How do we integrate thromboelastography with perioperative transfusion management?
From the Department of Pathology and Laboratory Medicine and the Department of Anesthesiology, University of Kentucky Medical Center, Lexington, Kentucky.Transfusion (Impact Factor: 3.53). 06/2012; DOI: 10.1111/j.1537-2995.2012.03728.x
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ABSTRACT: Thromboelastography (TEG) is a useful method of assessing perioperative coagulation function in patients undergoing cardiac surgery. The presence of significant amounts of heparin in blood samples, however, prevents determination of changes in coagulation function by TEG or introduces artifactual error if samples contain heparin that is not present in vivo. For these reasons, whole blood coagulation function monitoring with TEG has not been feasible during cardiopulmonary bypass (CPB) with heparin anticoagulation. In this study, data obtained from 42 volunteers are presented to describe the effects of heparinase on TEG variables in the presence and absence of heparin. These data indicate that heparinase does not affect TEG parameters of whole blood not containing heparin and reverses the TEG effects of low levels of heparin contamination. Subsequently, 51 patients undergoing coronary artery surgery were studied using a modified TEG assay that incorporates in vitro application of heparinase to allow measurement of TEG parameters before, during, and after CPB. Heparinase-modified TEG assays facilitated diagnosis of heparin contamination in preoperative blood samples and permitted baseline TEG evaluation in patients receiving preoperative heparin infusions. Heparinase-modified TEG assays revealed declines in alpha and MA values during CPB, which persisted and significantly correlated with values after protamine infusion (alpha: r = 0.77, P = 0.001; MA: r = 0.78, P = 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)Journal of Cardiothoracic and Vascular Anesthesia 05/1994; 8(2):144-9. · 1.45 Impact Factor
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ABSTRACT: Laboratory and point-of-care coagulation tests are frequently obtained to determine the presence of heparin after surgical procedures. The objective of this study was (1) to compare the sensitivity of the activated coagulation time (ACT), activated partial thromboplastin time (aPTT), protamine titration (Hepcon; HMS Medtronic, Hemotec, Englewood, CO), and thromboelastography (TEG) with heparin anticoagulation and (2) to determine how frequently residual heparin is present in the 24-hour period after heparin neutralization in cardiopulmonary bypass (CPB) patients. A prospective study. A tertiary care university teaching center that performs more than 15,000 surgical procedures per year. Vascular surgical (n = 17) and CPB (n = 29). In vascular surgical patients, coagulation tests (ACT, protamine titration [Hepcon], and TEG) were obtained before and 90 minutes after heparin (50 to 60 U/kg IV) and compared with heparin concentration determined by factor Xa inhibition assay. In cardiac surgical patients, ACT and heparin concentrations were measured after anesthesia induction, during CPB, after protamine neutralization, and 3 as well as 6 hours after CPB. In addition to heparin concentrations and ACT measures, platelet counts, fibrinogen levels, and bleeding times were determined before and 3 and 24 hours after CPB. Ninety minutes after heparin, significant heparin concentrations were present in all vascular surgical patients, but ACT was elevated in only 4 of 17 patients. Protamine titration (Hepcon) correlated with the factor Xa inhibitory assay for heparin (r2 = 0.76). All 17 patients had an abnormal TEG (mean "R" time = 81 +/- 39 minutes) and a marked elevation of aPTT (135 +/- 35 sec [normal 22 to 33 seconds]) 90 minutes after heparin. In CPB patients, ACT did not correlate with heparin assays. After protamine neutralization of heparin in CPB patients, ACT returned to baseline despite the presence of heparin in 3 of 29 patients (0.22, 0.18, and 0.33 U/mL). ACT was less sensitive to residual heparin anticoagulation than aPTT, TEG, and whole blood heparin assay. The whole blood heparin assay (Hepcon) provided sensitive and specific data about the presence of residual heparin. Despite the limitation of ACT in detecting heparin, the investigators found that residual heparin was not common in the period after uncomplicated CPB.Journal of Cardiothoracic and Vascular Anesthesia 03/1997; 11(1):24-8. · 1.45 Impact Factor
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ABSTRACT: 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 small amounts of heparin, which produces a nondiagnostic tracing. The purpose of this study was to compare heparin neutralization using heparinase or protamine in TEG blood samples obtained during CPB. TEG testing was performed on 48 patients before, during and after CPB. Tissue plasminogen activator activity and antigen were measured on a subset of 32 patients. We found: 1) heparinase neutralized at least 10 IU/ml heparin 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 good correlation for other TEG parameters between heparinase and protamine treated samples, heparinase treatment produced shorter K values and higher angle, MA and A60, 4) while fibrinolysis was detected using both methods, heparinase treatment suppressed fibrinolysis in the TEG in both samples from patients and after in vitro addition of tissue plasminogen activator, 5) TEG was not a sensitive indicator of t-PA activity, detecting only 21% of samples with increased t-PA activity during bypass, and 5) heparinase was at least 100 times more expensive than protamine. We conclude that while both heparinase and protamine can be used to neutralize heparin in TEG samples obtained during CPB, protamine neutralization is more sensitive to fibrinolysis and less expensive, but the protamine dose must be carefully selected to match the heparin level used at individual institutions.Thrombosis and Haemostasis 09/1997; 78(2):820-6. · 5.76 Impact Factor
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