Bleeding and Shock: Emergency Medical Care Essentials

Bleeding

One of the most time-sensitive conditions paramedics face, recognized for its potential to lead to shock.

Shock

A state of cardiovascular system collapse that causes inadequate tissue perfusion.

Heart

A muscular, cone-shaped organ (avg. 280-350g in men, 225-280g in women) located behind the sternum, responsible for pumping blood. It has four chambers: two atria (receiving blood) and two ventricles (pumping blood out).

Blood Flow

Deoxygenated blood enters the right atrium (via vena cava), passes to the right ventricle, then to the lungs (via pulmonary artery). Oxygenated blood returns to the left atrium (via pulmonary veins), flows to the left ventricle, and is then pumped into the aorta for systemic circulation.

Blood

Composed of plasma (92% water, 8% dissolved substances) and formed elements

Red Blood Cells (Erythrocytes)

Most numerous, disc-shaped, contain hemoglobin for oxygen transport.

White Blood Cells (Leukocytes)

Fight infection

Platelets

Small cells essential for clot formation (hemostasis) to control bleeding.

Blood Vessels

Arteries, veins, arterioles, capillaries, and venules form the network for blood circulation.

Perfusion

The circulation of blood within an organ or tissue in adequate amounts to meet cellular needs.

Organ Tolerance to Hypoperfusion (at 37.0°C)

Heart: Requires constant perfusion.

    ◦ Brain and Spinal Cord: Cannot go more than 4-6 minutes.

    ◦ Kidneys: Permanently damaged after 45 minutes.

    ◦ Skeletal Muscles: Tolerate up to 2 hours.

    ◦ GI Tract: Can exist with limited perfusion for several hours.

Cardiac Output

The amount of blood pumped through the circulatory system in 1 minute, calculated as pulse rate multiplied by stroke volume.

Starling Law of the Heart

Increased venous return stretches ventricles, resulting in increased cardiac contractility to maintain normal cardiac function.

Hemorrhage

Bleeding that can be minor or life-threatening.

External Bleeding

Visible blood loss due to a break in the skin.

Internal Bleeding

Bleeding that occurs within the body, often from trauma or nontraumatic causes.

Total Blood Volume

Adult males: approx. 70 mL/kg; adult females: approx. 65 mL/kg.

Tolerance

The body cannot tolerate an acute loss of more than 20% of total blood volume.

Compensated Shock

The earliest stage of shock where the body can still compensate for blood loss. 15-30%

Decompensated Shock

A stage of shock where blood pressure begins to fall and compensatory measures start to fail. Blood volume drops by more than 30%.

Irreversible Shock

The final, fatal stage of shock where organ failure becomes evident, ultimately leading to death.

Trauma Triad of Death

A critical combination of hypothermia, coagulopathy (poor blood clotting), and acidosis that significantly increases mortality in trauma patients.

Cardiogenic Shock

Failure of the heart's pumping ability (e.g., myocardial infarction, arrhythmias, severe acidosis). Leads to insufficient blood circulation and inadequate oxygen delivery.

Hypovolemic Shock 

Loss of fluid volume.

Hemorrhagic Shock

Most common cause, specifically from blood loss (external or internal).

    ◦ Other fluid loss: Plasma, electrolyte solution (e.g., dehydration, burns, crush injury, anaphylaxis).

Neurogenic Shock

Failure of vasoconstriction, usually from spinal cord injury, leading to loss of sympathetic nervous system tone and widespread vasodilation below the injury level. This causes blood to pool in expanded vascular beds, resulting in relative hypovolemia and inadequate perfusion. Characterized by warm, pink, dry skin and absence of sweating below the injury level.

Distributive Shock

Widespread dilation of blood vessels, causing circulating blood volume to pool and tissue perfusion to decrease.

Baroreceptors

Detect drops in arterial pressure, stimulating the sympathetic nervous system and vasoconstrictor center of the medulla.

Hormonal Release

Renin-angiotensin-aldosterone system and antidiuretic hormone (ADH) are activated, triggering salt and water retention and peripheral vasoconstriction

Adrenal Gland Hormones

Epinephrine and norepinephrine are released, increasing pulse rate, strength of contraction, and peripheral vascular resistance (vasoconstriction).

Spleen

Releases sequestered red blood cells. These mechanisms aim to increase preload, stroke volume, and pulse rate, thereby increasing cardiac output. However, if hypoperfusion persists, these mechanisms fail, leading to progressive deterioration.

Septic Shock

Result of widespread infection leading to an uncontrolled inflammatory response and tissue hypoperfusion.

Anaphylactic Shock

A severe allergic reaction causing widespread vascular dilation and relative hypovolemia.

Systemic Inflammatory Response Syndrome (SIRS)

A systemic inflammatory response to severe clinical insults, not always indicative of infection.

Manifested by two or more of:

• Temperature >38°C or <36°C

• Heart rate >90 beats/min

• Respiratory rate >20 breaths/min or PCO2 <32 mm Hg

• White blood cell count >12 × 10^9 cells/L or <4 × 10^9 cells/L Uncontrolled SIRS can lead to hypotension, inadequate perfusion, and ultimately MODS and death.

Permissive Hypotension

Titrating systolic blood pressure to 80-90 mm Hg in hemorrhagic shock to promote better clotting.