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 intergin receptors and what do they bind to?
Intergin 𝜶2𝜷1 → collagen
Intergin 𝜶II2𝜷3 (GP IIbIIIa) → fibrinogen
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
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) Esteogen
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
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!
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 functions
- Other mechanisms: increased NO and prostacyclin → inhibit platelet activation; direct platelet inhibition by uremix toxin
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
MNWH: 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
What is the main difference between vasopressin and desmopressin?
In Desmopression, 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
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
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
If a young cat has prolonged aPTT but is otherwise normal on PE without clinical evidence of bleeding, what is the congenital disease that should be on the differential list?
Factor XII deficiency (Hageman trait)
What is the dose for DDAVP to treat vWD?
1-4 mcg/kg SC
What is the proposed mechanism of hyperfibrinolysis in dogs with acute liver failure?
1) Decreased hepatic clearance of tPA
2) Decreased levels of PAI-1, 𝜶-2-antiplasmin, and TAFI.
True or False: Bleeding diathesis can be seen in about 1/3 of Angiostrongylus vasorum infection.
True
Where is streptokinase derived from?
𝜷-hemolytic streptococci
What is the difference between traumatic induced coagulopathy (TIC) and acute traumatic coagulopathy (ATC)?
TIC: ATC + resuscitation-associated coagulopathy (RAC)
ATC: endogenous coagulation abnormality
What are the two characteristics of acute traumatic coagulopathy?
Hypocoagulable state
Hyperfibrinolysis
What are the four main contributors to resuscitation-associated coagulopathy?
Hypothermia
Metabolic acidosis
Hemodilution
Explain the pathophysiology of acute traumatic coagulopathy (or acute coagulopathy of trauma shock).
During severe trauma, there is lots of catecholamine release & extensive endothelial damage → extensive activation of coagulation cascade; extensive release of thrombomodulin → many thrombins are formed; clotting factors and platelets are consumed → eventually hypocoagulable state
Many thrombins bind to thrombomodulin → activates protein C → protein C inactivates fVa, fVIIIa, and PAI, TAFI → hyperfibrinolysis
Thrombomodulin inhibits thrombin formation → tips the scales a bit over hypocoagulability
Endothelial shedding lots of heparin & tPA → hypocoagulability & hyperfibrinolysis
ATC requires two conditions to be present, what are they?
Severe tissue injury
Hemorrhagic shock
Where does PAI produced?
Many different types of cells
Where is tPA stored in the endothelium?
Weibel-Palade bodies!
When should you do a cross match in dogs and cats?
Dogs: if patient has a transfusion more than 4 days ago
Cats: always do a crossmatch due to possible anti-mik antibodies
True or False: Crossmatch can prevent all the transfusion reactions.
False
It can only prevent acute hemolytic transfusion reaction.
What are the components for CPDA?
Citrate
Phosphate
Dextrose
Adenine
What is Optisol solution and what is the function?
Optisol solution contains adenine, dextrose, NaCl and mannitol. It is a RBC additive solution that can provide RBCs nutrition and prolong the storage life. It needs to be used with anticoagulant (usually CPD).
How much blood can dogs and cats donate each time?
Dog: 20 ml/kg
Cat: 10 ml/kg
Define major and minor crossmatch.
Major crossmatch: Donor’s RBCs + Recipient’s plasma
Minor crossmatch: Recipient’s RBCs + Donor’s plasma
True or False: A blood have the genotype a/a or a/b; only homozygous b/b cats express the type B antigen on their RBCs.
True
- That’s why type B is so rare!
For a type AB cat that needs RBC transfusion, which type of the pRBC should be given if AB blood is not available.
Type A
True or False: A dog that was previously given a compatible transfusion from a donor dog may become incompatible with blood from the same donor 1 to 2 weeks later.
True
True or False: A dog that was previously given a compatible transfusion from a donor dog may become incompatible with blood from the same donor 1 to 2 weeks later.
True
What is the weight limit for dog and cat donors and what are the maximum blood volume (in ml) for donation?
Dog: 23kg; 450ml
Cat: 4kg; 40ml
Why acepromazine is not recommended for blood donor sedation?
1) Cause hypotension
2) Interfere with platelet function
What is open collection system and what is closed collection system?
