Review Question - QID 108165

A 52-year-old man who was recently hospitalized with a pulmonary embolism is put on an unfractionated heparin drip as a bridge to chronic warfarin therapy. During morning rounds, he is found to have diffuse bruising despite minimal trauma, and his heparin infusion rate is found to be faster than prescribed. A coagulation panel is obtained, which shows a aPTT of 130 seconds (therapeutic 70-120 seconds), and the decision is made to reverse the effects of heparin. Which of the following would most likely be administered in order to do this?