Non–Antithrombin-Mediated Heparin Resistance During Cardiac Surgery

Abstract

It is well known that antithrombin (AT) deficiency results in decreased heparin sensitivity, also known as “heparin resistance.” However, non–AT-mediated causes of heparin resistance are generally poorly characterized and less prevalent in the literature. We present 2 case reports of non–AT-mediated heparin resistance during cardiac surgery due to paraproteinemia and hyperfibrinogenemia. These cases highlight the challenges posed by unusual conditions in achieving adequate anticoagulation for cardiopulmonary bypass (CPB). The pros and cons of the treatment selections for these cases are discussed, and the potential complications of large doses of unfractionated heparin are considered.