HIT is seen more often at therapeutic heparin doses, but has been reported with minute doses administered by various routes. One third of patients with HIT will go on to develop thrombotic complications. These complications may include venous thrombi, arterial thrombi including thrombosis of the limbs, myocardial infarction and stroke. If thrombocytopenia develops in a patient receiving prophylactic heparin therapy, for example, for prevention of deep vein thrombosis, the heparin is stopped immediately. These patients may be at increased risk for thrombotic complications and alternative antithrombotic therapies are then considered, explained Kelton.
Many patients receive ongoing heparin therapy to maintain an anticoagulated state.
These patients may be candidates for an alternative defibrinogenating agent called ancrod. Ancrod is extracted from the venom of the Malayan pit viper. Components in the viper's venom have a potent anti-clotting effect which keep the bite wound of the victim open while the toxin is administered. We have had extensive experience with ancrod. The drug is administered intravenously over eight to 12 hours.