Anticoags Flashcards
heparin binds to what enhancing the formation of what complex?
antithrombin; thrombin-antithrombin complex
by how many range of times does heparin enhance thrombin-antithrombin complex formation?
1,000-10,000
antithrombin not only binds to thrombin (factor IIa), but also what other 4 factors?
IX, Xa, XI, XII
by binding to these factors, what does antithrombin do to them?
removes them from circulation
heparin also inhibits the function of what?
platelets
in one word, what is the IV onset of heparin?
immediate
what is the range of hours onset of subcutaneous heparin?
1-2 hours
Is heparin highly charged or highly uncharged and acidic or basic?
highly charged acidic molecule
is heparin highly or poorly lipid soluble?
poorly
since heparin is poorly lipid soluble, is it poorly or highly absorbed in the GI tract?
poorly
IM heparin is avoided d/t the possible formation of what?
hematoma formation
does heparin have a high or low molecular weight?
high
does heparins elimination half life increase or decrease with body temp below 37 degrees celsius?
decrease
heparin elimination is prolonged in what 2 organ dysfunctions?
liver, kidneys
is the dose response relationship of heparin linear?
no
does the anticoag response to heparin increase proportionately or disproportionately in intensity and DOA as dose increases?
disproportionately
what are the 4 reasons for the disproportionate anticoag responses to heparin? (TNOA, T, HCNOHWCPB, VOAR)
the need of antithrombin, temperature, highly charged nature of heparin which causes protein binding, variability of anticoag reponses
dose response example of heparin:
- 100 units/kg IV = what elimination half life in minutes?
- 400 units/kg IV = what elimination half life in minutes?
- 56 minutes
2. 152 minutes
Heparin is ued to prevent and treat what 3 things? (VS, PE, ACS)
venous thrombosis, PE, acute coronary syndrome
heparin is also used for what 2 siutations? (ECC, H)
extracorporeal circulation, HD
IV heparin needs to be discontinued within what hour range before surgery?
4-6 hours
what are the 2 types of heparin induced thrombocytopenia? (M, S)
mild, severe
Mild HITT:
- occurs what % range of the time?
- plts are less than how many?
- d/t what induced plt aggregation?
- seen between hours to what day range after initial dose?
- 30-40%
- <100,000
- drug induced
- 3-15 days
Severe HITT:
- occurs what % range of the time?
- plts are less than how many?
- resistant to effects of what drug?
- seen what range of days after heparin administration?
- can thrombotic events occur?
- d/t the formation of heparin dependent antiplatelet whats?
- what should be discontinued immediately?
- 0.5-6%
- <50,000
- heparin
- 6-10 days
- yes
- antibodies
- heparin
what is the most common AE of heparin?
hemorrhage
what are the 3 coag evals for heparin?
aPTT, Anti-Xa heparin assay, activated clotting time
for heparin treatment we want the aPTT to be what range of times larger than the predrug value?
1.5-2.5 times larger
what is the usual aPTT predrug value in range of seconds?
30-35 seconds
why have some labs switched to anti-Xa heparin assay with low dose heparin regimens instead of aPTT?
aPTT has variable responses
Activated clotting time (ACT):
- used for lower or higher doses of heparin?
- used for heparin > how many units per mL?
- used for what 2 procedures? (CB, CCL)
- best if measured at what 2 instances and every how many minutes thereafter?
- what is the target seconds range?
- higher
- > 1 units/mL
- cardiopulmonary bypass, cardiac cath lab
- pre-heparin, 3-5 minutes after; every 30 minutes thereafter
- 350-400 seconds
what are the 5 things that affect ACT? (H, H, T, CAI, CD)
hypothermia, hemodilution, thrombocytopenia, contact activation inhibitors (aprotinin), coagulation deficiencies
what drug is used to reverse heparin?
protamine
what does protamine work?
it’s positively charged alkaline so it combines with the negatively charged acidic heparin yielding a stable complex devoid of anticoag activity
how many mg of protamine for every 100 units of circulating heparin?
1 mg
why do ppl overdose protamine?
because they dose it based on the initial heparin given
protamine:
- what is its clearance in minutes?
- is clearance more or less rapid than heparin’s?
- what is heparin’s half life? (hours)
- may see heparin rebound which will require a smaller dose of what?
- 20 minutes
- more rapid
- 1 hour
- protamine
Protamine:
- what are two AEs?
- release of what causes hypotension?
- allergic reactions most often occur in pts who had this procedure and who are on what insulin?
- hypotension, pulm HTN
- histamine
- vasectomy, NPH
LMWH:
- what are the 2 uses? (T, ACS)
- stop at least how many hours before surgery and even longer in pts with what dysfunction?
- does protamine neutralize?
- increase chance of hematomas in what 2 areas with LMWH?
- how should you hold LMWH before doing a spinal or epidural block?
- thromboprophylaxis, acute coronary syndrome
- 12 hours, renal dysfunction
- no
- spinal, epidural
- 24 hours
LMWH:
- what are the 3 drugs? (F, E, D)
- what 2 are derived from UFH?
- which one is synthetic?
- Both heparin derivatives are more consistent between pts than heparin because they bind less avidly to what?
- in what pt population is LMWH’s effect so prolonged that UFH should be used?
- fondaparinux, enoxaparin, dalteparin
- enoxaparin, dalteparin
- fondaparinux
- protein
- renal failure