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Heparin Induced Thromobcytopenia-Thrombosis Syndrome

(Download  Heparin Induced Thrombocytopaenia.pdf)

These notes are produced for HAPS Hub partners to streamline the ordering of appropriate tests in patients where Heparin Induced Thrombocytopenia-Thrombosis Syndrome (HITTS) is a possibility. The clinical Haematologists of HAPS are available to discuss any questions arising from these guidelines or patients in whom appropriate tests are not obvious.

HITTS is a syndrome of thrombocytopenia and/or thrombosis occurring in patients on heparin (standard (SH) or low-molecular weight (LMWH)).

Clinical Features

  1. Patient has been on heparin (SH or LMWH) for at least 5 days if first exposure or has a history of HITTS (or unexplained thrombocytopenia on heparin) and has been re-exposed.

AND at least one of the following:

  1. Thrombocytopenia or a fall of greater than 100x109/L in platelet count.

OR

  1. Arterial thrombosis particularly "white" clots.

OR

  1. Venous thrombo-embolic disease progressing despite adequate heparinisation for 48 hours.

Treatment

  1. Cease heparin immediately if HITTS is suspected.
  2. Assess need for anticoagulation, if anticoagulation is necessary then:
    1. Administer Dextran 40 at 500mls per 12 hours as iv infusion and commence warfarin therapy immediately. Dextran is ceased when patient is warfarinised.

OR

    1. Orgaran (an heparinoid) may be used. Although there is a 10% laboratory cross-reactivity between Orgaran and SH in the HITTS test, the clinical significance of this is uncertain with one published paper [1] stating no clinical problems despite this cross-reactivity.

Points To Note

  1. There is an early (1-3 days) thrombocytopenia associated with heparin in which platelets do not fall below 100x109/l and is not associated with thrombosis. This problem is not serious and reverses despite continuation of heparin.
  2. The antibody causing HITTS rapidly reduces in strength and disappears at about 2 months after cessation of heparin, but can recur within 2 days of re-exposure.
  3. All forms of heparin administration have been associated with HITTS even "hep-saline" cannula flushes.
  4. All patients on heparin should have their platelets monitored at least twice per week.
  5. Low-molecular weight heparin (LMWH) has a significantly reduced the rate of HITTS (approximately 10%) compared to standard heparin (SH).
  6. The laboratory test for HITTS is time consuming and requires donation of platelets from a volunteer.

References

Warkentin, T.E. Blood 1996. 88, Suppl 1:626a.

Reviews

  1. Chong,B.H. BJH 1995;89:431-439.
  2. Chong,B.H. Aust NZ J Med 1992; 22:145-152

Written by:        Dr Michael Seldon, Haematology HAPS
Written:             May 1998

Last Reviewed:     10.5.2001