Bleeding & Shock

Bleeding & Hemorrhage

Hemorrhage

Overview

Early recognition and effective control of hemorrhage are essential in both medical and trauma patients. Severe blood loss can rapidly reduce tissue perfusion and lead to shock or death. In major trauma, life-threatening bleeding should be controlled as early as possible while airway and breathing problems are also addressed.

Cardiovascular Anatomy and Physiology

Structure of the Heart

The heart is located within the thoracic cavity behind the sternum, with most of the organ positioned slightly to the left of the midline.

The heart contains four chambers:

• Right atrium: Receives deoxygenated blood returning from the systemic circulation.
• Right ventricle: Pumps blood toward the lungs.
• Left atrium: Receives oxygenated blood returning from the lungs.
• Left ventricle: Pumps oxygenated blood into the systemic circulation.

Blood travels from the right atrium through the tricuspid valve into the right ventricle. It then passes through the pulmonary valve and enters the pulmonary circulation.

On the left side, blood moves from the left atrium through the mitral valve into the left ventricle. The left ventricle then pumps blood through the aortic valve and into the aorta.

Blood Flow Through the Heart and Lungs

Deoxygenated blood from the body returns through the superior and inferior vena cava and enters the right atrium. It then moves into the right ventricle and is pumped toward the lungs.

Within the lungs:

• Carbon dioxide is removed from the blood.
• Oxygen enters the bloodstream.
• Oxygenated blood returns to the left side of the heart.
• The left ventricle pumps the blood throughout the body.

This continuous movement maintains oxygen delivery and tissue perfusion.

The Cardiac Cycle

The cardiac cycle describes the repeated contraction and relaxation of the heart that keeps blood circulating.

Electrical activity begins primarily at the sinoatrial (SA) node, causing the atria to contract. The impulse then travels through the atrioventricular (AV) node and conduction system, resulting in ventricular contraction.

Important cardiovascular terms include:

• Preload: The volume of blood returning to and filling the ventricles before contraction.
• Afterload: The resistance or pressure the ventricles must overcome to eject blood.
• Stroke volume: The amount of blood pumped from a ventricle with each contraction.
• Heart rate: The number of heartbeats per minute.
• Cardiac output: The amount of blood pumped by the heart each minute.

Cardiac output = Heart rate × Stroke volume

Significant blood loss reduces venous return and preload, which can decrease stroke volume and cardiac output.

Components of Blood

Blood consists of plasma, red blood cells, white blood cells, and platelets. Each component contributes to circulation, oxygen delivery, immune defense, or clotting.

Plasma

Plasma is the liquid portion of blood and makes up more than half of total blood volume. It is mostly water and also contains:

• Electrolytes.
• Proteins.
• Nutrients.
• Hormones.
• Waste products.
• Clotting factors.

Red Blood Cells

Red blood cells (RBCs), also called erythrocytes, transport oxygen from the lungs to tissues and help carry carbon dioxide back toward the lungs.

RBCs contain hemoglobin, the protein responsible for binding and transporting oxygen.

Hemoglobin

Each hemoglobin molecule can bind multiple oxygen molecules. A sufficient amount of functioning hemoglobin is necessary for adequate oxygen delivery to tissues.

White Blood Cells

White blood cells (WBCs), or leukocytes, are involved in immune defense and help protect the body from infection.

Different types of white blood cells perform specialized immune functions.

Platelets

Platelets are essential for controlling bleeding. They gather at damaged blood vessels and interact with clotting proteins to help form a stable blood clot.

Normal coagulation also depends on several other factors, including calcium and clotting proteins.

Hematocrit

Hematocrit represents the percentage of blood volume composed of red blood cells.

Abnormal hematocrit values may suggest conditions such as:

• Blood loss.
• Anemia.
• Dehydration.
• Certain blood disorders.

Normal reference ranges vary according to age, sex, laboratory, and clinical circumstances.

Blood Circulation and Perfusion

Arteries generally carry blood away from the heart, while veins carry blood back toward the heart.

The vascular system consists of an extensive network of:

• Arteries.
• Arterioles.
• Capillaries.
• Venules.
• Veins.

