Chapter 106 - Thrombocytopenia Flashcards
What are three common causes of thrombocytopenia in humans in the ICU?
- Heparin induced thrombocytopenia
- TTP
- HUS
What in general causes the most severe form of thrombocytopenia?
Immune mediated diseases
When is clinically significant bleeding noted as a result of low platelet numbers?
Below 25-50 x 10^9/ L
T/F: Thrombocytopenia has been associated with decreased survival.
True
T/F: In dogs and cats with inflammatory diseases, the platelets tend to clump.
True
What is another reason why felines platelets might be miscounted in an automatic analyzer outside of clumping?
They are large and overlap in size with the RBC
A normal smear should contain how many platelets per hpf?
8-15 (Corresponds to 120-225,000 with each platelet being about 15,000/ mcL)
Thrombocytopenia is a result of what 4 general categories?
- Decreased production
- Consumption
- Sequestration
- Increased desctruction
What are two ways that drugs can induce immune mediated destruction of platelets?
Hapten dependent antibody formation and via production of antibodies that bind to platelet membranes
What drugs are associated with hapten dependent antibody formation?
Penicillins and cephalosporins
What drugs are associated with antibody production to platelet membrane proteins?
Quinine, vancomycin, sulfonamides, rifampin and fluroquinolones
What is the most common platelet membrane protein associated with antibody production in drug associated thrombocytopenia?
Glycoprotein IIbIIIa/ integrin a-IIbB3
What drugs are associated with bone marrow suppression or toxicity of the bone marrow? (8)
Phenobarbital, chloramphenicol, penicillin, cephalosporin, cancer chemotherapies, methimazole, azathiopine, albendazole
Indications for a bone marrow aspirate include? (3)
- Thrombocytopenia that does not respond to treatment
- Pancytopenia
- Animals suspicious for neoplasia
T/F: Splenic sequestration of platelets usually causes a significant thrombocytopenia.
False, mild
What type of hypersensitivity reaction is ITP?
Type II (after anti-platelet and/or antimegekaryocyte antibody attachment)
What is the reported mortality rate for idiopathic ITP patients?
25-30%
Idiopathic ITP is reported in what percentage of all thrombocytopenic dogs?
5%
T/F: Primary ITP is rare in cats.
True
T/F: In human children, ITP is often a self limiting disease and medical treatment is not recommended.
True
How does vincristine work to increase platelet counts?
Causes release of platelets from megakaryocytes via the microtubule system which controls the release of new platelets into circulation) and impairs phagocytosis of opsonized platelets by impairing microtubule assembly in macrophages
Why is splenectomy considered a last resort for treatment in animals with ITP?
Because of the possibility of exacerbation of hemoparasitic infections such as babesiosis and mycoplasmosis
In humans, when are platelet transfusions indicated?
<10K/mcL and in patients requiring a surgical procedure, <50k/mcL
T/F Addison’s disease can cause decreased platelet production.
True
What are some causes for platelet sequestration?
Splenomegaly and splenic congestion, neoplasia, severe hypothermia
What is the treatment for ITP in human kids?
None. It is self-limiting
T/F Vincristine does not change the prognosis but can decrease the hospitalization time
True
Name 5 blood products that can be given to increase platelet number
- FWB
- Platelet rich plasma
- Fresh platelet concentrate
- Crypreservative platelets
- Lymphilized platelets
If a dog is given 10mL/kg FWB, how much do you expect the platelet count to increase?
10.000/uL
