6. Thrombosis, embolism and shock Flashcards Preview

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Flashcards in 6. Thrombosis, embolism and shock Deck (20)
1

Thrombosis

The formation of a solid or semi-solid mass from the
constituents of the blood while moving within the vascular system during life.

2

Locations where thrombi may form

Lumen of the heart
Arteries
Veins
Capillaries

3

Capillaries (thrombi)

Disseminated intravascular coagulation:
Involves both thrombus formation and
haemorrhage!

Triggers include infections, septicaemia,
malaria, neoplasms and liver disease.

Capillaries may be occluded by minute
thrombi causing scattered ischaemic
lesions.

4

Factors that promote thrombosis

Virchow’s triad:
1. Abnormalities of the vessel wall
2. Abnormalities of blood flow
3. Abnormalities of the blood’s constituents

5

Abnormalities of the vessel wall

Arteries = Atheroma, Inflammation
Heart = Myocardial infarction, Rheumatic endocarditis
Veins = Trauma, Inflammation
Chemicals - sclerosants
(irritant substances injected to obliterate
varicose veins)
glucose
(atheroma in diabetes mellitus)
Capillaries = Inflammation

6

Abnormalities of blood flow

Arteries = Turbulence, aneurysms, plaques, spasm
Heart = Atrial fibrillation, Aneurysms
Veins = Local problem
compression
inactivity
(postoperative bed rest; economy class
syndrome)

General problem
heart failure
circulatory shock

7

Abnormalities of the blood constituents (1)

Increased viscosity:
Polycythaemia = Dehydration, Chronic hypoxia,
Polycythaemia rubra vera

Hyperproteinaemia = Multiple myeloma (Tumour of
plasma cells in bone marrow with
accumulation of immunoglobulins
in plasma)

8

Abnormalities of the blood constituents (2)

Abnormalties of clotting:
Pregnancy = (prevents bleeding when placenta detaches)
Some (older) contraceptive pills
Following trauma (liver produces more clotting factors)
Thrombocythaemia
Tumours
Inherited

9

Fate of thrombi

Resolution = Fibrinolysis. Very common fate.
Organisation = Incorporation into a scar (mural nodule or
web) by macrophages and fibroblasts.
Vessel lumen remains narrowed or
occluded.
Intimal cell proliferation, capillary invasion
and recanalisation. Vessel again becomes
patent.
Detachment = Thromboembolism

10

Embolism

The transport of abnormal material (solid, liquid, gas)
by the blood stream and its impacting in a blood vessel.

11

Types of emboli (1)

Thrombi
Fat
Gas = Infusions, Vascular surgery
Caisson disease - On ascending from the depths
too rapidly, bubbles of N2 form in the blood stream
and on entering the bones and joints cause the pain
known as “the bends.”

12

Types of emboli (2)

Tumour material = When tumour penetrates blood vessel
parts may break away to form
metastases.
Infective agents = Includes fragments of vegetations
growing on heart valves in infective
endocarditis.
Atheroma = Fragments of atheromatous plaque may
break off
Amniotic fluid = uterus may force amniotic fluid and
squames from infant into uterine veins of
mother.
Foreign bodies = intravenous drug abuse, iatrogenic

13

Shock

Shock is a physiological state characterized by a significant, systemic reduction in tissue perfusion, resulting in decreased tissue oxygen delivery and insufficient removal of cellular metabolic products, resulting in tissue injury

not the same as emotional shock

14

Hypovolaemic shock

haemorrhage – internal or external
severe burns

15

Cardiogenic shock

large acute myocardial infarction
other acute cardiac disease

16

Septic shock

endotoxins from Gram negative bacteria
exotoxins from Gram positive bacteria
both lead to dilation of blood vessels

17

Anaphyllactic shock

severe form of allergic reaction
- food, antibiotics, insect stings

18

Neurogenic shock

spinal cord trauma
regional anaesthesia

19

Obstructive shock

cardiac tamponade
tension pneumothorax
massive pulmonary embolism

20

Clinical features of shock

low systolic blood pressure: 90 beats/min
respiratory rate: 29 breaths/min
urine output: low
metabolic acidosis
hypoxia
cutaneous vasoconstriction or vasodilation
anxiety, agitation, indifference, lethargy, obtunded