[单选] 一位67岁的住院病人，因左小腿深静脉血栓形成和肺栓塞，目前正在接受肝素静脉滴注，每小时一次。不幸的是，由于一个计算错误，肝素滴速是正常滴速的100倍。硫酸鱼精蛋白立即静脉注射。这种代理是通过下列哪一种作用机制起作用的？A 67-year-old hospitalized patient with a deep venous thrombosis of the left calf and pulmonary embolism is currently on intravenous heparin on an hourly drip． Unfortunately， because of a calculation error， the heparin drip is running at 100 times the rate it should be running at． Protamine sulfate is immediately given intravenously． This agent works by which of the following mechanisms of action？