title: A novel thrombelastograph tissue factor/kaolin assay of activated clotting times for monitoring heparin anticoagulation during cardiopulmonary bypass.
abstract: We used a thrombelastograph (TEG) assay with tissue factor and kaolin (TEG TF/K) to measure activated clotting time (ACT) in 31 patients during cardiopulmonary bypass. For comparison, ACTs were also determined by a Hemochron Jr. Signature and a Hepcon HMS. The TEG TF/K correlated with both the Hepcon (r(2) = 0.789) and Hemochron (r(2) = 0.743) ACTs. The average ACT after heparin was 319 +/- 119 s (mean +/- sd) for the TEG TF/K compared with 624 +/- 118 s for the Hepcon instrument. To evaluate the effects of hemodilution on TEG TF/K and Hemochron assays, ACT assays were performed on blood diluted to 50% and titrated with heparin from 0 to 6 U/mL. Both instruments showed significant (P < 0.01) changes in the ACT-versus-heparin slope, but the 0 heparin intercept for the TEG TF/K ACTs was not significantly changed (P = 0.292), in contrast to that for the Hemochron device (P = 0.041). Both instruments also indicated the same 1.3:1 ratio of protamine to heparin for optimum heparin neutralization, with increasing ACTs at ratios >2.6:1. The TEG TF/K ACT assay rapidly monitors heparin anticoagulation, in addition to the capabilities of this instrument to monitor platelet function, clotting factors, and fibrinolysis.
authors.affiliation: *Department of Anesthesiology, University of Tennessee Graduate School of Medicine, Knoxville, Tennessee; †Haemoscope Corporation, Niles, Illinois; and the ‡Statistical Consulting Center, University of Tennessee at Knoxville.
authors.forename: Jack J
authors.initials: JJ
authors.lastname: Chavez
authors.forename: Donald E
authors.initials: DE
authors.lastname: Foley
authors.forename: Carolyn C
authors.initials: CC
authors.lastname: Snider
authors.forename: James C
authors.initials: JC
authors.lastname: Howell
authors.forename: Eli
authors.initials: E
authors.lastname: Cohen
authors.forename: Robert A
authors.initials: RA
authors.lastname: Muenchen
authors.forename: Roger C
authors.initials: RC
authors.lastname: Carroll
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000925:Anticoagulants / Q000494:pharmacology*; D001777:Blood Coagulation / Q000187:drug effects; D002315:Cardiopulmonary Bypass; D005260:Female; D006490:Hemostatics; D006493:Heparin / Q000494:pharmacology*; D006801:Humans; D066298:In Vitro Techniques; D007616:Kaolin; D008297:Male; D008875:Middle Aged; D011479:Protamines / Q000494:pharmacology; D013916:Thrombelastography; D013925:Thromboplastin; D014914:Whole Blood Coagulation Time
chemical_list: D000925:Anticoagulants; D006490:Hemostatics; D011479:Protamines; C065206:protamine zinc; D007616:Kaolin; D006493:Heparin; D013925:Thromboplastin