Oedema, Congestion, Infarction and Shock Flashcards
What is edema?
Edema is the accumulation of fluid in tissues, either localized or generalized.
What can cause edema (4)?
◾ Increased hydrostatic pressure;
◾ Reduced plasma osmotic pressure;
◾ Lymphatic obstruction;
◾ Sodium and water retention
What are the causes of increased hydrostatic pressure leading to edema (2)?
◾ Impaired venous outflow (e.g., deep vein thrombosis, heart failure);
◾ Increased arterial pressure
What are the effects and causes (3) of reduced plasma osmotic pressure?
Loss of fluid from circulation into tissues;
It is commonly caused by reduced albumin levels due to:
◾ nephrotic syndrome,
◾ liver cirrhosis,
◾ protein malnutrition
How does lymphatic obstruction contribute to edema? What may cause lymphatic obstruction?
Prevents fluid reabsorption from interstitial spaces;
Causes include inflammatory or neoplastic obstruction and parasitic infections (e.g. filariasis)
What happens in nephrotic syndrome regarding plasma proteins?
Increased permeability of glomerular capillaries resulting in loss of plasma proteins (e.g., albumin) in urine.
What is the mechanism of edema in heart failure?
◾ In heart failure, the heart’s ability to pump blood is compromised. This leads to a backup of blood in the veins, increasing the pressure within the capillaries. This forces fluid out of the capillaries and into the surrounding tissues, hence oedema results.
◾ Additionally, heart failure reduces the cardiac output, leading to decreased renal blood flow. In response, the kidneys activate mechanisms to retain sodium and water (e.g. RAAS) in an attempt to increase blood volume and improve perfusion. This will result in an increase in overall fluid volume in the body, contributing to oedema.
What are the clinical features of nephrotic syndrome that contribute to edema?
◾ Massive protein loss in urine (proteinuria);
◾ Hypoalbuminemia, leading to reduced plasma osmotic pressure;
◾ Secondary hyperaldosteronism due to decreased plasma volume
How does inflammation lead to edema?
Increased vascular permeability due to endothelial cell contraction;
Leakage of protein-rich fluid (exudate) into interstitial spaces
What is anasarca?
Severe, generalized edema affecting the entire body; Typically associated with hypoalbuminemia or severe systemic conditions
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Briefly describe the morphology of cerebral oedema.
Briefly describe the morphology of pulmonary oedema.
What is effusion?
Effusion refers to the escape of fluid into a body cavity or tissue.
What are the different forms of effusion based on fluid type?
◾ Transudate: Low protein content, specific gravity < 1.012 (e.g., heart failure)
◾ Exudate: Protein-rich, specific gravity > 1.020 (e.g., inflammation)
Further notes:
Specific gravity is a measure of the density of a substance compared to the density of water. It is a dimensionless quantity, meaning it has no units. The specific gravity of a substance is calculated by dividing the density of the substance by the density of water at a specified temperature (usually 4°C, where water has its maximum density).
Give the medical term for the following:
(a) fluid in the pleural cavity
(b) fluid in the pericardial sac
(c) fluid in the peritoneal cavity
(a) Hydrothorax
(b) Hydropericardium
(c) Ascites
Define:
(a) serous effusion
(b) serosanguinous effusion
(c) haemorrhagic effusion
(d) chylous effusion
(a) serous effusion: accumulation of clear, pale yellow fluid that is similar to serum
(b) serosanguinous effusion: this type of effusion contains both serous fluid and blood; typically light red
(c) haemorrhagic effusion: this type of effusion involves the presence of a significant amount of blood in the effusion fluid. It appears red.
(d) chylous effusion: this type of effusion contains a milky fluid rich in triglycerides, known as chyle. It is often caused by damage to the lymphatic system.
Define congestion.
This refers to the abnormal accumulation of blood within the blood vessels of an organ or tissue.
State the two broad types of congestion and give a brief description of each.
(1) Active congestion (Hyperemia)
This occurs when there is increased blood flow to a particular area due to the dilation of blood vessels. It is often a result of increased metabolic activity, inflammation, or exercise. The affected area typically appears red and warm due to the increased blood supply.
(2) Passive congestion (Venous congestion)
This occurs when there is an obstruction to the outflow of blood, leading to the accumulation of blood in the affected area. It is often caused by conditions such as heart failure or venous thrombosis. The affected area may appear bluish or purplish due to the deoxygenated blood.
Outline consequences of impaired venous outflow.
◾ Congestion: stasis of deoxygenated blood.
◾ Haemorrhage: increase in capillary pressure which can lead to capillary rupture
◾ Oedema: due to increased intravascular pressure
◾ Chronic hypoxia
Differentiate between shock and infarction.
◾ Shock is a condition where the body’s organs and tissues do not receive enough blood flow, leading to a lack of oxygen and nutrients. It is as a result of overall failure of the circulatory system.
