Hemorrhage

Introduction

Recognizing and controlling hemorrhage in both medical and trauma patients is essential for reducing both morbidity and mortality. In trauma care, bleeding control is a top priority and should be addressed immediately after airway management, or simultaneously if enough resources and personnel are available.

Anatomy & Physiology

Heart Structures

The heart sits within the thoracic cavity behind the sternum, with roughly two-thirds positioned in the left mediastinum. It is composed of four chambers: the right atrium and ventricle, which send deoxygenated blood to the lungs and receive systemic venous return, and the left atrium and ventricle, which distribute oxygenated blood to the systemic circulation and receive blood from the pulmonary system.

Blood moves from the right atrium to the right ventricle through the tricuspid valve and is then pumped into the pulmonary circulation via the pulmonary semilunar valve. On the left side, blood flows from the left atrium to the left ventricle through the mitral valve and is then ejected into systemic circulation through the aortic semilunar valve.

Pulmonary and Systemic Flow

Deoxygenated blood returns to the heart through the superior and inferior vena cava into the right atrium. It is then sent to the lungs via the right ventricle, where carbon dioxide is exchanged for oxygen. Oxygen-rich blood then returns to the left heart to be circulated throughout the body.

Cardiac Cycle

The cardiac cycle describes the continuous sequence of heart contractions. It is regulated by electrical activity originating in the SA and AV nodes. Atrial contraction fills the ventricles, followed by ventricular contraction that pushes blood into the pulmonary and systemic circulations.

Preload refers to the volume of blood returning to the heart, which influences cardiac stretch and performance. Afterload is the resistance the left ventricle must overcome to eject blood into the aorta. Stroke volume is the amount of blood ejected per heartbeat, while cardiac output is the total blood pumped per minute, calculated as stroke volume multiplied by heart rate.

Blood Components

Plasma makes up over half of total blood volume and consists mostly of water with dissolved electrolytes, nutrients, and proteins.

Red blood cells (erythrocytes) account for about 45% of blood volume and transport oxygen using hemoglobin, which can bind up to four oxygen molecules per unit.

White blood cells and platelets make up about 1% of blood volume and are essential for immune defense and clot formation, respectively. Platelets work with clotting proteins and calcium to stop bleeding.

Hematocrit measures the percentage of red blood cells in blood, with normal ranges of approximately 40.7–50.3% in males and 36.1–44.3% in females.

Circulation and Perfusion

Arteries carry blood away from the heart, while veins return blood back to it. Perfusion refers to adequate blood flow reaching tissues to meet metabolic demands. The autonomic nervous system helps regulate vascular tone and blood distribution.

Pathophysiology of Hemorrhage

External Bleeding

Hemorrhage severity depends on the type of vessel injured. Capillary bleeding usually appears as slow oozing but can become significant in large surface injuries.

Arterial bleeding is typically bright red and may initially spurt due to high pressure before becoming a steady flow as pressure drops. The direction and nature of arterial injury can influence bleeding control.

Venous bleeding is darker in color and flows in a steady, continuous manner due to lower pressure.

Internal Bleeding

Internal hemorrhage may occur in various body regions and can be either contained or freely expanding. Long bone fractures can cause significant blood loss within surrounding tissues. Injuries involving the abdomen, chest, pelvis, or brain can lead to rapid and life-threatening bleeding.

Non-traumatic internal bleeding may result from gastrointestinal sources, ectopic pregnancy, aneurysm rupture, or organ injury. Visible signs may be delayed, so clinicians must rely on clinical assessment and vital signs.

Significance of Hemorrhage

Average blood volume is approximately 70 mL/kg in males and 65 mL/kg in females. Loss of more than 20% of total blood volume can lead to significant physiologic instability.

Children are particularly vulnerable due to lower total blood volume. The severity of bleeding depends on both volume and rate of loss, as well as overall patient health.

Signs of significant hemorrhage include trauma mechanism, shock symptoms, rapid blood loss, and inability to control bleeding.

Physiologic Response

Initial arterial bleeding may be forceful but weakens as blood volume decreases. Venous and capillary bleeding are more likely to clot spontaneously due to lower pressure. Exposure to air and tissue contact promotes clot formation.

Hemostasis occurs through vessel constriction and platelet aggregation. Conditions such as anticoagulant use, clotting disorders, hypothermia, and severe vessel damage can impair clot formation.

Hemorrhagic Shock

Hemorrhagic shock occurs when blood loss prevents adequate tissue perfusion. It is especially common in trauma involving major vascular structures or solid organs.

Classification (ACS System)

Class I (Mild/Compensated)

<15% blood loss (<750 mL)
Vital signs often normal or near normal
Minimal symptoms
Fluids may be used if needed

Class II (Early Shock)

15–30% loss (750–1500 mL)
Tachycardia, narrowed pulse pressure, mild anxiety
Delayed capillary refill
Crystalloid fluids indicated

Class III (Decompensated)

30–40% loss (1500–2000 mL)
Hypotension, confusion, tachycardia >120
Poor perfusion and altered mental status
Fluids and blood products required

Class IV (Severe/Irreversible)

40% loss (>2000 mL)
Severe hypotension, lethargy, cyanosis
Minimal or absent urine output
Requires aggressive resuscitation and transfusion

Clinical Presentation

Early compensation includes anxiety, tachycardia, thirst, and pale skin with normal blood pressure. As shock worsens, patients develop hypotension, weak pulses, altered mental status, and signs of organ hypoperfusion.

Management

External Hemorrhage Control

Immediate direct pressure is the first-line intervention. Rapid transport is required for unstable patients. Wound packing and pressure dressings are effective for large wounds.

Head or facial bleeding after trauma should not be aggressively blocked if skull fracture is suspected.

Tourniquets

Used for severe extremity bleeding. Applied 2–3 inches above the injury site and tightened until bleeding stops or distal pulse is lost. Additional tourniquets may be needed in extreme cases.

Splinting

Fracture stabilization reduces movement and bleeding. Air splints act as circumferential pressure devices but do not control arterial bleeding. Traction splints are specifically used for femur fractures to reduce hemorrhage risk.

Hemostatic Agents

These are used for severe bleeding in areas not suitable for tourniquets. They promote clot formation and vasoconstriction, with impregnated dressings preferred over powders due to lower complication risk.

Internal Hemorrhage Care

Management focuses on shock support, oxygenation, minimizing movement, and rapid transport. Definitive treatment requires surgical intervention.

Key interventions include:

Airway management and oxygen support
Large-bore IV access and fluid resuscitation per protocol
Monitoring vital signs frequently
Keeping patient warm
NPO status to reduce aspiration risk