Prehospital Academy Lesson 30.1
Hemorrhage Control: Vascular Dynamics and the MARCH Algorithm
Hemorrhage is the leading cause of preventable death in trauma. The transition from a controlled state to irreversible shock can occur in minutes, necessitating a rapid, aggressive approach to vascular integrity. This companion explores the transition from traditional ABCs to the MARCH algorithm, the physiological "Lethal Triad" that thwarts clotting, and the advanced clinical application of mechanical and chemical hemostasis in the field.
The Priority Shift: From ABC to MARCH
Modern trauma management has evolved to prioritize Massive Hemorrhage above all other interventions. The MARCH algorithm (Massive Hemorrhage, Airway, Respiration, Circulation, Head/Hypothermia) reflects the clinical reality that an arterial bleed from a femoral or brachial artery can result in exsanguination within 2-4 minutes far faster than the time it takes for a patient to die from an airway obstruction.
The EMT must differentiate between the three types of external bleeding:
Arterial: Bright red, pulsatile flow under high pressure. This is the highest priority (X in XABC).
Venous: Dark red, steady flow. While voluminous, it lacks the high-pressure "spurt" of arterial bleeding but can still lead to shock if not controlled.
Capillary: Oozing, bright red blood. Generally controlled by the body's natural hemostatic mechanisms.
The Lethal Triad of Trauma
Stopping the bleeding is only the first step. To save the patient, the EMT must prevent the Lethal Triad of Trauma, a self-reinforcing cycle of physiological failure:
Hypothermia: As the patient loses blood, they lose the ability to thermoregulate. Enzyme activity, including those in the clotting cascade, is temperature-dependent. A "cold" patient cannot form stable clots, regardless of how much pressure is applied.
Acidosis: Poor perfusion leads to cellular hypoxia and a shift to anaerobic metabolism. The resulting lactic acid buildup lowers the blood pH, further inhibiting the clotting factors.
Coagulopathy: The combination of cold and acid leads to a failure of the blood to clot (coagulopathy). This is exacerbated by the "dilutional" effect of aggressive crystalloid (IV fluid) resuscitation, which thins the remaining clotting factors and platelets.
Mechanical Hemostasis: Tourniquets and Junctional Packing
The Tourniquet is the definitive tool for extremity hemorrhage. It must be applied "high and tight" in high-threat environments or 2-3 inches above the wound in controlled settings. The goal is the Total Occlusion of Arterial Flow. If the distal pulse is still palpable, the tourniquet is only occluding venous return, which will actually increase blood loss by preventing venous drainage while allowing arterial inflow.
For Junctional Hemorrhage (groin, axilla, or neck), where tourniquets cannot be applied, Wound Packing is required. Hemostatic agents like Kaolin-impregnated gauze (e.g., QuikClot) work by activating Factor XII of the clotting cascade, while Chitosan-based agents (e.g., Celox) work by electrostatically binding to red blood cells to form a "mucoadhesive" plug. Both require at least 3 minutes of continuous manual pressure after packing to be effective.
Internal Hemorrhage: The "Five Places You Can Bleed to Death"
Internal bleeding is often occult, yet the body can hide massive volumes of blood in specific anatomical compartments. The EMT must assess for blood loss in the following "Five Places":
The Chest: Each hemothorax can hold up to 1,500 mL of blood.
The Abdomen: The peritoneal cavity can hold the patient's entire blood volume.
The Pelvis: A "book-opening" pelvic fracture can lead to 2,000 mL of retroperitoneal hemorrhage.
The Long Bones: A single femur fracture can account for 1,000 - 1,500 mL of blood loss.
"The Street": External bleeding that was missed during the initial assessment.
Critical Thinking Questions
How does the "Lethal Triad of Trauma" explain why a patient who is kept warm has a better chance of surviving an arterial bleed than one who becomes hypothermic?
Explain the physiological risk of applying a tourniquet that is "mostly tight" but still allows a distal pulse to be felt. What happens to the pressure in the limb?
Using the MARCH algorithm, justify why you would address a femoral artery bleed before managing a patient's partially obstructed airway.
Contrast the mechanism of action between Kaolin-based and Chitosan-based hemostatic agents. Why is "manual pressure" still required for both?
A patient presents with a rigid, distended abdomen and signs of compensated shock following a fall. Based on the "Five Places" framework, how much blood volume could potentially be sequestered in this space?