Tag Archives: TEG

The Thromboelastogram (TEG®): A Five-Minute Primer for the Emergency Physician

Author: Erica Simon, DO, MHA (@E_M_Simon, EM Chief Resident at SAUSHEC, USAF) // Edited by: Alex Koyfman, MD (@EMHighAK, EM Attending Physician, UTSW / Parkland Memorial Hospital) and Brit Long, MD (@long_brit, EM Attending Physician, SAUSHEC)

It’s three o’clock in the morning on your fourth night shift in a row.  While mustering the courage to rescue your energy drink from the dank, dark depths of the staff mini-fridge, you hear a familiar page: “trauma team to the trauma room.”  As you walk towards the ambulance bay, the trauma surgeon approaches with information regarding the incoming transfer:

  • 17 year-old male – MVC versus pedestrian
  • Seen at OSH where CTs demonstrated: epidural hematoma, grade III liver laceration, grade II splenic laceration, open book pelvic fracture, and extraperitoneal bladder rupture
  • Patient underwent external pelvic fixation and transfusion of blood products (8U PRBCs, 8U FFP and 4U Plts)
  • Most recent VS: BP 136/89, HR 92, RR (intubated/ventilated):14, SpO2 99% (FiO2 70%)

Drawing your attention to a piece of paper in his hand, detailing what appear to be labs from the outside facility, the surgeon points to a colorful figure: “I’m very concerned about this”:

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Scanning your mind for intelligent thought, you realize that it’s been some time since you’ve ordered a thromboelastogram (TEG), let alone interpreted one.

If you’re like this physician, take a few minutes to scan the following review – the quick and dirty on TEGs is coming your way.

Thromboelastography – What is it?

Developed in 1948 by Dr. Hellmut Harter, thromboelastography is a mechanism of assessing coagulation based upon the viscoelastic properties of whole blood.2-8  In contrast to traditional, static measurements of hemostasis (PT, aPTT, INR, fibrinogen level, and fibrin degradation products), thromboelastography allows for an assessment of near real-time, in-vivo clotting capacity, providing the interpreter information regarding the dynamics of clot development, stabilization, and dissolution.7  When utilized as a point-of-care assay, graphic interpretation of thromboelastography (the TEG), offers the opportunity for an expedited assessment of coagulopathies (thrombocytopenia, factor deficiency, heparin effect, hypofibrinogenemia, and hyperfibrinolysis).7,9,12,13

How is a TEG performed?

In order to perform a TEG, a citrated-sample of whole blood is placed into a heated sample cup with calcium chloride (to overcome the effects of the citrate), kaolin (a negatively charged molecule known to initiate the intrinsic pathway10), and phospholipids (required for optimal functioning of the extrinsic pathway11) (Figure 2).  As the sample cup oscillates in a limited arc, formation of clot results in the generation of rotational forces on a pin suspended from a torsion wire.  Forces translated to the torsion wire are then, in turn, transmitted to an electrical transducer, creating a characteristic waveform (Figure 3).

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I’ve heard of the Rapid TEG (r-TEG), is there a Difference?

When performed by a trained laboratory specialist, an r-TEG may be completed within 15 minutes as compared to the average 30-45 minutes processing time for a standard TEG.4,5,14  In contrast to a TEG, whole blood samples for an r-TEG may be performed with citrated or non-citrated samples.4 Samples utilized for an r-TEG are combined with tissue factor (activating the extrinsic pathway), and kaolin (activating the intrinsic pathway as above) +/- calcium chloride as applicable.4

I’ve also heard of ROTEM, what is it?

Although utilizing the technique developed by Dr. Harter, rotational thromboelastometry (ROTEM) differs from traditional thromboelastography in its mechanical application.  Unlike traditional thromboelastography, which utilizes a sample cup rotating in a limited arc, ROTEM employs a static sample cup with an oscillating pin/wire transduction system.  By comparison, ROTEM is also a more complex diagnostic test as it requires a number of differing reagents.  A complete discussion of ROTEM is outside the scope of this review.  If interested in further reading, see:

Tanaka K, Bolliger D. Practical aspects of rotational thromboelastometry (ROTEM). Available from: https://www.scahq.org/sca3/events/2009/annual/syllabus/workshops/subs/wkshp6pdfs/ROTEM%20-%20Tanaka.doc.pdf

Haemoview Diagnostics. ROTEM analysis: thromboelastometry. Available from http://www.haemoview.com.au/rotem-analysis.html

Haemoview. The 5 ROTEM tests. Available from http://www.haemoview.com.au/uploads/2/5/4/9/25498232/the_5_rotem_tests.pdf

How Do I Interpret TEG and r-TEG Results?

