By Zack LaDuke, Pharm.D., PGY1 pharmacy resident, St. Joseph Mercy Hospital, Ann Arbor
First introduced in 1980, thromboelastography (TEG®) is a diagnostic process that analyzes components of a patient's blood and allows clinicians to get a clearer picture of a patient's intrinsic hemostatic activity. Over the years, the technology has evolved into a point-of-care machine that can be used in multiple different clinical situations, including, but not limited to pre-operative, post-operative and trauma patients. On a general level, the different hemostatic components of the blood that the TEG® system analyzes includes: coagulation factors, heparin, cross-linked fibrin and platelets. To go more in depth, a demonstration of the TEG® interpretation result can be seen below (Figure 1). The R-value represents the time it takes for the patient to form the initial clot. A prolonged R-time is indicative of a clotting factor deficiency. The "Clot Strength (Fibrin)" component represents the amplitude of only the cross-linked fibrin clot. The "Clot Strength (Total)" component represents both the strength of the cross-linked fibrin and the aggregated platelets. Intuitively speaking, one would then be able to calculate the platelet component by subtracting the fibrin clot strength from the total clot strength. By analyzing each of these components, the clinician can determine if, and what type of, transfusion or procedure may need to be initiated for their patient.
Figure 1. Thromboelastography Interpretation Guide. Reference Ranges: R (4.6-9.1 mins), Fibrin Clot Strength (15-32 mm), Total Clot Strength (52-70 mm).
Several studies have shown that TEG® is an early predictor of coagulopathy. For example, at a level one trauma center that sees approximately 1,000 activations per year, TEG® was able to identify that of the patients with major active bleeding, 45 percent demonstrated hypercoagulability, 16 percent demonstrated hypocoagulability and nine percent had primary hyperfibrinolysis as the major cause of the bleed.1 Furthermore, there have been studies that show use of the TEG system has been associated with decreased resource utilization due to its ability to analyze each patient's hemostatic activity, resulting in targeted therapy. At The Toledo Hospital, usage of the TEG® system led to a 62 percent, 50 percent and 23 percent reduction in fresh frozen plasma (FFP), cryoprecipitate and platelets, respectively, per procedure. There was also a 50 percent reduction in reoperations for bleeding. This resulted in an estimated $250,000 annual savings for the hospital.2
As part of the primary care team, pharmacists have an opportunity to be involved in the interpretation of the TEG® assay and the subsequent treatment choice. Medications are either a cause or a solution to most of these hemostasis instabilities; therefore, it makes sense that a pharmacist would have a hand in the utilization of a TEG® assay. One instance where pharmacists would be valuable is deciding whether or not there is a need for prothrombin complex concentrate (PCC) for reversal of pre-admission use of either warfarin. By analyzing the R time, pharmacists will be able to interpret the affect that the anticoagulant agent may be having on the patient's hemostatic state. If the R-time is prolonged (>9.1 minutes), the patient would be deemed hypocoagulable, indicating that the patient may still have the anticoagulant on board and that administration of PCC would be appropriate. Another instance where a pharmacist would be involved in determining an appropriate course of action would be for the possible reversal of pre-admission antiplatelet use. For example, if the total clot strength is normal, but the fibrin component is larger than the normal reference range, then that would indicate that the patient is deficient in platelets and administration of 1-deamino-8-D-arginine vasopressin (DDVAP) may be appropriate if the patient was on an antiplatelet agent at home. A platelet infusion may be an appropriate intervention as well if the DDAVP proves to be inadequate.
In addition to determining appropriate transfusions for a bleeding patient, pharmacists will be able to assess certain drug therapies that the patient may be taking as an outpatient. By analyzing the clot strength of the platelets that the patient has, the pharmacist can determine if a patient on an antiplatelet agent, such as clopidogrel, is being treated with an appropriate dose. Furthermore, using this same analyzation could prove useful in determining when a patient who was using antiplatelet agents prior to surgery would be an appropriate candidate for operating. Instead of waiting an arbitrary amount of time before operating, the TEG® assay can be used to determine when the patient is back to normal platelet function.
With the implementation of the point-of-care TEG® system at St. Joseph Mercy Hospital Ann Arbor, the hospital is taking another step in the right direction for providing high-quality care for patients. Furthermore, the hospital will likely experience the added benefit of cost savings from utilizing less blood product resources in bleeding patients.
1. Johansson, PI. Treatment of massively bleeding patients: introducing real-time monitoring, transfusion packages and thromboelastography (TEG®). ISBT Science Series 2007;2(1):159–167.
2. Shapiro S, Fleming K, Rachwal W, Morant M. Case Study: The TEG® system has helped The Toledo Hospital save approximately $250,000 annually. Haemonetics Corporation website.