Thrombosis, Embolism and Shock

Question 1

Whats haemostasis?

Answer 1

Reflex vasoconstriction of arterioles immediately after injury. Endothelial injury exposes highly thrombogenic extracellular matrix. Platelets adhere and become “activated”. Platelet activation causes release of chemokine that causes recruitment of additional platelets (haemostatic plug)

Question 2

How does the body limit coagulation?

Answer 2

Clotting Factor activation is restricted to sites of exposed phospholipids after injury.

Question 3

What are the anticaogulant mechanisms?

Answer 3

Antithrombin
Proteins C and S (vit. K dependant, inactivate Va and VIIIa)
Plasmin activation - breaks down fibrin

Question 4

What is International Normalised Ratio (Prothrombin Time)

Answer 4

High INR means reduced clotting. Can be pathological or intended treatment outcome.

Question 5

What causes High INR?

Answer 5

Warfarin therapy, vit. K deficiency, Malabsorption (intestine cant adequately absorb certain nutrients in the bloodstream), liver disease (poor VII synthesis), increased clotting factor consumption

Question 6

What is thrombosis?

Answer 6

Inappropriate activation of blood clotting in vessels resulting in the formation of a solid or semi-solid mass from the constituents of blood

Question 7

Effect of thrombus in the heart

Answer 7

Abnormalities of the vessel wall and altered blood flow. May result in MI or rheumatic endocarditis.
Abnormalities of blood flow - atrial fibrillation, aneurysms

Question 8

Effect of thrombus in the arteries

Answer 8

Abnormalities of the vessel wall - atheroma, inflammation. Abnormalities of the vessel wall - turbulence (aneurysms, plaques, spasms)

Question 9

Effect of thrombus in the veins

Answer 9

Oedema caused by DVT. Stasis - alters normal laminar flow of blood. Immobility/inactivity due to loss of function, post-operative recovery or other factors. Direct compression of veins. Characteristically at sites of stasis (a period or state of inactivity)

Question 10

What factors promote coagulation?

Answer 10

Virchow’s Triad: abnormalities of blood vessel wall, abnormalities of blood flow, abnormalities of blood constituents

Question 11

Fate of thrombi

Answer 11

Resolution - fibrinolysis (enzymatic breakdown of fibrin in blood clots.
Organisation - incorporation into a scar by macrophages and fibroblasts.
Detachement - thromboembolism

Question 12

What is embolism?

Answer 12

Detached intravascular solid, liquid or gas mass that is carried by the by the bloodstream to a site distant to its point of origin.

Question 13

Causes of embolism

Answer 13

Thombus, fat, gas, tumour amniotic fluid, foreign body

Question 14

What is shock?

Answer 14

Medical emergency where organs and tissues of the body are not receiving an adequate flow of blood. This deprives the organs and tissues of oxygen and allows build up of waste products. Can cause serious damage and death

Question 15

What are the clinical features of shock?

Answer 15

Low systolic BP: <110mmHg
Tachycardia: >90bpm
RR: <7 or >29
Low urine output
Metabolic acidosis
hypoxia
cutaneous vasoconstriction or vasodilation
anxiety, agitation, indifference, lethargy, loss of sensitivity

Question 16

What causes Hypovolemic Shock?

Answer 16

Haemorrhage - internal or external. High output fistulae, severe burns

Question 17

What causes Cardiogenic Shock?

Answer 17

Large acute MI, other acute cardiac disease

Question 18

What causes septic shock?

Answer 18

endotoxins from Gram negative bacteria, exotoxins from gram positive bacteria, shock is consequence of dilation of blood vessels, bowel infarction, limb ischaemia

Question 19

What causes neurogenic shock?

Answer 19

spinal cord trauma, regional anaesthesia, spinal cord damage

Question 20

What causes obstructive shock?

Answer 20

Cardiac temponade, tension pneumothorax, massive pulmonary embolism