23.3 Major Trauma, Hemorrhagic Shock, and Massive Transfusion Protocols

23.3 Major Trauma, Hemorrhagic Shock, and Massive Transfusion Protocols

Exsanguinating hemorrhage remains the leading cause of preventable mortality following major trauma. Modern trauma resuscitation has evolved from aggressive crystalloid volume expansion to the integrated paradigm of Damage Control Resuscitation (DCR), combining permissive hypotension, immediate hemorrhage control, balanced hemostatic transfusion, and prevention of the lethal triad.

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1. Primary Survey: The (C)ABCDE Paradigm

The Advanced Trauma Life Support (ATLS) algorithm incorporates catastrophic hemorrhage control as the foremost clinical priority:

+--------------------------------------------------------------------------+
|                       (C)ABCDE RESUSCITATION SEQUENCE                    |
+--------------------------------------------------------------------------+
| (C) | Catastrophic Hemorrhage: Arrest life-threatening external bleeding |
|     | with tourniquets, junctional clamps, and hemostatic packing.       |
+-----+--------------------------------------------------------------------+
|  A  | Airway with Cervical Spine Restriction: Manual in-line             |
|     | stabilization (MILS), video-laryngoscopy, or surgical airway.       |
+-----+--------------------------------------------------------------------+
|  B  | Breathing and Ventilation: Exclude tension pneumothorax, open      |
|     | chest wounds, and massive hemothorax; finger thoracostomy.         |
+-----+--------------------------------------------------------------------+
|  C  | Circulation and Internal Hemorrhage: eFAST examination, pelvic     |
|     | binder placement, wide-bore IV access, balanced blood transfusion. |
+-----+--------------------------------------------------------------------+
|  D  | Disability: Neurological evaluation (GCS, pupil symmetry, spinal). |
+-----+--------------------------------------------------------------------+
|  E  | Exposure and Environment: Complete visualization while strictly    |
|     | maintaining normothermia (prevent hypothermia).                    |
+-----+--------------------------------------------------------------------+

• Airway Control with Cervical Spine Restriction: Ensure manual in-line stabilization (MILS) during airway instrumentation. Minimize cervical movement by releasing the anterior collar piece while maintaining axial stabilization. Induction agents must be drastically down-titrated in hypovolemia (e.g. ketamine $0.5\text{--}1.0\text{ mg/kg}$ or etomidate $0.15\text{--}0.2\text{ mg/kg}$) to avoid post-induction cardiovascular collapse.
• Decompression of Tension Pneumothorax: Immediate finger thoracostomy or needle decompression using a large-bore cannula ($14\text{--}16\text{ G}$) at the fourth or fifth intercostal space just anterior to the mid-axillary line in adults (ATLS 10th edition; the second intercostal space in the mid-clavicular line remains the site in children), followed promptly by chest drain placement.
• Circulatory Assessment: Perform an extended Focused Assessment with Sonography for Trauma (eFAST) to identify free fluid in the right upper quadrant (Morison's pouch), left upper quadrant (splenorenal recess), pelvis, pericardium, and pleural spaces. In unstable pelvic fractures, immediately apply a pelvic binder centered over the greater trochanters (not the iliac crests).

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2. ATLS Classification of Hemorrhagic Shock

Note: The ATLS 10th edition (2018) presents these signs as directional changes rather than fixed thresholds and adds base deficit; the numeric values above are traditional teaching values.

Clinical Pearl: Class III shock represents the critical tipping point where compensatory vasoconstriction and tachycardia fail to preserve cardiac output, precipitating overt systemic hypotension and tissue hypoperfusion.