Open collection system: the blood can be in contact with the environment and increase the risk of contamination
- needle + Three-way stopcock + syringe + blood bag
Closed collection system: the blood is not exposed to the environment at any time point during the collection or separation into blood components.
- commercial blood bag with needle
What is the diameter of the microfilter pores?
170 um
According to the blood bank standard, after pRBC transfusion, how many percentage of RBC should survive after 24 hours (if there is no bleeding or hemolysis)?
70-80%
How many ml of PRP can be made from 1 unit of FWB? What about platelet concentrate?
PRP: 200ml
PC: 50ml
- 1 unit FWB = 450ml
One unit PRP can increase how many platelet in a 30kg dog?
10K/uL
What is the common dose for cryoprecipitate? What about cryo-poor?
cryoprecipitate: 1-2 ml/kg
cryo-poor: 6-10 ml/kg
List 5 adverse effects that can be caused by hemoglobin.
1) NO scavenging → vasoconstriction
2) Increase oxidative stress and cause oxidative injury
3) Pro-inflammatory
4) Endothelial damage
5) Increase risk of AKI
6) Increase pulmonary arterial pressure
What is the FDA standard if a blood product is considered “Leukoreduced?”
No more than 5 x 10^6 of leukocytes should be present per unit of human pRBC
What are the two mechanisms of leukoreduction?
1) Mechanical filtration
2) Cell adhesion (to the filter)
During leukoreduction, how many ml of blood can be lost from the filter and tubing?
about 51-52 ml
There are two type of leukoreduction - pre-storage and post-storage leukoreduction. Which one is superior? Why?
Pre-storage leukoreduction is superior
It reduces the accumulation of the metabolites produced by WBCs and platelets
What are the three types of storage lesions? List 3 examples for each.
1) Biochemical changes
- Decreased ATP
- Increased potassium
- Decreased 2,3-DPG
- Dysfunction of NO
- Accumulation of ammonia
- Oxidative injury
- Accumulation of cell free hemoglobin
2) Biomechanical changes
- Decreased RBC deformability
- Accumulation of microparticles
- RBC shape changes
- Adhesion to endothelial cells
3) Immunological changes
- Leukocyte contamination
- Transfusion-related immunomodulation
Explain why there may be decreased ATP in RBCs during storage?
Erythrocytes do not have mitochondria → they generate ATP via anaerobic glycolysis → generate pyruvate, hydrogen ion → accumulate of hydrogen ions inhibit PFK function (key enzyme in glycolysis) → decrease ATP
Are microparticles pro-inflammatory or anti-inflammatory?
Pro-inflammatory and also pro-thrombotic
What are the 4 definitions of massive transfusion?
1) Receive 1 whole blood volume within 24 hours
2) Receive half of the blood volume within 3-4 hours
3) Receive 1.5 times of the blood volume regardless of time
4) Receive blood at 1.5 ml/kg/min for 20 minutes
List 3 common electrolytes imbalances associated with massive transfusion.
1) Hypocalcemia
2) Hypomagnesemia
3) Hyperkalemia
What is the recommended transfusion ratio for plasma: platelet: RBC?
1:1:1
List 3 complications associated with massive transfusion besides electrolyte abnormalities.
1) Hypothermia
2) Metabolic acidosis
3) Coagulopathy
4) Immunosuppression
5) TRALI
List 5 substances that are in Weibel-Palate bodies.
1) vWf
2) fVIII
3) tPA
4) P-selectin
5) IL-8
What is the function of ADAMTS13?
It is a von Willebrand factor-cleaving protease. It cleaves vWf into smaller multimers → preventing accumulation of ultra large multimers of vWf which can lead to diffuse microvascular thrombosis
What are the three mechanisms of decreased AT in critical illness?
1) consumption
2) eliminated by neutrophil elastase
3) decrease production (negative acute phase protein)
List 5 places that TFPI can be found.
Endothelial cells
Platelets
Mononuclear cells
Fibroblasts
Vascular smooth muscles
List 5 causes of hypofibrinogenemia
1) Hemodilution
2) Hepatic dysfunction
3) DIC
4) Sepsis
5) After thrombolytic therapy
What does thrombin time test?
It tests functional fibrinogen, via measure of the time taken for a standardized thrombin solution to convert fibrinogen to fibrin
True or False: Dal is a special RBC antigen than only presents in Dalmatian.
