Next generation viscoelasticity assays in cardiothoracic surgery: Feasibility of the TEG6s system

Abstract

Background: Viscoelastic near-patient assays of global hemostasis have been found useful and cost-effective in perioperative settings. Shortcomings of current systems include substantial laboratory intensity, user-dependent reproducibility, relatively large sample volumes, sensitivity to ambient vibration and limited comparability between techniques and devices. The aim of this study was to assess feasibility of a new, resonance-based viscoelastic whole blood methodology (TEG6s) in cardiac surgery with cardiopulmonary bypass (CPB) and to compare the parameters this system produces with the ROTEM delta system and standard coagulation tests.

Methods: In a prospective evaluation study, twenty-three consecutive cardiac surgery patients underwent hemostasis management according to current guidelines, using the ROTEM delta system and standard coagulation tests. Blood samples were collected prior to CPB before anesthetic induction (pre-CPB), during CPB on rewarming (CPB), and 10 minutes after heparin reversal with protamine (post-CPB). ROTEM and standard coagulation test results were compared with TEG6s parameters, which were concurrently determined using its multi-channel microfluidic cartridge system.

Results: TEG6s provided quantifiable results pre-CPB and post-CPB, but only R (clotting time) of CKH (kaolin with heparinase) was measurable during CPB (full heparinization). Spearman's correlation coefficient (rs) was 0.78 for fibrinogen levels and MA CFF (functional fibrinogen). Correlation of several TEG6s parameters was good (0.77 to 0.91) with MCF FIBTEM, and poor (<0.56) with prothrombin time and activated partial thromboplastin time (<0.44). Rs with platelet count was moderate (0.70, MA CK; 0.73, MA CRT). Accuracy of MA CFF for detection of fibrinogen deficiency < 1.5 g/L was high (ROC-AUC 0.93).

Conclusions: The TEG6s system, which is based on resonance viscoelastic methodology, appears to be feasible for POC hemostasis assessment in cardiac surgery. Its correlations with standard coagulation parameters are quite similar to those of ROTEM and there is good diagnostic accuracy for fibrinogen levels lower than 1.5 g/L. During full heparinization, TEG6s testing is limited to R measurement. Larger studies are needed to assess superiority over other POC systems.

Conflict of interest statement

The authors have declared that no competing interests exist.

Figures

Fig 1. Pattern of TEG6s parameters in the course of cardiothoracic surgery.

(A) reaction time (R), (B) maximum amplitude (MA), and (C) activated clotting time equivalent (ACT) values are shown before cardiopulmonary bypass (CPB; Pre), during (CPB) and after (Post). Abbreviations: CK, Kaolin TEG; CRT, rapid TEG; CKH, TEG with heparinase; CFF, TEG functional fibrinogen.

Fig 2. Accuracy of TEG6s results for hypofibrinogenemia (

ROC curves of (A) MA CFF and (B) MA CKH are shown. (A) Area under the ROC curve (AUC) of MA CFF was 0.93 (95% CI 0.84, 1.00). At a threshold of 17.2 mm sensitivity was 100% (95% CI 47.8, 100.0) and specificity 81.4% (95% CI 66.6, 91.7); (B) AUC of MA CKH 0.79 (95% CI 0.66, 0.93). At a threshold of 57.3 mm sensitivity was 100% (95% CI 71.5, 100.0) and specificity was 51% (95% CI 36.3, 65.6).