Monitoring Of Coagulation During

Coagulation monitoring is not standardised in centres across the world. The evolution of surgical techniques and coagulation management by anaesthesiologists has significantly decreased the use of blood product transfusions required for OLT. Some centres rely on "traditional clotting studies'', such as, prothrombin time (PT), partial thromboplastin time (PTT), international normalised ratio (INR), platelet (PLT) count, and/or fibrinogen levels. Other centres manage coagulation monitoring with thromboelastography (TEG Analyser Hemascope®, Skokie, IL, USA).

When patients with ESLD are first evaluated for OLT, their coagulation status is usually measured by the above listed ''traditional clotting studies''. Often elevations in PT, PTT, and INR are seen. This is due to decreased synthesis and consumption of coagulation proteins. Platelet counts are usually low due to consumption, hyper-splenism, decreased formation, and immune-mediated destruction. Patients with active bleeding can be treated with fresh frozen plasma (FFP) and/or PLT transfusions as indicated.

After patients enter the operating room, rapid diagnosis of clotting abnormalities is essential for quick intervention. Thrombelas-tography (TEG) is a comprehensive test of whole blood coagulation. It enables measurement of the initial formation of fibrin strands, measured by reaction time (r), within 10 to 14 minutes.5 Clot formation rate (a) or the speed at which solid clot forms, is normally

53 to 67 degrees and is a function of fibrinogen and platelets. Normal coagulation is represented by a progressive increase in amplitude. It reaches a maximum amplitude (MA) of 59 to 68 mm. MA is a function of the elasticity of the blood clot. The value is increased by improved quality of platelets, fibrinogen, and factor XIII (fibrin stabilising factor). Hartert originally developed the method in 1948, and Kang introduced it to the field of transplantation. Figures 1 and 2 illustrate

Fig. 1 Thromboelastograph tracing. R = reaction time 10-14 min R + k = coagulation time 13-20 min

= clot formation rate 53--67 MA = maximum amplitude 59-66 A60 = amplitude 60 min after MA A6o/MA x 100 = whole blood clot lysis index > 85% F = whole blood clot lysis time > 300 min.

Hemophilia Fibrinolysis

Normal Thrombocytopenia Hypercoagulation

Hemophilia Fibrinolysis

Normal Thrombocytopenia Hypercoagulation

Fig. 2 Various TEG patterns.

Fig. 1 Thromboelastograph tracing. R = reaction time 10-14 min R + k = coagulation time 13-20 min

= clot formation rate 53--67 MA = maximum amplitude 59-66 A60 = amplitude 60 min after MA A6o/MA x 100 = whole blood clot lysis index > 85% F = whole blood clot lysis time > 300 min.

Fig. 2 Various TEG patterns.

the various TEG parameters measurable and the sample tracings of various pathologic conditions.

Thromboelastography provides information on the interaction of PLT, clotting factors, and thrombolytic systems. The patient's whole blood may also be evaluated by the addition of protamine sulfate, epsilon aminocaproic acid, or aprotinin. This will help to detect if there is a significant heparin effect or fibrinolysis contributing to coagulopathy during the procedure. The advantage of TEG is that results are immediately available in the operating room and within 10 to 15 minutes a coagulation defect may be determined and specifically corrected.

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