HIT

Question 1

what are the types of Heparin Induced Thrombocytopenia

Answer 1

• Nonimmune heparin associated thrombocytopenia (Type I)

- Heparin-induced thrombocytopenia (Type II)

Question 2

cause and frequency of HIT Type I

Answer 2

• absence of heparin-dependent antibodies

- frequency 10-20% of open heart pts

Question 3

how long before the onset of HIT Type I

Answer 3

1-4 days following heparin admin

Question 4

nadir count of HIT type I

Answer 4

100,000/mcl

Question 5

out of the two HIT types, which is the bad one?

Answer 5

Type II

Question 6

what does it mean when it says HIT Type II is immune mediated

Answer 6

IgG antibody binds to platelets in the presence of heparin

Question 7

what does HIT Type II result in?

Answer 7

platelet activation and a prothrombotic state

• increased risk of arterial and venous thrombosis
• associated with thrombocytopenia or decreased in platelet count

Question 8

what is the onset if HIT Type II

Answer 8

• 5-14 days following admin of heparin

- platelet drop of 50% of baseline

Question 9

nadir count of HIT Type II

Answer 9

30,000 - 50,000

• lowest platelet count
• digested before produced

Question 10

serious complication of heparin therapy for HIT Type II

Answer 10

• 38-76% develop thrombosis
• 10% of those require limp amputation
• mortality: 20-30% within one month

Question 11

occurrence of HIT Type II

Answer 11

unfractionated and LMWH
IV and subcutaneous injections
Pts receiving large or small doses of heparin including: line or port flush solutions, heparin coated catheters

Question 12

incidence of HIT Type II

Answer 12

0.5-5% of pts treated with heparin for at least 5 days

• greater the %, the greater the time on heparin
• you will find higher time of heparin in VAD and ECMO pts

Question 13

HIT Type II Clinical manifestations

Answer 13

• venous thrombosis
• arterial thrombosis
• adrenal hemorrhagic infarction
• heparin induced skin lesions (at injection sites)
• acute systemic reactions (post IV heparin bolus)
• disseminated intravascular coagulation (DIC)

Question 14

diagnosis of Type II HIT

Answer 14

• platelet count prior to initiation of heparin

- platelet counts monitored every 2 to 3 days while pt is on heparin

Question 15

HIT is suspected:

Answer 15

• platelet count decrease by 50%
• new thrombosis within 5-14 days of heparin initiation
• other causes of thrombocytopenia have been excluded

Question 16

diagnosis of HIT can be lab confirmed of antibodies the……

Answer 16

heparin/platelet factor 4 complex by PAF4 titer

Question 17

Type II HIT treatment

Answer 17

• discontinue all heparin immediately
• alternative anticoagulant regimens such as intravenous direct thrombin inhibitors and antiplatelet therapies may be used in conjunction with other anticoagulants

Question 18

what should not be given to Type II HIT patients

Answer 18

platelet transfusion not recommended (potential to contribute to thrombosis)

Question 19

what can be done for pts with current or previously identified HIT requiring cardiac surgery

Answer 19

delay surgery if possible to allow antibody titer to drop