Hemodynamic Disorders Lecture 1

Hemodynamic Disorders 1

• Lectures cover hyperemia, congestion, edema, hemorrhage, infarction, shock, hemostasis, thrombosis, and embolism.

Aims and Purpose of Lectures

• Topics include hyperemia and congestion, edema, hemorrhage, infarction, shock, hemostasis and thrombosis, and embolism.

Hyperemia and Congestion

• Hyperemia: An active process caused by arteriolar dilation and increased blood flow. Tissues appear red due to oxygenated blood.
• Examples: Inflammation sites, exercising skeletal muscle.
• Congestion: A passive process where venous blood outflow from tissues is impaired. Tissues appear blue-red (cyanotic) due to deoxygenated blood.
• Examples: Systemically (e.g., cardiac failure), locally (e.g., venous obstruction).

Edema

• Edema is the accumulation of interstitial fluid within tissues.
• Extravascular fluid can accumulate in body cavities: pleural cavity (hydrothorax), pericardial cavity (hydropericardium), peritoneal cavity (hydroperitoneum or ascites).
• Anasarca is severe, generalized edema. Fluid can be protein-poor (transudate) or protein-rich (exudate).

Causes of Edema

• Increased Hydrostatic Pressure: Impaired venous return (e.g., heart failure, deep vein thrombosis (DVT)), arteriolar dilation (e.g., heat, early inflammation).
• Increased Vascular Permeability: Inflammation.
• Reduced Plasma Osmotic Pressure: Decreased albumin synthesis (e.g., liver disease, protein malnutrition), increased albumin loss (e.g., nephrotic syndrome, protein-losing gastroenteropathy).
• Lymphatic Obstruction: Localized obstruction due to inflammatory or neoplastic conditions. Parasitic infection (filariasis) can cause massive edema (elephantiasis). Infiltrations (e.g. breast cancer) can cause edema (peau d'orange). Lymphedema can result from therapies like axillary lymph node resection/irradiation.
• Sodium and Water Retention: Increased hydrostatic pressure, reduced plasma osmotic pressure.

Increased Hydrostatic Pressure

• Local: Impaired venous return (e.g., deep vein thrombosis) can cause edema in the affected area.
• Generalized: Systemic edema, most commonly linked to congestive heart failure.

Reduced Plasma Osmotic Pressure

• Albumin loss from circulation or insufficient synthesis.
• Nephrotic syndrome: loss of albumin in urine leads to generalized edema.
• Protein-losing enteropathy (malabsorption): reduced albumin synthesis associated with liver disease (e.g., cirrhosis) or protein malnutrition.

Morphology of Edema

• Most common: subcutaneous tissues, lungs, and brain.
• Subcutaneous edema: Legs, sacrum, dependent edema (pitting edema).
• Periorbital edema: Nephrotic syndrome.
• Pulmonary edema: Left-sided heart failure.

Hemorrhage

• Extravasation of blood from vessels.
• Accumulates within tissue as a hematoma.
• Large bleeds into body cavities (hemothorax, hemopericardium, hemoperitoneum, hemarthrosis).

Appearances of Hemorrhage

• Petechiae: Minute hemorrhages (1-2 mm) in skin, mucous membranes, or serosal surfaces. Causes include low platelet counts, defective platelet function, or vitamin C deficiency.
• Purpura: Slightly larger hemorrhages (3-5 mm). Associated with trauma, vasculitis, increased vascular fragility.
• Ecchymoses: Larger subcutaneous hematomas (bruises, 1-2 cm). Color changes due to hemoglobin breakdown (red-blue to blue-green to golden-brown hemosiderin).

Clinical Significance of Hemorrhage

• Volume of blood lost: Rapid losses of up to 20% of blood volume may not cause significant impact, but larger losses can cause hypovolemic shock.
• Rate of bleeding: Slow, prolonged bleeding may have less immediate impact than rapid loss, but can still indicate underlying problems.
• Site of bleeding: Bleeding in vital areas (e.g., brain) can be life-threatening.
• Chronic bleeding: Can lead to iron deficiency anemia (e.g., peptic ulcer, heavy menstruation).