Abstract: This invention provides a method for inhibiting thrombosis in a patient whose blood is subjected to extracorporeal blood circulation which comprises contacting the extracorporeal circulating blood with a Factor IXa compound in an amount effective to inhibit thrombosis in the patient. The Factor IXa compound may include an active site-blocked Factor IXa compound or Glu-Gly-Arg chloromethyl ketone-inactivated human factor IXa compound. This invention also provides that the effective amount may be from about 0.1 &mgr;g/ml plasma to about 250 &mgr;g/ml plasma or from about 0.5 &mgr;g/ml plasma to about 25 &mgr;g/ml plasma. The patient may be subjected to extracorporeal blood circulation during transplant surgery or cardiopulmonary bypass surgery or any surgery in which obligate clamping of a blood vessel is required. This invention further provides for a pharmaceutical composition which includes an effective amount of a Factor IXa compound and a pharmaceutically acceptable carrier.

Abstract: This invention provides a method for inhibiting thrombosis in a patient whose blood is subjected to extracorporeal blood circulation which comprises contacting the extracorporeal circulating blood with a Factor IXa compound in an amount effective to inhibit thrombosis in the blood of a patient and under conditions such that the Factor IXa compound circulates in the patient. The Factor IXa compound may include an active site-blocked Factor IXa compound or Glu-Gly-Arg chloromethyl ketone-inactivated human factor IXa compound. This invention also provides that the effective amount may be from about 0.1 &mgr;g/ml plasma to about 250 &mgr;g/ml plasma or from about 0.5 &mgr;g/ml plasma to about 25 &mgr;g/ml plasma. The patient may be subjected to extracorporeal blood circulation during transplant surgery or cardiopulmonary bypass surgery.

Abstract: This invention provides an assay to monitor antithrombic activity of a Factor IXa compound infused into circulation of a patient which includes: (a) obtaining Factor IXa-deficient plasma; (b) mixing the plasma from step (a) with diatomaceous and with plasma from the patient; (c) incubating the mixture with a source of lipid and calcium chloride under conditions suitable for clot formation; and (d) measuring time necessary for clot formation in the incubate, thereby monitoring the antithrombic activity of the Factor IXa compound infused into the circulation of the patient.