Heparin Induced Thrombocytopenia

Question 1

What is HIT?

Answer 1

What is HIT?

prothrombotic disorder associated with Unfractioned heparin UFH or Low Molecular Weight Heparin (LMWH)

Question 2

Pathophysiology

Answer 2

Pathophysiology

immune complication caused by antibodies formed against complexes of platelet factor PF4 and heparin.

Question 3

Types of HIT

Answer 3

Types of HIT

1. HIT: isolated HIT- labs are positive but patient doesn’t have a clot
2. HITT: HIT complicated by thrombosis

Question 4

Risk Factors

Answer 4

Risk Factors

1. source of heparin: Bovine (cattle) has higher risk than porcine (pig)
2. UFH > LMWH
3. surgical pts > medical and obstetric pts
4. Longer exposure= higher risk
5. risk with IV> risk with SQ

Question 5

Steps to Diagnosis of HIT

Answer 5

Steps to Diagnosis of HIT

1. notice a Platelet trend decreasing while patient recieiving heparin or LMWH
2. Determine PRe-test Probability SCore with…
   a. 4T score
   b. HEP score
3. if score is not low, stop all heparin, consider alternative Anticoagulant, and send testing
4. tests are recommended based on capability of laboratory resources

a. PF4 ELISA Immunoassay (not diagnostic, detects heparin dependent Ig-G antibodies potential false positives)
b. Seretonin Release Assay (SRA)
validation test. detects actual pathologic response

Question 6

4 Ts Pretest Score

what is it

Answer 6

a clinical scoring system to differentiate patients with HIT from those with other causes of thrombocytopenia.

Question 7

4 Ts Pretest Score

categories

Answer 7

4 Ts Pretest Score

Thrombocytopenia:
2 pt-platelet drop > 50,000
NAdir (lowest point) >/= 20,000/mm^3

1 pt- between 2 and 0

0 pt-Platelet drop <30% or
Nadir <10,000

Timing
2 pt: 5-10 days or within 1 day if recent exposure
1 pt  uncertain
         1 day and exposure >30 days
         After day 10
0 pt:  = 4 days without exposure

Thrombosis
2 pt: new thrombosis
1 pt: progressive or recurrent thrombosis
0 pt: thrombosis suspected or no new thrombosis

oTher Cause of Decline
2 pt: no alternative explanation
1 pt: other possible cause (all hospital pts have a possible other cause for thrombocytopenia)
0 pt: other probably cause

= 3. low probably for HIT. 4-5 points: intermediate probability
6-8 points: high probability

Question 8

Duration of Therapy of HIT

Answer 8

Duration ofTherapy of HIT

HIT: 30 days
HITT: 3 months

Question 9

Treatment Choices

Answer 9

Treatment Choices

strong: in patients with HIT or HITT, guideline recommends discontinuation of heparin and initiation of a non heparin anticoagulant

conditional: non heparin anticoagulants for selection
a. argatroban, bivalirudin, fondapainux, or a DOAC

conditional: selected DOAC, Rivaroxaban

Rivaroxaban dosing
HIT:15 mg bid until platelet count recovery
(platelet count >150k, then 20 mg daily

HITT: 15mg bid x 3 weeks, then by 20 mg daily

Question 10

Rivaroxaban dosing FOR HIT

Answer 10

Rivaroxaban dosing
HIT:15 mg bid until platelet count recovery
(platelet count >150k, then 20 mg daily

HITT: 15mg bid x 3 weeks, then by 20 mg daily

Question 11

Argatroban

Class:

Indication:

Mechanism of Action:

Effects of mechanism of Action:

Route of administration:

DOSE: –

Adverse Effects:–

Absolute Contraindications: –

Half life: 139-51 minutes

Pregnancy: –

Warning/ Precautions:–

DDI: –

Body Weight Considerations: –

Renal Adjustments:

Monitoring Parameters:

Pearls:

Answer 11

Argatroban

Class: Anticoagulant

Indication: Heparin Induced Thrombocytopenia (HIT)

Mechanism of Action:Direct Thrombin Inhibitor

Effects of mechanism of Action: Increase bleeding time

Route of administration: continuous IV infusion

DOSE: –

Adverse Effects:–

Absolute Contraindications: –

Half life: 139-51 minutes

Pregnancy: –

Warning/ Precautions:–

DDI: –

Body Weight Considerations: a–

Renal Adjustments: approx 15% renal elimination, will likely need lower infusion rates. not Dialyzable

Monitoring Parameters:
1. aPTT 1.5-3x ULN
Monitor hgb, hematocrit, platelets

Pearls:
85% hepatobiliary elimination
argatroban increases INR. this is NOT necessarily a reflection of degree of anticoagulation. effects INR more than bivaliruin.

Question 12

Bivalirudin

Class:

Indication:

Mechanism of Action:

Effects of mechanism of Action:

Route of administration:

DOSE: –

Adverse Effects:–

Absolute Contraindications: –

Half life:

Pregnancy: –

Warning/ Precautions:–

DDI: –

Body Weight Considerations: a–

Renal Adjustments:

Monitoring Parameters:

Pearls:

Answer 12

Bivalirudin

Class: Anticoagulant

Indication: Heparin Induced Thrombocytopenia (HIT)

Mechanism of Action:Direct Thrombin Inhibitor

Effects of mechanism of Action: Increase bleeding time

Route of administration: continuous IV infusion

DOSE: –

Adverse Effects:–

Absolute Contraindications: –

Half life: 10-24 minutes

Pregnancy: –

Warning/ Precautions:–

DDI: –

Body Weight Considerations: a–

Renal Adjustments: approx 15% renal elimination, will likely need lower infusion rates. not Dialyzable

Monitoring Parameters:
1. aPTT 1.5-3x ULN
Monitor hgb, hematocrit, platelets

Pearls:
85% hepatobiliary elimination
argatroban increases INR. this is NOT necessarily a reflection of degree of anticoagulation. effects INR less than argatroban

Question 13

non heparin alternative anticoagulants for HIT

Answer 13

fandaparunix
bivalirudin
argatroban