ECMO143

TEG: Watching the Life of a Clot in Real Time

Key Points:

I used to think I understood TEG. Then a nurse asked me to explain it, and I was trying to make sense of it as I was explaining it. I knew the R time had something to do with when the clot starts, and MA was the widest part of the graph, but beyond that? Blank.

So, I did what any good ECMO Specialist would do: I went home, pulled out my notes, rewatched some TEG videos, and realized something that changed everything:

Labs like PT, INR, fibrinogen, aPTT, platelets, and anti-Xa are snapshots. But TEG is a movie.

It doesn’t just tell you what’s in the blood. It shows you what the blood can do, from the moment fibrin starts to form to when the clot breaks down. For ECMO patients, especially those receiving multiple blood products, undergoing trauma resuscitation, or living on the edge of DIC, TEG offers a dynamic look at coagulation in real time.

Two Halves of the TEG Story

Clot Formation and Clot Lysis

Think of the TEG tracing as the lifespan of a clot, split into two acts:

The X-axis is time. The Y-axis is the strength of the clot, measured by the movement of a pin suspended in the blood sample.

The standard test takes about 30–60 minutes, but Rapid TEG compresses it into 15 minutes—ideal in trauma, surgery, or acute ECMO changes.

TEG Parameters Explained

R Time (Reaction Time)

R-Time (Reaction Time). Time to initial fibrin formation

Tip: Always check a heparinase TEG if R is prolonged. It helps separate drug effect from true deficiency.

K Time (Kinetics)

K-Time (Kinetics). Time to reach 20 mm clot strength

Alpha Angle (α)

Alpha Angle. How fast a clot forms

Note: K time and alpha angle are interrelated; abnormalities in one often reflect in the other.

Maximum Amplitude (MA)

MA (Maximum Amplitude). Strongest point of the clot.

Everything to the left of the MA is about building the clot. Everything to the right is about breaking it down.

LY30 (Lysis at 30 Minutes)

LY30 (Lysis at 30 min). How much of the clot is broken down after 30 min of MA.

Clinical Use Cases in ECMO

TEG is particularly helpful in:

Heparinase-Modified TEG: Differentiating Heparin Effect from Coagulopathy

In patients receiving heparin therapy, interpreting coagulation status can be challenging. Standard TEG may show prolonged R times due to heparin’s anticoagulant effect, potentially masking underlying coagulopathies. Heparinase-modified TEG addresses this by neutralizing heparin in the blood sample, allowing for accurate assessment of the patient’s intrinsic coagulation function.

When to Use Heparinase TEG

Consider heparinase-modified TEG in the following scenarios:

Performing Heparinase TEG

Heparinase TEG is conducted by running two assays simultaneously:

  1. Standard TEG: Measures coagulation parameters in the presence of heparin.

  2. Heparinase TEG: Measures coagulation parameters after neutralizing heparin with heparinase.

Comparing these results helps determine if prolonged clotting times are due to heparin or an underlying coagulopathy.

Interpreting Results

This differentiation is crucial for guiding appropriate treatment, such as administering protamine for heparin reversal or providing specific blood products for coagulopathy management.

Should a Standard TEG Be Performed Simultaneously?

Yes, conducting both standard and heparinase TEG assays concurrently is essential. This dual approach allows for a direct comparison, facilitating accurate identification of heparin’s role in any observed coagulopathy.

Final Thought

Most of us learned labs like INR and aPTT in school, but ECMO patients live in a different world. Their coagulation status is a moving target, and TEG is one of the only tools that lets you watch that target shift in real time. TEG should always be interpreted in the clinical context—trends over time are more important than isolated results, and normal ranges may vary by institution or patient population. When considering interventions, always address the underlying cause and clinical scenario before transfusing blood products. For those working internationally, note that ROTEM is a similar tool with some different parameters but the same core principle. Whether you’re adjusting blood products, titrating heparin, or trying to figure out why your patient is bleeding (or clotting) despite “normal” labs, TEG is a practical game changer. Once you learn how to read the curve, you’ll never want to go back to relying solely on traditional lab tests.

AI and My ECMO Learning Journey

AI plays a significant role in how I research, understand, and communicate complex ECMO topics. From analyzing source materials to organizing ideas and generating podcast outlines, AI helps me stay curious and keep learning, so I can continue sharing insights with you.

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Disclaimer:

This article is for educational purposes only and reflects the author’s understanding and interpretation of available guidelines, literature, and bedside learning. It does not constitute medical advice or represent institutional protocols. Always consult your ECMO team and local policies when making clinical decisions.

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