Drs. Semon and Cheatham of the Orlando Regional Medical Center Department of Surgical Education generated an excellent quick reference chart:

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*Note: TEG-ACT (rapid) – reported for r-TEG only.

A TEG-Guided Transfusion Strategy

In addressing TEG and r-TEG abnormalities, experts recommend the following3:

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The Quick and Dirty: Pattern Recognition

Perhaps most useful for the ED physician is knowledge of qualitative TEG representations:

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Some clarification on DIC Stage 1 and 2:

  • Stage 1: Fibrinolysis results in the degradation of fibrin, increasing fibrin degradation products (FDPs). Excess FDPs result in clot de-stabilization.1
  • Stage 2: The cycle of clot formation and breakdown results in platelet and clotting factor consumption.1

Why Might an Emergency Medicine Physician Want to Know about this Test?

Coagulation abnormalities in trauma patients have demonstrated a significant association with infection, multi-organ failure, and death.15-18 Given its ability to quickly detect hematologic pathology, the TEG is becoming a tool for the evaluation of transfusion requirements/coagulopathy post transfusion in this patient population.3,12,13

What does the literature say?

Cotton, et al., 20114:

  • Pilot study to evaluate the timeliness of r-TEG results, their correlation to conventional coagulation testing (CCT – PT, aPTT, INR, platelet count, fibrinogen), and the ability of r-TEG to predict early blood transfusion.
    • 272 patients meeting requirements for major trauma activation
    • Outcomes:
      • All r-TEG values available within 15 minutes vs. 48 minutes for CCTs
      • ACT, r-value, k-time correlated with PT, INR, PTT (r >0.70; p<0.001)
      • MA and a-angle correlated with platelet count (p<0.001, p<0.001)
      • Controlling for demographics and ED vitals: ACT>128 predicted massive transfusion (>10 U) in the first 6 hours of presentation and treatment

Bottom line – r-TEG results were available within minutes, results correlated with conventional coagulation test results, and were predictive of the requirement for early massive transfusion.

Holocomb, et al., 201219:

  • Study to evaluate the reliability of r-TEGs versus CCTs in predicting blood product transfusion
    • 1974 major trauma patients, median ISS 17 (25% meeting criteria for shock; 28% transfused, 6% died within 24 hours)
    • Outcomes
      • When controlling for age, injury mechanism, weighted-Revised Trauma Score, base excess and hemoglobin, ACT predicted RBC transfusion and a-angle predicted massive transfusion better than PT/aPTT or INR (p<0.001).
      • a-angle was superior to fibrinogen for predicting plasma transfusion, and MA was superior to platelet count for predicting platelet transfusion (p<0.001)

Bottom line – r-TEG was more accurate in the prediction of requirements for RBC, plasma, and platelet transfusions as compared to traditional CCTs.

Wikkelso A, et al., 201612:

  • Cochrane Review including 17 current RCTs (n=1493 participants)
    • Per the authors:
      • Low quality studies: numerous biases
      • Limited generalizability: majority of studies center on cardiac patients undergoing surgical intervention

Bottom line – There is growing evidence to suggest that the utilization of TEG and ROTEM reduce transfusion requirements and improve morbidity in patients with bleeding, but additional studies are required.

Back to Our Case

Why was the trauma surgeon concerned? If we interpret our TEG values:

  • R time 20.0 => well above the upper limit of normal (10.0 minutes) = significantly prolonged time for clot formation
  • K time 13.2 => normal: up to 10.0 = prolonged fibrin cross-linking
  • a-angle 16.5 => normal >53.0 = limited clot formation
  • MA 38 => normal platelet function >50 = limited platelet function

More importantly, one quick glance at our TEG and through pattern recognition, we known that aside from his significant traumatic injuries, the patient is in trouble. This waveform is characteristic of DIC Stage 2.

Key Pearls

  • A TEG can be used as a rapid assessment of thrombosis and fibrinolysis.
  • Although additional RCTs are needed, TEGs utilized in trauma patients have been demonstrated to reduce transfusion requirements (important when we consider TACO/TRALI, risk of DIC, and blood-borne pathogens).
  • If nothing else, take a few minutes to review the characteristic TEG waveforms – depending on your laboratory processing time, knowledge of above tracings could allow early identification of coagulopathy and immediate treatment.

