Hemodynamic Disorders
🟢 Lite — Quick Review (1h–1d)
Rapid summary for last-minute revision before your exam.
Hemodynamic Disorders — Key Facts for FMGE Core concept: Edema, congestion, hemorrhage, thrombosis, embolism, and infarction result from disruptions in normal blood flow and fluid balance High-yield point: Virchow’s triad (stasis, endothelial injury, hypercoagulability) explains thrombosis risk ⚡ Exam tip: Know the difference between congested and infarcted organs on pathology examination
🟡 Standard — Regular Study (2d–2mo)
Standard content for students with a few days to months.
Hemodynamic Disorders — FMGE Study Guide
Edema
Definition
Excess fluid accumulation in interstitial tissue spaces or body cavities
Mechanisms
1. Increased hydrostatic pressure:
- Systemic venous congestion (right heart failure)
- Local venous obstruction (DVT → leg edema, portal hypertension → ascites)
- Arterial vasodilation (heat, inflammation)
2. Decreased plasma oncotic pressure (hypoalbuminemia):
- Nephrotic syndrome (proteinuria → albumin loss)
- Liver cirrhosis (decreased synthesis)
- Malnutrition/protein deficiency
- Protein-losing enteropathy
3. Increased vascular permeability:
- Acute inflammation (histamine, kinins)
- Allergic reactions (angioedema)
- Burns, toxins
- Angioedema (C1 esterase inhibitor deficiency)
4. Lymphatic obstruction:
- Lymphedema: Non-pitting edema, skin thickening
- Causes: Lymphadenectomy (post-mastectomy), filariasis (Wuchereria bancrofti)
- Elephantiasis: Severe lymphatic obstruction with skin thickening
Transudate vs Exudate
| Feature | Transudate | Exudate |
|---|---|---|
| Protein | <3 g/dL | >3 g/dL |
| Specific gravity | <1.015 | >1.015 |
| Cell count | <500 WBCs/μL | >500 WBCs/μL |
| LDH | Low | High |
| Causes | CHF, nephrosis, cirrhosis | Inflammation, infection |
Serous effusion: Transudate from systemic causes Purulent effusion: Exudate with脓性 cells (empyema)
Sites of Edema
- Dependent edema: Feet/ankles (gravitational, CHF)
- Pulmonary edema: Left heart failure, kidney disease (pink frothy sputum)
- Cerebral edema: Trauma, tumors, encephalitis (herniation risk)
- Periorbital edema: Nephrotic syndrome (morning puffiness)
- Ascites: Portal hypertension (liver cirrhosis)
- Anasarca: Generalized severe edema (severe hypoalbuminemia)
Congestion
Active (Hyperemic) Congestion
- Inflow of oxygenated blood exceeds outflow
- Red, warm tissue (inflammation)
- Cause: Vasodilation (heat, inflammation, prostaglandins)
Passive (Congestive) Congestion
- Impaired outflow (venous drainage)
- Dark, bluish discoloration (cyanosis)
- Acute: Single organ affected (e.g., hepatic vein occlusion - sudden death)
- Chronic: Systemic venous congestion (left/right heart failure)
Chronic Congestive Changes
Liver (Nutmeg liver/Central congestion):
- Enlarged, tender, dark red central zones with pale peripheral zones
- Histology: Central vein dilation, hepatocyte atrophy, necrosis
- Eventually leads to cardiac cirrhosis
Lung (Brown induration):
- Firm, brown lungs due to hemosiderin-laden macrophages (heart failure cells)
- Alveolar capillary congestion, interstitial fibrosis
Spleen (Splenic congestion):
- Enlarged, firm, dark (chronic congestive splenomegaly)
Hemorrhage
Types
- External: Bleeding from body surface
- Internal: Bleeding into tissue/cavity (hemothorax, hemopericardium, hemoperitoneum, intracranial hemorrhage)
Effects
- Small bleed: Absorbed without significant effect
- Large bleed: Hemorrhagic shock, organ dysfunction
- Localized collection: Hematoma (organized/calcified → ossify)
- Apoplexy: Sudden massive hemorrhage (brain, adrenal gland)
Petechiae and Purpura
- Petechiae: 1-2 mm hemorrhages in skin/mucosa (thrombocytopenia)
- Purpura: 3-10 mm (coagulation disorders, vasculitis)
- Ecchymosis: >10 mm bruise
- Vibices: Linear hemorrhages (increased intra-abdominal pressure)
Thrombosis
Definition
Thrombus: Blood clot formed in situ within the cardiovascular system during life
Virchow’s Triad (Predisposing Factors)
1. Endothelial injury:
- Trauma, surgery, catheterization
- Atherosclerosis (intimal damage)