These vessels distribute oxygen and nutrients throughout the body and return waste products for removal.

Perfusion refers to the delivery of blood through tissues in an amount sufficient to meet cellular demands for oxygen and nutrients.

The autonomic nervous system helps regulate blood flow by adjusting heart rate, cardiac contractility, and vascular tone according to the body’s needs.

How Hemorrhage Affects the Body

Hemorrhage may be external or internal. The severity depends on the blood vessel involved, location of bleeding, speed of blood loss, and patient’s ability to compensate.

External Hemorrhage

External bleeding can often be classified by the type of blood vessel involved.

Capillary Bleeding

Capillary bleeding usually appears as slow, steady oozing from the surface of a wound.

Although individual capillaries produce limited bleeding, extensive abrasions or injuries involving a large surface area can still result in significant blood loss.

Arterial Bleeding

Arterial bleeding may initially:

• Spurt or pulse with the heartbeat.
• Flow rapidly under pressure.
• Appear bright red because of its relatively high oxygen content.

As blood pressure falls, the classic spurting pattern may become less obvious. Arterial bleeding can cause life-threatening blood loss rapidly.

Venous Bleeding

Venous bleeding usually produces a steady continuous flow. Blood commonly appears darker red because it contains less oxygen than arterial blood.

Injury to large veins can also produce severe and potentially fatal hemorrhage.

Internal Hemorrhage

Internal bleeding occurs when blood collects inside the body rather than leaving through an external wound.

It may occur in:

• The chest.
• Abdomen.
• Pelvis.
• Retroperitoneal space.
• Skull.
• Muscles and soft tissues around fractures.

Long-bone fractures can produce substantial bleeding into surrounding tissues, even without visible external blood loss.

Bleeding into the chest, abdomen, or pelvis can be particularly dangerous because these spaces can conceal a large volume of blood.

Nontraumatic internal hemorrhage may result from conditions such as:

• Gastrointestinal bleeding.
• Ruptured ectopic pregnancy.
• Ruptured aneurysm.
• Intracranial bleeding.
• Other spontaneous vascular or organ injuries.

Bruising or swelling may take time to develop, so significant internal hemorrhage can be present before obvious external signs appear.

Clinical Importance of Blood Loss

The effect of hemorrhage depends not only on how much blood is lost but also on how quickly the loss occurs and the patient’s underlying health.

Adults generally have approximately 65–70 mL of blood per kilogram of body weight, although actual blood volume varies.

As blood loss progresses, patients may develop:

• Increasing heart rate.
• Faster respirations.
• Pale, cool, or clammy skin.
• Weak peripheral pulses.
• Anxiety or restlessness.
• Delayed capillary refill.
• Altered mental status.
• Falling blood pressure as shock becomes more severe.

Children have a smaller total circulating blood volume, so what appears to be a relatively small amount of bleeding can represent a significant percentage of their total blood volume.

Hemorrhage should be considered especially serious when there is:

• A significant mechanism of injury.
• Rapid or uncontrolled bleeding.
• Evidence of substantial blood loss.
• Poor general appearance.
• Signs of shock.
• Altered mental status.
• Unexplained tachycardia or hypotension.

Early identification and control of life-threatening hemorrhage, combined with rapid treatment for shock and appropriate transport, are critical to maintaining circulation and tissue perfusion.

Physiologic Effects of Blood Loss

When significant bleeding occurs, the body immediately activates mechanisms designed to preserve circulating blood volume and maintain perfusion to vital organs. The patient’s response depends on the amount and speed of blood loss, type of vessel injured, overall health, medications, and ability to form clots.

Arterial hemorrhage may be especially difficult to control because blood is moving under higher pressure. As circulating volume and blood pressure decrease, the force of arterial bleeding may become less obvious even though serious blood loss has already occurred.

Venous bleeding usually flows steadily at a lower pressure, while capillary bleeding commonly appears as slow oozing. These forms of bleeding may clot more readily than major arterial hemorrhage.

