SN3 SHORT NOTE 5M ★ High-yield

Classify haemorrhage and describe its effects.

Pathology · 2nd Professional — Para-Clinical

Definition

Haemorrhage is the escape of blood from the vascular compartment, either to the exterior, into a body cavity, or into the tissues.

Classification BY Size and Site

Term	Size	Significance
Petechiae	1–2 mm	Thrombocytopenia, defective platelet function, vasculitis, raised intravascular pressure
Purpura	3–10 mm	The same causes, plus trauma and vasculitis
Ecchymosis ("bruise")	Over 1–2 cm	Trauma; coagulation defects
Haematoma	Variable, a mass of blood	May be trivial or fatal depending on the site
Haemothorax, haemopericardium, haemoperitoneum, haemarthrosis	Accumulation in a cavity	Haemarthrosis is characteristic of haemophilia

The colour change of a bruise records the breakdown of haemoglobin — red-blue (haemoglobin), then green (biliverdin), then yellow-brown (bilirubin then haemosiderin); useful in estimating the age of an injury

Classification BY Source and Timing

Basis	Types
Source	Arterial — bright red, spurting; venous — dark, steady flow; capillary — oozing
Timing (surgical)	Primary — at the time of injury; reactionary — within 24 hours, as blood pressure recovers and a clot is dislodged; secondary — after 7–14 days, from infection eroding a vessel
Visibility	Revealed (external) and concealed (internal)

Effects

Blood loss	Effect
Under 10%	Usually no effect — as in blood donation
20%	Postural hypotension, tachycardia
30–40%	Hypovolaemic shock
Over 40%	Life-threatening
Chronic slow loss	Iron deficiency anaemia — the body cannot recycle iron that has left it

CLINICAL PEARL

The site matters more than the volume. Two litres into the peritoneum may be survivable; 50 mL into the brainstem or a small volume into the pericardium causing tamponade is fatal. Never assess a haemorrhage by quantity alone.

Applied Aspects

Chronic occult gastrointestinal bleeding presents as iron deficiency anaemia, and in an adult over 40 this demands investigation for a colonic carcinoma
Petechiae do not blanch on pressure, which distinguishes them from erythema — and a non-blanching rash with fever suggests meningococcal sepsis
Cardiac tamponade — Beck triad of hypotension, raised jugular venous pressure and muffled heart sounds; relieved by pericardiocentesis
Secondary haemorrhage indicates infection and is more dangerous than reactionary bleeding, since the vessel wall itself is destroyed
Concealed haemorrhage must be actively sought in trauma — chest, abdomen, pelvis, retroperitoneum and the long bones can each hide litres

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