Abstract and Introduction
Evaluation of coagulation is vital in the care of the orthopaedic patients, particularly in the subspecialties of trauma, spine, arthroplasty, and revision surgery resulting from blood loss and coagulopathies. Although conventional tests (prothrombin time/international normalized ratio, activated partial thromboplastin time, platelet count, and fibrinogen) are most commonly used, others like thromboelastography (TEG) are also available to the orthopaedic surgeons. TEG is a blood test developed in the 1950s, which provides a snapshot of a patient's coagulation profile by evaluating clot formation and lysis. Recently, TEG has been used to assess traumatic coagulopathy. The coagulation parameters measured by the TEG are reaction time (R-time), time to reach a certain clot strength (K-value), speed of fibrin build up (α-angle), maximum clot amplitude, and percentage decrease of clot in 30 minutes (LY30). Using these values, traumatologists have developed a better, faster, and more accurate overview of a patient's resuscitation and more successfully direct blood product use. However, many orthopaedic surgeons—despite performing surgical procedures that risk notable blood loss and postoperative clotting complications—are unaware of the existence of the TEG blood test and the critical information it provides. Increasing awareness of the TEG among orthopaedic surgeons could have a notable effect on numerous aspects of musculoskeletal care.
Thromboelastography (TEG) is a laboratory blood test that was initially described by Hartert in 1948 and made available for clinical practice in the early 1950s.[1,2] TEG provides a detailed, real-time assessment of a patient's hemostasis profile by measuring the viscoelastic properties of a small blood sample as it progresses from clot formation to lysis.[1,3] To achieve these measurements, the TEG system oscillates a sample of whole blood around a pin, which stimulates clot formation. As the clot forms, the viscoelastic strength of the clot exerts a rotational force on the torsion wire close to the pin, which is detected by an electromechanical transducer (Figure 1). The rotational force is followed from clot formation to lysis, producing the TEG graph that allows the physician to determine the patient's coagulation profile (Figure 2). This profile can then guide physicians in determining the appropriate coagulation factors, inhibitors, anticoagulants, and blood products needed to optimize clot formation and fibrinolysis.[3–6] Initial results are available within 15 to 20 minutes—much faster than conventional coagulation tests (CCTs) such as prothrombin time (PT)/activated partial thromboplastin time (PTT), international normalized ratio (INR), platelet count, and fibrinogen levels—making TEG an ideal test for emergent situations.[3,7]
Compared with CCT, TEG is faster, cheaper, and more predictive of transfusion needs, as well as improves the outcomes in trauma patients. TEG coagulation profile determinations can be repeated as often as needed, as long as the patient has a whole blood sample that can be obtained from either a venipuncture or an arterial source. Because of these advantages, TEG can be used to serially follow a patient's resuscitation. Thus, TEG can serve a vital role in the operating room as an adjunct to CCT, providing real-time information about the dynamic coagulation profile of a hemorrhaging patient, from either trauma or surgery. Although exploring the advantages and disadvantages of CCT versus TEG in the orthopaedic patients would be ideal, the focus of this discussion is to introduce the orthopaedic surgeons to TEG.
TEG is not currently available at every hospital for a few reasons. First, although an urgent assessment of a patient's hemostasis profile is required at trauma centers, most hospitals are not tertiary referral centers whereby the use of standard coagulation assessment modalities, such as PT/PTT, is sufficient. Second, TEG involves a notable investment of both time and money; specialized equipment and dedicated training are required for laboratory personnel to develop sufficient technical expertise in this method. Because of these factors, TEG may not be a high priority in all hospitals and orthopaedic surgery centers. However, it may prove vital in trauma centers and facilities conducting procedures with high blood loss, such as posterior spinal fusion, total joint arthroplasty, and revision surgery, where additional information about a patient's coagulation can be beneficial.
J Am Acad Orthop Surg. 2019;27(14):503-508. © 2019 American Academy of Orthopaedic Surgeons