 

References / Further Reading

  1. Williams. Haemscope Basic Clinician Training: Fibrinolysis and Hyperfibrinolysis TEG Analysis. Available from: www.medicine.wisc.edu/~williams/TEG5_analysis.ppt
  2. Walsh M, Thomas S, Howard J, Evans E, Guyer K, et al. Blood component therapy in trauma guided with the utilization of the perfusionist and thromboelastography. J Extra Corpor Technol. 2001; 43(4):162-167.
  3. Semon G, Cheatham M. Thromboelastography in Trauma. Surgical Critical Care Evidence-Based Guidelines Committee. 2014. Available from: www.surgicalcriticalcare.net/Guidelines/TEG%202014.pdf
  4. Cotton B, Faz G, Hatch Q, Radwan Z, Podbielski J, et al. Rapid thromboelastography delivers real-time results that predict transfusion within 1 hour of admission. J Trauma. 2011; 71:407-417.
  5. Teodoro da Luz L, Nascimento B, Rizoli S. Thromboelastography (TEG): practical considerations on its clinical use in trauma resuscitation. Scand J Trauma Resusc Emerg Med. 2013; 21:29.
  6. Bollinger D, Seeberg M, Tanaka K. Principles and practice of thromboelastography in clinical coagulation management and transfusion practice. Transfus Med Rev. 2012: 26(1): 1-13.
  7. Thakur M, Ahmed A. A review of thromboelastography. Int J periop Ultrasound Apply Technol. 2012; 1(1):25-29.
  8. Nickson C. Critical Care Compendium: Thromboelastogram (TEG). 2014. Available from http://lifeinthefastlane.com/ccc/thromboelastogram-teg/
  9. Kashuk J, Moore E, Sawyer M, Wolhauer M, Pezold M, et al. Primary fibrinolysis is integral in the pathogenesis of acute coagulopathy of trauma. Ann Surg. 2010; 252: 434-444.
  10. Zhu S, Diamond S. Contact activation of blood coagulation on a defined kaolin/collagen surface in microfluidic assay. Thromb Res. 2014; 134(6): 1335-1343.
  11. Heemskerk J, Bevers E, Lindhout T. Platelet activation and blood coagulation. Throm Haemost. 2002; 88(2):186-193.
  12. Wikkelso A, Wetterslev J, Moller A, Afshari A. Thromboelastography (TEG) or thromboelastometry (ROTEM) to monitor haemostatic treatment versus usual care in adults or children with bleeding (Review). Cochrane Database of Systematic Reviews. 2016; 8:1-149.
  13. Luddington R. Thromboelastography/thromboelastometry. Clin Lab Haematol. 2005; 27(2):81-90.
  14. Jeger V, Zimmerman H, Exadaktylos A. Can rapid TEG accelerate the search for coagulopathies in the patient with multiple injuries? J Trauma. 2009; 66:1253-1257.
  15. Niles S, McLaughlin D, Perkins J et al. Increased mortality associated with the early coagulopathy of trauma in combat casualties. J Trauma. 2008; 64:1459-1463.
  16. Brohi K, Sing J, Heron M. Coats T. Acute traumatic coagulopathy. J Trauma. 2003; 54:1127-1130.
  17. Cotton B, Gunter O, Isbell J, et al. Damage control hematology: the impact of a trauma exsanguination protocol on survival and blood product utilization. J Trauma. 2008; 64;1177-1182.
  18. Cohen J, Call M, Nelson M, et al. Clinical and mechanistic drivers of cute traumatic coagulopathy. J Trauma Acute Care Surg. 2013; 75:S40-47.
  19. Holocomb J, Minei K, Scerbo M, Radwan Z, Wade C, et al. Admission rapid thromboelastography can replace conventional coagulation tests in the emergency department: experience with 1974 consecutive trauma patients. Ann Surg. 2012

PEM Playbook – Multisystem Trauma in Children Part II: Massive Transfusion, Trauma Imaging, and Resuscitative Pearls

Originally published at Pediatric Emergency Playbook on March 1,
2016 – Visit to listen to accompanying podcast. Reposted with permission.

Follow Dr. Tim Horeczko on twitter @EMTogether

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A 5-year-old boy was playing with his older brother in front of their home when he was struck by a car. He sustained a femur fracture, splenic laceration, and blunt head trauma – the so-called Waddell’s triad.

On arrival, he was in compensated shock, with tachycardia. He needs blood.

He decompensates…

How do we manage his hemodynamics and when do we perform massive transfusion?

Pediatric Massive Transfusion

40 mL/kg of blood products given at any time within the first 24 hours.

Adolescents and Adult Massive Transfusion

6-8 units of packed red blood cells (PRBCs)

  • Adults have about 5 L of circulating blood.
  • Not including plasma, one could replace all circulating erythrocytes with about 10 units of PRBCs
  • The best ratio of PRBCs:Plasma:Platelets is unknown, but consensus is 1:1:1.
  • 1 unit of PRBCS is typically 300 mL of volume.

