13.2 Disseminated Intravascular Coagulation (DIC) & Trauma-Induced Coagopathy (TIC)

13.2 Disseminated Intravascular Coagulation (DIC) & Trauma-Induced Coagopathy (TIC)

Clinical Summary: Trauma-Induced Coagopathy (TIC) is an immediate, endogenous impairment of clot formation driven by shock, tissue hypoperfusion, and endothelial activation, whereas Acute DIC involves systemic microvascular thrombosis and consumption coagulopathy. Management requires rapid goal-directed hemostatic resuscitation using Thrombelastography (TEG/ROTEM), 1:1:1 balanced transfusion, early Tranexamic Acid (TXA), and ionized calcium correction.

Coagulopathy in the severely injured trauma patient is a major driver of preventable mortality. Historically attributed solely to hemodilution and hypothermia, research has identified Trauma-Induced Coagopathy (TIC) as an immediate, biologically complex phenotype distinct from classical Disseminated Intravascular Coagulation (DIC). The TCRN must understand the pathophysiologic differences, advanced point-of-care viscoelastic testing, and goal-directed blood component therapy.

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Pathophysiology: TIC vs. Acute DIC

The Diamond of Death

Severe hemorrhage initiates a lethal spiral. The classic "Lethal Triad" of trauma—Hypothermia, Acidosis, and Coagulopathy—has been expanded to the Diamond of Death by recognizing Hypocalcemia as an independent primary driver.

       [Hypothermia]
      /             \
 [Acidosis] ─── [Coagulopathy]
      \             /
      [Hypocalcemia]

• Hypothermia (< 35°C): Impairs platelet function and inhibits enzymatic clotting factor activity (clotting factor activity drops ~10% per 1°C core temp decline).
• Acidosis (pH < 7.20): Inhibits coagulation factor complex assembly on lipid surfaces; factor Xa/Va activity is reduced by 50% at pH 7.10.
• Hypocalcemia ($iCa^{2+} < 1.1 \text{ mmol/L}$): Calcium (Factor IV) is an essential cofactor in almost every step of the coagulation cascade and platelet cross-linking.
• Coagulopathy: Exacerbates ongoing microvascular bleeding, amplifying hypoperfusion, hypothermia, and acidosis.

Trauma-Induced Coagopathy (TIC) Pathophysiology

TIC develops within minutes of severe injury before significant fluid resuscitation occurs. It is driven by two principal mechanisms: severe tissue injury and shock-induced tissue hypoperfusion.

1. Activated Protein C (APC) Pathway: Hypoperfusion causes endothelial hypoxia, triggering thrombomodulin-thrombin complex formation. This activates Protein C, which consumes and inactivates Factors Va and VIIIa while neutralizing Plasminogen Activator Inhibitor-1 (PAI-1). Uninhibited tissue plasminogen activator (tPA) induces rapid hyperfibrinolysis.
2. Endothelial Glycocalyx Degradation: Shock causes shedding of the endothelial glycocalyx layer, releasing heparin-like glycosaminoglycans into circulation ("endogenous heparinization").
3. Platelet Dysfunction: Trauma induces profound platelet exhaustion and impaired aggregation, even when total platelet counts appear normal.

Comparison: TIC vs. Acute DIC

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Laboratory Evaluation & Viscoelastic Testing

Traditional coagulation tests—Prothrombin Time (PT/INR), activated Partial Thromboplastin Time (aPTT), and Platelet count—have significant limitations in trauma. They are performed on cell-free plasma incubated at 37°C, taking 45–60 minutes to return, failing to reflect true in vivo cellular and temperature-dependent coagulation.

Traditional Coagulation Thresholds in Trauma

• Fibrinogen: Normal 200–400 mg/dL. Critical threshold in trauma: < 150–200 mg/dL requires urgent replacement with cryoprecipitate or fibrinogen concentrate.
• Platelets: Target $> 50,000/\mu\text{L}$ in ongoing hemorrhage, $> 100,000/\mu\text{L}$ in severe traumatic brain injury.
• PT/INR & aPTT: INR $> 1.5$ or aPTT $> 1.5 \times$ control indicates significant factor depletion requiring plasma.

Viscoelastic Hemostatic Assays (TEG and ROTEM)

Viscoelastic point-of-care testing—Thrombelastography (TEG) and Rotational Thromboelastometry (ROTEM)—evaluates whole-blood clot formation, strength, and lysis in real-time within 10–15 minutes.

TEG Trace Morphology:
  R time       K        Alpha Angle (α)
 |------|   |---|   /
 ~~~~~~~\ /~~~~~~~/ 
          X       /   Maximum Amplitude (MA)
 ~~~~~~~~/ \~~~~~~~/ |====================|
                     \
                      \____________________ LY30 (%)

TEG Parameters and Targeted Therapy:

ROTEM Equivalent Terms: $R\text{ time} = CT$ (Clotting Time); $K\text{ time} = CFT$ (Clot Formation Time); $MA = MCF$ (Maximum Clot Firmness); $LY30 = ML$ (Maximum Lysis).

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Targeted Hemostatic Resuscitation Protocols

Modern resuscitation of severe hemorrhagic shock relies on Damage Control Resuscitation (DCR) to prevent worsening TIC.

1. Massive Transfusion Protocol (MTP)

• Balanced Transfusion Ratio: Administer Packed Red Blood Cells (PRBCs), Fresh Frozen Plasma (FFP), and Platelets in a fixed 1:1:1 ratio to mimic whole blood transfusion and prevent dilutional coagulopathy.
• Avoid Crystalloids: Limit isotonic crystalloid administration ($< 1\text{--}1.5 \text{ L}$) because crystalloids dilute clotting factors, degrade the glycocalyx, and worsen hypothermic acidosis.

2. Tranexamic Acid (TXA) Administration

TXA is a synthetic lysine analog that competitively inhibits plasminogen activation, blocking fibrin breakdown.

• CRASH-2 Protocol: Administer 1 gram IV loading dose over 10 minutes within 3 hours of injury, followed by a continuous 1 gram IV infusion over 8 hours.
• Timing Warning: TXA administered $> 3 \text{ hours}$ post-injury is ineffective and increases mortality due to pro-thrombotic side effects and late hypofibrinolytic shift.

3. Fibrinogen Replacement & Ionized Calcium Management

• Cryoprecipitate: Administer 10 units (or $2\text{--}3 \text{ g}$ fibrinogen concentrate) for fibrinogen $< 150\text{--}200 \text{ mg/dL}$ or TEG $\alpha$-angle $< 53^\circ$.
• Ionized Calcium Correction: Citrate preservative in blood products chelates ionized calcium. Monitor $iCa^{2+}$ every 30 minutes during MTP. Administer 1–2 grams Calcium Chloride (or Calcium Gluconate) IV to maintain $iCa^{2+} > 1.1\text{--}1.2 \text{ mmol/L}$.