Platelets Flashcards

Question

Tests for Platelet Function

Answer 1

Buccal Mucosal Bleeding TIme (BMBT) Clot Retraction - Test platelet function Platelet Aggregometry - GOLD Standard

Answer 2

* Indicator of primary hemostasis or platelet status * Spring-loaded cassette delivers percise cut * Avoids the hair and thick skin * May require anesthesia * Test reserved for patients adequate platelet concentrations but platelet function is questioned * BMBT especially useful in doberman pinschers * BMBT cannot be used to detect coagulopathies * hemophiliacs have normal buccal mucosa bleeding times * Dog: 1.5-4 mins * Cat: 1-2.5 mins

Answer 3

* Draw 0.5mls blood directly into plastic syringe contianing 4.5mls of cold saline * Mix gently * Dispense 2 mls of the mixture inot each of 2 glass tubes containing 0.1ml to 10 units/ml thrombin * Cap and mix the tubes. Place the tubes in a refrigerator for 30 minutes * Transfer tubes to a 37C water bath * Record the degree of clot retraction at 1 and 2 hours as 1+ to 4+

Answer 4

GOLD STANDARD the definitive means for evaluating platelet function Highly specialized and not readily available Testing must be completed within 4 hours of collection Platelets are stirred in front of a light source in a siliconized glass cuvette. Various agents are added to the cuvette and the ability of the platelets to respond is recorded on a strip chart recorder

Answer 5

* ~10 times more reactive than other species * Highly variable in size * Giant platelets are a common finding * Impedance hematology analyzers do not give accurate platelet concentrations * Cats with thrombocytopenia and bleeding usually have another underlying problem * Cats with FeLV infection may have any combination of platelet concentration and clinical signs

Answer 6

* Affects \>90% of Cavalier King Charles Spaniels in US * carrier of affected * Affected do NOT have clinical bleeding * Platelets between 30,000 and 100,000/uL * Heterozygotes have platelets concentrations between homozygote and unaffected * Mutation is the gene encoding beta 1-Tubulin * Identical or similar mutaions identified in other breeds * English toy spaniels, Shih tzu, matlese, jack russel terrier, havanese, toy poodles, boxer, cocker spaniels, bichon frise, miniature schnauzer, komondor, chihuahua, labrador retriever, norfolk and cairn terriers, and several crossbreed dogs * Misdiagnosis can lead ot inappropriate treatment with steroids and or antibiotics

Answer 7

* Immune-mediated * Drug-induced * Enhanced consumption * Virus-induced * Decreased production * Sequestration

Answer 8

Circulating platelts and/or megakaryocytes are destroyed by immune-mediated mechanisms: Platelets concentration is usually very low Confirmed by blood smear evaluation

Answer 9

* Primary or autoimmune * Secondary to immune-complex absorption or neoantigen expression * Incompatible transfusion

Answer 10

* Ehrlichia Canis * Anaplasma platys * Anaplasma Phagocytophilum * Rickettsia rickettsia (Rocky mountain spotted fever) Immune mediated clearance Decreased life-span Vasculitis-induced consumption

Answer 11

circulating platelets are destroyed by drug interaction

Answer 12

Drug-Dependent vs. Independent

Answer 13

Estrogen; antifungals; anticancer drugs; antibiotics; antivirals; and anti-inflammatory drugs

Answer 14

Pathological process characterized by the widespread activation of the clotting cascade that results in the formation of blood clots throughout the body Can occur secondary to any event that causes massive tissue damage: Septicemia Neoplasia Parasites Vasculitis Viruses

Answer 15

Myelophthsis/myelofibrosis Myeloproliferative disease Inflammatory disease

Answer 16

* most common inherited bleeding disorder in dogs, rare in cats, cattle, rabbits, pigs, and horses. Pigs are a common disease model * An extrinsic platelet function disorder * persentation is like taht of thrombocytopenia, however, platelet concentration is normal * Von Willebrand Factor is markedly reduced * decreased platelet adhesion * Diagnosed using ELISA to determin antigen levels * ALWAYS USE PLASMA\< NOT SERUM * DNA-based testing available for some breeds * Clot retraction test is normal * APTT is normal