◾ Infarction refers to the death of tissue due to a lack of blood supply. This is usually caused by a blockage in an artery, e.g. a blood clot, which prevents blood from reaching the affected area.
List the types of shock.
🩺 Cardiogenic shock
🩺 Hypovolemic shock
🩺 Septic shock
🩺 Neurogenic
🩺 Anaphylactic
What are the common causes of shock?
◾ Hypovolemia;
◾ Cardiogenic failure;
◾ Sepsis;
◾ Anaphylaxis
What is the main pathological feature of shock?
systemic hypoperfusion
What is the sequence of vascular events in shock?
Vasoconstriction during compensatory stage;
Progressive vasodilation in later stages
What are the stages of shock progression?
(1) Non-progressive (compensated)
(2) Progressive
(3) Irreversible
What happens during the non-progressive stage of shock?
◾ Activation of compensatory mechanisms;
◾ Maintenance of organ perfusion
What occurs in the progressive stage of shock?
Worsening tissue hypoxia; Metabolic acidosis;
Vital organ dysfunction
What occurs in the irreversible stage of shock?
Widespread cell death; Organ failure; Unresponsiveness to therapy
What is the physiological response in early hypovolemic shock?
Tachycardia;
Peripheral vasoconstriction; Increased thirst
What is the clinical presentation of hypovolemic shock?
Rapid, weak pulse;
Cold, clammy skin;
Decreased urine output
What is the main difference between hypovolemic and septic shock in terms of skin appearance?
Hypovolemic: cold and clammy skin;
Septic: warm and flushed skin (initially)
What are the clinical features of irreversible shock?
Severe hypotension unresponsive to treatment;
Profound metabolic acidosis;
Multi-organ failure
What are the key systemic effects of septic shock?
Persistent hypotension;
Metabolic acidosis;
Multi-organ dysfunction syndrome (MODS)
List clinical features of septic shock.
Hypotension; Warm, flushed skin (initially); Fever or hypothermia; Organ dysfunction
What role do bacterial toxins play in septic shock?
Activate immune cells;
Induce cytokine release;
Cause endothelial damage
What is the role of cytokines in septic shock?
TNF-alpha and IL-1 initiate systemic inflammation;
IL-6 and IL-8 amplify immune response; Cause vasodilation, vascular leakage, and activation of coagulation cascade
What are the consequences of widespread endothelial activation in septic shock?
Increased vascular permeability; Hypotension;
Disseminated intravascular coagulation (DIC)
What is the pathogenesis of lung injury in septic shock?
Inflammatory mediators damage alveolar capillary membrane; Results in acute respiratory distress syndrome (ARDS)
What causes multi-organ dysfunction in septic shock?
Persistent hypoperfusion; Microthrombosis leading to ischemia;
Direct cellular injury by inflammatory mediators
What are the complications of prolonged septic shock?
Acute respiratory distress syndrome (ARDS);
Renal failure;
DIC (disseminated intravascular coagulation)
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How does anaphylactic shock develop?
Allergen exposure leads to massive release of histamine and other mediators;
Results in vasodilation and increased vascular permeability
What is the role of histamine in anaphylactic shock?
Causes systemic vasodilation; Increases vascular permeability; Leads to edema and hypotension
What is the most common cause of cardiogenic shock?
Myocardial infarction
What are the clinical manifestations of an acute myocardial infarction?
Chest pain radiating to the left arm or jaw;
Shortness of breath;
Sweating and nausea
What causes cold extremities in late-stage shock?
Peripheral vasoconstriction to preserve central perfusion
What is the hallmark of progressive shock?
Worsening lactic acidosis due to impaired tissue oxygenation
What is the primary goal of management in shock?
Restore adequate tissue perfusion; Maintain oxygen delivery to vital organs
What organs are most susceptible to hypoperfusion during shock?
Brain; Heart; Kidneys
What is the definition of infarction?
Tissue death (necrosis) due to inadequate blood supply.
What is the morphological difference between acute and chronic infarction?
Acute: characterized by necrosis and inflammation; Chronic: replaced by fibrous scar
What are the main causes of arterial occlusion in infarction?
Thrombosis;
Embolism;
Atherosclerosis
What are the microscopic changes seen in an infarct within 6-12 hours?
Eosinophilic cytoplasm; Nuclear changes (pyknosis, karyorrhexis, or karyolysis)
What are the microscopic features of an infarcted area after 12-24 hours?
Coagulative necrosis;
Nuclear changes: pyknosis, karyorrhexis, karyolysis; Surrounding inflammation
What happens microscopically in an infarcted area after 1-3 days?
Peak neutrophil infiltration; Ongoing necrosis; Surrounding hyperemia
What are the key features seen in an infarcted area after 1-2 weeks?
Macrophage infiltration;
Fibroblast activation;
Granulation tissue formation
What is the primary pathological process of scar formation after infarction?
Deposition of collagen by fibroblasts;
Replacement of necrotic tissue with fibrous scar
What organs are resistant to infarction and why?
