Hemostasis Flashcards
What is hemostasis?
bodys ability to maintain the integrity of the blood and blood vessels
Any deviation from normal hemostasis is=
disease
What responses are in primary hemostasis
- Vascular response
2.Platelet response
What is the vascular response in hemostasis
vessel contract and almost immediately when injured, this narrows the lumen of the vessel, which decreases rate of blood loss and creates an area for platelets to adhere
What is the platelet response in hemostasis?
-become “sticky” (adhere to vessel wall and each other)
-this requires von Willebrand factor, which serves to stabilize the platelet plug
-granules become activated and release, which send a message to begin the Coagulation Cascade
What component is in secondary hemostasis?
Coagulation cascade
What happens in the coagulation cascade?
-these factors are made in the liver
-domino effect that eventually forms a stable fibrin clot
What is the ultimate purpose of primary and secondary hemostasis?
to form a clot and then dissolve that clot
Primary hemostasis is the formation of the _ _
platelet plug
Secondary hemostasis is formation of a stable _ _
fibrin clot
What is fibrinolysis
lysis of clot or thrombus through the activation of plasminogen into plasmin
What two components must be present for hemostasis?
- Vascular component
2.Platelets, number and function
What 2 parts are in the vascular component of hemostasis?
- Vascular spasm
2.Production of factor VIII and vonWillebrand’s factor by endothelial cells
Vascular spasm is _ but _ closure of blood vessel by contraction of smooth muscle
Immediate but temporary
Vascular spasm is stimulated by
nervous system response, platelets release thromboxane and serotonin
Platelet plug formation is stimulated by
vWF
vWF resides in the _, subendothelial metrix, and storage granules within endothelial cells and platelets
plasma
Platelets plug formation consists of
- adhesion of platelets
- aggregation of platelets
3.secretion of platelets
The following is _ of platelets:
-Platelets stick to subendoethelial surface
-Sticking activates platelets
adhesion
The following describes _ of platelets:
-Forms platelet plug
-Thromboxane stimulates other platelets to join
-Platelet plug is very short-lived (secs-min)
-Only works on SMALL vessels
aggregation
The following describes _ of platelets:
-Platelets have lots of substances in them
-Caused by vasoconstriction and further platelet aggregation
-Some substances activate 2 hemostasis
Secretion
Defects in primary hemostasis may be _ or _ and may be defects in _ or _
hereditary or acquired; vascular component or platelet component
Acquired vascular component defects
vasculitis, collagen deficiency, extensive vascular injury
Inherited vascular component defects of primary hemostasis
vonWillebrand’s disease
What is the number one acquired defect of primary hemostasis?
thrombocytopenia
What is a defect in function of platelets called?
thrombopathia or thrombocytopathy
Acquired platelet component defects
drugs, DIC, uremia
Hereditary platelet component defect
vWB disease (most common inherited bleeding disorder). platelet fail to adhere to subendothelial collagen
What is vonWillebrand’s disease?
an inherited bleeding disorder caused by lack of vWF protein
What protein circulates in the blood stream and must be present at the site of blood vessel injury in order to control bleeding from that vessel?
vWF
vWD is a distinct disorder, it is not _
hemophilia
What breed is most commonly affected with the mildest form of vWD?
doberman
What breeds are affected with the most severe form of vWD?
Chesapeake Bay Retrievers and Scottish Terriers
What breeds have abnormally low concentrations of vonWillebrand factor?
Scottish Terriers and Shetland Sheepdogs
Many dogs w/ vWD never show outward evidence of having the disease, but when they do, what do those signs look like?
-Spontaneously hemorrhage from the nose, vagina, urinary bladder, or oral MM
-Prolonged bleeding after trauma or sx and bruising or bleeding after a spay/neuter may be first time noticed
-in affected dogs w/ uncontrollable bleeding, death may occur
Tx of a severe bleeding episode requires
transfusion of canine blood products
_ products can be transfused pre-operatively to prevent surgical hemorrhage
plasma
_ _ can also be used to improve hemostasis in dogs with mild subtype (Type 1) vWD
Desmopressin acetate (DDAVP)
Bleeding from minor injuries may be controlled using
sutures, bandages, or wound glue
Dogs affected with vWD should not be given drugs that interfere with normal blood clotting mechanisms, These drugs include:
aspirin, sulfa-type antibiotics, and heparin
Dogs having low plasma VWF-ag (below _) are predicted at risk of transmitting or expressing the vWD trait.
50%
2 Hemostasis- Synopsis requires
coagulation factors and cofactors (calcium, tissue factors, vitamins)
Coagulation factors all made in the _
liver
Cascade=
conversion of inactive factors to active factors (like domino effect)
Synopsis is _ lasting (minutes to hours)
long
When do coagulation factors become activated?
when blood vessel or tissue injury occurs, or in co-operation with platelets, produce a clot at the site of injury
There are _ different clotting factors. These factors are activated in a specific sequence following two different pathways or sequences
13
What are the pathways of coagulation
intrinsic, extrinsic, and a final common pathway
What pathway is described?
