Hemorrhagic Disorders Summary

Hemorrhagic Disorders

  • Hemorrhagic disorders result from defects in vessel walls, platelets, or coagulation factors.
  • Abnormal bleeding presentations vary:
    • Massive bleeds: Result from ruptures of large vessels (e.g., aorta, heart).
      • Often fatal due to overwhelming hemostatic mechanisms.
      • Examples: aortic dissection, abdominal aortic aneurysm (Chapter 11), myocardial infarction complicated by rupture (Chapter 12).
    • Subtle defects: Evident under hemostatic stress (surgery, childbirth, dental procedures, menstruation, trauma).
      • Common causes: inherited vWF defects (Chapter 14), aspirin consumption, uremia (renal failure).
      • Uremia alters platelet function through unknown mechanisms.
    • Coagulation factor deficiencies (hemophilias, Chapter 14):
      • Usually inherited, lead to severe bleeding if untreated.
  • General principles related to abnormal bleeding:
    • Defects of primary hemostasis (platelet defects, von Willebrand disease):
      • Present with small bleeds in skin or mucosal membranes.
      • Petechiae: minute 1- to 2-mm hemorrhages.
      • Purpura: slightly larger (≥3 mm) than petechiae.
      • Capillaries of mucosa and skin are prone to rupture following minor trauma.
      • Platelets normally seal these defects immediately.
      • Mucosal bleeding: epistaxis (nosebleeds), gastrointestinal bleeding, menorrhagia (excessive menstruation).
      • Thrombocytopenia (very low platelet counts) can lead to fatal intracerebral hemorrhage.
    • Defects of secondary hemostasis (coagulation factor defects):
      • Present with bleeds into soft tissues (muscle) or joints.
      • Hemarthrosis (bleeding into joints) is characteristic of hemophilia (Chapter 14) following minor trauma.
      • Severe platelet defects may also result in intracranial hemorrhage, sometimes fatal.
    • Generalized small vessel defects:
      • "Palpable purpura" and ecchymoses (bruises).
      • Ecchymoses: hemorrhages of 1 to 2 cm.
      • Hematoma: palpable mass of blood due to large extravasated blood volume in purpura and ecchymoses.
      • Characteristic of systemic disorders disrupting small blood vessels (e.g., vasculitis, Chapter 11) or causing blood vessel fragility (e.g., amyloidosis, Chapter 6; scurvy, Chapter 9).
  • Clinical significance of hemorrhage depends on:
    • Volume of the bleed.
    • Rate at which it occurs.
    • Location.
  • Rapid loss of up to 20% of blood volume may have little impact in healthy adults; greater losses can cause hemorrhagic (hypovolemic) shock.
  • Trivial subcutaneous bleeding can be fatal if located in the brain; intracranial hemorrhage may increase intracranial pressure and cause brain stem herniation (Chapter 28).
  • Chronic or recurrent external blood loss (e.g., peptic ulcer, menstrual bleeding) causes iron loss, leading to iron deficiency anemia.
  • When red cells are retained (e.g., hemorrhage into body cavities/tissues), iron is recovered and recycled for hemoglobin synthesis.