False
Dal is present in most dogs but is lacking in some Dalmatians.
What is the phenotypes for canine universal donor?
DEA 1.1, 1.2, 3, 5, and 7 negative but positive for DEA 4
True or False: Cats should always receive type-specific plasma.
True
According to the 2014 guidelines for viscoelastic test, how long should the blood sample to be held at room temperature for prior to testing for TEG/ROTEM?
30 min
Longer → hypercoagulable
What is the difference between the TEG and ROTEM in terms of the relationship of the pin and the cup?
TEG: cup oscillates around the stationary pin
ROTEM: Pin oscillates while the cup is stationary
What activators can be added to the TEG test? Which pathway does it stimulate?
All the samples need to add calcium
Kaolin: stimulate intrinsic pathway
Tissue factor: stimulate extrinsic pathway
T-PA: used to assess fibrinolysis
What are the four assays in ROTEM?
INREM
- Activator: ellagic acid
EXTEM
- Activator: tissue factor
FibTEM
- Activator: tissue factor
- Modification: cytochalasin D is added to inhibit the platelet contribution to the clot → assess fibrinogen
ApTEM
- Activator: tissue factor
- Modification: aprotinin is added to inhibit fibirnolysis → assess the impact of hyperfibrinolysis
How does Sonoclot work and what does it test?
it involves a vertically oscillating probe immersed in a cuvette of whole blood in which glass beads activate coagulation.
It tests ACT, clot rate, and platelet function
What is ACT comparable to?
aPTT
Both test the intrinsic and common pathway
What is the parameter to assess the rate of clot formation in TEG? What about in ROTEM?
TEG: K
ROTEM: Clot forming time (CFT)
What is the parameter to assess the time it takes to initiate the fibrin formation in TEG? What about in ROTEM and VCM?
TEG: R
ROTEM: Clot time (CT)
VCM: Clot time (CT)
Does the higher or lower lysis index in VCM mean increase fibrinolysis?
Lower (more residual clot being lysed)
True or False: According to the CURATIVE guidelines, antithrombotic administration should be considered as a routine treatment in dogs with Cushing’s disease.
False
Unless other risk factor exists
What are the two conditions in dogs and one condition in cats that warrant routine antithrombotic administration?
Dogs: IMHA, PLN
Cat: Cardiac disease
- For canine pancreatitis, only acute necrotizing pancreatitis is indicated
What are the three conditions that are considered high risk for thrombosis
1) Dogs with IMHA or PLN
2) Cats with cardiomyopathy and associated risk factors (history of ATE, LA enlargement, spontaneous echo contrast, reduced LA appendage flow velocity)
3) Dogs or cats with > 1 disease/risk factor for thrombosis (e.g. pancreatitis with sepsis)
Which blood clot have higher composition of platelets, arterial clot or venous clot?
Arterial clot
List an example for arterial clot and venous clot, respectively.
Arterial clot: ATE from HCM
Venous clot: IMHA, PLN, PTE
According to the CURATIVE guidelines, which anticoagulant is superior, LMWH or UFH?
LMWH in both dogs and cats
(positive safety profile, reliable bioavailability)
According to the CURATIVE guidelines, which anticoagulant is superior, direct Xa inhibitor or UFH?
Direct Xa inhibitor in both dogs and cats
(efficacy, reliable pharmacokinetics, ease of oral dosing)
According to the CURATIVE guidelines, which anticoagulant is superior, direct Xa inhibitor or LMWH?
Either one is reasonable
According to the CURATIVE guidelines, is the combination of antiplatelet with anticoagulant outweigh the anticoagulant alone?
Dog: aspirin/clopidogrel in addition to LMWH or individually adjusted UFH therapy may be considered in dogs at high risk of VTE
Cat: insufficient data; combination therapy may be considered where there is a high risk of thrombosis
According to the CURATIVE guidelines, what is the recommended loading dose and daily dose of clopidogrel in dogs and cats?
Dog:
- Loading dose: 4-10 mg/kg
- Daily dose: 1.1-3 mg/kg q24h
Cat:
- Loading dose: 37.5mg
- Daily dose: 18.75mg q24h
What are the recommended UFH IV and SC doses in dogs?