-ALL component needed for this pathway are present in the blood
-Outside tissue damage is NOT needed to stimulate this pathway
-Contact activation= activated by contact with collagen and some platelet products
-Has factors XII, XI, IX, VIII (cost $12 not $11.98)
Intrinsic
What pathway is described?
-Requires a tissue factor for activation (tissue factor= thromboplastin)
-Thromboplastin is released from injured cells of any kind
-Reacts with factor VII
Extrinsic
What pathway is described?
-Where intrinsic and extrinsic pathways converge
-Has 2 stages (prothrombin to thrombin and fibrinogen to fibrin)
Common
What are the Vitamin K dependent factors?
II, VII, IX, X
In 2 Hemostasis- production of coag factors, the liver synthesizes all factors except part of factor _
VIII (the endothelium produces part of VIII)
2 Hemostasis defects may be _ or _
hereditary or acquired
2 hemostasis hereditary defects
Hemophilias A (-VIII) B (-IX)
What is the most common inherited blood clotting disorder in dogs
Hemophilia A
What is the Hemophilia A
the result of a mutation of a specific gene, causing a deficiency of blood clotting Factor VIII, which interferes with the blood clotting cascade
Clinical sign of hemophilia A
spontaneous bleeding
Dx of hemophilia A
Lab test called APTT (activated partial thromboplastin time) can test for clotting disorders but cannot distinguish among the various types of hemophilia
How to get a specific diagnosis of Hemophilia A
by measuring the activity of Factor VIII
2 Hemostasis acquired defects
-Deficiency of Vitamin K-dependent factors
-Liver disease/failure
-DIC
What is DIC
Disseminated intravascular coagulopathy
-small clots for throughout the body which results in consumption of coagulation factors and then hemorrhage occurs
DIC is secondary to conditions like
heat stroke, viremia, endotoxemia, massive necrosis, trauma, septicemia, IV hemolysis
Clinical signs of 2 hemostasis defects
-hematomas
-bleeding into muscles, joints, and body cavities
-delayed bleeding after venipuncture
-rarely see petechia or ecchymoses
What is fibrinolysis
breakdown of the fibrin clot
what is fibrinolysis-synopsis
lysis of a clot or thrombus through activation of plasminogen into plasmin
What is plasminogen called when it binds with fibrin (clot) and becomes activated
plasmin
Bound plasmin hydrolyses fibrin which produces
FDPs (fibrinogen degradation products)
FDPs have _ activity; block thrombin and inhibit platelets
anticoagulant
Fibrinolysis defects
Excessive FDP/FSP production (DIC and liver failure)
DIC leads to increased levels of
FDP/FSP
DIC leads to what due to obstruction of microcirculation
multiple organ dysfunction
Clinical signs of DIC
signs of BOTH 1 and 2 hemostasis disorders
_ hemostatic disorders are caused by failure of platelet plug formation due to quantitive or qualitative platelet disorders or due to von Willebrand factor deficiency
Primary
Clinical signs of primary hemostatic disorders
petechia, mucosal hemorrhage, prolonged bleeding at site of injury
Specific primary hemostatic disorders and diagnostic tests
-Thrombocytopenia: platelet count, platelet estimate from blood smear
-Platelet dysfunction: in vivo bleeding time, platelet aggregation, drug history and metabolic profile
Secondary hemostatic disorders are caused by
failure of fibrin clot formation due to deficiency of one or more coagulation factors
Tests to evaluate secondary hemostatic disorders
Rodenticide toxicity: aPTT, pT, vitamin K-dependent factors (II, VII, IX, X)
Liver failure: aPTT, PT, fibrinogen
Hemophilia: aPTT, factors VIII, IX
What does buccal mucosal bleeding time (BMBT) evaluate
both aspects of primary hemostasis, evaluates interaction b/w platelets and endothelium that causes primary platelet plug to form
What is normal BMBT for dogs and cats
1-5 mins
> 5 min BMBT =
thrombocytopenia or platelet dysfunction
What tube should be used for activated clotting time (ACT) method
DET tube which activates the intrinsic and common pathways
Vitamin K should be given with
food
What are the fat soluble vitamins
A, D, E, K
Normal ACT in dogs
60-90 sec
Normal ACT in cats
<65 sec
PTT (partial thromboplastin time) tests _ and _ pathways
intrinsic and common
OSPT, PT (prothrombin time) tests _ and _ pathways
extrinsic and common
TT (thromboplastin time) detects
decreased fibrinogen
FDP evaluates
fibrinolysis
Tube used for platelet estimate and count
LTT
Tube needed to measure von Willebrand’s factor
BTT- MUST BE FULL
Mixing ratio for blue top tube
1 part citrate : 9 parts blood
BTT is used for tests for coagulation factors of what pathways
intrinsic, extrinsic, and common pathways
Extrinsic clotting factor
VII
gray TT must be full and can be used for tests for what pathways
intrinsic and common
RTT is used for what testing
chemistry profile of liver function
