6 Thrombosis, embolism and shock

Question 1

Thrombosis

Answer 1

The formation of a solid or semi-solid mass from the

constituents of the blood while moving within the vascular system during life.

Question 2

Locations where thrombi may form

Answer 2

Lumen of the heart
Arteries
Veins
Capillaries

Question 3

Factors that promote thrombosis

Answer 3

Virchow’s triad:

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

Question 4

Abnormalities of the vessel wall

Answer 4

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

Question 5

Abnormalities of blood flow

Answer 5

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

Question 6

Abnormalities of the blood constituents

Answer 6

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)

Abnormalties of clotting

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

Question 7

Fate of thrombi

Answer 7

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

Question 8

Embolism

Answer 8

The transport of abnormal material (solid, liquid, gas)

by the blood stream and its impacting in a blood vessel.

Question 9

Types of emboli

Answer 9

Thrombi:

• pulmonary thromboembolus
• Arterial thromboembolism

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.”

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

Question 10

Shock

Answer 10

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

Question 11

Shock

Answer 11

Hypovolaemic shock
- haemorrhage – internal or external
severe burns

Cardiogenic shock
large acute myocardial infarction
other acute cardiac disease

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

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

Neurogenic shock
spinal cord trauma
regional anaesthesia

Obstructive shock
cardiac tamponade
tension pneumothorax
massive pulmonary embolism

Question 12

Clinical features of shock

Answer 12

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