Liver: dual blood supply from hepatic artery and portal vein; Lungs: dual blood supply from pulmonary and bronchial arteries
What is the role of neutrophils in infarction?
Infiltrate the infarcted tissue; Contribute to the removal of necrotic debris
What is the time frame for macrophage infiltration in infarction?
Begins around 3-7 days after infarction; Peaks during the second week
What is the main consequence of prolonged ischemia?
Tissue necrosis
What are the effects of ischemia on cell organelles?
Swelling of mitochondria; Disruption of lysosomal membranes;
Fragmentation of endoplasmic reticulum
What are the cellular effects of ATP depletion during ischemia?
Sodium-potassium pump failure;
Cellular swelling;
Lactic acid accumulation
What are the common sites of venous infarction?
Brain (due to venous sinus thrombosis);
Intestines (volvulus or strangulation)
What is the role of coagulation in ischemia-reperfusion injury?
Reperfusion may trigger platelet aggregation; Formation of microthrombi worsens ischemia
What is the significance of granulation tissue in infarction healing?
Provides a scaffold for scar formation; Indicates the transition from inflammation to repair
What is the gross appearance of a white infarct?
Pale, wedge-shaped area; Sharp demarcation between normal and infarcted tissue
What is the gross appearance of a red infarct?
Hemorrhagic, dark red tissue; Poorly defined margins
What type of shock is most associated with severe burns?
(a) Cardiogenic shock
(b) Hypovolemic shock
(c) Septic shock
(d) Neurogenic shock
(b) Hypovolemic shock
Which of the following is involved in pathogenesis of septic shock?
(a) Bacterial Wall Lipopolysaccharides
(b) IL-1
(c) IL-8
(d) All of the above
(e) None of the above
(d) All of the above
Name the cytokine responsible for septic shock syndrome.
(a) IL-1
(b) IL-2
(c) IFN-γ
(d) TNF-γ
(e) β-TGF
(a) IL-1
Septic shock associated with Gram-negative bacteria is primarily due to:
(a) Platelet aggregation
(b) Lipopolysaccharide
(c) Enterotoxin superantigen
(d) Peptidoglycans
(e) Switch off to cytokine release
(b) Lipopolysaccharide
Organs which are less susceptible than others to infarction because of a dual
blood supply include:
(a) Liver and Lungs
(b) Liver and Kidney
(c) Lung and Spleen
(d) Spleen and Kidney
(e) Pancreas and Lung
(a) Liver and Lungs
What type of shock may occur in a patient with pulmonary embolism?
(a) neurogenic shock
(b) cardiogenic shock
(c) hypovolemic shock
(d) anaphylactic shock
(e) septic shock
(b) cardiogenic shock
Which of the following does not characterize shock?
(a) diffuse alveolar damage of the lung
(b) hyaline arteriosclerosis of the arterioles
(c) acute tubular necrosis of the kidney
(d) coagulation necrosis of the heart
(e) ischaemic encephalopathy of the brain
(b) hyaline arteriosclerosis of the arterioles
What type of shock may occur in a patient with allergy to penicillin?
(a) septic shock
(b) anaphylactic shock
(c) hypovolemic shock
(d) neurogenic shock
(e) cardiogenic shock
(b) anaphylactic shock
Endotoxin produced by gram-negative and some gram-positive bacteria can contribute to septicaemic shock in cases of bacteremia. Which cytokine pair plays the leading role in the production of septicaemic shock?
(a) TNF-α and IL-1
(b) IL-1 and IL-2
(c) IL-2 and IL-4
(d) IL-4 and IL-12
(e) TNF-α and IL-12
(a) TNF-α and IL-1
Neurogenic, septic and cardiogenic shock are all characterized by:
(a) Equal prognosis if untreated
(b) Need for blood transfusion
(c) Peripheral vasodilation at onset
(d) Normal blood volume at early stage
(e) Progression to irreversible shock
(e) Progression to irreversible shock
Following a hypotensive shock which lasted for hours, which of the following tissues is most likely to withstand the ischemia?
(a) Skeletal muscle
(b) Small Intestinal Epithelium
(c) Retina
(d) Myocardium
(e) Hippocampus
(a) Skeletal muscle
The causes of Hypovolemic shock do not include ________.
(a) severe vomiting
(b) severe diarrhea
(c) blood loss
(d) acute hemorrhagic pancreatitis
(e) extensive burning
(d) acute hemorrhagic pancreatitis
Pathological effects of shock do not include ________.
(a) gastric ulceration
(b) D.I.C.
(c) Acute Renal Tubular Necrosis
(d) metabolic alkalosis
(e) Adult Respiratory Distress Syndrome
(d) metabolic alkalosis
Which of the following is a complication of cardiogenic shock?
(a) Chronic Pyelonephritis
(b) Acute Tubular Necrosis
(c) Nodular Glomerulosclerosis
(d) Renal Vein Thrombosis
(e) Rapidly Progressive Glomerulonephritis
(b) Acute Tubular Necrosis
