BACKGROUND: Heparin released from grafted liver immediately after declamping is one of causes of coagulopathy, and its presence has been diagnosed by comparing thromboelastography(TEG) of blood treated with 0.01% of protamine and untreated blood. However, protamine may affect coagulation if the amount of protamine is not optimal to heparin in the blood sample. Heparinase, an enzyme isolated from Flavobacterium Heparinum, neutralizes heparin without adversely affecting coagulation. Therefore we compared the TEGs of blood treated with heparinase and protamine to clarify the sensitivity and reliability of heparinase in reversing the heparin effect. METHODS: Differences in Reaction time(R time), Alpha angle, Maximal Amplitude(MA) between native and heparinase treated TEG on reperfusion in 8 cases of orthotopic liver transplantations were compared with those between native and protamine in 14 cases of OLT. RESULTS: On reperfusion, all of TEGs treated with heparinase showed more improved data rather than native one in R time, Alpha angle and MA. But, in protamine treated blood, R time and Alpha angle in 6 patients and MA in 3 patients were more depressed. The scattergram show that TEGs treated with heparinase on reperfusion have almost positive difference, but TEGs treated with protamine did not have positive results consistently. CONCLUSIONS: Heparinase is a more reliable reagent and activator than protamine on TEG for detecting heparin effects on reperfusion without showing in-vitro anticoagulation. Those results suggest that heparinase on TEGs can make diagnosis of coagulopathy developed immediately after reperfusion efficiently.