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3. The Lethal Triad and Trauma-Induced Coagulopathy (TIC)

                      [ THE LETHAL TRIAD OF TRAUMA ]
                                    |
         +--------------------------+--------------------------+
         |                                                     |
  [ Hypothermia ] <====================================> [ Acidosis ]
   - Core temp <35°C                                       - Base excess <-6 mmol/L
   - Clotting enzyme kinetics                              - Inhibits factor complexes
     drop ~10% per 1°C                                       (FVIIa/TF drops 90% at pH 7.0)
         ^                                                     ^
         |                                                     |
         +=================> [ Coagulopathy ] <================+
                              - Glycocalyx shedding (syndecan-1)
                              - Fibrinogen consumption
                              - Hyperfibrinolysis (tPA excess)

1. Hypothermia ($<35\text{°C}$): Cold exposure, exposure of body cavities, and rapid infusion of unwarmed fluids impair hemostasis. The enzyme kinetics of the coagulation cascade decline linearly by approximately 10% per $1\text{°C}$ drop in temperature. Platelet activation, adhesion (glycoprotein Ib-IX), and aggregation (glycoprotein IIb/IIIa) are severely paralyzed.
2. Metabolic Acidosis ($pH < 7.20$, Base Excess $< -6\text{ mmol/L}$): Lactic acidosis secondary to tissue hypoperfusion directly suppresses clotting factor complex assembly on platelet phospholipid surfaces. At a $pH$ of 7.0, the enzymatic activity of the factor VIIa / tissue factor complex decreases by more than 90%, and prothrombinase complex activity falls by 70%.
3. Trauma-Induced Coagulopathy (TIC): TIC is an endogenous, phenotypic coagulopathy present in up to one-third of major trauma patients prior to significant IV fluid administration. Driven by tissue hypoperfusion and sympathoadrenal activation, the endothelial glycocalyx sheds syndecan-1 and heparan sulfates (endogenous auto-heparinization). Thrombomodulin expression surges, activating Protein C, which irreversibly degrades factors Va and VIIIa while neutralizing plasminogen activator inhibitor-1 (PAI-1), culminating in uninhibited hyperfibrinolysis and profound consumptive hypofibrinogenemia.

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4. Principles of Damage Control Resuscitation (DCR)

Damage Control Resuscitation is an integrated clinical strategy designed to sustain vital organ perfusion while preventing exacerbation of the lethal triad.

Permissive Hypotension (Deliberate Hypotension)

• Target: Maintain a systolic blood pressure of $80\text{--}90\text{ mmHg}$ (or Mean Arterial Pressure of $50\text{--}60\text{ mmHg}$, or palpable radial pulse) until definitive surgical or endovascular hemostasis is attained.
• Rationale: Aggressive fluid administration elevates hydrostatic pressure, "popping nascent clots" and worsening dilutional coagulopathy and hypothermia.
• Crucial Exception: Traumatic Brain Injury (TBI): Permissive hypotension is strictly contraindicated in patients with known or suspected severe TBI. Autoregulation is lost, and cerebral perfusion pressure ($CPP = MAP - ICP$) becomes entirely pressure-dependent. Even brief episodes of hypotension ($SBP < 90\text{ mmHg}$) double mortality in TBI. In neurotrauma, the target systolic blood pressure must be maintained at $\ge 100\text{--}110\text{ mmHg}$ (or $MAP \ge 80\text{ mmHg}$).

Damage Control Surgery (DCS)

Abbreviated initial surgical intervention ($<60\text{--}90\text{ minutes}$) dedicated strictly to: 1) controlling surgical hemorrhage (packing, vascular shunts); 2) controlling contamination (stapling bowel perforations); and 3) temporary abdominal closure (vacuum packs). Definitive anatomical reconstruction is deferred while the patient is transferred to the ICU for correction of hypothermia, acidosis, and coagulopathy.

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5. Massive Transfusion Protocols, Viscoelastic Testing, and TXA

Definitions of Massive Transfusion

• Replacement of $\ge 1$ complete circulating blood volume within 24 hours (~70 mL/kg in adults).
• Transfusion of $>10\text{ units}$ of packed red blood cells (PRBC) within 24 hours.
• Transfusion of $>4\text{ units}$ of PRBC within 1 hour with anticipated ongoing bleeding.
• Replacement of $>50\%$ of total blood volume within 3 hours.