- Hypertension, vasculitis
2. Stasis/turbulent flow:
- Immobility, prolonged bed rest
- CHF, atrial fibrillation
- Varicose veins
3. Hypercoagulability:
- Primary (rare): Factor V Leiden, Protein C/S deficiency, antithrombin III deficiency, prothrombin mutation
- Secondary: Malignancy (Trousseau syndrome), pregnancy, oral contraceptives, smoking, hyperhomocysteinemia
Thrombus Characteristics
Arterial thrombus: White (fibrin + platelets) - grey-white, attached to damaged wall Venous thrombus: Red (RBCs + fibrin) - dark red, gelatinous Mixed thrombus: Lines of Zahn (alternating pale platelet/fibrin and dark RBC layers) Mural thrombus: Attached to heart chamber or aortic wall Occlusive thrombus: Blocks entire lumen (common in veins)
Fate of Thrombus
- Resolution: Fibrinolysis dissolves thrombus
- Organization: Ingrowth of granulation tissue → fibrosis → recanalization
- Propagation: Continued growth, can cause complete obstruction
- Embolization: Part breaks off → thromboembolism
Embolism
Definition
Embolus: Detached intravascular mass carried by blood to distant sites
Types of Emboli
Thromboembolism (most common):
- Venous → right heart → pulmonary arteries (pulmonary embolism)
- Arterial → systemic organs (kidney, spleen, brain)
- Paradoxical embolism: Venous thrombus crosses to arterial side via patent foramen ovale
Fat embolism:
- Bone marrow fat enters circulation after long bone fractures
- Classic triad (Arnold Gurd criteria): Respiratory distress, neurological symptoms, petechial rash
- Appears within 24-72 hours of injury
Air embolism:
-
100 mL air rapidly entering venous system
- Diving accidents (decompression sickness, “the bends”)
- Surgical procedures, catheter placement
Amniotic fluid embolism:
- Rare, catastrophic (DIC, sudden death)
- Squamous cells and fetal tissue in maternal circulation
- During labor/delivery (tear in uterine veins)
Septic embolism:
- Infected material (vegetations in infective endocarditis)
- Pyaemic abscesses (multiple small abscesses)
Cholesterol embolism:
- Atheromatous plaque disruption → cholesterol crystals
- “Blue toe syndrome”, renal failure
- Post-catheterization or anticoagulation
Tumor embolism:
- Cancer cells entering circulation
- Precursor to metastasis
Pulmonary Embolism
Risk factors: Virchow’s triad (especially stasis from immobility), hypercoagulable states Causes: DVT (most common), pelvic vein thrombosis Clinical features: Dyspnea, chest pain, hemoptysis, tachycardia Types:
- Saddle embolism: Large, blocks both pulmonary arteries → sudden death
- Massive: >50% obstruction → hypotension
- Small/segmental: May be asymptomatic
Infarction
Definition
Infarct: Area of tissue necrosis resulting from ischemia (inadequate blood supply)
Types
White (Anemic) infarct:
- Solid organs with end-arterial blood supply
- Kidneys, spleen, heart (arterial occlusion)
- Pale, well-demarcated wedge shape
- Firm consistency
Red (Hemorrhagic) infarct:
- Loose tissues with dual blood supply or venous occlusion
- Lungs (bronchial collateral supply), liver, GI tract
- Also occurs with: arterial occlusion in tissues that can bleed (brain, though = liquefactive)
- Hyperemic, red-brown appearance
Factors Determining Severity
- Duration of ischemia (complete vs incomplete occlusion)
- Collateral blood supply (liver has dual → rarely infarcts)
- Oxygen content of blood (anemia worsens ischemia)
- Metabolic demand of tissue (neurons require constant oxygen)
Common Infarcts
| Organ | Type | Common Cause |
|---|---|---|
| Heart | White (coagulative) | Coronary atherosclerosis, thrombus |
| Brain | Liquefactive | Cerebral atherosclerosis, emboli |
| Kidney | White | Renal artery thrombosis, emboli |
| Lung | Red (hemorrhagic) | Pulmonary embolism |
| Intestine | Red | Mesenteric artery emboli, volvulus |
| Spleen | White | Splenic artery emboli |
Wound Healing
- Acute inflammation → neutrophils (24-72 hours)
- Macrophages (3-7 days)
- Granulation tissue (1-3 weeks)
- Fibrosis and scar formation (months)
Content adapted based on your selected roadmap duration. Switch tiers using the selector above.