Primary haemostasis Flashcards
List the 3 steps of haemostasis
Primary= platelet plug
Secondary= fibrin plug that requires the coagulation cascade
Tertiary= Clot lysis
List the clinical signs of dysfunction of primary coagulation
Petechiae/ ecchymoses common
bleeding from mucous membranes
often more than one site of bleeding
Haematomas rare
List the clinical signs of dysfunction of secondary coagulation
Petechiae/ ecchymoses rare
Deep or cavity bleeds
can bleed from mucous membranes
sometimes single sites of bleeding
Haematomas common
What is needed to make a platelet clot
cells
protein (vWF and others)
Facilitators
Physiological inhibitors
What cells are the source of von Willebrand factors
Endothelial cells
What is diascopy and what does it test
Does the lesion blanch under a glass slide
Yes= vascular vasodilation
No= Petechiae
List 3 reasons why primary haemostasis be dysfunctional
Thrombocytopaenia
Thrombocytopathia
vWBF deficiency
What is Thrombocytopathia
platelet dysfunction
Describe how primary haemostatic disorders are investigated
Signalment
Platelet count and morphology
Buccal mucosal bleeding time
vWF assay
Platelet function assays
List 3 causes of thrombocytopaenia
defective platelet production
Accelerated platelet removal (IMTP)
Platelet sequestration or loss (haemorrhage)
What is the most common acquired cause of primary haemostatic defects in dog
IMTP- immune-mediated thrombocytopaenia
What is Evans syndrome
IMHA + IMTP
Describe how is IMTP treated
treat any underlying disease
Immunosuppression
What are the negative prognostic indicators in IMTP
melaena
high BUN (blood urea nitrogen)
List 3 causes of thrombocytopathia
Inherited
drug induced defects (NSAIDs)
platelet dysplasia
DEcsribe how you diagnose a thrombocytopathia
normal platelet count but prolonged BMBT
normal levels of vWF
platelet function tests
to a degree often a diagnosis of exclusion
Describe how thrombocytopathia is treated
no specific therapy
platelet transfusion not possible
withdraw any drug use (NSAID)
treat symptomatically- blood transfusion if marked anaemia
What is the most common inherited bleeding disorder in dogs
vWD- Von Willebrans disease
List te differences between the 3 types of vWD
1= abnormally low concentrations of structurally normal vWF
2= structurally abnormal vWF
3= Essentially no plasma vWF, diagnosed by ELISA
What breed of dog is most prone to vWD
Dobermans
What are the clinical signs of vWD
mucosal haemorrhage
cutaenous bleeding
prolonged bleeding from wound
Describe the diagnostic testing used for vWD
platelet count will be normal
BMBT screening test
Diagnosis is confirmed by demonstration of low vWF antigen concentrations
Genetic testing can be performed
How is vWD treated in severe cases
plasma - in severe cases
stabilisation
cessation of active haemorrhage
red cells if O2 carrying capacity compromised
Describe how type 1 vWD is treated
Desmopressin - acts by causing release of vWF from endothelial cells
below what platelet concentration does spontaneous bleeding occur
50 x 10^9