IV
- 100 U/kg IV
- CRI 480-900 U/kg/24hr
SC
- 150-300 U/kg SC q6h
What is the recommended UFH dose in cats?
250 U/kg SC q6h
What is the recommended dose of rivaroxaban in dogs and cats?
Dog: 1-2 mg/kg/d PO
Cat: 0.5-1 mg/kg/d PO
What is the recommended monitoring modality for dogs and cats on UFH treatment?
Dog: Anti-Xa activity (target: 0.35-0.7 U/ml)
Cat: insufficient data
According to the CURATIVE guidelines, what is the recommended monitoring modality for dogs and cats on LMWH treatment?
insufficient evidence to make strong recommendations for therapeutic monitoring
- targeting anti-Xa levels of 0.5–1.0 U/mL 2–4 hours postdose can be considered (dog)
True or False: According to the CURATIVE guidelines, antithrombotic treatment should not be discontinued prior to invasive procedure in patients with high risk of thrombus formation.
True
- Doesn’t matter anti-platelet or heparin
According to the CURATIVE guidelines, if a previous arterial blood clot has resolved, should you discontinue the antithrombotic therapy?
- If underlying causative conditions have resolved → d/c
- Unknown or unsolved underlying cause → continue
According to the CURATIVE guidelines, if a previous venous blood clot has resolved, should you discontinue the antithrombotic therapy?
- If underlying causative conditions have resolved → d/c
o Unknown or unsolved underlying cause → continue
What is the recommendation in the CURATIVE guidelines regarding the weaning of UFH, LMWH and direct-Xa inhibitor?
UFH: need to wean (from IV to SC)
* “rebound” hypercoagulation phenomenon following discontinuation of heparin therapy may be observed
LMWH: no need to wean
direct-Xa inhibitor: weaning is recommended
What are the two formulas to calculate the required pRBC for transfusion?
1) Volume (ml) = PCV rise desired % x body weight x 1.5
2) Volume (ml) = Body weight x blood volume x (Desired PCV - Patient PCV)/Donor PCV
*Blood volume: dog 90 ml/kg; cat 60 ml/kg
Under normal condition, which phospholipids are inside and which are outside the membrane?
Phosphatyldserine (PS)
Phosphatidylethanolamine (PE)
Phosphatidylcholine (PC)
Sphingomyelin
Sugar-linked sphingolipids
Inside: PS, PE
Outside: Phosphatidylcholine (PC), Sphingomyelin, Sugar-linked sphingolipids
What are the functions of flippase, floppase and scramblase
The functions of flippase and floppase are to maintain the resting state
- Flippase: flip PS in
- Floppase: flip PC out
The function of scramblase is to facilitate the activation state
- Scramblase: transpot PS, PE out
List 4 substances/conditions that can stimulate microparticle formation.
1) cytokines (e.g. TNF-𝜶)
2) thrombin
3) hypoxia
4) shear stress
List 8 endogenous anticoagulant.
1) Heparan sulfate proteoglycans
2) NO
3) Tissue factor pathway inhibitor
4) Thrombomodulin
5) Protein C & Protein S
6) Prostacyclin
7) Physical barrier
8) Ecto-adenosine diphosphatase
9) Antithrombin
Name three functions of Protein C-protein S complex.
1) Cleaves fV and fVIII
2) Inhibits PAI-1
3) Shut down thrombin formation
4) Inhibit TAFI
Which coagulation factor is the only one that is routinely circulating in the blood in active forms?
fVII (about 1% is active form)
True or False: In the initiation phase of the cell-based model, fXa is only functional at the surface of the TF-bearing cells, while fIXa can dissociate to the distant cells.
True
fXa will be degraded by TFPI and AT once it leaves the cell surface
What are the three coagulation factors thrombin activates during amplification phase?
fV, fVIII, fXI
5,8,11
What is the difference in terms of the components in cryoprecipitate and cryo-poor plasma?
Cryoprecipitate
- Fibrinogen, vWf, fVIII,fXIII, fibronectin
Cryo-poor plasm
- Vitamin K dependent factors, albumin
What are the special structures on the vitamin K dependent coagulation factors?
Glutamic acid (Gla)
- Need 𝛄-carboxylation to be able to bind to membrane surface
What are the two substances that can induce TFPI release?
1) Heparin
2) Activated platelets
Describe how TFPI interfere with the coagulation pathway?
