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BAMS > Haemostais, Haemorrhage And Shock > Flashcards

Haemostais, Haemorrhage And Shock Flashcards

1
Q

What does excessive blood loss result in

A
  • medical emergency
  • impaired delivery of nutrients to cells
  • state is called shock
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2
Q

Immediate physiological response to blood loss

A

Stop the bleeding

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3
Q

Short term physiological responses to blood loss

A

Restore blood pressure

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4
Q

Medium term physiological responses to blood loss

A

Restore fluid volume

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5
Q

Long term physiological response to blood loss

A

Replace blood constituents

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6
Q

What components are involved in immediate blood loss control

A
  • vascular response
  • platelet response
  • plasma response (coagulation)
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7
Q

Describe the vascular response to immediate blood loss

A
  • smooth muscle : spasm due to trauma, myogenic response, humoral factors (vasoconstrictors)
  • endothelium : platelet adhesion and aggregation, anti clotting and fibrinolysis
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8
Q

What induces the platelet response to blood loss

A

Damage to blood vessel > turbulent blood flow > platelets come into contact with the vessel wall (collagen)

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9
Q

Describe the platelet response immediately after blood loss

A
  • platelets adhere - clump together
  • release chemicals that cause further aggregation (positive feedback)
  • formation of platelet plug
  • effective in sealing small blood vessels
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10
Q

Describe the process of a platelet plug forming

A

Damaged blood vessel causes platelets to aggregate and release chemicals which results in the platelet plug

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11
Q

What causes vasoconstriction in the platelet plug

A

Thromboxane A2

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12
Q

Describe coagulation in the immediate response to blood loss

A
  • various plasma proteins and tissue components combine to convert fibrinogen > fibrin to form the blood clot
  • numerous clotting factors are involved
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13
Q

Where are the clotting factors made

A

Many made in the liver

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14
Q

What vitamin is required for synthesis of clotting factors

A

Vitamin K

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15
Q

The clotting factors are involved in…

A

An enzyme cascade

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16
Q

What disease can affect the production of clotting factors

A

Liver disease

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17
Q

What deficiency can affect the production of clotting factors

A

Vitamin K deficiency

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18
Q

Examples of blood clotting factors

A

I - Fibrinogen
II - prothrombin
III - tissue factor (thromboplastin)
IV - calcium ions
V - proaccelerin
VI - calcium ions ???? Doesnt exist
VII - proconvertin
VIII - antihaemophilic globulin
IX - Christmas factor
X - Stuart-prower factor
XI - plasma thromboplastin antecedent
XII - Hageman factor
XIII - Laki-Lorand factor

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19
Q

Describe the intrinsic coagulation pathway

A
  • vascular damage
  • contact activation involving factors : XII, XI, IX, VIII
20
Q

What converts factor X to factor Xa

A

Phospholipid and calcium ions

21
Q

Describe the extrinsic pathway

A
  • tissue damage
  • tissue factors (tissue thromboplastin) factor VII
22
Q

Where is the extrinsic pathway more important

A

Seems to be more important in initiating clotting after an injury

23
Q

Where is the intrinsic system more important

A

Serves to maintain the process once it has started
(Extrinsic pathway first)

24
Q

Plasminogen is converted to…

A

Plasmin by a plasminogen activator

25
Q

Fibrin is converted into

A

Soluble fibrin fragments by plasmin

26
Q

Describe the short term response to blood pressure

A
  • loss of blood volume
  • fall in blood pressure
  • compensatory mechanisms triggered by the arterial baroreceptors
  • these mechanisms aim to restore the blood pressure
27
Q

What mediates baroreceptor reflexes

A

Mediated by
- sympathetic nerves
- hormones : adrenaline, angiotensin II, vasopressin (ADH)

28
Q

Decrease in blood pressure results in ….

A

Decrease in baroreceptor firing > CVS centres brainstem > increase in sympathetic NS activity > increase heart rate >increases cardiac output > increases mean arterial blood pressure

29
Q

What is the most important function of a haemorrhage

A

Increasing mean arterial pressure

30
Q

Describe medium term responses to blood loss

A

Restore blood loss by
- shifting interstitial fluid back into blood vessels
- decreasing fluid loss in kidney
- increasing fluid intake

31
Q

What does a decrease of fluid loss in the kidney cause

A

Decrease in glomerular filtration
Increase in reabsorption of Na+ and H20 by stimulating the release of
- renin-angiotensin aldosterone
- antidiuretic hormone

Both vasoconstrictors

32
Q

What hormone drives erythropoesis

A

Erthyropoietin (EPO) which is a glycoprotein cytokine

33
Q

What causes erythropoietin

A

Decrease in red blood cell numbers > decrease in oxygen levels > kidney > erythropoietin > red bone marrow > increase in red blood cell production

34
Q

What is shock

A

Shock is characterised by inadequate blood flow to tissues

Often associated with decreased cardiac output, decreased blood or ECF volume

35
Q

Describe hypovolaemic shock

A

Decrease in extracellular fluid volume, due to haemorrhage, sweating, diarrhoea, burns, ect

36
Q

Describe low resistance (or distributive) shock

A

Decrease in peripheral resistance, due to widespread vasodilation eg anaphylactic shock

37
Q

Describe cardiogenic shock

A

Heart fails as a pump

38
Q

Describe the long term responses to blood loss

A
  • restore plasma proteins (released from liver 3-4 days)
39
Q

Describe the stimuli associated with first

A

Increases plasma osmolarity > decreases ECF volume
Angiotensin II also promotes thirst
Dry mouth

40
Q

Describe how medium term responses restore blood volume

A
  • shifting interstitial fluid back into blood vessels
  • decreasing fluid loss in kidney
  • increasing fluid intake
41
Q

Renin converts…

A

Angiotensinogen to angiotensin I

42
Q

What converts Angiotensin I to angiotensin II

A

Angiotensin converting enzyme (ACE)

43
Q

Increase in aldosterone release causes

A

Increases Na+ and H20 reabsorption in DCT and cortical collecting ducts

44
Q

Decrease in plasma volume…

A

Decrease in plasma volume> decrease baroreceptor distension > increases ADH release (post pituitary) > increases H2) permeability of collecting ducts

45
Q

Increase in plasma osmolarity…

A

Increases osmoreceptor activation > increases ADH release (post pituitary) > increasing H20 permeability of collecting ducts

BAMS (41 decks)

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