Hemostasis I Flashcards
Primary Hemostasis
- Damage to endothelium of blood vessel
- vWF and GP1a released from collagen causing platelets to adhere
- Platelets are stimulated to release ADP, TxA2, vWF recruiting more platelets= platelet plug
What factors are involved in the intrinsic pathway of secondary Hemostasis?
XII, XI, IX, VIII
Clinical signs of primary Hemostasis vs Secondary Hemostasis?
Primary: Petechia, Echymosis
Oozing from mucosal sites (oral cavity, nose, bladder, GI)
Secondary: bleeding in the body cavity, large sq hematomas
How low are plts when we start to worry about spontaneous bleeding/hemorrhage?
10,000
Breed differences that can be normal (but look like plt disorders)
CKCS- macro thrombocytopenia
Greyhounds- slightly lower plt counts
How low are plts when we start to get concerned?
30,000
What tests can we use to Dx to assess Primary Hemostasis? What are the normal values?
BMBT
Dog-
Rapid point of care test used to assess secondary Hemostasis? Adv vs Disadvantages?
Activated clotting time (diatomaceous earth or kaolin activates fXII)
Adv: inexpensive and easy
Dis: only assessing intrinsic pathway,
Tests available at larger hospitals/commercial labs to assess secondary Hemostasis?
PT, aPTT, fibrinogen, FDPs and D dimers
PT and aPTT asses common pathway
What are some reasons for thrombocytopenia (primary Hemostasis disorder)
Bone marrow dz (not generating enough) Bleeding/loss Sequestration- spleen probs Consumption- DIC Destruction/immune mediated - severe thrombocytopenia
Bone marrow Dz causes, dx, tx
Causes: neoplasia, myelosuppressive drugs (chemo), drug rxns (chloramphenicol, estrogen), immune destruction at the level of a precursor
Dx: bone marrow sampling
Tx: eliminate the underlying cause
ITP, what is it, plt count, causes
Accelerated destruction of platelets by the immune system
- Platelet count usually
Causes of secondary ITP
- Rickettsial Diseases
- Vaccines/Medications – within the past 30 days
- Manifestation of systemic lupus erthematosus
- Secondary to neoplasia (high grade lymphoma, hemangiosarcoma, others
Additional diagnostics (other than plt count) for ITP?
-Antiplatelet Antibody Testing (limited availability)
Evaluates for platelet associated Ab’s
Does NOT discern between primary or secondary IMTP
Turn around time: 24-48 hours
-Antinuclear Antibody
One of the tests used to screen for SLE
What rickettsial dz’s may play a role in ITP
Ehrlichia canis
Ehrlichia platys
Anaplasma phagocytophilum
Rocky Mountain spotted fever
Tx for ITP
Glucocorticoids (cornerstone of therapy)
Vincristine
Human Immunoglobulin
Mycophenolate
Azathrioprine
Cyclosporine
Leflounomide
Acute management of ITP if normal PCV
Doxy
Pred
Gastroprotectancts
Cage rest
No jug sticks
Monitor PCV BID and plt count every 1-2 hours
Pt stable/released once unlikely to bleed/need blood production (PCV > 15,000-20,000)
Acute management of unstable ITP pt
Marked concurrent anemia 12-15%) while awaiting plt count increase (5-7 days)- multiple transfusions may be needed
Vincristine
Human IVIG
How do glucocorticoids help with ITP
At immunosuppressive doses:
-downregulate Fc receptor expression on macs
- decrease Ig affinity for red blood cell
- suppress T cell function
- induce apoptosis of T cells
- B cell Ab production may be inhibited
Results in phagocytosis
How does vincristine work for ITP
Premature release of plts from marrow
How does human IVIG work for ITP?
Temporary blockade of Fc receptors of phagocytes
How does Mycophenolate mofetil work for ITP?
Inhibits inosine-5’-monophosphate
dehydrogenase (enzyme resp for synth of guanosine nucleotides); high levels in activated lymphocytes
-Leads to depletion of guanosine
-Rapid onset of action (2-4 hours for max
enzyme suppression)
What does long term monitoring for ITP look like?
Continue prednisone at immunosuppressive dose until platelets are normal for 2 weeks.
-If no response in a stable patient within 7-14 days add another immunosuppressant (mycophenolate, other)
- Taper prednisone over 2-4 months once platelets are normal (25% reduction every 2 weeks)
- Recheck platelet counts while tapering prednisone (ie every 2 weeks)
- If there is a decrease in platelets -> increase prednisone