TFPI has three domains - K1, K2, and K3. The K2 domain binds to fXa and inhibit it (reversible, no Ca needed). The K1 domain then binds to fVII-TF complex (irreversible, need Ca).
- K3 domain binds to protein S
True or False: AT can inhibit coagulation factors 2, 7, 9, 10, 11, 12
True
AT can inhibit 2, 9, 10, 11, 12 without heparin (slow)
AT NEEDS heparin to inactivate factor 7
What are the three other factors needed for activated protein C to work?
Protein S
Calcium
Phospholipid
What are the four functional binding sites on thrombin (B-chain)
1) Sodium binding site
2) Active site
3) Exosite I
4) Exosite II
When Na binds to the thrombin sodium binding site, does it make the thrombin procoagulant or anti-coagulant?
Procoagulant
What does thrombin exosite I and exosite II bind to? What does it make thrombin become, more procoagulant or anti-coagulant?
Exosite I: hirudin (from leech!), fibrinogen
Exosite II: heparin, thrombomodulin, AT
Anticoagulant
Explain the cell-based model.
Why protein C and AT/heparin has synergic anticoagulant effect?
The complexes of 10-5 and 9-8 are more resistant to AT inactivation than 10 or 9 are alone.
Activation of the APC pathway leads to the reduced production of 5 and 8 → decreases 10-5 and 9-8 complex formation
True or False: The effect of inflammation on endothelial cells appears to initially result in increased concentrations of plasminogen activators (tPA), but a more sustained rise in PAI-1 predominates.
True
The diagnosis of DIC is based on a clinical condition capable of inciting DIC plus two of the laboratory abnormalities. What are they?
Thrombocytopenia
Prolong aPTT/PT
Hypofibrinogenemia
Decreased AT
Elevated FDPs or D-dimer
Erythrocyte fragmentation on a blood smear (schistocytes, keratocytes, acanthocytes)
Define type 1 and type 2 TRALI.
The major difference: whether there is an ARDS risk factor or the presence of mild ARDS
Type 1
- Patients who have no risk factor of ARDS and meet the following criteria
1) Acute onset
2) Hypoxemia: P/F ≤ 300 or SPO2 < 90% on room air
3) No evidence of left atrial hypertension (LAH) on echo (if LAH is present, it is judged not to be the main cause)
4) Clear evidence of bilateral pulmonary edema on imaging (chest radiographs, chest CT or ultrasound)
5) Onset of pulmonary signs within 6 hours of transfusion
6) No temporal relationship to an alternative risk factor for ARDS
Type 2
- Patients who have risk factors for ARDS or who have existing mild ARDS (P/F 200–300), but whose respiratory status deteriorates and is judged to be due to transfusion based on
1) Findings as described in the type 1 (1) to (5)
2) Stable respiratory status in the 12 hr before transfusion
What is the incidence of TRALI in dogs?
3.7%
Describe the pathophysiology of TRALI.
In human medicine, it has been hypothesized that TRALI is the result of two clinical insults,
which is also call the “Two-hit model,” or “Two-event model.”
The first insult is that the pulmonary vascular endothelium is activated (pro-inflammatory) resulting in priming (adherence) and sequestration of neutrophils by one or more endogenous stimuli (i.e. sepsis, surgery)
The second insult is the blood product transfusion. The antibodies in the blood products, such as antibodies to human leucocyte antigen (HLA) class I and II, and various neutrophil antigens (HNA), can cause compliment activation and result in a full activation of those sequestrated neutrophils and released of cytotoxic agents, which eventually lead to endothelial injury and pulmonary edema
Define febrile non-hemolytic transfusion reaction (FNHTR).
- Acute non-immunologic or immunologic reaction
- Temperature > 39C (102.5 F) AND an increase in temperature of > 1C (1.8 F) from the pre-transfusion body temperature during or within 4 hrs of the end of a transfusion
- External warming, underlying patient infection, AHTR, TRALI, and TTI have been ruled out.
What cause FNHTR?
Secondary to donor WBCs or platelet antigen-antibody reactions or due to transfer of pro-inflammatory mediators in stored blood products.
List 5 causes of respiratory reaction during transfusion.
1) TRALI
2) TACO
3) FNHTR
4) TAD (transfusion associated dyspnea)
5) allergy reaction
Define transfusion associated dyspnea (TAD).
