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NAPLEX > Thromboembolism > Flashcards

Thromboembolism Flashcards

1
Q

Virchow’s Triad

A

Vascular Injury
Venous stasis
Hypercoagulable state

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2
Q

Non pharmacological intervention for VTE

A

External pneumatic compression
Graduated compression stockings
Venous foot pumps

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3
Q

Unfractionated Heparin

A

Mech: heparin catalyses the inhibition of thrombin (followed by warfarin therapy)

UFH catalyzes inactivation of thrombin (factor-IIa), activated factor Xa, activated factor IXa by antithrombin

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4
Q

Monitoring of UFH

A

aPTT (activated partial thromboplastin time)
First before therapy
Tgen monitored after 6 hr of commencing therapy
Dose adjustment on base of results

aPTT ratio= measured value / mean normal lab value aPTT

Therapeutic effects are achieved at a ratio of 1.5 to 2.5 for most
Varies for different reagents

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5
Q

Oral Anticoagulant

A

Warfarin
Vit-K antagonist

Interferes with cyclic conversion of vit K & it’s 2-3 epoxide (vit k epoxide)
Depletiin of vitKh2 results in haemostatically defective coagulation protein

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6
Q

Warfarin fun facts

A

Racemic mixture
Rapid GI absorption
Reaches max level in blood in 90 min
Patient in warfarin shouldn’t take green leafy veg (vit k)

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7
Q

INR

A

International Normalized Ratio= (observed PT / normal PT) ^ISI

Isi international sensitivity index= measure of responsiveness of a given thromboplastin to reduction of Vit k dependant coagulation factors

Normal value 2.0 to 3.0
For mechanical prosthetic valves & Anterior Myocardial infarction to prevent recurrent infarction range is
2.5 to 3.5

Low INR means blood is thick(coagulates easily)
High INR risk of bleeding

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8
Q

Warfarin Monitoring

A

INR once every week in the first 7 to 14 weeks

At week 15 till end of therapy monitor INR once every 4 weeks

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9
Q

LMWH

A

Prevention of venous thrombosis
Treatment of VTED
Management of unstable Angina /non Q wave MI

Daltaparin Fragmin. 6k Da
Enoxaparin Lovenox. 4.5k Da
Tinzaparin Innohep. 6k Da

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10
Q

LMWH chemistry

A

Fragments of standard commercial grade heparin by chemical or enzyme depolymerization

Almost 1/3rd the size of Heparin

Heparin MW 15k Da (3k to 30k)

LMWH 1k to 10k Da

Virtually all LMWH contain at least 18 sachharide units (or more)

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11
Q

LMWH

A

Mech: binding to antithrombin through a unique pentasaccharide sequence that enhances the ability of antithrombin to inactivate factor IIa (thrombin) and factor X

Binding ratio of heparin 1:1
Binding ratio of LMWH 2:1 or 4:1

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12
Q

Pentasaccharide synthetic

A

Fondaparinux (Arixtra)

Of DVT/PE after
Hip fracture surgery
Knee replacement surgery
Hip replacement surgery
Abdominal surgery

Treatment of acute DVT and acute PE

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13
Q

Fondaparinux mech

A

Selective factor Xa inhibitor
Inhibit blood coagulation cascade by inhibition of factor Xa

Does not inactivate thrombin so no effect on platelets

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14
Q

Fondaparinux contra

A 
Sever renal impairment
Patients weigh-in above 50kg when for prophylaxis
Patients with active major bleeding
Bacterial endocarditis
Thrombocytopenia
Hypersensitivity
Pregnancy lactation
Elderly

Protamine does not work as antidote

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15
Q

Oral factor Xa inhibitor

A

Rivaroxaban (Xarelto)
Elective hip or knee replacement surgery

Mech :
The antithrombin direct inhibition of factor Xa
Both free & clot associated factor Xa activity & has no direct effect upon platelets

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16
Q

Rivaroxaban elimination

A

Oxidative metabolism CYP 3A4 & hydrolysis & is eliminated 1/3rd by renal excretion, 2/3rd by hepatic metabolism
Elimination half life 5 to 9 hrs

17
Q

Rivaroxaban contra precautions

A

No INR necessary

Hypersensitivity
Drugs with CYP 3A4 metabolism and plama glycoprotein contra
Severe renal or hepatic impairment
Special care with neurexial anesthesia or spinal puncture

18
Q

CYP 3A4

A

Inhibitors:
Azole antifungal
HIV protease inhibitors (ritonavir)

Inducers:
Rifampicin
Phenytoin
Carbamazepine
Phenobarbital
St. John's Wort (Hypericum Perforatum) plant
19
Q

Oral direct Thrombin inhibitir

A

Thrombin (factor IIa) inhibitor
Dabigartan (Pradaxa)

Directly selective inhibition of factor IIa

Conjugation metabolism in liver
Elimination half life 12 to 7 hrs

20
Q

Contra for dabigartan

A 
Hypersensitivity
Bleeding risk
NSAIDs
P-gp inducers rifampin 
Care with nurexial anesthesia spinal puncture

NAPLEX (6 decks)

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