Platelets Too Few and Too Many Flashcards
thrombocytopenia
- too few platelets
thrombocytosis other name
- thrombocythemia
thrombocytosis
- too many platelets
when evaluating a patient with thrombocytopenia, first make sure the patient doesn’t have
- pseudothrombocytopenia
another name for pseudothrombocytopenia
- platelet clumping
platelet count in tubes in pseudothrombocytopenia
- falsely low
- make a substance that causes platelets to clump when blood added to EDTA tubes
platelet count in vivo in pseudothrombocytopenia
- higher
bleeding consequences in pseudothrombocytopenia
- no bleeding consequences
treatment in pseudothrombocytopenia
- no treatment needed
first symptoms appear at a platelet count of
50-20
usually need to treat at a platelet count of
20-10
risk of spontaneous intracranial hemorrhage at a platelet count of
< 10
three categories of thrombocytopenia
- underproduction
- peripheral destruction
- splenic sequestration
underproduction due to
- marrow failure
- marrow infiltration
- marrow toxins
marrow failure conditions
- myelodysplasia
- asplastic anemia
- vitamin deficiencies
marrow infiltration conditions
- tumor
- granulomatous diseases
- fibrosis
- leukemias
- lymphomas
marrow toxins
- drugs (chemo)
- radiation
- infections
- alcohol
non-immune mechanisms of peripheral destruction
- DIC
- TTP
immune mechanism of peripheral destruction
- antibody mediated platelet destruction
antibody mediated platelet destruction
- provoked by drugs
- associated with HIV
- associated with other autoimmune disease
- can be idiopathic
DIC characterized by
- abnormal activation of coagulation
- generation of thrombin
- consumption of clotting factors
- destruction of platelets
- activation of fibrinolysis
DIC diagnosis
- PT
- platelets
- fibrinogen
- D dimers
- peripheral smear
- elevated PT
- low platelets
- low fibrinogen
- elevated D dimers
- schistocytes on peripheral smear
elevated PT in DIC due to
- consumption of factor VII
treatment of DIC
- treat underlying cause
DIC etiologies
- gram negative sepsis
- severe burns
- obstetrical disasters
- leukemias
- shock
- insect or snake venoms
supportive measures of DIC
- transfusion of platelets
- clotting factors (FFP)
- fibrinogen (cryoprecipitate)
TTP characterized by
- abnormal activation of platelets and endothelial cells with vWF and fibrin deposition in microvasculature
- peripheral destruction of platelets and red cells
TTP diagnostic features
- MAHA
- low platelets
- fever
- neurologic manifestations
- renal manifestations
MAHA features in TTP
- elevated LDH
- elevated bilirubin
- schistocytes
renal manifestations in TTP
- hematuria
- proteinuria
- elevated BUN/creatinine
TTP etiology
- due to antibody against ADAMTS-13 protease
role of ADAMTS-13 protease
- cleaves large molecular weight vWF
result of antibody blocking function of ADAMTS-13 protease
- accumulation of large molecular weight vWF multimers
result of large vWF multimers
- abnormal platelet activation
TTP can be induced by
- drugs
- pregnancy
- HIV/AIDS
drugs that can induce TTP
- quinine
- cyclosporine
- tracrolimus
% fatality of TTP without therapy
> 90%
% who survive TTP with therapy
80-90%
TTP treatment relies on
- plasma exchange (PLEX)
- corticosteroids
secondary measures of TTP treatment
- spenectomy
- rituximab
TTP and platelet transfusions
- avoid platelet transfusions
HUS preciptated by
- diarrheal illness
- shiga toxin E. coli
atypical HUS
- HUS without diarrhea
atypical HUS cause
- inherited disorder of complement regulation
trigger of atypical HUS
- infection
- pregnancy
clinical features of Atypical HUS
- MAHA
- thrombocytopenia
- renal failure
- evidence of complement activation
treatment of atypical HUS
- plasma exchange
- eculizumab
drugs that can cause thrombocytopenia
- beta lactams
- trimoprim-sulfamethoxozole
- sulfa drugs
- quinine
- heparin
heparin induced cytopenia caused by
- antibodies against heparin/PF4
if platelets fall while patient is on heparin
- stop heparin immediately
heparin induced thrombocytopenia can also lead to
- thrombosis
diagnostic test for ITP-
- no diagnostic test
suspect ITP in patients with
- isolated thrombocytopenia
In adults specific therapy required for ITP if patient’s platelet count is
- < 20-30
initial therapy of ITP relies on
- corticosteroids
if platelet count is <10 or patient is bleeding In ITP, what do you use to treat
- IVIg
second line treatment of ITP
- rituximab
- splenectomy
blood bank platelet count
- will have a platelet count above which they will not release platelets
- not a magic number that should serve as a trigger to transfuse platelets
platelet transfusions in ITP
- only if severe bleeding
platelet transfusion in TTP
- contraindicated
platelet transfusion in DIC
- give to treat bleeding
platelets transfusions for splenic sequestration
- only for severe bleeding
hypo production platelet number to transfuse
- 10K
