Viscoelastometric method for haemostasis testing in whole blood

Thromboelastometry (TEM®)

Thromboelastometry is a viscoelastometric method for haemostasis testing in whole blood. TEM® measures the interactions of coagulation factors, inhibitors and cellular components during the phases of clotting and subsequent lysis over time. The rheological conditions of this method mimic the sluggish flow of blood in veins. TEM® is performed on the ROTEM® system, an enhancement of the traditional thromboelastography (TEG®) method, developed by Hartert in 1948.

Measuring principle

A whole blood sample is placed into a cuvette and a cylindrical pin is immersed. Between pin and cuvette remains a gap of 1 mm, bridged by the blood. The pin is rotated by a spring to the right and the left. As long as the blood is liquid, the movement is unrestricted. When blood starts clotting, the clot increasingly restricts the rotation of the pin with rising clot firmness. This kinetic is detected mechanically and calculated by an integrated computer to the typical curves (TEMogram) and numerical parameters.

With a set of dedicated assays, TEM® detects hypo- and hyperfunctional stages of the clotting process. The rapidly available results enable a differential diagnosis. They discriminate between surgical bleeding and a haemostasis disorder, hyperfibrinolysis, the extent of dilutional coagulopathy, requirement for fibrinogen or platelet substitution and allow heparin and protamin dosage monitoring.
The traditional TEG® by Hartert works with a free-pending pin in a rotating cuvette. The clotting process is detected via a torsion wire. Due to the free suspension of the pin, the TEG®, according to Hartert, is extremely sensitive to vibrations and mechanical shocks. This flaw is overcome by the ROTEM® system by using a rotating pin, fixed on a steel axis which is stabilised by a unique ball bearing and the precise optical detection method. The advanced technology of ROTEM®, combined with automated pipette, touch screen operation and intuitive user-friendly software in ROTEM® has optimised the TEM® for use in point of care (POC), emergency laboratories and deployed settings.

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