The heparin-induced thrombocytopenia syndrome: an update.

One hundred sixty-nine patients with heparin-induced thrombocytopenia are reported and compared with the 62 patients reported in 1983. Prompt recognition of heparin-induced thrombocytopenia and immediate cessation of heparin administration lowered the complication and death rates from 61% (38/62) to 22.5% (38/169) and from 23% (14/62) to 12% (21/169), respectively. Platlet count and duration of heparin administration were not useful in predicting the outcome of the heparin-induced thrombocytopenia syndrome. Patients who received heparin in therapeutic doses were at higher risk for developing complications than were patients receiving lower doses of heparin. Platelet aggregation tests became negative as early as 7 days after discontinuation of heparin but persisted as long as 28 months. Heparin reexposure (2 days to 34 months after positive aggregation studies) was uneventful in 13 of 15 patients, whereas two patients suffered devastating thrombotic complications. Five patients continued to receive heparin despite positive platelet aggregation tests. The serious complications suffered by two of these five patients illustrate the necessity to discontinue heparin as soon as the diagnosis of heparin-induced thrombocytopenia is established.