Pharm 15- Procoagulants/Antifibrinolytics Flashcards
Protamine
small protein that’s critical in maturation of sperm; stronly cationic protamine forms stable soluble salt w/ strongly anionic heparin
What ratio does protamine bind with heparin?
1:1; so for every 100 units of heparin 1 mg of protamine should effect heparin reversal
What happens to the coagulation pathway when Heparin: Protamine complex is formed?
Does not effectively interact with ATIII so the coagulation pathway continues unimpeded
What type of drug is protamine by itself? How does it work?
An anticoagulant; decreases thrombin generation by inhibiting Factor V activation
Why are dosing heparin/protamine protocols not 1:1 then?
Protamine is eliminated rapidly from the plasma (faster than heparin) so dosing protocols of 1.1:1.0 to 1.3:1.0 protamine: heparin have been developed
How is protamine administered? How fast is onset of action?
Parenterally, rapid onset of action <5 minutes
What is the median half-life of protamine?
5 minutes
What is the median half-life of heparin?
1-2 hours
What is the metabolic fate of the protamine:heparin complex?
Has not been completely elucidated. One possibility is that some of the complex is degraded by fibrinolysin which would liberate free heparin
Heparin Rebound
Give your dose of protamine, ACTs normalize, over time it appears that increased bleeding happens often over hte course of minute to ~5 hours
What are some theories to explain heparin rebound?
Free heparin released from the protamin:heparin complex; heparin’s variable half-life outlives protamine’s ~2 hour clinical effect; heparin from tissue stores, too much reversal protamine given; or it doesn’t exist and its a proline deficiency
What’s a more effective way of dosing protamine to prevent post-op bleeding?
Smaller initial doses of protamine with well-regulated, well-calculated post-bolus infusions are a more effective way to prevent post-op bleeding
Protamine is a component of what type of insulin?
Neutral Protamine Hagedorn
What are some other uses of protamine?
Only partially/unpredictably reverses LMWH (which sort of limits LMWH’s use)
No effect on fondaparinux
What are some precautions and problems of protamine?
- Protamine is an anticoagulant
2. Protamine rxns
What are some contributing factors to protamine reactions?
Rapid administration
Sensitization to protamine
What are some reasons a pt would have sensitization to protamine?
Redo Surgeries Fish allergies Diabetics Vasectomy Excessive dosage
Protamine Reactions
Clinically manifest themselves as anaphylaxis and extreme hypotension, pulmonary hypotension, and CV collapse
Often necessitates crashing back on CPB
How are protamine reactions minimized?
Slow administration
Intra-aortic administration
Administration with steroids and antihistamines
Vitamin K
Fat soluble vitamin
Vitamin K is essential for the production of what factors?
Factors II, VII, IX, X
What are the two types of Vitamin K?
- K1: Phytonadione (Mephyton)
2. K2: Menaquinone
Where can you get K1: Phytonadione?
Green leafy vegetables
Supplemented
Where can you get K2: Menaquinone?
Meat, poultry, eggs, butter
How is Vitamin K related to VAD patients?
Destination vad and now theyre on warfarin; infections and bleeding problem kill cad patients (either too much or too little)
What is the more clinically relevant form of vitamin K to perfusionists?
K1
How much vitamin K is given for warfarin overdosage?
1.0-2.0 mg of K1 is given by injection; this dose will lower the PT but not completely eliminate the desirable warfarin effects
How must Vitamin K be given?
SLow IV (anaphylaxis is a common side effect); requires at least 6 hours to be effective
What is the typical FFP dose for warfarin overactivity?
15ml/kg
What are two antifibrinolytics?
Aminocaproic Acid (EACA, Amicar) Tranexamic Acid (Cyklokapron, Lysteda)
What are the two antifibrinolytics derivatives of? How do they work?
Synthetic derivatives of the amino acid lysine; both prevent plasminogen activation and directly inhibit plasmin which prevents fibrinolysis; both significantly reduce post bypass hemorrhage espeically in patinets who have received previous fibrinolytic therapy
What is the difference between Aminocaproic Acid (Amicar) and Tranexamic Acid (Cyklokapron, Lysteda)
Tranexamic acid is 10x more potent than EACA
How are both fibrinolytic durgs cleared?
Renally
What percent are fibrinolytics used as part of the pump prime?
85%
How much Amicar is typically added to the pump?
5 or 10 grams
What is an example of a serine protease inhibitor?
Aprotinin (Trasylol)
How does Aprotinin (Trasylol) work?
Blocks plasmin and dose other ill-defined stuff to prevent post-op bleeding
What are the benefits of using aprotinin (Trasylol)?
Dramatically reduces post-op blood loss
Particuarly in redos, jehovah’s witnesses, post fibrinolytic therapy
What are the side effects of aprotinin (trasylol)?
Kidney failure
heart attacks
strokes
When was aprotinin (trasylol) pulled from the market?
2007
What is aprotinin (trasylol) currently avaiable for?
Investigational use
compassionate use
What is Desmopressin (DDAVP)
Synthetic form of ADH or vasopressin, a small protein
How does Desmopressin (DDAVP) compare to vasopressin?
Desmopressin has much less pressor activity than vasopressin
How does Desmopressin work?
Causes the release of vWF from vascular endothelium which increases Factor VIII and Factor XII activity; causes platelets adhesiveness to increase in patients with platelet dysfunction secondary to uremia or hepatic dysfunction
What is Desmopressin useful for?
Mild Hemophilia A and vWF disease
What forms is Desmopressin found in?
Many forms including nasal spray
Describe the research and use of DDAVP
No research that indicates the use of DDAVP for bleeding post-bypass decreases the use of blood products; may be somewhat beneficial when administered in advance
What are two blood products?
Fresh frozen plasma (FFP)
Cryprecipitate (Cryo)
How is FFP formed?
Plasma is separated from whole blood and stored at <0 degrees F within 8 hrs of donation
What is FFP often given for post bypass?
Bleeding
FFP is preferably given with what?
ABO cross-matching
What equipment may alter the use-habits of FFP in the future?
TEG
FFP contains which factors?
I, II, V, VII, IX, X, Xi, XIII, At-iii and proteins C and S
What is FFP used for?
Bleeding; immediate warfarin reversals
atiii deficinecy
large volumes of PRBC administration
colloidal volume replacement
What dose of FFP will raise a pt’s atiii levels how much?
20ml/kg of FFP raises a patient’s ATIII by 20%
Cryprecipitate is derived from what?
Precipitate that forms after FFP is thawed nad centrifuged
How is cryo usually given?
as a pooled (4-6 units) product but abo cross-matching is considered desirable
What is cryo used for?
Factor I, VIII , and vWF replacement; but levels of viii and vwf are iffy and cryo is not treated in any way to decrease the risk of viral exposure
How much is 1 unit of cryo in mls?
15 mls
15 mls of cryo is how much fibrinogen
250-350 mg fibrinogen