Hemostasis and Clot Formation

Hemostasis is the body’s process for stopping bleeding. It involves blood-vessel constriction, platelet activity, and the formation of a stable clot.

Important factors include:

• Injured blood vessels constrict to help decrease blood flow.
• Platelets collect at the damaged area and form an initial plug.
• Clotting factors strengthen the platelet plug with fibrin.
• Large wounds or severely damaged vessels may continue bleeding despite the body’s clotting response.
• Anticoagulant and antiplatelet medications can interfere with normal clot formation.
• Certain medications, including beta-blockers, may blunt the expected increase in heart rate, making shock more difficult to recognize.
• Hypothermia impairs coagulation and can make hemorrhage increasingly difficult to control.

Preventing the patient from becoming cold is therefore an important part of hemorrhage management.

Hemorrhagic Shock

Hemorrhagic shock develops when blood loss becomes severe enough that the circulatory system cannot deliver adequate oxygen to body tissues. It may occur with either external or internal hemorrhage.

Major injuries involving the heart, chest, abdomen, pelvis, liver, spleen, or major blood vessels can cause rapid and life-threatening blood loss.

As circulating volume decreases:

• Venous return to the heart falls.
• Preload decreases.
• Stroke volume decreases.
• Cardiac output declines.
• The heart rate commonly increases.
• Peripheral blood vessels constrict.
• Tissue perfusion progressively worsens.

Approximate Classes of Hemorrhage

These categories are useful for recognizing trends, but actual patients may not fit perfectly into one class.

Class I – Mild Blood Loss

Approximately less than 15% of circulating blood volume has been lost.

The patient may have:

• Near-normal heart rate and blood pressure.
• Normal or slightly anxious mental status.
• Normal respiratory rate.
• Warm or slightly pale skin.
• Little change in urine output.

Compensation is generally effective at this stage.

Class II – Moderate Blood Loss

Approximately 15–30% of circulating blood volume may be lost.

Possible findings include:

• Increasing heart rate.
• Narrowing pulse pressure.
• Mild anxiety or restlessness.
• Increased respiratory rate.
• Pale or cool skin.
• Decreasing urine output.

Blood pressure may still appear relatively normal because compensatory mechanisms remain active.

Class III – Severe Blood Loss

Approximately 30–40% of circulating blood volume may be lost.

Findings may include:

• Significant tachycardia.
• Falling blood pressure.
• Narrow pulse pressure.
• Rapid respirations.
• Confusion or increasing anxiety.
• Cool, pale, clammy skin.
• Markedly reduced urine output.
• Weak peripheral pulses.

At this stage, compensation is failing and decompensated shock is developing.

Class IV – Critical Blood Loss

More than approximately 40% of circulating blood volume may be lost.

Possible findings include:

• Profound hypotension.
• Very rapid or weak pulse.
• Severely altered mental status.
• Cold, pale, mottled, or cyanotic skin.
• Minimal or absent urine output.
• Weak or absent peripheral pulses.
• Respiratory deterioration.
• Impending cardiovascular collapse.

This condition requires immediate hemorrhage control, aggressive resuscitation, and rapid definitive care.

Compensated and Decompensated Shock

During compensated shock, the body is still able to maintain blood pressure through increased heart rate and vasoconstriction.

Early findings may include:

• Anxiety or restlessness.
• Feeling that something is seriously wrong.
• Rapid, weak pulse.
• Pale or cool skin.
• Delayed capillary refill.
• Nausea or vomiting.
• Increased thirst.

Children may maintain a normal blood pressure until relatively late in shock.

During decompensated shock, the body’s compensatory mechanisms begin to fail.

Possible findings include:

• Altered mental status.
• Decreasing level of consciousness.
• Hypotension.
• Weak or absent peripheral pulses.
• Rapid, labored, or irregular breathing.
• Cool, clammy, mottled, or cyanotic skin.
• Reduced urine output.
• Progressive cardiovascular collapse.

Management of Hemorrhage and Hemorrhagic Shock

External Bleeding

Life-threatening external bleeding should be recognized and controlled as early as possible.

