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TEG / ROTEM — R, K, MA, LY30 Reading + Goal-Directed Replacement
TEXTCoagulation · 7 min read
Viscoelastic testing replaced the empiric MTP ratio in modern cardiac + trauma practice. R is FFP, K is fibrinogen, MA is platelets, LY30 is TXA — the four-letter algorithm that runs the room.
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3 min read6 sectionsWhat viscoelastic testing measures
The amplitude of oscillation reflects clot strength.
Unlike PT/aPTT (which use plasma, measure only initiation, take 30+ min in the lab), TEG/ROTEM use whole blood and capture initiation, propagation, maximal strength, AND fibrinolysis on one tracing in 15-30 min.
They reflect cell-based coagulation including platelet-fibrin interaction — closer to in vivo hemostasis than plasma-based tests.
TEG parameters — R, K, α, MA, LY30
Prolonged R give FFP or PCC.
K (kinetics, normal 1-3 min): time from R to 20-mm amplitude = clot strengthening, primarily fibrinogen.
Prolonged K give cryoprecipitate or fibrinogen concentrate. α-angle (normal 53-72°): rate of clot formation, also fibrinogen-driven.
MA (maximum amplitude, normal 50-70 mm): peak clot strength = platelet contribution (~80%) + fibrinogen (~20%).
Low MA platelets.
LY30 (% lysis 30 min after MA, normal <8%): fibrinolysis.
Elevated LY30 tranexamic acid 1 g IV.
G = global clot strength derived from MA (an index, not directly read).
ROTEM parameters — same physiology, different names
CFT (clot formation time) ≈ K.
A10 (amplitude at 10 min) ≈ early MA proxy — actionable faster.
MCF (maximum clot firmness) ≈ MA.
ML (maximum lysis) ≈ LY30.
ROTEM offers channel-specific assays: INTEM (intrinsic pathway activator, like aPTT), EXTEM (extrinsic, like PT), FIBTEM (platelets blocked measures fibrinogen contribution alone — low FIBTEM MCF = give fibrinogen concentrate), APTEM (aprotinin added if APTEM clot is normal but EXTEM shows lysis, hyperfibrinolysis is confirmed), HEPTEM (heparinase neutralizes heparin compare INTEM vs HEPTEM to detect residual heparin).
Goal-directed replacement algorithm
Typical algorithm: bleeding patient TEG.
25-50 mg/kg or cryoprecipitate 10 units.MA <50 mm 1 platelet pheresis unit.
LY30 >3% TXA 1 g IV.
Repeat TEG after each intervention.
ITACTIC trial (2021): viscoelastic-guided resuscitation in trauma reduced transfusion volume without increased mortality.
Cardiac surgery RCTs (Weber 2012, Karkouti 2016): TEG/ROTEM-guided algorithms reduced RBC + FFP + platelet use 30-50% with improved or unchanged outcomes.
Limitations + adjuncts
Direct oral anticoagulants (apixaban, rivaroxaban) — anti-Xa level is the test.
Vitamin K antagonist effect — INR remains the gold standard. von Willebrand disease — needs vWF panel.
TEG/ROTEM are sensitive to temperature (test at 37°C even if patient is hypothermic — gives misleading 'normal' result in hypothermic coagulopathy).
Mild factor deficiencies may be missed.
Special situations
Obstetric hemorrhage: FIBTEM A5 <12 mm predicts need for fibrinogen — pregnancy maintains a baseline hyperfibrinogenemia (4-6 g/L), so 'normal-range' fibrinogen in PPH is actually low.
Liver transplant: classically uses TEG to titrate FFP during anhepatic phase + detect hyperfibrinolysis at reperfusion.
Trauma: hyperfibrinolysis on admission TEG (LY30 >3%) predicts massive transfusion + mortality — give TXA within 3 hours per CRASH-2.
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