CVT Critical Care Flashcards
(74 cards)
What is Virchow’s Triad?
endothelial damage, alterations in blood flow, hypercoagulability
What occurs with arterial thrombosis?
High shear = Large # platelets, held by fibrin strans (Tx: Inhibit further arterial thrombogenesis)
What occurs with venous thrombosis?
Low shear = Fibrin and RBCs (Tx: Anti-coagulants)
What is the MOA of Aspirin?
irreversible acetylation of platelet COX site = decreased TxA2 synthesis ? TxA2 (produced by activated platelets) ? platelet aggregation and stimulates activity of new platelets via increased GPIIb/IIIa expression on platelet membranes
? Permanent effects lasting the lifetime of platelets (7-10days)
What is the MOA of clopidogrel?
? Thienopyridines: ADP receptor antagonists
? Irreversible inhibition of ADP binding to specific ADP receptors (P2Y12) on platelet membranes
? Impairs platelet release reaction and ADP-mediated activation of GPIIb/IIIa
What is the MOA of Fibrinogen receptor antagonists?
? Glycoprotein GPIIb/IIIa Blockers: fibrinogen receptor antagonists
? Abciximab (monoclonal Ab that binds to receptor) and eptifibatide (competitive memetic of fibrinogen)
? Abciximab + aspirin in cats = decreased thrombus formation compared to aspirin alone
? Eptifibatide causes circulatory failure and death in cats = BAD
? Activation of GPIIb/IIIa final common pathway of platelet aggregation (regardless of the initiating stimuli)
? Inhibit fibrin binding to GPIIb/IIIa
What is the goal of an anticoagulant?
Inhibit generation of fibrin
What is the MOA of warfarin?
Coumadin ? Vitamin K antagonist altering synthesis of K-dependent coagulation factors (II, VII, IX, X, protein C and S
? Interferes with hepatic reductase activity = impaired post translational carboxylation
? Delayed anticoagulant activity (4-5 days)
? Inactive clotting factors replacing previous functional counterparts
? Rapid inhibition of protein C and S = transient period of hypercoagulability in humans (not documented in vet med)
How do you measure warfarin tx?
Measure PT and calculate INR (International Normalized Ratio)
Goal: INR = 2-3
Why do you need to administer heparin when starting warfarin?
With rapid inhibition of Protein C and protein S = hypercoagulbility but other vit k dependent coag factors not affected for 4-5 days - thus heparin to prevent hypercoagulability that may be seen
Which 2 factors are most responsive to inhibition by antithrombin?
Iia (thrombin) and Xa
How does heparin bind to antithrombin?
Via high affinity pentasaccharide sequence
What is unfractionated heparin?
Glycoaminoglycan that binds to antithrombin and then bind to inactivate factor Xa and about 1/3 are able to bind to and inactivate thrombin (Iia)
What are the effects of unfractionated heparin and how are they monitored?
Unpredictable effect! Binds to plasma proteins Check PTT (1.5-2.5X baseline PTT)
What is low molecular weight heparin?
Depolymerization of unfractionated heparin = Smaller
100% binds to antithrombin and that binds to and inactivates factor Xa (DOES NOT bind to thrombin)
What are the effects of low molecular weight heparin and how are they monitored?
More predictable
Check with Anti-Xa levels
Name the 5 types of shock.
? Hypovolemic: decreased circulating blood volume
? Hemorrhage, dehydration, trauma
? Can include ?relative hypovolemia? = GDV, tamponade
? Cardiogenic: decreased forward flow
? Congestive heart failure, arrhythmias, tamponade, drug OD
? Distributive: loss of systemic vascular resistance
? Sepsis, obstruction, anaphylaxis
? Metabolic: deranged cellular metabolism
? Hypoglycemia, cyanide, mitochondrial dysfunction, cytopathic hypoxia of sepsis
? Hypoxemic: decreased O2 content in arterial blood
? Anemia, severe pulmonary disease, CO toxicity, methemoglobinemia
What are considered to be the 3 stages of shock?
Compensatory, Early Decompensatory, Late Decompensatory
Why do some cats in shock present with respiratory dysfunction?
The lungs are the shock organ in the cat
What is SvO2?
Mixed venous O2 saturation = Assessmen of global tissue oxygenation
What is ideal to maintain SvO2 (from jug cath)?
About 70%
How do hypertonic solutions work?
? Hypertonic Solutions: 7% NaCl: osmotic shift of water from extracellular to intracellular
? Transient volume expansion (<30 mintes), follow with crystalloids
? 5ml/kg over 5-10 minutes
? ?endothelial swelling, ?cardiac contractility, mild peripheral vasodilation, ?ICP
What are the labile coag factors that are not present in FFP?
Factor V, VIII, vWB (also no platelets)
What is the MOA of epinephrine?
? Potent pressor: mixed a/b activity
? Beta effects are variable between patients, but more potent compared to norepi
? May impair splanchnic blood flow = strong vasoconstriction in regional vasculature
? Inhibits mast cell and basophil degranulation= good for anaphylaxis