The typical initial transfusion of PRBCs in children is 10 mL/kg.

Massive transfusion in children is defined as 40 mL/kg of any blood product.

Once you start to give a child with major trauma the second 10 mL/kg dose of PRBCs – start thinking about other blood components, and ask yourself whether you should initiate your massive transfusion protocol.

The goal is to have the products ready to use in the case of the dynamic trauma patient.

The Thromboelastogram (TEG)

TEG directly measures the four components of clot formation. When there is endolethial damage and bleeding, the sequence that your body takes to address it is as follows:

  1. Platelets migrate and form a plug
  2. Clotting factors aggregate and reinforce the platelets
  3. Fibrin arrives an acts like glue
  4. Other cells migrate and support the clot.

R time – reaction time – the initial line in the tracing that shows time to beginning of clot formation.

  • Treated with platelets

K factor – kinetics of the clot –how much the clot allows the pin to move, or the amplitude.

  • Treated with cryoprecipitate

Alpha angle – the slope between the R and K measurements – reflects how quickly the fibrin glue is working.

  • Treated with cryoprecipitate

Ma – maximum amplitude – reflects the overall strength of the clot.

  • Treated with platelets

LY30 – the clot lysis at 30 min – is the decrease in strength of the clot’s amplitude at 30 min.

  • Treated with an antifibrinolytics (tranexamic acid)

Shape Recognition

Red wine glass: a normal tracing with a normal reaction time and a normal amplitude. That patient just needs support and monitoring.

Champagne glass: a coagulopathic TEG tracing – thinned out, with less amplitude. This patient needs specific blood products.

Puffer fish or blob: a hyperfibrinolytic tracing. That patient will needs clot-stablizer.

TEG – like the FAST – can be repeated as the clinical picture changes.

The Trauma Death Spiral

Lethal triad of hypothermia, acidosis, and coagulopathy.

Keep the patient perfused and warm.

Each unit of PRBCs contains 3 g citrate, which binds ionized calcium, causing hypotension. In massive transfusion, give 20 mg/kg of calcium chloride, up to 2 g, over 15 minutes. Calcium chloride is preferred, as it is ionically readily available – just use a larger-bore IV and watch for infiltration. Calcium gluconate could be used, but it requires metabolism into a bioavailable source of calcium.

Prothrombin complex concentrate (PCC)

Prothrombin complex concentrate (PCC) is derived from pooled human plasma and contains 25-30 times the concentration of clotting factors as FFP. Four-factor PCCs contain factors II, VII, IX and X, while 3-factor PCCs contain little or no factor VII.

The typical dose of PCC is 20-50 units/kg

In the severely hemorrhaging patient – you don’t have time to wait for the other blood products to thaw – PCC is a powder that is reconstituted instantly at the bedside.

Tranexamic acid (TXA)

Tranexamic acid (TXA), is an anti-fibrinolytic agent that functions by stopping the activation of plasminogen to plasmin, and the degradation of fibrin. The Clinical Randomisation of an Antifibrinolytic in Significant Hemorrhage (CRASH-2) investigators revealed a significant decrease in death secondary to bleeding when TXA was administered early following trauma.

Based on the adult literature, one guideline is to give 15 mg/kg loading dose of TXA with a max 1 g over 10 minutes followed by 2 mg/kg/h for at least 8 h or until bleeding stops.

Resuscitative Pearls

Our goal here is damage control. Apply pressure whenever possible. Otherwise, resuscitate, identify the bleeding source, and slow or stop the bleeding with blood products or surgery.

How Children are Different in Trauma

In adults, we speak of “permissive hypotension” (also called “balanced resuscitation” or “damage control resuscitation”). The idea is that if we bring the adult patient’s blood pressure up to normal, we may be promoting clot rupture. To avoid this, we target a MAP of 65 and look for clinical signs of sufficient perfusion. Adults tolerate hypotension relatively well, and is sufficient until we send them to the OR or interventional radiology suite.

In children, this is simply not the case. Hypotension in children is a sign of pre-arrest. Remember, they compensate with an increased systemic vascular resistance and tachycardia to maintain blood pressure.

We should not allow children to become hypotensive – severe tachycardia alone should prompt us to resuscitate.

In other words, permissive hypotension is not permissible for children.

FAST is not sensitive enough to rule-out abdominal trauma.

Fox et al. in Academic Emergency Medicine found a sensitivity of 52%; with a 95% confidence interval [CI] = 31% to 73%.

