Viscoelastic testing: Transforming hemostasis management in patients in the medical intensive care unit

Table 1 Significance of key parameters used in rotational thromboelastometry and thromboelastography

Parameter on ROTEM	Parameter on TEG	Definition	Significance
CT	Reaction time	Time to 2 mm clot firmness amplitude	Reflects coagulation factor activity and thrombin generation
Clot formation time	Kinetic time	Time from 2 mm to 20 mm clot firmness amplitude	Reflects fibrin polymerization, stabilization of the clot with platelets and factor XIII
α angle	α angle	Angle between the baseline and a tangent to the clotting curve through the 2 mm point	Reflects fibrin polymerization, stabilization of the clot with platelets and factor XIII
MCF	MA	The MA reached during the test	Reflects clot strength depending on platelets, fibrinogen, factor XIII
Lysis index at 30 minutes, 45 minutes, 60 minutes after CT	Lysis index at 30 minutes, 60 minutes after MA (Ly30, 60)	The residual clot firmness at 30 minutes, 45 minutes, 60 minutes after CT (ROTEM) in percentage of MCF. The reduction in clot firmness at 30 minutes, 60 minutes after MA (TEG) in percentage of MA	Reflects clot lysis depending on fibrinolytic activators or inhibitors, factor XIII, and platelet-mediated clot retraction

CT: Clotting time; MA: Maximum amplitude; MCF: Maximum clot firmness; ROTEM: Rotational thromboelastometry; TEG: Thromboelastography.

Table 2 Classic and cartridge-based assays for rotational thromboelastometry and thromboelastography

Assay (platform)	Activator/reagent	Main pathway assessed/information
ROTEM Delta EXTEM	Tissue factor	Extrinsic
ROTEM Delta INTEM	Ellagic acid	Intrinsic
ROTEM Delta FIBTEM	Tissue factor + cytochalasin D (platelet inhibitor)	Fibrinogen, factor XIII
ROTEM Delta HEPTEM	INTEM reagents + heparinase	Intrinsic, heparin effect
ROTEM Sigma Complete cartridge	Includes EXTEM, INTEM, FIBTEM, APTEM	-
ROTEM Sigma Complete + heparin cartridge	Includes EXTEM, INTEM, FIBTEM, HEPTEM	-
TEG 5000 CK	Kaolin	Intrinsic
TEG 5000 CKH	Kaolin + heparinase	Intrinsic, heparin effect
TEG 5000 CRT	Tissue factor (RapidTEG)	Extrinsic
TEG 5000 CFF	Functional fibrinogen (tissue factor + GPIIb/IIIa inhibitor)	Fibrinogen, factor XIII
TEG 6S® Global Hemostasis Cartridge	Includes CK, CK with heparinase, citrated RapidTEG, and citrated functional fibrinogen	-

CK: Citrated kaolin; ROTEM: Rotational thromboelastometry; TEG: Thromboelastography.