what are the types of Heparin Induced Thrombocytopenia
- Nonimmune heparin associated thrombocytopenia (Type I)
- Heparin-induced thrombocytopenia (Type II)
cause and frequency of HIT Type I
- absence of heparin-dependent antibodies
- frequency 10-20% of open heart pts
how long before the onset of HIT Type I
1-4 days following heparin admin
nadir count of HIT type I
100,000/mcl
out of the two HIT types, which is the bad one?
Type II
what does it mean when it says HIT Type II is immune mediated
IgG antibody binds to platelets in the presence of heparin
what does HIT Type II result in?
platelet activation and a prothrombotic state
- increased risk of arterial and venous thrombosis
- associated with thrombocytopenia or decreased in platelet count
what is the onset if HIT Type II
- 5-14 days following admin of heparin
- platelet drop of 50% of baseline
nadir count of HIT Type II
30,000 - 50,000
- lowest platelet count
- digested before produced
serious complication of heparin therapy for HIT Type II
- 38-76% develop thrombosis
- 10% of those require limp amputation
- mortality: 20-30% within one month
occurrence of HIT Type II
unfractionated and LMWH
IV and subcutaneous injections
Pts receiving large or small doses of heparin including: line or port flush solutions, heparin coated catheters
incidence of HIT Type II
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
HIT Type II Clinical manifestations
- 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)
diagnosis of Type II HIT
- platelet count prior to initiation of heparin
- platelet counts monitored every 2 to 3 days while pt is on heparin
HIT is suspected:
- platelet count decrease by 50%
- new thrombosis within 5-14 days of heparin initiation
- other causes of thrombocytopenia have been excluded
diagnosis of HIT can be lab confirmed of antibodies the……
heparin/platelet factor 4 complex by PAF4 titer
Type II HIT treatment
- discontinue all heparin immediately
- alternative anticoagulant regimens such as intravenous direct thrombin inhibitors and antiplatelet therapies may be used in conjunction with other anticoagulants
what should not be given to Type II HIT patients
platelet transfusion not recommended (potential to contribute to thrombosis)
what can be done for pts with current or previously identified HIT requiring cardiac surgery
delay surgery if possible to allow antibody titer to drop
