hemodynammic

• Hyperaemia


  An active process resulting from arteriolar dilation and increased blood inflow, as occurs at sites of inflammation or in exercising skeletal muscle
• Congestion


  A passive process resulting from impaired outflow of venous blood from a tissue
• Conjunctival hyperaemia


  • Tortous, dilated conjunctival arterioles
• Liver with chronic passive congestion and hemorrhagic necrosis

  • Central areas are red and slightly depressed compared with the surrounding tan viable parenchyma, creating "nutmeg liver" (so called because it resembles the cut surface of a nutmeg)
• Liver with chronic passive congestion and hemorrhagic necrosis

  • Microscopic preparation shows centrilobular hepatic necrosis with hemorrhage and scattered inflammatory cells
• Oedema


  An accumulation of interstitial fluid within tissues
• Transudate


  The edema fluid that accumulates owing to increased hydrostatic pressure or reduced intravascular colloid, typically is a protein-poor fluid with a specific gravity less than 1.012
• Exudate


  The edema fluid that accumulates due to increased vascular permeability, is a protein-rich fluid with a specific gravity usually greater than 1.020
• Pathophysiologic Categories of Oedema

  • Increased Hydrostatic Pressure
  • Reduced Plasma Osmotic Pressure (Hypoproteinemia)
  • Lymphatic Obstruction
  • Sodium Retention
  • Inflammation
• Increased Hydrostatic Pressure (Local)

  Increases in intravascular pressure can result from impaired venous return, e.g. a deep venous thrombosis in the lower extremity can cause edema restricted to the distal portion of the affected leg
• Increased Hydrostatic Pressure (Generalized)

  Increases in venous pressure, with resultant systemic edema, occur most commonly in congestive heart failure
• Increased Hydrostatic Pressure in Congestive Heart Failure

  1. Reduced cardiac output leads to hypoperfusion of the kidneys, triggering the renin-angiotensin-aldosterone axis and inducing sodium and water retention (secondary hyperaldosteronism)

  2. Failing heart often cannot increase its cardiac output in response to the compensatory increases in blood volume, leading to a vicious cycle of fluid retention, increased venous hydrostatic pressures, and worsening edema
• Reduced Plasma Osmotic Pressure


  Conditions in which albumin is either lost from the circulation or synthesized in inadequate amounts, e.g. nephrotic syndrome, liver cirrhosis, protein malnutrition
• Lymphatic Obstruction


  Impaired lymphatic drainage and consequent lymphedema usually result from a localized obstruction caused by an inflammatory or neoplastic condition, e.g. filariasis, breast cancer
• Sodium and Water Retention

  Excessive retention of salt (and its obligate associated water) can lead to edema by increasing hydrostatic pressure and reducing plasma osmotic pressure, seen in diseases that compromise renal function
• Effects of Edema


  • Can range from annoying to rapidly fatal, e.g. subcutaneous edema can impair wound healing or clearance of infections, pulmonary edema can interfere with normal ventilatory function and create a favorable environment for infections, brain edema can cause herniation and compression of the brain stem vascular supply
• Herniation syndromes


  Displacement of brain parenchyma across fixed barriers can be subfalcine, transtentorial, or tonsillar (into the foramen magnum)
• Haemorrhage


  The extravasation of blood from vessels
• Haemorrhage


  • Can occur in a variety of settings, e.g. capillary bleeding in chronically congested tissues, trauma, atherosclerosis, or inflammatory or neoplastic erosion of a vessel wall
  • May accumulate within a tissue as a hematoma, ranging from trivial (e.g. a bruise) to fatal (e.g. a massive retroperitoneal hematoma from a ruptured aortic aneurysm)
  • Large bleeds into body cavities are called hemothorax, hemopericardium, hemoperitoneum, or hemarthrosis
  • Extensive hemorrhages can occasionally result in jaundice from the massive breakdown of red cells and hemoglobin
• Petechiae


  Minute (1 to 2 mm in diameter) hemorrhages into skin, mucous membranes, or serosal surfaces, caused by low platelet counts, defective platelet function, or loss of vascular wall support
• Purpura


  Slightly larger (3 to 5 mm) hemorrhages, resulting from the same disorders that cause petechiae, as well as trauma, vascular inflammation, and increased vascular fragility
• Ecchymoses


  Larger (1 to 2 cm) subcutaneous hematomas (colloquially called bruises), with characteristic color changes due to the enzymatic conversion of hemoglobin and bilirubin
• Clinical significance of hemorrhage

  Depends on the volume of blood lost and the rate of bleeding, with rapid loss of up to 20% of blood volume being tolerated in healthy individuals
• Haemorrhages


  Massive breakdown of red cells and haemoglobin that can occasionally result in jaundice
• Petechiae


  • Minute (1 to 2 mm in diameter) hemorrhages into skin, mucous membranes, or serosal surfaces; causes include low platelet counts (thrombocytopenia), defective platelet function, and loss of vascular wall support, as in vitamin C deficiency
• Purpura


  • Slightly larger (3 to 5 mm) hemorrhages that can result from the same disorders that cause petechiae, as well as trauma, vascular inflammation (vasculitis), and increased vascular fragility
• Ecchymoses


  • Larger (1 to 2 cm) subcutaneous hematomas (colloquially called bruises); extravasated red cells are phagocytosed and degraded by macrophages, causing characteristic color changes
• Clinical significance of hemorrhage

  Depends on the volume of blood lost and the rate of bleeding; rapid loss of up to 20% of blood volume or slow losses of even larger amounts may have little impact in healthy adults, but greater losses can cause hemorrhagic (hypovolemic) shock; the site of hemorrhage is also important, as bleeding that would be trivial in the subcutaneous tissues can cause death if located in the brain; chronic or recurrent external blood loss frequently culminates in iron deficiency anemia, while internal bleeding does not lead to iron deficiency
• Hemorrhage


  • Punctate petechial hemorrhages of the colonic mucosa, a consequence of thrombocytopenia
  • Fatal intracerebral hemorrhage
• Outline


  • Hyperaemia
  • Congestion
  • Oedema
  • Haemorrhage
  • Thrombosis
  • Embolism
  • Infarction
  • Shock
• Hemostasis


  A series of regulated processes that maintain blood in a fluid, clot-free state in normal vessels while rapidly forming a localized hemostatic plug at the site of vascular injury
• Thrombosis


  The formation of blood clot (thrombus) within intact vessels, the pathologic counterpart of hemostasis
• Virchow's triad


  • The three primary abnormalities that lead to thrombus formation: endothelial injury, stasis or turbulent blood flow, and hypercoagulability of the blood
• Thrombosis


  • Venous thrombus
  • Histological section showing the characteristic laminated or coralline structure of a thrombus
• Antemortem clot (Thrombus)


  Firm, focally attached to vessel walls, and contain gray strands of deposited fibrin; characterized by lines of Zahn (pale platelet and fibrin layers alternating with darker red cell–rich layers)
• Postmortem clot


  Gelatinous, usually not attached to the underlying vessel wall, with a dark red dependent portion and a yellow "chicken fat" upper portion
• Causes of endothelial injury

  • Atherosclerosis
  • Vasculitis
  • High levels of homocysteine
• Causes of stasis or turbulent blood flow


  • Immobilisation
  • Cardiac wall dysfunction
  • Aneurysm
• Hypercoagulability


  Due to excessive procoagulant or defective anticoagulant proteins, may be inherited or acquired; classic presentation is recurrent DVTs or DVT at a young age; DVT usually occurs in the deep veins of the legs, other sites include hepatic and cerebral veins
• Protein C or S deficiency

  • Increased risk for warfarin skin necrosis