Thrombosis Flashcards
describe consequences of thrombosis and thromboembolism
- obstructive shock: due to
-impaired regional oxygen delivery
-impaired blood flow - organ dysfunction/failure
-primarily microthrombosis - complicates therapy:
-catheter associated thrombosis
describe diagnosis of thrombosis
- physical exam
-one extremity colder than the others
-ischemic muscles are painful and hard (ischemic myopathy)
-thrombophlebitis characterized by warmth and swelling over vein, usually at site of prior venipuncture or catheter
-acutely painful abdomen: thrombosis of GI tract - signs of organ failure:
-pulmonary thromboembolism characterized by acute onset dyspnea
-acute kidney injury
-hepatic injury
-stroke or other acute neuro dysfunction - sudden death may occur from massive thrombosis
- ultrasound or other imaging (CT) may ID thrombi in situ
describe virchow’s triad of hypercoagulability
- endothelial damage/dysfunction
-alterations of glycocalyx exposing procoagulant triggers: due to inflammation, fluid therapy, or direct injury
-release of vWF: from activated endothelial cells
- hypercoagulable state: either
-increased procoagulant proteins: due to sepsis, inflammation, post-surgery (fibrinogen increase), hyperadrenocorticism, heritability
OR
-decreased anticoagulant proteins: sepsis, inflammation, loss (GI, renal)
- blood stasis/alterations in blood flow
-activation of intrinsic pathway: decreased or abnormal blood flow
-intravascular foreign material: negative charge or biofilm production
describe arterial versus venous thrombosis
- arterial clots are white clots
-predominantly composed of platelets = white
-activated/tickled with high shear blood flow
-antiplatelet agents as primary therapy - venous clots are red clots:
-low pressure/venous stasis
-rich in fibrin and erythrocytes = red
-anticoagulant agents as primary therapy
related cardiac disease to thrombosis
- feline cardiac disease:
-left atrial dilation, spontaneous echocontrast, reduced left atrial appendage velocity are all risk factors
-thromboembolic sequelae primarily: arterial thromboembolism (ATE)
- heartworm/ pulmonary artery thrombosis
-worm thrombus versus clot; both are bad - transvenous pacemakers: uncommon but can cause clot formation on lead
relate immune mediated hemolytic anemia to thromboemboli
- strongly associated with thrombosis in dogs!!!
- anticoagulation is standard component of therapy
- risk factors include:
-severe inflammatory response: high fibrinogen, decreased antithrombin, RBC membranes in circulation (good spot for clotting factors to set up)
-CSA therapy
-IV access
-multiple blood transfusions
describe protein losing conditions and thromboemboli
- protein losing nephropathy:
-associated with thrombosis
-presumably due to loss of antithrombin - protein losing enteropathy
-loss of proteins including antithrombin
-small and large animals
relate glucocorticoids and hyperadrenocortism to thrombosis
- treatment with corticosteroids is associated with hypercoagulable state
- hyepradrenocorticism (dogs)
-may favor hypercoagulable state
-considered to be a risk factor
-elevated: factors II, V, VII, IX, X, XII, fibrinogen, thrombin-antithrombin complexes, antithrombin
relate infectious disease to thrombosis
primarily due to causing inflammation!
- dogs with depsis without coagulopathy are at risk of thrombosis
- small subset of cats with sepsis
- neonatal sepsis: foals, presence of coagulopathy worsens prognosis
- EHV-1 infection in adult horses: vasculitis, thrombosis leads to myeloencephalopathy
relate equie gastrointestinal disease to thrombosis
- jugular thrombophlebitis or other thrombosis
-ischemic/strangulating GI lesions
-colitis
-duadenitis/proximal jejunitis
-right dorsal colitis - jugular thrombophlebitis more likely in horses with surgically treated colic that develop fever or diarrhea
- salmonellosis is also a risk factor
- thrombosis may initiate at venipuncture site or on catheter
relate neoplasia, cerebrovascular disease, pancreatitis, and extracorporeal circuits to thrombosis
neoplasia:
-carcinomas in dogs associated with risk
cerebrovascular disease: may result from thrombotic event rather than cause one
pancreatitis: dogs
extracorporeal circuits (dialysis): activates coag during treatment
relate vascular access/devices to thrombosis
transvenous pacemaker leads
IV catheters:
-central lines
-catheter-associated thrombi generally in patients with severe inflammation
-catheter alone not usually a risk factor
when are anticoagulant drugs indicated?
- in animals with existing thrombi/thromboembolism
- in animals with a single strong risk factor
- animals with multiple moderate risk factors
- ALWAYS indicated for dogs with IMHA and cats with heart disease
describe anticoagulant drugs
- no clear evidence of one superior drug
- include antiplatelet, antithrombotic, and fibrinolytic drugs
describe clopidogrel (plavix)
- P2Y12 ADP receptor inhibitor:
-decreases degree of platelet aggregation
-decreases platelet activation state - prodrug:
-requires hepatic conversion
-P450-dependent so individual variability - irreversible block of receptor!
-will stay blocked for platelet life (approx 5 days, so need 7 days after stopping drug to return to full platelet function, more like 3 days clinically bc bone marrow always making platelets) - effective in dogs, cats, and horses
-dogs: rapid onset
-horses: variable onset and termination
