Page 124 - Textbook of Pathology, 6th Edition

108 from varicose veins due to high pressure in the veins of legs
or oesophagus.
EFFECTS. The effects of blood loss depend upon 3 main
factors:
the amount of blood loss;
the speed of blood loss; and
the site of haemorrhage.
The loss up to 20% of blood volume suddenly or slowly
generally has little clinical effects because of compensatory
SECTION I
mechanisms. A sudden loss of 33% of blood volume may
cause death, while loss of up to 50% of blood volume over a
period of 24 hours may not be necessarily fatal. However,
chronic blood loss generally produces iron deficiency
anaemia, whereas acute haemorrhage may lead to serious
immediate consequences such as hypovolaemic shock.

SHOCK
Definition
Shock is a life-threatening clinical syndrome of cardio-
vascular collapse characterised by:
an acute reduction of effective circulating blood volume
Figure 5.13 CVC spleen (Congestive splenomegaly). Sectioned (hypotension); and
surface shows that the spleen is heavy and enlarged in size. The colour an inadequate perfusion of cells and tissues
of sectioned surface is grey-tan.
(hypoperfusion).
1. Trauma to the vessel wall e.g. penetrating wound in the If uncompensated, these mechanisms may lead to
heart or great vessels, during labour etc. impaired cellular metabolism and death.
2. Spontaneous haemorrhage e.g. rupture of an aneurysm, Thus, by definition “true (or secondary) shock” is a
septicaemia, bleeding diathesis (such as purpura), acute circulatory imbalance between oxygen supply and oxygen
leukaemias, pernicious anaemia, scurvy. requirements at the cellular level, and is also called as
General Pathology and Basic Techniques
3. Inflammatory lesions of the vessel wall e.g. bleeding from circulatory shock.
chronic peptic ulcer, typhoid ulcers, blood vessels traversing The term “initial (or primary) shock” is used for transient
a tuberculous cavity in the lung, syphilitic involvement of and usually a benign vasovagal attack resulting from sudden
the aorta, polyarteritis nodosa. reduction of venous return to the heart caused by neurogenic
4. Neoplastic invasion e.g. haemorrhage following vascular vasodilatation and consequent peripheral pooling of blood
invasion in carcinoma of the tongue. e.g. immediately following trauma, severe pain or emotional
5. Vascular diseases e.g. atherosclerosis. overreaction such as due to fear, sorrow or surprise.
6. Elevated pressure within the vessels e.g. cerebral and retinal Clinically, patients of primary shock suffer from the attack
haemorrhage in systemic hypertension, severe haemorrhage lasting for a few seconds or minutes and develop brief
unconsciousness, weakness, sinking sensation, pale and

Figure 5.14 CVC spleen. The sinuses are dilated and congested. There is increased fibrosis in the red pulp, capsule and the trabeculae.
Gamna-Gandy body is also seen.