Empirical 1:1:1 Ratio vs Goal-Directed Viscoelastic Resuscitation

The PROPPR trial (2015) compared fixed-ratio resuscitation with 1 unit of PRBC : 1 unit of Fresh Frozen Plasma (FFP) : 1 unit of Platelets (e.g. 6 PRBC : 6 FFP : 1 apheresis platelet pack) against a 1:1:2 ratio. There was no significant difference in all-cause mortality at 24 hours or 30 days, but the 1:1:1 group achieved haemostasis more often and had fewer deaths from exsanguination within 24 hours.

Modern European trauma guidelines strongly recommend viscoelastic hemostatic assays (ROTEM / TEG) to drive individualized, goal-directed resuscitation:

+----------------+-------------------------------+----------------------------+
| ROTEM TEST     | PATHOLOGY IDENTIFIED          | DIRECTED INTERVENTION      |
+----------------+-------------------------------+----------------------------+
| EXTEM CT >80s  | Clotting factor deficiency    | Fresh Frozen Plasma (FFP)  |
|                | or delayed thrombin generation| or 4-factor PCC (25 IU/kg) |
+----------------+-------------------------------+----------------------------+
| FIBTEM A10     | Severe hypofibrinogenemia     | Fibrinogen Concentrate     |
| <10 mm         | (<1.5-2.0 g/L)                | (2-4 g) or Cryoprecipitate |
+----------------+-------------------------------+----------------------------+
| EXTEM A10 <40mm| Thrombocytopenia or platelet   | Platelet Concentrate       |
| (normal FIBTEM)| dysfunction                   | (1 adult pool)             |
+----------------+-------------------------------+----------------------------+
| EXTEM ML >15%  | Pathological systemic         | Tranexamic Acid (TXA)      |
|                | hyperfibrinolysis             | 1 g IV bolus               |
+----------------+-------------------------------+----------------------------+

Tranexamic Acid (TXA) and the CRASH-2 Trial

• Mechanism: Synthetic lysine analogue that competitively binds plasminogen lysine-binding sites, preventing plasminogen activation and fibrin degradation.
• CRASH-2 Evidence: Administration of TXA ($1\text{ g}$ IV over 10 minutes, followed by $1\text{ g}$ IV infusion over 8 hours) in bleeding trauma patients within 3 hours of injury significantly reduced all-cause mortality (RR 0.91; $p=0.0035$) and death due to bleeding (RR 0.85; $p=0.0077$).
• Critical Time Dependence: When administered $>3\text{ hours}$ after injury, TXA increased the risk of death due to bleeding (RR 1.44; $p=0.004$), without an excess of vascular occlusive events. TXA should not be started if $>3\text{ hours}$ have elapsed since injury.

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6. Complications of Massive Blood Transfusion

1. Citrate Toxicity and Acute Hypocalcemia: Citrate anticoagulant in PRBCs and FFP chelates ionized calcium and magnesium. Hepatic clearance of citrate is impaired by hypothermia and hypoperfusion. Ionized calcium levels drop ($Ca^{2+} < 0.9\text{ mmol/L}$), precipitating myocardial depression, blunted systemic vascular resistance, prolonged QT intervals, and coagulopathic failure (calcium is Factor IV). Management: Prophylactically infuse $10\text{ mL}$ of 10% calcium chloride IV for every $2\text{--}4\text{ units}$ of blood products transfused.
2. Hyperkalemia: Extracellular potassium concentrations in stored PRBCs rise by approximately $1\text{ mmol/L/day}$, exceeding $25\text{--}30\text{ mmol/L}$ near expiration ($35\text{--}42\text{ days}$). Rapid, pressurized infusion can precipitate lethal ventricular arrhythmias.
3. Hypothermia: Transfusing cold PRBCs ($4\text{°C}$) directly into the central circulation causes cardiac dysrhythmias and worsens coagulopathy. Use high-flow fluid warmers (e.g. Belmont, Level 1) capable of delivering fluids at $37\text{--}40\text{°C}$ at rates $>500\text{ mL/min}$.
4. TRALI vs TACO Differential Diagnosis: