ANAESTHESIOLOGY & THE TEG MACHINE
Thromboelastography, or TEG for short, is a method used to test the efficiency of blood coagulation, i.e., to monitor haemostasis. It is easy to use in the operation theatre and it provides accurate results to the anaesthesiologist. It can assess the viscoelastic properties and mechanical properties of a developing clot in all its phases from a single sample.
Thus, thromboelastography is a test used to assess the function of the coagulation system and the entire clotting process. It measures coagulation, platelet function, platelet-fibrinogen interaction and fibrinolysis. The results are depicted as a graph displaying readings from the beginning of a clot to fibrinolysis, measuring the time taken for the clot to form.
It is important to monitor haemostasis in patients with related pre-existing abnormalities or in patients that are bleeding profusely.
Coagulation is the process by which blood thickens and forms a blood clot or thrombus. This results in haemostasis, or stoppage of blood loss from an injured part and this is followed by the necessary repair. Platelets that are present in our blood form the plug or clot.
When the lining of a blood vessel is broken, platelets are attracted to the site forming a primary platelet plug. Platelets have thrombin receptors on their surface. This binds serum thrombin molecules. This in turn converts soluble fibrinogen to fibrin. The fibrin forms long strands of tough insoluble protein that are attached to the platelets. An enzyme called Factor XIII or fibrin stabilizing factor additionally strengthens or toughens the fibrin crosslinking. Without Factor XIII, the stability of the clot will be affected. Fibrin crosslinking finally seals the clot.
Excessive generation of fibrin leads to thrombosis. Sometimes, fibrinolysis happens in some people, that is, blood clots are prevented from forming. This leads to haemorrhage. Liver disorder can result in reduced production of fibrin’s precursor or can lead to the production of abnormal fibrinogen with reduced activity. This can lead to ineffective clots. The TEG measures both thrombosis and fibrinolysis.
Role in Anaesthesiology
The TEG machine is used in surgeries for rapid assessments and treatments. The most important information that TEG provides is that of clot strength. It helps identify if the bleeding is due to coagulopathy (weak clot formation) or due to surgical reasons. TEG allows the medical personnel present to differentiate faster between a haemostasis disorder and a surgical bleeding. Informed medical interventions can be made quicker, ensuring rapid management of the situation. Especially, in the case of patients who are at risk of severe bleeding, in particular, during a surgical procedure.
TEG enables the anaesthesiologist to be well-informed about the patient’s changing haemostatic profile before, during and after a surgical procedure. This will help in choosing the right medical interventions and ensure adequate care is present to address any eventualities. TEG, thus, helps in effective anaesthesia management.
TEG allows assessment of the coagulation process during a surgical procedure providing valuable early information. This will provide foresight and hence, will enable the judicious use of medications and allogenic blood products. The correct form of anaesthesia appropriate to the patient can be administered, depending on the results obtained from TEG.
The TEG is different from other tests because it is done in whole blood, while other conventional tests are done in plasma without platelets and tissue bearing cells, assessing isolated stages of blood clot. Graphical TEG results are available in minutes, whereas conventional test results are not rapidly available.
TEG can be used a point of care test. Most conventional tests — candidates as point of care tests — are mostly set up in a laboratory. In addition, the turnaround times are longer for such tests. However, emergency medical decisions cannot take that long, and require prompt results. TEG remedies these issues well.