Difference between revisions of "Haemorrhage"

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[[Category:Circulatory Disorders - Pathology]]
 
[[Category:Circulatory Disorders - Pathology]]
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[[Category:Cardiology Section]]

Latest revision as of 15:38, 15 October 2013

Introduction

  • Haemorrhage is the escape of blood from within the cardiovascular system.
  • Can be distinguished microscopically from congestion.
    • Congestion - the blood remains within the vessels.
    • Haemorrhage - blood is seen outside the vessels.
  • Haemorrhage may be of capillary, venous, arterial and rarely cardiac origin.
  • May be external or internal (within body cavities).
  • Associated with:
    • Wounds or trauma.
    • Inflammation, where toxins are involved.
    • Neoplastic disease.
  • "Haemorrhagic diathesis" describes a predisposition to bleeding, either spontaneous or associated with trifling mechanical damage.
    • Often manifests as purpuric disease.
    • Haemorrhagic diatheses and purpura may be a feature of a number of diseases of different aetiology (poisoning, septicaemia or neoplastic disease).

Types of Haemorrhage

  • Two main types of haemorrhage are recognised and are considered in more detail below:
    • Rhexis
      • Actual physical rupture of a vessel wall
    • Diapedesis
      • The escape of blood from vessels.
      • It may be difficult to detect a disruption to the vessel wall.

Haematoma

  • A large blood clot within the tissues.
    • A localised collection of blood confined by surrounding tissues resulting in a modular formation.
  • Often sub-cutaneous.
  • May form space-occupying lesions.
    • E.g. in brain.

In Body Cavities

  • Haemothorax, Haemopericardium and Haemoperitoneum.
    • Blood escapes into the respective body cavities.

Petechiae

  • These are minute - foci are 1-2mm in diameter.
  • Of capillary origin.
  • Usually seen on the skin, mucous membranes and serosal surfaces.

Ecchymoses

  • Of capillary origin. .
  • Foci are 3-23mm in diameter.
  • Are blotchy.
  • Often confluent.
  • Usually seen on the skin, mucous membranes and serosal surfaces.

Purpura

  • Purpura is a clinical syndrome.
  • Multiple small spontaneous haemorrhages develop in tissues (e.g. skin, mucosae, serosal surfaces and joints).
  • A mixture of petechiae and ecchymoses.

Haemorrhage by Rhexis

  • This is of venular or arteriolar (or larger vessel) origin.
    • Results in major bleeding.
  • There are several causes of haemorrhage by rhexis.
    • Trauma.
    • Haemorrhagic enteritis.
    • Erosion of blood vessels by tumours or abscesses.
    • Idiopathic rupture of arteries.
  • In the horse intrapericardial rupture of the aorta may occur, although this is uncommon.

Haemorrhage by Diapedesis

Septicaemia

  • Causes large numbers of petechiae and ecchymoses.

Toxaemia and Poisoning

  • Causes petechiae and ecchymoses.
    • These haemorrhages are probably due to direct damage to the vessel walls.

Purpura haemorrhagica

  • Pupura haemorrhagica is a condition that occurs in horses after an infection.
  • Endothelial damage is caused by accumulation of immune complexes.

Haemophilia

  • Failure of the normal clotting of the blood.
    • Due to absence of one of the clotting factors.
  • Rare.
  • Reported in dogs and pigs.

Dicoumeral poisoning

  • Dicoumeral is an antagonist to Vitamin K.
    • Vitamin K is needed by the liver to synthesise prothrombin and various clotting factors.
  • Occurs with:
    • Warfarin poisoning
      • Warfarin is a common rat poison)
    • Prolonged feeding of sweet clover.

Gross Appearance of Haemorrhage

  • The gross appearance of haemorrhage can vary depending on the tissue in which it occurs.

Epistaxis

  • Epistaxis is a nose bleed.
  • The haemorrhage may originate anywhere in the respiratory system.
  • Can occur in the lungs following heavy exercise in the horse.
    • Appears bright red and perhaps frothy.

Gastric Haemorrhage

  • Gastric secretion soon turns the blood a dark brown.
  • When vomited up it is called Haematomesis.
  • Blood originating in the stomach and upper small intestine that is passed through the anus and is called Melena.

Dysentery

  • Occurs when the bleeding is low down the alimentary tract.
  • The blood is passed in the faeces relatively unchanged.

Haematuria

  • Blood is present in the urine.
    • Imparts a red colour to it.
  • It is important to distinguish this from haemoglobinuria.
    • In haemoglobinuria, the breakdown products of red blood cells appear in the urine following intravascular haemolysis.
    • In haemorrhage, the red blood cells will separate out and sediment to the bottom of a test tube.

Bruising

  • Brusing is the result of haemorrhage.
  • Appears red for 48 hours and then begins to turn yellow.
    • Due to macrophages converting haemoglobin into haemosiderin.

Effects of Haemorrhage

Local

  • Haemorrhage may result in a diffuse mass of red blood cells and fibrin in loose connective tissues and in organs.
    • E.g. in the cutaneous connective tissues, the spleen and the gut wall.
  • Alternatively, a local accumulation may form a haematoma and become a space- occupying lesion.
    • This may interfere with organ function.
      • E.g in intracranial haemorrhage, haemopericardium, and pulmonary haemorrhage.

Systematic

  • The systematic effects of haemorrhage are usually associated with uncontrolled blood loss.
    • I.e. from a major artery associated with trauma.
  • Rate of loss is critical, e.g.
    • Loss of 30-40 per cent in a few minutes is often fatal.
    • Loss of over 50% over a 24 period may be tolerated in the dog.