7.2 Hemorrhage Control and Massive Transfusion Protocols (MTP)

Hemorrhage Control and Massive Transfusion Protocols (MTP)

Mechanical Hemorrhage Control

In the critical care transport environment, immediate hemorrhage control is the first priority of resuscitation. Uncontrolled hemorrhage is the leading cause of preventable death in trauma.

1. Tourniquets

Tourniquets are the gold standard for controlling life-threatening extremity hemorrhage. According to Tactical Combat Casualty Care (TCCC) guidelines, tourniquets should be applied immediately for arterial bleeding.

• Application Principles: In a care-under-fire or high-threat environment, tourniquets are applied "high and tight" over the clothing. In low-threat environments or during secondary assessment, the tourniquet is applied directly to the skin, 2-3 inches proximal to the wound, avoiding placement over joints.
• Assessment: The tourniquet must be tightened until distal pulses are obliterated and bleeding stops. If bleeding continues, a second tourniquet should be applied immediately proximal to the first.
• Conversion: Tourniquet conversion (replacing a tourniquet with hemostatic dressings and pressure dressings) should be attempted within 2 hours of application if the patient is hemodynamically stable, the wound is monitorable, and there is no amputation. Tourniquets left in place for more than 6 hours are rarely converted in the prehospital phase due to the risk of releasing necrotic toxins (myoglobin, potassium) and causing reperfusion injury.

2. Pelvic Binders

Pelvic fractures, particularly "open-book" anteroposterior compression fractures, can increase retroperitoneal volume by up to 3-4 liters, creating a massive space for occult hemorrhage. Pelvic binders stabilize the pelvis, decrease pelvic volume, and promote tamponade of venous plexus bleeding.

• Application Technique: The pelvic binder must be centered directly over the greater trochanters of the femurs, NOT the iliac crests. Placing the binder too high fails to stabilize the pelvic ring and can worsen bleeding.
• Complications: Binders should not be left on for more than 24 hours to prevent skin necrosis. Direct inspection of pressure points is essential during long transport flights.

3. REBOA (Resuscitative Endovascular Balloon Occlusion of the Aorta)

REBOA is a minimally invasive technique utilizing a balloon catheter placed via the femoral artery into the aorta to control non-compressible torso hemorrhage (NCTH) and support central perfusion.

• Zones of Occlusion:
  • Zone I: Descending thoracic aorta (left subclavian to celiac artery). Indicated for severe intra-abdominal or retroperitoneal hemorrhage. Inflation is limited to a maximum of 30-45 minutes to prevent irreversible distal organ ischemia.
  • Zone II: Paravisceral aorta (celiac to lowest renal artery). This is a non-occlusion zone.
  • Zone III: Infrarenal aorta (lowest renal artery to aortic bifurcation). Indicated for severe pelvic, junctional, or groin hemorrhage. Can be inflated longer (up to 60 minutes) due to lower ischemic risk to visceral organs.
• Management: Balloon deflation must be performed slowly to prevent profound reperfusion shock, metabolic wash-out (lactic acid, potassium), and sudden cardiovascular collapse.

Massive Transfusion Protocol (MTP) and Balanced Resuscitation

Massive transfusion is historically defined as the administration of >= 10 units of packed red blood cells (PRBCs) within 24 hours, or >= 4 units within 1 hour. Modern transport medicine relies on dynamic predictors like the Assessment of Blood Consumption (ABC) score (positive if >= 2 of: penetrating mechanism, SBP < 90 mmHg, HR > 120 bpm, or positive FAST) to trigger MTP early.

Balanced Ratios

Resuscitation with crystalloids leads to dilution coagulopathy. MTP utilizes a balanced, ratio-driven approach of 1:1:1 consisting of:

• 1 unit of PRBCs (for oxygen-carrying capacity).
• 1 unit of Fresh Frozen Plasma (FFP) (for clotting factors and fibrinogen).
• 1 unit of Platelets (for primary hemostasis). The PROPPR trial demonstrated that a 1:1:1 ratio compared to a 1:1:2 ratio achieves better early hemostasis and reduces death from exsanguination. Many transport programs utilize Low-Titer O-Positive or O-Negative Whole Blood (LTOWB) as it provides all components in physiological ratios, minimizes donor exposure, and contains fewer preservatives.

Calcium Management

Blood products are preserved with sodium citrate, which chelates calcium ions. During rapid transfusion (especially rates > 1 unit every 5 minutes), the liver cannot metabolize citrate quickly enough, leading to hypocalcemia (ionized calcium < 1.1 mmol/L). Because calcium is essential for coagulation factor activation, hypocalcemia worsens coagulopathy.

• Management: Flight crews must administer 1 gram of Calcium Chloride IV or 3 grams of Calcium Gluconate IV after every 3-4 units of blood products. Calcium chloride delivers three times more elemental calcium than calcium gluconate but requires a secure, preferably central, line due to the risk of tissue necrosis if extravasation occurs.

CAMTS Blood Storage Requirements

The Commission on Accreditation of Medical Transport Systems (CAMTS) mandates strict blood product storage and transport standards:

• Blood must be stored in specialized transport coolers that maintain a temperature of 1-6°C.
• Coolers must have continuous temperature monitoring or verification logs.
• Unused blood products must be returned to the blood bank within strict timeframes (typically within 24-48 hours depending on validation) to prevent wastage.

Tranexamic Acid (TXA)

Tranexamic acid is a synthetic lysine analogue that acts as an antifibrinolytic.

• Mechanism of Action: TXA competitively inhibits the activation of plasminogen to plasmin. By blocking the lysine-binding sites on plasminogen molecules, it prevents plasminogen from binding to fibrin, thereby inhibiting clot breakdown (fibrinolysis).
• Clinical Evidence (CRASH-2): The landmark CRASH-2 trial demonstrated that TXA reduces all-cause mortality in trauma patients with, or at risk of, significant hemorrhage.
• Timing Constraint: TXA must be administered within 3 hours of the injury. Administration after 3 hours is associated with an increased risk of death, potentially due to pro-thrombotic complications or a shift in the inflammatory response.
• Dosing Protocol: The standard regimen is a loading dose of 1 gram IV infused over 10 minutes (to avoid transient hypotension associated with rapid boluses), followed by an infusion of 1 gram IV over the subsequent 8 hours. Some modern protocols use a single 2g bolus, but the 1g + 1g regimen remains the benchmark for examinations.