Midterm Refresher: Coagulation Cascade

types of arterial thrombosis

Myocardial infarction, stroke

what plays a major role in arterial thrombosis

platelets play a major role

examples of venous thromboembolism

deep vein thrombosis, pulmonary embolism, portal/hepatic vein thrombosis

what plays a major role in venous thromboembolism?

clotting factors and clotting cascade play a major role 

function of platelets

regulate hemostasis

Removed by spleen, liver and bone marrow

platelet reference range

150,000 - 450,000

thrombocytopenia

low platelets

what value is risk for bleeding with trauma

platelet count <50,000

what lab value is risk for spontaneous bleeding

<20,000

what is thrombocythemia/thrombocytosis

high platelets c

clinical consequence of thrombocythemia/thrombocytosis

Arterial or venous thrombosis

Hemorrhage

what drugs can cause thrombocytopenia

antineoplastics

HEPARIN

Anti-infectives

Patient has LOW platelets

Patient is at risk for bleeding with trauma (<50,000)

What is MPV

Mean platelet volume 7-11 fl

Useful to distinguish hypoproductive and hyper destructive causes (part of CBC)

Platelet tests monitor:

anticoagulant therapy to assess efficacy or confirm presence or absence of drug

(dose is usually proportional to effect)

Can also be used to identify deficiencies of coagulation factors

PT/INR

Warfarin monitoring, hepatic function

aPTT

Heparin!!!!!!A

ACT

High dose heparin or DTIs

Anti-Xa

LMWH, factor Xa inhibitors

how does heparin work

inhibits the activation of clotting factors

how does warfarin work

blocks synthesis of clotting factors

Blocks vit K synthesis → this is why you avoid vitamin K diets with warfarin

what is PT

measures the time for clot formation in seconds

what is a NORMAL range for INR?

0.9-1.1

what is the THERAPEUTIC range for INR?

2-3

or

2.5-3.5

11/29: INR 3.4 → Supratherapeutic (high)

01/10: INR is therapeutic

04.04: INR is subtherapeutic (low)

Therapeutic range is 2-3 or 2.5-3.5

Patient is at risk for heparin induced thrombocytopenia (due to low platelets)

LMWH

enoxaparin, dalteparinf

factor xa inhibitors

Apixaban

Rivaroxaban

Edoxaban

Anti-Xa is used to confirm the presence of a drug as efficacy is generally achieved via weight based dosing

T/F Routine monitoring of LMWH is done via anti-xa

Not routinely done due to weight based dosing

• maybe good for pregnancy, chronic kidney disease, obesity (due to changes in weight)

We are looking to 0.5-1

This is therapeutic

Draw again 4 hours from now (for LMWH)

Factor Xa inhibitor; taking for a fib; presents with slurred speech and left-sided weakness

Factor Xa test is good for adherence to see levels of apixaban; this is not a routine monitoring

T/F An advantage of POC devices is their slow turn around time

FALSE

POC devices are convenient and cost effective

causes of thrombophillia

antithrombin III deficiency

Protein C or S deficiency

Protrombin G20210A mutation

Activated protein C resistance

Factor V leiden

what is the clinical usefulness of a D-Dimer?

A negative test can RULE out a venous thromboembolism (DVT, PE)

If it is positive maybe investigate PE further

D-Dimer: Not elevated so PE can be ruled out (Normal range: variable; < 0.5 mcg/ml or < 200ng/ml)

aPTT is normal (Normal range: 22 – 38 sec (variable)

D-dimer range

<200 ng/mL