Exam 3 - Disorders of Primary Hemostasis Flashcards
what does the endothelium of the vessels synthesize?
collagen, fibronectin, & VWF
what is the platelet phase of primary hemostasis?
platelet adhesion
- vessel damage exposes subendothelium & platelets adhere
- VWF helps bind the platelets to the subendothelium
platelet aggregation
- platelet conformational change - release of substances that stimulate aggregation
- primary plug forms serving as the surface for secondary hemostasis
what clinical signs are associated with disorders of primary hemostasis?
petechiae/ecchymoses, bleeding from mucosal surfaces, melena/hematochezia/hematemesis, hematuria, & pulmonary bleeds
what is the purpose of using a BMBT in disorders of primary hemostasis?
test for primary hemostatic disorder other than thrombocytopenia
T/F: vasculitis is a common cause of primary hemostatic disease
false - uncommon
can cause petechiae/ecchymoses
if vasculitis is to be definitively diagnosed for a primary hemostatic disease, what must happen?
biopsy is the only way to definitively diagnose
what is von willebrand’s disease?
deficiency of vWF
why does von willebrand’s disease resemble a platelet disorder?
VWF is a part of normal primary hemostasis
what is the most common inherited bleeding disorder in the dog?
von willebrand’s disease
when should you test for von willebrand’s disease?
patients that are clinically bleeding, making decisions about breeding, & prior to surgery
how is type I VW disease characterized? what breeds are affected?
low concentration & normal structure of vWF - variable severity of disease
dobermans
how is type II VW disease characterized? what breeds are affected?
low concentration & abnormal structure of vWF - severe
GSP & GWP
how is type III VW disease characterized? what breeds are affected?
vWF markedly reduced or absent
familial - shetlands, scotties
sporadic - blue heelers, labs
if doing a surgery on a VWD patient, what should you do in prep & have on hand?
prep - give VWF, cryoprecipitate & plasma
give donor desmopressin to the blood donor prior to collection
have blood products on hand in case a transfusion is required
what are the 2 general diseases that are included in decreased platelet function?
VWD & thrombocytopathia
what are some causes of acquired thrombocytopathies?
drugs - nsaids, clopidogrel, & high dose colloids
neoplasia
infectious agents - ehrlichia canis & platys
hepatic disease
uremia
DIC
what are 4 general mechanisms of decreased platelet numbers?
- destruction
- sequestration
- decreased production
- utilization or loss
what is the common signalment of a patient with immune mediated thrombocytopenia?
common in dogs, some breed predispositions, young-middle aged
what are some primary causes of ITP?
idiopathic
evan’s syndrome - ITP & IMHA
systemic lupus erythematous
what are some secondary causes of ITP?
infectious - ehrlichia, babesia, leishmania, leptospira, HW, FeLV/FIV
neoplasia - lymphoma, hemangiosarcoma, carcinoma
drugs - sulfas, cephalosporin, phenobarbital
how is ITP diagnosed?
diagnosis of exclusion
medication/vaccine history, infectious disease testing, thoracic rads, abdominal ultrasound, FNA of enlarged peripheral lymph nodes, & bone marrow evaluation only when there is no response to therapy
T/F: thrombocytopenia is a contraindication to bone marrow collection
false - not a contraindication
how is ITP treated?
avoid or d/c nsaids, cage rest, avoid trauma, monitor for rapid blood loss usually through the gi tract, & transfuse with packed red blood cells or whole blood
how does vincristine help in treating ITP?
- increases circulating platelet count
- accelerates fragmentation of megakaryocytes
- stimulates thrombopoiesis
- impairs platelet phagocytosis by macrophage
what are the risks of using vincristine for treating ITP?
severe tissue damage if extravasated
how do glucocorticoids help in treating ITP?
mainstay of therapy - immunosuppression
may also give doxycycline while tests are pending
what is the dosage used for glucocorticoids when treating ITP? when is a response expected?
pred 2mg/kg/day
2-11 days - mean of 4 days
why is a 2nd line immunosuppressive drug added when treating ITP with glucocorticoids?
allows for more rapid tapering of prednisone
how does monitoring of ITP affect treatment?
monitor every 2-3 weeks
if platelet count is normal - taper pred by 25%
continue on pred at 0.5mg/kg every 48 hours for 2-3 weeks & discontinue
monitor for relapse!!
what is the prognosis for most cases of ITP? what are some negative prognostic factors?
overall good - 89% survived to discharge
bleeding into CNS/lungs - typically fatal
60% survival rate in dogs with ITP & melena or elevated BUN
what is the percentage of relapse of ITP?
31% at an average of 79%
what are some differentials that should be considered for pancytopenia?
drugs - chloramphenicol, sulfas, chemo drugs, anti-fungals, phenobarbital
toxins - estrogen or radiation
infection - chronic ehrlichia, parvo, histoplasmosis
immune-mediated
dysmyelopoiesis (hematopoietic neoplasia)/myelophthisis (crowding out)
myelofibrosis - idiopathic or secondary
myelodysplasia
what clinical signs are common in patients with a primary hemostatic disorder?
petechiae are common, hematomas are rare, bleeding at mucosal membranes, & bleeding after venipuncture
what clinical signs are common in patients with a secondary hemostatic disorder?
petechiae are rare, hematomas are common, bleeding into muscles, joints, body cavities, & delayed bleeding after venipuncture