Often children even with high-grade splenic and liver lacerations can be managed non-operatively. If they are supported adequately, they are observed in the ICU and can avoid surgery in many cases. Unfortunately, a negative FAST cannot help with detecting or grading the laceration for non-operative management. In other words, feel free to use ultrasound – especially for things that we in the ED will react to and intervene on – but CT may help to manage the traumatized child non-operatively.

General Guideline for Imaging in Pediatric Trauma

CT Head and Neck, non-contrast: in concerning mechanisms of injury, patients that are difficult to assess (especially those under 3 months), those with a GCS of 13 or lower.

CT Chest, IV contrast: for suspicion of vascular injury that needs exploration, especially in penetrating trauma. Otherwise, chest xray will tell you everything you need to know in children – especially in blunt trauma. Hemo or pneumothoraces are readily picked up by US or CXR. Rib fractures on CXR predict pulmonary contusions. If you are concerned about great vessel injury, then CT Chest may be helpful; otherwise consider omitting it.

CT Abdomen and Pelvis, IV contrast: helpful in grading splenic and liver lacerations with goal to manage non-operatively. Abdominal tenderness to palpation, significant bruising, or a seat belt sign are concerning and would generally warrant a CT. Also, consider in liver function test abnormalities, or hematuria.

Extremity injuries: in general can be evaluated with physical exam and plain films. However, some injuries in high-risk anatomically complex areas such as the hand and wrist, tibial plateau, and midfoot may be missed by plain films, and CT may be helpful here.

Remember: you can help to mitigate post-traumatic stress and risk for adult healthcare aversion.

Summary

  1. Massive transfusion in children is at 40 mL/kg of total blood products. Think about it if you are giving your second transfusion to the traumatized child.
  2. Do everything you can to support perfusion and avoid the death spiral of hypothermia, coagulopathy, and acidosis. Keep the child perfused with blood as needed, correct coagulopathy, avoid too much crystalloid, and make sure to use the least high-tech of all of these interventions – keep him dry and covered with warm blankets.
  3. Do a careful physical exam, and use CT selectively with an end-point in mind – the default is not the pan-scan – evaluate possible injuries depending on your suspicions from history, physical, and lab tests.
  4. Become familiar with the relatively new modalities in trauma such as TXA, cryoprecipitate and the emerging technology of thromboelestogram – red wine is good for you, champagne is weak, and a puffer fish is trouble.

Selected References

Dehmer JJ, Adamson WT. Massive transfusion and blood product use in the pediatric trauma patient. Semin Pediatr Surg. 2010 Nov;19(4):286-91. doi: 10.1053/j.sempedsurg.2010.07.002.

Fox JC, Boysen M, Gharahbaghian L, Cusick S, Ahmed SS, Anderson CL, Lekawa M, Langdorf MI. Test characteristics of focused assessment of sonography for trauma for clinically significant abdominal free fluid in pediatric blunt abdominal trauma. Acad Emerg Med. 2011 May;18(5):477-82.

Harvey V, Perrone J, Kim P. Does the use of tranexamic acid improve trauma mortality? Ann Emerg Med. 2014 Apr;63(4):460-2.

Holscher CM, Faulk LW, Moore EE, Cothren Burlew C, Moore HB, Stewart CL, Pieracci FM, Barnett CC, Bensard DD. Chest computed tomography imaging for blunt pediatric trauma: not worth the radiation risk. J Surg Res. 2013 Sep;184(1):352-7.

Nosanov L, Inaba K, Okoye O, Resnick S, Upperman J, Shulman I, Rhee P, Demetriades D. The impact of blood product ratios in massively transfused pediatric trauma patients. Am J Surg. 2013 Nov;206(5):655-60.

Ryan ML, Van Haren RM, Thorson CM, Andrews DM, Perez EA, Neville HL, Sola JE, Proctor KG. Trauma induced hypercoagulablity in pediatric patients. J Pediatr Surg. 2014 Aug;49(8):1295-9.

Scaife ER, Rollins MD, Barnhart DC, Downey EC, Black RE, Meyers RL, Stevens MH, Gordon S, Prince JS, Battaglia D, Fenton SJ, Plumb J, Metzger RR. The role of focused abdominal sonography for trauma (FAST) in pediatric trauma evaluation. J Pediatr Surg. 2013 Jun;48(6):1377-83.

This post and podcast are dedicated to Larry Mellick, MS, MD, FAAP, FACEP. Thank you for your dedication to medical education, and sharing your warm bedside manner, extensive knowledge and talents, and your patient interactions with the world.


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