Hematology

Question 1

International Normalized Ratio (INR)

Answer 1

• INR = (PT test) / (PT normal)

- Therapeutic range with anti-coagulants = 2-3. (Exceptions: mechanical mitral valve = 2.5-3).

Question 2

Prothrombin Time (PT)

Answer 2

• Measures extrinsic + common pathways - factors I (fibrinogen), II (prothrombin), V, VII, and X

Question 3

Activated Partial Thromboplastin Time (aPTT)

Answer 3

• Measures intrinsic + common pathways -

Question 4

Clotting Cascade

Answer 4

-

Question 5

Hemophilia

Answer 5

A

B

Question 6

Anticoagulants - Warfarin

Answer 6

MOA
- Antagonizes effect of vit K –> dec coagulation (vit K dependent factors = 2, 7, 9, 10, protein C + S)

Adv
- Can reverse immediately, cheap, can use for mechanical heart valves

Diasdv
- Dependent on vit K in diet/ gut, needs high INR monitoring, narrow therapeutic range, high drug interactions, also reverses vit K anti-coagulant proteins (C, S, Z), effect is slow to start (depends on ½ life of the circulating clotting factors), initially causes a hypercoagulable state (GIVE HEP first), teratogenic during 1st trimester

• Monitored with PT/ INR
• Efficacy dec by: green leafy vegetables (Vit K), fresh frozen plasma (FFP), or prothrombin complex concentrate (PCC)
• Continue for at least 3 mos after an event

Question 7

Anticoagulants - Std/ Unfractionated Heparin

Answer 7

MOA
- Binds to anti-thrombin 3 and dramatically inc its effect (inactivation of 2a, 11a, 9a, 10a), then dissociates and binds to another one.

Adv
- Used in renal failure, morbidly obese, open heart surgery, and when you need to start + stop quickly (effect is pretty immediate)

Diasdv
- Narrow therapeutic range, mix of ingredients predictability

• Monitored with aPTT
• Monitor platelet counts at least every 2nd day for HIT

Question 8

Anticoagulants - Low Molecular Weight Heparin (LMWH)

Answer 8

MOA
- Conformational change in the active site binding loop of anti-thrombin, specifically inhibiting factor 10a.

Adv
- Just based on weight (until a max) so not monitored, more predictable, reach therapeutic goal faster, wider therapeutic range, longer ½ life (less x/day)

Disadv
- Contraindications (renal failure, etc), $

• Monitored with anti-Xa assay if needed (little affect on aPTT)
• After an event, continue heparin until the INR has reached its target range (2-3) for >2 days, with a min of 5 days of heparin.
• Ex: daltaperrin