Answer 17

Quantitative disorder Von Willebrand Factor is detectable but low Most common form of Von Willebrand Disease in Dogs Very common in Doberman Pinschers

Answer 18

Qualitative disorder Von Willebrand Factor multimers are altered Less common in domestic species

Answer 19

Quantitative Disorder Von willebrand factor is not detectable Rare in dogs Scotties, Shelties,, Chesapeake Bay Retriever

Answer 20

Prolonged bleeding at tail docking, ear cropping, or dew claw removal, spay/neuter are common +/- mucosal bleeding primarily manifested by gingival bleeding, epistaxis, and hematuria Many dogs that carry this disease in thier genetic makeup go undetected until a minor surgery or small, superficial injury results in significant blood loss

Answer 21

* vWF antigen: * EDTA or cirtrated Plasma * do NOT let the sample clot * Clotting will result in vWF incorporated into clot * DNA test

Answer 22

* Glanzmazz thrombasthenia * CALDAG-GEFI thrombopathias * basset hound thrombopathia * Spitz thrombopathia * Landseer-ECT thrombopathia * Bovine Thrombopathia * P2Y12 ADP receptor defect * LAD-III syndrome * Cycline Hematopoiesis * CHediak-Higashi syndrome * Dense Granule Defect * Scott syndrome

Answer 23

Inherited disorder described in otterhounds, Great pyrenees, and horses Clot retraction is absent Clinical Signs: Platelets type bleeding Chronic epistaxis, gingival bleeding

Answer 24

Mutations in the gene encoding calcium diacylglycerol regulated quanine nucleotide exchange factor 1 resulting in signal transduction abnormalitity DNA testing available at Auburn University * Clinical Signs: * epistaxis, gingival bleeding, petechiation, hematuria, excessive bleeding with minor procedures * Platelet, vWF, coagulation screening assays – normal * Defect of signal transduction resulting in decreased binding of platelets to fibrinogen * Thrombin-induced aggregation – extent normal, but rare impaired. Clot retraction – normal

Answer 25

autosomal recessive Abnormal leukocyte, melanocyte, and platelet granulation Platelets do not form tight aggregates in response to ADP Prolonged bleeding at incision sites, and the development of hematomas following venipuncture

Answer 26

Autosomal recessive grey collies Cyclic fluctuations in neutrophils, reticulocytes, and platelets Neutropenic episodes occurring approximately every 12 days Mortality is high, most puppies die prior to 6 months of age due to fulminating infections Platelet numbers usually do not decline below the normal range and fluctuate between 300,000 and 700,000/uL Platelet reactivity is defective Platelet dense granules are absent Clot retraction and platelet adhesiveness are impaired

Answer 27

~60% of the dogs tested are wither Carriers or Affected for the mutation The gene pool is small, prevalence is likely high, be careful Carriers have been reported to have clinical signs **Clinical signs of bleeding in affected or carrier dogs are not recognized unless they are challenged with significant trauma or surgery** Most common reports have described severe bleeding following routine spays/castrations; many die

Answer 28

When platelets become activated they express a negatively charged surface due to the flip-flop of negatively charged phosphatidyl serine Negatie surface required for assembly of coagulation factors A platelet disorder wiht clinical signs more typical of a coagulopathy German Shepherd Dogs Rare

Answer 29

Platelets are normal. A protein necessary for platelet function is either absent, reduced, or dysfunctional.

Answer 30

Platelets are abnormal Abnormalities may be related to granules, membrane glycoproteins, signal transduction proteins

Answer 31

Seen in cavalier king charles spaniels and other breeds Does not result in clinical bleeding NO TREATMENT NECESSARY

Answer 32

Viral accumulation in cytoplasm of megakaryocytes resutls in infection of platelets Thrombocytopenia, thrombocytosis or function defects may result

Answer 33

Drugs can impair platelet funciton by inhibiting receptor binding agonists, by inhibiting transduction of messages or by inhibitinng response Drug-induced impairment is usually not clinically significant unless coupled with another underlying disorder or the patient requires surgery

Platelets Flashcards

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