A COMPARISON OF THROMBOELASTOGRAPHY WITH HEPARINASE OR PROTAMINE SULFATE ADDED IN-VITRO DURING HEPARINIZED CARDIOPULMONARY BYPASS

Thromboelastography (TEG) has been used after cardiopulmonary bypass ( CPB) to diagnose excessive postoperative hemorrhage. Conventional TEG during CPB is not possible due to the sensitivity of the TEG to even s mall amounts of heparin, which produces a nondiagnostic tracing. The p urpose of this study was to compare heparin neutralization using hepar inase or protamine in TEG blood samples obtained during CPB. TEG testi ng was performed on 48 patients before. during and after CPB. Tissue p lasminogen activator activity and antigen were measured on a subset of 32 patients. We found: 1) heparinase neutralized at least 10 IU/ml he parin while 1.6 ug/ml protamine neutralized up to 7 IU/ml heparin, 2) in samples with complete heparin neutralization by both methods, there was no significant difference in the R values, 3) while there was goo d correlation for other TEG parameters between heparinase and protamin e treated samples, heparinase treatment produced shorter K values and higher angle. MA and A60. 4) while fibrinolysis was detected using bot h methods, heparinase treatment suppressed fibrinolysis in the TEG in both samples from patients and after in vitro addition of tissue plasm inogen activator, 5) TEG was not a sensitive indicator of t-PA activit y. detecting only 21% of samples with increased t-PA activity during b ypass, and 5) heparinase was at least 100 times more expensive than pr otamine. We conclude that while both heparinase and protamine can be u sed to neutralize heparin in TEG samples obtained during CPB. protamin e neutralization is more sensitive to fibrinolysis and less expensive. but the protamine dose must be carefully selected to match the hepari n level used at individual institutions.