Can low molecular weight heparins and heparinoids be safely given to patients with heparin-induced thrombocytopenia syndrome?
BACKGROUND
Low molecular weight heparin (LMWH) and heparinoids have been offered as alternatives to unfractionated heparin (UH) to patients with heparin-associated antiplatelet antibodies (HAAb) and heparin-induced thrombocytopenia syndrome (HIT). Some of these patients have had continued HIT in the presence of the UH substitutes. It would seem important to know whether the heparin substitute is likely to cause patients' platelets to aggregate before administering the substitute to patients with HAAb.


METHODS
Patients with HIT were identified as having HAAb by positive platelet aggregometry testing with commercial UH. Plasmas from 51 patients with HAAb were tested for the ability to aggregate platelets in the presence of two LMWHs (Mono-Embolex NM and Fragmin) and one heparinoid (Org 10172).


RESULTS
The proportions of plasmas reacting to each UH substitute are Mono-Embolex NM, 60.8%; Fragmin, 25.5%; and Org 10172, 19.6%. Although Fragmin and Org 10172 aggregated platelets in the presence of HAAb significantly less often than Mono-Embolex NM (p < 0.001), a patient with HAAb has a substantial chance of reacting to one of these UH substitutes.


CONCLUSIONS
Before giving a LMWH or heparinoid to a patient with HAAb, one should determine with in vitro testing that the patient's HAAb will not cause platelet aggregation in the presence of the heparin substitute.
Kikta
M J
MJ
Department of Surgery, University of Missouri, Columbia.
Keller
M P
MP
Humphrey
P W
PW
Silver
D
D
D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000906:Antibodies / Q000032:analysis; D002809:Chondroitin Sulfates; D017985:Dalteparin / Q000627:therapeutic use; D003871:Dermatan Sulfate; D004087:Dihydroergotamine / Q000627:therapeutic use; D004338:Drug Combinations; D005260:Female; D006025:Glycosaminoglycans / Q000627:therapeutic use; D006493:Heparin / Q000009:adverse effects* / Q000276:immunology / Q000627:therapeutic use; D006495:Heparin, Low-Molecular-Weight / Q000627:therapeutic use*; D006496:Heparinoids / Q000627:therapeutic use*; D006497:Heparan Sulfate; D006801:Humans; D008297:Male; D008875:Middle Aged; D010974:Platelet Aggregation / Q000187:drug effects; D013921:Thrombocytopenia / Q000097:blood / Q000139:chemically induced* / Q000188:drug therapy*
D000906:Antibodies; D002809:Chondroitin Sulfates; D017985:Dalteparin; D003871:Dermatan Sulfate; D004087:Dihydroergotamine; D004338:Drug Combinations; D006025:Glycosaminoglycans; D006493:Heparin; D006495:Heparin, Low-Molecular-Weight; D006496:Heparinoids; D006497:Heparan Sulfate; C031388:heparin-dihydergot; C035838:danaparoid