more potent, TXA or EACA?
TXA is 6-10x more potent than EACA
How are TXA and EACA metabolized?
Mainly excreted via kidneys
What is the half-life for TXA and EACA?
TXA: 1-2 hours
EACA: 2-3 hours
Side effects of EACA and TXA
EACA can induce myonecrosis
TXA vomiting and seizure (glycin receptor)
What is fibrinolytic shutdown?
Inflammatory cytokines (post-op) induce large amount of PAI - stop physiologic fibrinolysis
What is the main difference between vasopressin and desmopressin?
In Desmopressin, the L-arginine is switched to D-arginine → no effect on V1 receptor (vasoconstriction) but more effective on V2 (antidiuretic & release vWF and fVIII from endothelium)
Which coagulation factor is hemophilia A lacking? What about hemophilia B and C?
hemophilia A: fVIII (8)
hemophilia B: fIX (9)
hemophilia C: fXII (11)
Which amino acid composes the 2/3 of protamine?
arginine
List 5 adverse effects of protamine.
1) Hypotension
2) Anaphylaxis reaction
3) Pulmonary hypertension
4) Delayed noncardiogenic pulmonary edema
5) Paradoxical bleeding (e.g. thrombocytopenia, thrombocytopathia, heparin-rebound effect)
- Heparin-rebound effect: protein-bound heparin that is incompletely bound by protamine. After the protamine-heparin complexes are cleared from the circulation, remaining protein-bound heparin dissociates slowly and binds to antithrombin to produce an anticoagulant effect
Can protamine reverse any type of heparin? why?
No, it is much more efficient in reversing unfractionated heparin as it prefers long chains.
It can only reverse 60% of LMWH.
What is the proposed mechanism for conjugated estrogen in hemostasis?
Increased vWF, fVII and fXII
- Often used in uremic patients
What is the difference of the thrombus components between arterial and venous thrombus?
Arterial thrombus
- White clot; platelets + fibrins
Venous thrombus
- Red clot; fibrins + red blood cells
When a patient is on UFH therapy, what is the common target range?
1.5 - 2.5x prolongation of aPTT
What is the 5P rules in FATE?
Pallor (i.e. purple or pale toes)
Polar (i.e. cold extremities)
Pulselessness
Paralysis
Pain
What are the two factors are associated with better prognosis in FATE?
Presence of motor function
Only one limb is affected
List 7 causes of aortic thrombosis in dogs.
1) Neoplasia
2) Hyperadrenocorticism
3) PLN
4) PLE
5) Hypothyroidism
6) IMHA
7) Infective endocarditis
35% cryptogenic
What is the pathophysiology of heparin-induced thrombocytopenia
- Non-immunogenic: direct interaction between heparin and platelets causing platelets clumping or sequestration
- Immunogenic: Heparin bids to platelet factor 4 (released from alpha granules) → becomes immunogenic and cause release of IgG targeting at heparin-PF4 complex → The heparin–PF4–IgG multimolecular immune complex activates platelets via their FcγIIa receptors → release of prothrombotic platelet‐derived microparticles, platelet consumption, thrombocytopenia
*Thrombosis
True or False: Both tPA and uPA requires the presence of fibrin to activate plasminogen.
False
uPA does not require the presence of fibrin
Describe the difference between fibrin degradation products (FDPs) and D-dimers.
Fibrin degradation products (FDPs): degradation of fibrin, fibrinogen and cross-linked fibrin
D-dimers: degradation of fibrin that are cross-linked by fXIII
What are the two plasma proteins that can inhibit plasmin function?
𝜶-2-antiplasmin
𝜶-2-macroglobin
What are the two inhibitors for plasminogen activators?
Plasminogen activator inhibitor-1 (PAI-1)
Protease nexin
What are the two activators for TAFI?
Thrombin-thrombomodulin complex
Plasmin
How does TAFI inhibit fibrinolysis?
It eliminates carboxyl-terminal lysine residues from fibrin → reduces the ability of plasminogen to bind fibrin
True or False: Primary hyperfibrinolysis can be seen in chronic liver failure secondary to increased concentrations of tPA.
True
List 4 substances that can induce endothelial PAI-1 release.
LPS
IL-1
TNF-𝜶
TGH-𝜷
True or False: Increase D-Dimer level indicates hyperfibrinolysis.
False
Increase D-Dimer can be a result of increase fibrinolysis or increase thrombosis → cannot identify hypo or hyper-fibrinolysis!
In ROTEM, there are two assays called INTEM, EXTEM, and APTEM, which are used to evaluate intrinsic and extrinsic pathways, as well as the effect of hyperfibrinolysis on other assays, respectively. What are the activators/inhibitors for them?
INTEM: ellagic acid
EXTEM: tissue factor
APTEM: aprotinin