Clotting disorders

Question 1

Formation of thrombosis is explained by virchow’s Triad

which include…

Answer 1

damage to vessel wall
alateration in blood flow (stasis)
hypercoagulability of the blood

Question 2

Which VTE is more common and which VTE has more severe mortality?

Answer 2

DVT is more common

PE has higher mortality

Question 3

The risk factors of VTE are?

Answer 3

age, obesity, previous thrombosis, surgery, trauma, acute illness, long travel, coagulation abnormalities, drugs, HF (not pumping well), COC, superficial thrombophlebitis (veins near skin surface is inflamed), paralysis, hospitalisation, cancer

Question 4

What could lead to coagulation abnormalities?

Answer 4

lupus anticoagulant (antibodies against phospholipids),
protein C, S deficiencies
hyperhomocysteniaemia
high clotting factor levels

Question 5

What are the examples of drugs that increase VTE?

Answer 5

COC (3x risk)
HRT (2-4x risk)
chemotherapy
tamoxifen

Question 6

VTE prophylaxis Tx options are:

Answer 6

Heparin - inhibit 2a, 10a
LMWH (Fractionated) - inhibit 10a
factor 10a inhibitors
direct thrombin inhibitors

Question 7

Explain about heparin

Answer 7

no need for dosage reduction renal impairment (ONLY ONE)
SC injection
ADE: thrombocytopenia (decrease in platelets)

Question 8

Explain HITS

Answer 8

TYPE 1: first few days, platelets stay over 100
they are transient and reversible BUT
TYPE 2: YOU NEED TO STOP HEPARIN
platelets are less than 100
by heparin + antibodies complex and aggregate platelets

Question 9

What is an example of LMWH and explain its use

Answer 9

eg. enoxaparin
decrease dose in renal impairment
SC injection OD

Question 10

What are examples of factor 10a inhibitors?

Answer 10

fondaparinux,

apixaban, rivaroxaban

Question 11

How should you use factor 10a inhibitors in renal impairment?

Answer 11

AVOID

if CrCl is less than 30, 25, 15mL/min

Question 12

What is an example of direct thrombin inhibitors?

Answer 12

dabigatran

Question 13

How should you use direct thrombin inhibitors in renal impairment?

Answer 13

avoid if CrCl is less than 30

Question 14

What is the difference between arterial and venous thrombi?

Answer 14

venous trombi: low flow and low shear stress on the wall
mainly fibrin strands, RBC and FEW platelets
whereas
arterial thrombi: high flow, high shear stress, platelet rich

Question 15

What are the non-drug tx options of VTE prophylaxis??

Answer 15

foot pump, intermittent pneumatic compression, graduated compression stockings

Question 16

What are the tx options of DVT?

Answer 16

Heparin or LMWH (enoxaparin) + Vitamin K antagonist (Warfarin) or
Heparin + DTI (direct thrombin inhibitors) (dabigatran)
or 10a inhibitors (fondaparinux, rivaroxaban, apixaban)

Question 17

What is the difference between heparin and LMWH?

Answer 17

heparin needs monitoring (aPPT), LMWH does not need monitoring

Question 18

Vitamin K antagonists (Warfarin) act on which clotting factors?

Answer 18

2,7,9,10, protein C and S
factor 7 (anticoagulant effect) and protein C (procoagulant) half lives are very short 
but the rest vary from 20 to 100 (factor 2 - antithrombotic) hours so the full effect cannot be seen for about 3-4 days

Question 19

INR is very sensitive to which factor?

and less sensitive to which factors?

Answer 19

sensitive to factor 7

less sensitive to 2,5 and 10

Question 20

INR rises very quickly when..?

Answer 20

after commencement of warfarin

Question 21

how many days of overlap with heparin does warfarin need?

Answer 21

5 days

INR > 2 for 2 days

Question 22

Explain the onset of rivaroxaban

Answer 22

rapid Cmax 2-4 hours

Question 23

Does rivaroxaban need monitoring for DVT management?

Answer 23

No

Question 24

The duration of anticoagulation in different cases?

Answer 24

if: transient (risk factors): 3 months
if: idiopathic (no risk factors): 6-12 months
if: recurrent, cancer: indefinite

Question 25

Should i keep taking OC in VTE?

Answer 25

No, VTE risk increases

Question 26

S-warfarin is metabolised by CYP2C9 so CYP2C9 inhibitors can do what?
and what should you do?

Answer 26

it can increase warfarin concentration
and increase INR
very quickly

I should decrease the warfarin dose and monitor INR

Question 27

The risk of bleeding can increase in use of warfarin by?

Answer 27

antiplatelets, SSRI
NSAIDS
hypothrombinaemic effect

Question 28

What drugs are enzyme inducers?

Answer 28

anti-epileptic drugs, St Johns’ Wort

Question 29

What drugs are enzyme inhibitors?

Answer 29

azoles, antibiotics