Pro & Anticoagulants Flashcards
4 locations that constitute “major” bleeding:
1) intracranial
2) intraspinal
3) intraocular
4) mediastinal
Risk factors for bleeding while on anticoagulation:
- anti-coagulation effect (long half-life, no great tests)
- increased age
- female
- hx of GI bleed
- use of ASA with other anticoagulation
3 As of platelet plug formation:
- adhesion
- activation
- aggregation
How is primary hemostasis defined?
any disruption in endothelium
Adhesion is dependent on what?
von Willebrand’s factor (vWF)/Factor III
How does vWF work and where is it synthesized?
- acts as a bridge; one end attaches to the PLT and the other to the damaged tissue
- synthesized and released from endothelial cells
Which clotting factor is not made in the liver?
vWF (localized in the endothelial cell)
MOA of Desmopressin/DDAVP:
- stimulates large release of vWF from the endothelium (adhesion)
- shortens bleeding time in patients with mild hemophilia A or VWD (quantitative issue)
Desmopressin is most effective in which types of VWD?
type I and III (quantitative issues)
Dose of desmopression:
0.3mg/kg over 15-30 min to avoid hypotension
Describe what happens during the activation stage of clot formation:
- thrombin combines with a thrombin receptor on PLT surface
- PLT changes shape and releases mediators that promote aggregation (adhesion)
- these important mediators = ADP and Thromboxane A2
MOA of theinopyridine derivatives:
antiplatelet effect results from the inhibition of ADP-induced PLT aggregation
Most common theinopyridine derivative:
Clopidogrel (Plavix)
- irreversible - lasts the life of the PLTs
When should Plavix be d/c’ed prior to surgery? The other drugs of this class?
Plavix - 7 days
other drugs - 2-3 days
MOA of cyclooxygenase inhibitors:
inhibit PLT cyclooxygenase and prevent the synthesis of thromboxane A2 (activation)
What substance triggers the formation of thromboxane A2?
Thrombin A2
Which drugs are considered cyclooxygenase inhibitors?
- ASA
- NSAIDS
- Celebrex (COX-2 inhibitor)
Pre-op recommendations for COX inhibitors?
ASA - 7-10 days
NSAIDs - 1-2 days
- COX-2 inhibitors take as scheduled
After the 3 steps of primary hemostasis, the clot remains (lipid/water) soluble until activated by ____.
water soluble until activated by fibrinWhat
What are the 2 major parts of the 3rd step in primary hemostasis?
1) ADP and thromboxane A2 uncover fibrin receptors (GPIIb/IIIa)
- fibrin links PLTs together
(this is all part of aggregation)
MOA of GPIIb/IIIa inhibitors:
inhibit PLT aggregation by interfering with the PLT-fibrin receptors (GPIIb/IIIa)
Most common GPIIa/IIIb inhibitor:
Reopro (abciximab)
Reopro should be stopped ___ days/hours before surgery
3 days
(others in this class need just 1 day)
What is the key player in secondary hemostasis?
fibrin
Describe the events of secondary hemostasis:
- fibrin production incorporates all clotting factors
- after PLT aggregation, fibrin is woven into the PLTs, they are crosslinked and insoluble in water
What is a major factor in secondary hemostasis?
thrombin activation
Which clotting factors are Vitamin K dependent?
2, 7, 9, 10
Prothrombin
Stable
Christmas Factor
Stuart Prower Factor
Most clotting factors are produced in the _____ except:
liver
except: Factor III (vWF) produced in the endothelium and Factor IV (Calcium) which is taken from the diet
MOA of coumadin:
- binds to the Vitamin K receptors in the liver and competitively inhibits Vitamin K
- depresses production of Vitamin K dependent clotting factors
Lab tests to monitor coumadin levels:
PT & INR
When to stop coumadin prior to procedure:
5 days & may need bridging depending on reason for taking it and risk for clotting if they stopped