- acute
- development of acute respiratory distress during or within 24 hours of the end of a transfusion
- TACO, TRALI, allergic reaction, and underlying pulmonary disease have been ruled out
What is the incidence of TACO in dogs and cats?
Dog 4.7%
Cat 3%
Define transfusion associated fluid overload (TACO).
- acute, non-immunologic reaction secondary to an increase in blood volume mediated by blood transfusion
- acute respiratory distress and hydrostatic pulmonary
edema within 6 hours of transfusion - Evidences of LA hypertension or volume overload
- These patients typically have a positive response to diuretic therapy.
Describe Threshold model of TRALI.
The neutrophils need to be primed/activated by either substances in the donor blood or by the recipient’s condition (e.g. surgery, sepsis). For TRALI reaction to happen, the primed/activated neutrophils need to overcome a threshold.
What type of hypersensitivity is allergic transfusion?
Type I hypersensitivity
True or False: hemolytic transfusion reaction is always immunogenic.
False
Non-immunogenic: mechanical, chemical, osmotic, thermal
When is the timeframe of delayed hemolytic transfusion reaction?
24 hours to 28 days after transfusion
For cats receiving canine RBC, what is the lifespan of these RBC?
2-4 days
- compared to feline RBCs 30 days
What is the proposed mechanism of hypotensive transfusion reaction?
- A hypotensive transfusion reaction is an acute, non-immunologic reaction.
- There is usually a decrease in systolic blood pressure of at least 30 mmHg from baseline.
- Activation of coagulation factor XII → high-molecular-weight kininogen to bradykinin → vasodilation and increased vascular permeability
- Bradykinin is metabolized via ACE, and the use of ACE inhibitors before or during a transfusion has been associated with the development of HyTRs.
True or False: According to the TRACS guidelines, it is recommended to used fresher RBC transfusion products in dogs with sepsis or hemolytic causes of anemia.
True
According to the TRACS guidelines, is it recommended to administer antihistamine prior to transfusion routinely?
No
What is the recommended transfusion method for dogs and cats pRBC transfusion?
Dog: standard 170–260 micron in-line blood administration set with gravity flow
* Peristaltic and rotary infusion pumps should be avoided!!!
Cat: syringe pump + 18-micron microaggregate filter works
What are the three ways neutrophils execute their innate immunologic effect?
1) Phagocytosis
2) Degranulation
3) Neutrophil Extracellular Traps (NETs)
What are the three main components of NETs?
1) Cell free DNA
2) Histone
3) Neutrophil granule proteins & peptides
- Myeloperoxidase (MPO), Lactoferrin, Cathepsin G, Neutrophil elastase (NE), Defensins
Explain NETosis.
Neutrophils expose to PAMPs, DAMPs, cytokines, pathogens, autoantibodies, immune complexes → citrullination of histone, disassembly of the nuclear envelope, chromatin decondensation → release of NETs.
NETs are prothrombogenic or anti-thrombotic?
Prothrombogenic
What are the two ways of platelet to activate NETs?
Adhesive interaction
Soluble interaction
Which biomarker is highly specific for NETs?
citrullinated histone
What is the equation used to calculate whole blood transfusion?
Transfusion volume (ml) = (PCVdesire - PCVcurrent)/PCVdonor x body weight x blood volume
List 5 things that can stimulate tPA.
Histamine
Acetylcholine
Bradykinin
Platelet activating factor
𝜶 adrenergic agonist
What are the two things that activate TAFI?
Thrombin-thrombomodulin complex
Plasmin
Draw the traditional coagulation cascade.
What is the function of dimethyl sulfoxide (DMSO) in cyropreserved platelet?
It inhibits platelet activation via thromboxane A2-dependent, COX-1-mediated effect
Describe DOGiBAT score.
It is used to evaluate the severity of bleeding
9 categories
0-2 → the higher the worse
How long can the refrigerated plasma last?
2-6C for 14 days
List 2 difference between FFP and FP
FFP
- Frozen with 24 hours after being made
- Last 1 year in -30C
- Contains all the clotting factors, vWf, fibrinogen, Albumin
FP
- FFP stored in -30C for more than 1 year
- Last 5 years in -30C
- Contains everything minus fV and fVIII
