Hemorrhage: Causes and Classification

Hemorrhage

• Hemorrhage is the escape of blood outside the blood vessels or heart.

Causes of Hemorrhage

• Rupture of an artery or vein can cause a hemorrhage
• Laceration of a normal vessel due to trauma or a tumor is a common cause
• Laceration of a diseased vessel, such as from hypertension or atheroma, can lead to hemorrhage
• Hemorrhage may arise from systemic diseases like leukemia
• Bacterial infections like septicemia can induce hemorrhage
• Capillary bleeding due to minor trauma can also cause hemorrhage

Classification of Hemorrhage

• Hemorrhage can be categorized as external, internal, or interstitial, depending on where the blood escapes

External Hemorrhage

• Is when blood escapes outside the body
• Types of external hemorrhage include:
  • Bleeding from skin wounds
  • Epistaxis (bleeding from the nose)
  • Hemoptysis (coughing up blood)
  • Hematemesis (vomiting blood)
  • Melena (digested blood in stool)
  • Bleeding from the rectum (fresh blood in stool)
  • Hematuria (blood in urine)

Internal Hemorrhage

• Internal hemorrhage involves blood accumulating in serous cavities
• Types of internal hemorrhage:
  • Hemothorax (accumulation of blood in the pleura)
  • Hemopericardium (accumulation of blood in the pericardium)
  • Hemoperitoneum (accumulation of blood in the peritoneum)
  • Hemoarthrosis (accumulation of blood in a joint space)

Interstitial Hemorrhage

• Blood escapes into the tissue spaces
• Types of interstitial hemorrhage include:
  • Petechial hemorrhage, characterized by pinhead-sized spots
  • Purpura, indicated by tiny bleeding areas larger than 3 mm in diameter
  • Ecchymoses (bruises), which are skin discolorations consisting of large, irregular hemorrhagic areas (over 1 cm)
  • Hematoma, which involves a large amount of blood causing swelling

Effect of Hemorrhage

• The effect of hemorrhage depends on:
  • Volume of blood loss
  • Rate of blood loss
  • Site of bleeding
• Loss of a small amount of blood (≤10% of blood volume) typically has no immediate effect
  • Repeated small losses can lead to iron deficiency anemia
• Moderate blood loss (15% of blood volume) results in:
  • Decreased blood volume
  • Decreased venous return
  • Decreased cardiac output (COP)
  • Decreased blood pressure
• Massive blood loss (>25% of blood volume) leads to:
  • Hypovolemic shock
  • Death

Circulatory Shock

• Inadequate blood and oxygen perfusion to tissues and cells due to a sudden, severe drop in cardiac output or blood volume defines circulatory shock

Types of Shock

• Neurogenic
• Hypovolemic
• Cardiogenic
• Anaphylactic
• Septic

Stages of Shock

• Stages of shock: non-progressive (compensated), progressive (decompensated), and irreversible (terminal)

Non-Progressive (Compensated) Stage

• Compensatory mechanisms are activated
• Increased heart rate and respiratory rate
• Vasoconstriction of blood vessels occurs everywhere except in the heart and CNS to maintain blood flow to vital organs

Progressive (Decompensated) Stage

• Compensatory mechanisms fail to maintain adequate perfusion to the brain and vital organs

Irreversible Stage

• Represents the point of no return
• Rapid deterioration of the cardiovascular system occurs

Commonality Among Different Types of Shock

• Decreased cardiac output leading to decreased tissue perfusion

Neurogenic Shock

• Any factor stimulating parasympathetic activity, which leads to:
  • Decreased heart rate
  • Decreased cardiac output
• Inhibition of sympathetic effect on vascular smooth muscle causes:
  • Loss of vascular tone
  • Widespread vasodilation
  • Decreased effective blood volume

Hypovolemic Shock

• Any factor causing severe blood or fluid loss, leading to:
  • Decreased blood volume
  • Decreased venous return
  • Decreased cardiac output
  • Decreased tissue perfusion

Cardiogenic Shock

• Heart suddenly cannot pump enough blood to meet the body's needs
• Occurs due to failure of the myocardial pump
• Obstruction to the outflow of blood, leading to decreased cardiac output

Anaphylactic Shock

• A severe allergic reaction caused by an allergy to food, insect bites, or certain medications which causes:
  • Systemic vasodilation
  • Increased vascular permeability
  • Decreased effective blood volume

Septic Shock

• Characterized by bacterial toxins which causes:
  • Vasodilation by chemical mediators, causing decreased effective blood volume
  • Endothelial damage by toxins, leading to disseminated intravascular coagulation (DIC)
  • Toxic cell injury of organs

Causes of Different Types of Shock

• Neurogenic cause: spinal cord injury
• Hypovolemic cause: blood loss in hemorrhage, fluid loss in severe vomiting, diarrhea, or burns
• Cardiogenic cause: myocardial infarction, cardiac surgery, or pulmonary embolism
• Anaphylactic cause: Immunoglobulin E-mediated hypersensitivity reaction
• Septic cause: severe bacterial infections and septicemia by gram-negative organisms like E. coli, gram-positive organisms like meningococci, infected burns or immunodeficiency states

Effects of Septic Shock

• Multi-organ dysfunction and failure of kidneys, liver, lungs, and heart
• Metabolic abnormalities, such as hyperglycemia due to insulin resistance and altered lipid metabolism
• Immune suppression through the production of anti-inflammatory mediators