Page 98 - Concise Pathology for Exam Preparation ( PDFDrive )

4 Haemodynamic Disorders, Thrombosis and Shock 83

• �Anaphylactic reaction amniotic fluid
to
(
i
o
• �Haemorrhage the patient survives the initial phase, she may bleed extensively due dis-
t
f
seminated intravascular coagulation DIC)
r
o
Q. Write briefly on air embolism.
in
Ans. Air bubbles the circulation can obstruct vascular flow and cause ischaemic injury.
Causes
n
e
b
i
Air can sucked into the arterial and venous circulation the following conditions:

• �Operative procedures (surgery the head and neck and cardiothoracic regions or

in

obstetric manipulations)
• �Trauma, particularly penetrating chest wall injury
• �Decompression sickness
• �Intravenous infusions
• �Angiography/arteriography
e
t
a
b
a
r
o
i
Arterial embolism can also associated with paradoxical embolus that can travel the
arterial circulation from the venous side across patent foramen ovale arteriovenous shunts.
o
r
a
a
a
of
Caisson disease is specialized form air embolism, which occurs when person
decompresses suddenly across areas with major pressure differences.
Pathogenesis
• �Decompression sickness or caisson disease occurs individuals exposed sudden

to

in
in
changes atmospheric pressure, eg, scuba and deep-sea divers.

of

at

is

• �When air breathed high pressure, large amounts gas particularly nitrogen,
dissolves blood and tissue.
in
of
• the diver rapidly ascents from water (depressurizes), the nitrogen bubbles out the
If
�

blood form gas emboli. These bubbles lodge the blood vessels muscles and

in
of

to

joints causing ‘bends’ and oedema and haemorrhage in lungs causing respiratory

distress ‘chokes’.
or
in
is
• �Chronic decompression sickness seen workers pressurized vessels used bridge
of
in

of
in

construction and may cause multiple foci avascular necrosis femur, tibia and

humerus.
Q. Define and classify infarcts.
of
of
by
Ans. An infarct area ischaemic coagulative necrosis caused occlusion arterial
is
an
or
supply venous drainage.
all
• �Almost infarcts result from thromboembolic events affecting arterial circulation.

• �Others may result from vasospasm, twisting vessels (testicular torsion or bowel

of

or
volvulus), vascular compression (by oedema, entrapment hernial sac tumour),
a
in
and traumatic vessel rupture.
• �Venous thrombosis usually results venous congestion; can, however, cause infarction
i
n
i
n
i
n
a
rare instances (as organs with single venous outflow channel, eg, testes and ovaries).
Infarcts are classified on the basis of the following:
Colour (amount of haemorrhage)
1.
or
(a)
Red haemorrhagic infarcts
White
or
(b) anaemic infarcts
2.
Presence or absence of microbial infection
Septic infarcts
(a)
(b) infarcts
Bland
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