[Heparin-induced thrombocytopenia. Results from the Comprehensive Hospital Drug Monitoring (CHDM) Bern/St. Gallen]

Of 23,520 consecutive hospitalizations from 1980-1988 (corresponding to 16,628 individual patients) in three departments of general internal medicine, 8261 were treated with heparin. All observations of patients displaying a probable, possible or questionable relationship of thrombocytopenia to heparin (administered i.v. or subcutaneously) were electronically collected by the CHDM program, revised on the basis of the primary case records and selected by standardized criteria. 13 of the 8261 patients exposed to heparin were considered to have a probable or possible HIT, corresponding to a frequency of 0.157%. In two of them severe thrombocytopenia was observed (corresponding to 0.024%) accompanied in one case by a white clot syndrome. Thrombocytopenia was defined as a platelet value below 100 x 10(9)/l and severe thrombocytopenia as one below 30 x 10(9)/l. In the literature we found slight, asymptomatic thrombocytopenia in < or = 1-8% of heparin treated patients. Our result of 11 out of 8261 (corresponding to 0.133%) is low, partly because the thrombocyte count was not controlled systematically, the heparin used was mainly produced from swine intestinal mucosa, and no antibody tests had been carried out. To prevent severe thrombocytopenia from heparin we propose monitoring the platelet count if the treatment is to be continued for more than 5 days. The newer low molecular weight heparins, all of swine origin, are much safer compared to the traditional preparations in regard to risk of HIT and white clot syndrome.