Reproducibility and interchangeability of the Thromboelastograph®, Sonoclot® and Hemochron® activated coagulation time in cardiac surgery

Purpose: Despite their common use in cardiac surgery, few studies hove evaluated the reproducibility of the Thromboelastograph (R) (TEG), of the Sonoclot (R) (SCT), and of the activated coagulation time with celite (ACT-C) or kaolin (ACT-K) measured with the Hemochron (R), in clinical conditions of on-site monitoring of hemostasis, This study determined the reproducibility of those measurements, and evaluated the ability of various devices to substitute for the ACT-C. Methods. Blood samples collected from 20 volunteers and 21 patients undergoing myocardial revascularization were analyzed in the two channels of the TEG, in two SCT and four Hemochron (R) analyzers. The overall of TEG and SCT coagulation profiles were analyzed by a computerized TEG and an experienced observer respectively. The variation rate (V%) was calculated for each variable. The ability of ACT-K and SCT to substitute for ACT-C under different clinical conditions was evaluated. Results. ACT-C andACT-K V% ranged between 5.6% and 10.8% and between 6.7% and 12.4% respective. TEG and SCT V% ranged between 3.1 % and 9.5% and between 5.8% and 33.6% respectively, according to different conditions and parameters. In volunteers and nonheparinized patients, the ACT-C and ACT-K were interchangeable. No other test con substitute for the ACT-C when patients ore heparinized during cardiopulmonary bypass (CPB). Conclusions: In the clinical conditions of use, on-site hemostasis monitoring devices providing the most reproducible measurements are, in decreasing order, the TEG, the Hemochron (R) and the SCT In heparinized patients and during CPB, results from different tests are not interchangeable, stressing the importance of establishing appropriate instrument-specific values for monitoring anticoagulation during cardiac surgery.