haemostasis, haemorrhage and shock Flashcards

1
Q

what is haemorrhage?

A

an acute loss of blood from a damaged blood vessel

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2
Q

what is shock?

A

the state in which the decreased blood volume results in a fall in blood pressure and impaired delivery of nutrients to cells

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3
Q

what should the immediate action to blood loss be?

A

stop the bleeding

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4
Q

what should the short term action to blood loss be?

A

restore the blood pressure

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5
Q

what should the medium term action to blood loss be?

A

restore fluid volume

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6
Q

what should the long term action to blood loss be?

A

replace blood consitiuents

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7
Q

what is haemostasis?

A

stopping blood loss

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8
Q

what are the components involved in haemostasis?

A
  • vascular response
  • platelet response
  • plasma response
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9
Q

what is coagulation?

A

plasma response

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10
Q

describe the vascular response in haemostasis?

A

Smooth muscle
- Spasm due to trauma
- Myogenic response
- Humoral factors (vasoconstrictors)
Endothelium
- Platelet adhesion and aggregation
- Anticlotting and fibrinolysis

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11
Q

describe the platelet response in haemostasis?

A
  • Damage to blood vessel causes turbulent blood flow so platelets come into contact with vessel wall (collagen)
  • Platelets adhere; clump together (aggregate)
  • Release chemicals that cause further aggregation (Positive feedback)
  • Formation of platelet plug
  • Effective in sealing small blood vessels
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12
Q

describe the formation of a platelet plug

A
  • damaged blood vessel
  • platelets aggregate and release chemicals
  • thromboxane A2 and ADP
  • vasoconstriction
  • platelet plug
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13
Q

describe coagulation in haemostasis?

A
  • Various plasma proteins and tissue components combine to convert fibrinogen to fibrin to form the blood clot
  • Numerous ‘clotting factors’ are involved (many made in the liver)
  • The synthesis of several clotting factors requires the presence of vitamin K
  • The clotting factors are activated in an enzyme cascade
  • One activated factor activates the next one in the sequence
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14
Q

where are many of the clotting factors involved in coagulation made?

A

the liver

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15
Q

what is required for the synthesis of many clotting factors?

A

vitamin K

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16
Q

what can have an affect on coagulation?

A

calcium deficiency

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17
Q

which blood clotting factor doesnt exist?

A

VI (same as IV)

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18
Q

what are the two pathways of coagulation?

A

intrinsic and extrinsic

19
Q

how is the intrinsic coagulation pathway activated?

A

vascular damage

20
Q

how is the extrinsic coagulation pathway activated?

A

tissue damage

21
Q

what are required for both the intrinsic and extrinsic coagulation pathways?

A

phospholipid and calcium ions

22
Q

which blood coagulation pathway is more important at initiating clotting after injury?

A

extrinsic

23
Q

which blood coagulation pathway is more important to maintain the process?

A

intrinsic

24
Q

what is thrombosis?

A

blood clots form inside intact blood vessels causing blockages

25
Q

which coagulation pathway is involved in thrombosis?

A

intrinsic

26
Q

what is fibrinolysis?

A

dissolving the blood clot once it has served its purpose

27
Q

which enzyme is involved in fibrinolysis?

A

plasmin

28
Q

what triggers the compensatory mechanisms when there is a fall in blood pressure?

A

arterial baroreceptors

29
Q

what are the hormones released in baroreceptor relflexes?

A

adrenaline
angiotensin II
vasopressin (ADH)

30
Q

which nerves control baroreceptor reflexes?

A

sympathetic

31
Q

sequence of events following a decrease in blood volume

A
  • decrease in BP
  • decrease in baroreceptor firing
  • CVS centres
  • increase in sympathetic NS activity
  • increase in HR, vent. const, veso const. and arteriole const
  • increase in ventricular and vaso constriction increases stroke volume
  • increase in HR increases cardiac output
  • increase in artieriole const, increases peripheral resistance
  • overall increase in mean arterial blood pressure
32
Q

what are the medium term responses to blood loss?

A
  • Shifting interstitial fluid back into blood vessels
  • Decreasing fluid loss in kidney
  • Increasing fluid intake
33
Q

what does a decrease in arterial blood pressure cause through baroreceptor reflexes?

A
  • vasoconstriction of arterioles
    • increases total peripheral resistance
    • decreases capillary blood pressure
  • decreases hydrostatic pressure pushing fluid out the capillary
  • more fluid is drawn back into the capillaries by oncotic pressure
34
Q

what does a decrease in fluid loss in the kidney cause?

A
  • decreased glomerular filtration
  • increased reabsorption of sodium ions and water by stimulating the release of renin-angiotensin-aldesterone and the antidiuretic hormone (both vasoconstrictors)
35
Q

renin-angiotenisn-aldosterone system

A
36
Q

antidiuretic system

A
37
Q

antidiuretic system

A
38
Q

what are stimuli of thirst?

A
  • increase in plasma osmolarity and decrease in ECF volume
  • angiotensin II
  • dry mouth
39
Q

feed-forward regulation

A
40
Q

what are the long term responses after blood loss?

A

Restore plasma proteins
- Released from liver (3-4 days)
Replace blood cells, esp. RBCs
Erythropoiesis
- Regulated by erythropoeitin (EPO)
- EPO released from kidney
- Stimulates RBC production in bone marrow
- Return to normal in 2-3 months

41
Q

what are the different types of shock?

A
  • hypovolaemic shock
  • low resistance/distributive shock
  • cardiogenic shock
42
Q

describe hypovolaemic shock

A
  • decrease in ECF volume due to haemorrhage
  • sweating, diarrhoa, burns etc
43
Q

describe low resistance/distributive shock

A
  • decrease in peripheral resistance due to vasodilation
  • eg anaphylactic shock