Initial management includes:

• Apply firm direct pressure over the bleeding site.
• Use an appropriate pressure dressing when bleeding is controlled.
• If bleeding remains severe, rapidly progress to another method such as a tourniquet or hemostatic dressing, depending on the wound location.
• Treat associated shock and arrange rapid transport.
• Keep the patient warm to reduce hypothermia and clotting problems.

Following serious head trauma, blood or fluid coming from the nose or ears should generally be allowed to drain freely rather than tightly packed or obstructed when a skull-base injury is suspected.

Tourniquet Use

Tourniquets are used for life-threatening extremity hemorrhage that cannot be rapidly controlled with simpler measures or when immediate control is necessary.

Important principles include:

• Position the tourniquet proximal to the wound, avoiding placement directly over a joint.
• If the exact bleeding site cannot be seen during an emergency, a high-and-tight placement may be appropriate according to protocol.
• Tighten until bleeding completely stops.
• If bleeding continues, apply a second tourniquet above the first when necessary.
• Record the time of application.
• Once correctly placed for life-threatening hemorrhage, do not routinely loosen the tourniquet in the field unless directed by an appropriate protocol or medical authority.

The primary goal is complete hemorrhage control.

Splinting and Bleeding Control

Fractured bones can damage nearby blood vessels and soft tissues. Movement of unstable fractures may worsen hemorrhage and disrupt developing clots.

Splinting can:

• Stabilize fractured bones.
• Reduce additional tissue injury.
• Decrease pain.
• Help limit further bleeding.
• Improve patient comfort during transport.

Distal circulation, sensation, and movement should be checked before and after splint application whenever possible.

Traction Splints

Traction splints may be used for selected isolated midshaft femur fractures when no contraindications are present.

They can help:

• Align the fractured femur.
• Reduce muscle spasm.
• Limit movement of sharp bone fragments.
• Decrease pain and potential internal bleeding.

Continued distal neurovascular monitoring is essential.

Hemostatic Dressings

Hemostatic dressings are designed to assist clot formation and are particularly useful for severe bleeding in locations where a tourniquet cannot be applied effectively, such as certain junctional wounds.

Modern agents may work by concentrating clotting components or activating clotting pathways.

When used:

• Pack the dressing firmly into the bleeding wound when appropriate.
• Apply strong direct pressure for the recommended period.
• Continue monitoring for recurrent bleeding.
• Follow local EMS protocols and product instructions.

Suspected Internal Hemorrhage

Internal bleeding cannot usually be controlled directly in the prehospital environment. Management focuses on supporting circulation and getting the patient to definitive care quickly.

Important measures include:

• Maintain the airway, breathing, and circulation.
• Control any accompanying external hemorrhage.
• Minimize unnecessary movement.
• Splint associated fractures when indicated.
• Monitor vital signs and mental status frequently.
• Establish vascular access according to protocol.
• Provide appropriate fluid or blood-product resuscitation when available and indicated.
• Prevent hypothermia.
• Provide pain management when appropriate.
• Keep the patient NPO because surgery or another procedure may be required.
• Arrange rapid transport to an appropriate trauma facility.

Many causes of internal hemorrhage require surgery, interventional radiology, or other hospital-based procedures for definitive bleeding control.

Prehospital Care for Hemorrhagic Shock

Treatment priorities are aimed at maintaining perfusion while controlling the source of blood loss.

EMS management may include:

• Control life-threatening external bleeding immediately.
• Maintain a patent airway.
• Support oxygenation and ventilation when required.
• Treat associated chest, pelvic, or extremity injuries.
• Establish appropriate vascular access without unnecessarily delaying transport.
• Use warmed resuscitation fluids or blood products according to local protocol.
• Avoid excessive crystalloid administration when it may worsen dilution, hypothermia, or bleeding.
• Continuously reassess mental status, pulse quality, blood pressure, skin condition, and respiratory status.
• Keep the patient warm.
• Transport rapidly to a facility capable of definitive hemorrhage control and blood-product resuscitation.

The most important priorities are rapid bleeding control, prevention of hypothermia, recognition of shock, and minimizing the time to definitive care.