Thromboelastogram (TEG)

Reviewed and revised 16 February 2014

OVERVIEW

  • Thromboelastography measures the visco-elastic properties of whole blood as it clots
  • it shows the interaction of platelets with the coagulation cascade (aggregation, clot strengthening, fibrin cross linking and fibrinolysis)
  • does not necessarily corrleate with blood tests such as INR, APTT and platelet count
  • This page describes TEG®

TEG® VERSUS ROTEM®

  • Two commercial types of thromboelastography are available: thromboelastography =TEG® (older, from USA) and rotational thromboelastogram = ROTEM® (from Germany)
  • differences in diagnostic nomenclature for identical parameters between the two
  • TEG® operates by moving a cup in a limited arc (±4°45′ every 5s) filled with sample that engages a pin/wire transduction system as clot formation occur
  • ROTEM® has an immobile cup wherein the pin/wire transduction system slowly oscillates (±4°45′every 6s)

METHOD

  • TEG® measures the physical properties of the clot in whole blood via a pin suspended in a cup from a torsion wire connected with a mechanical–electrical transducer
  • As the blood sample clots, the changes in rotation of the pin are converted into electrical signals that a computer uses to create graphical and numerical output
  • point of care test (quick -> takes around 30min)
  • can be repeated easily and compared and contrasted
  • requires calibration 2-3 times daily
  • should be performed by trained personell
  • susceptible to technical variations

TEG 1

USE

Studies show reduction in blood products in:

  • liver transplantation
  • cardiac surgery

May be useful in:

  • trauma
  • obstetrics (some data to show that it may decrease transfusion rates; this is controversial)

Hard to interpret in certain situations:

  • LMWH
  • aspirin
  • post cardiac bypass
  • fibrinolysis
  • hypercoagulability

NORMAL TEG

TEG 2

  • R = reaction time (s); time of latency from start of test to initial fibrin formation
  • K = kinetics (s); time taken to achieve a certain level of clot strength (amplitude of 20mm)
  • alpha = angle (slope between R and K); measures the speed at which fibrin build up and cross linking takes place, hence assesses the rate of clot formation
  • TMA = time to maximum amplitude(s)
  • MA = maximum amplitude (mm); represents the ultimate strength of the fibrin clot
  • A30 or LY30 = amplitude at 30 minutes; percentage decrease in amplitude at 30 minutes post-MA and gives measure of degree of fibrinolysis
  • CLT = clot lysis time (s)

IMPORTANT PATTERNS

TEG 3

TEG AS A GUIDE TO TREATMENT

  • Increased R time => FFP
  • Decreased angle => cryopreciptate
  • Decreased MA => platelets (consider DDAVP)
  • Fibrinolysis =>  transexamic acid (or aprotinin or aminocaproic acid)

VIDEO

Explanatory video by Joe Elbeery (consider muting the music):

References and Links

Journal articles

  • Bolliger D, Seeberger MD, Tanaka KA. Principles and practice of thromboelastography in clinical coagulation management and transfusion practice. Transfus Med Rev. 2012 Jan;26(1):1-13. doi: 10.1016/j.tmrv.2011.07.005. Epub 2011 Aug 26. Review. PubMed PMID: 21872428. [Free Fulltext]
  • da Luz LT, Nascimento B, Rizoli S. Thrombelastography (TEG(R)): practical considerations on its clinical use in trauma resuscitation. Scand J Trauma Resusc Emerg Med. 2013 Apr 16;21(1):29. [Epub ahead of print] PubMed PMID: 23587157. [Free Fulltext]
  • Ganter MT, Hofer CK. Coagulation monitoring: current techniques and clinical use of viscoelastic point-of-care coagulation devices. Anesth Analg. 2008 May;106(5):1366-75. doi: 10.1213/ane.0b013e318168b367. Review. PubMed PMID: 18420846. [Free Fulltext]

FOAM and web resources

Print Friendly

Comments

Trackbacks

Comments