A case report of heparin resistance due to acquired antithrombin III deficiency.

A case of heparin resistance and its management during cardiopulmonary bypass is reported. A patient with a history of post-infarct angina and arrhythmias was treated with intravenous heparin infusion for five days prior to myocardial revascularisation surgery. He required 13,500 IU/kg of heparin to increase his activated clotting time to a therapeutic level for safe institution of cardiopulmonary bypass. This phenomenon of heparin resistance was postulated to be due to consumption of circulating antithrombin III as a result of prior heparinisation. Treatment with fresh frozen plasma restored heparin effectiveness.