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Exercise & Environment > Haemorrhage and shock > Flashcards

Haemorrhage and shock Flashcards

1
Q

haemorrhage

A

loss of blood

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2
Q

type of haemorrhage

A

external - skin cut
revealed - blood in faeces
concealed - haemorrhage stroke

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3
Q

where is BP highest

A

artery

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4
Q

where is a dangerous haemorrhage

A

artery, because BP is so high lots of blood will be lost quickly

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5
Q

symptoms and signs of haemorrhage

A
  • pale, grey or cyanotic with clammy skin
  • rapid shallow breathig
  • constricted veins
  • tachycardia but weak pulse giving low stroke volume
  • intense thirst
  • reduced urin output
  • nausea
  • muscular weakness
  • reduced mental awareness
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6
Q

how does body responds to haemorrhage (overview)

A

arterial blood pressure is reduced.

Cascade of passive events that are counteracted by reflexes

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7
Q

CV resposes to haemorrhage

A
  • decrease in arterial BP determined by decrease in stoke volume and CO
  • increase in HR and TPR to help stroke volume, CO and MAPB return to normal
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8
Q

what is altered directly by blood volume loss in haemorrhage

A

stroke volume, cardiac output and MABP

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9
Q

what is altered by reflex responses to haemorrhage

A

heart rate and TPR

- neural or integrated changes

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10
Q

stages of relfex response to haemorrhage

A

survival: seconds to minutes, by the baroreceptors

returning to normal: hours to days, absorption to restore blood

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11
Q

role of baroreceptors in haemorrhage

A

survival reflex response that occurs within seconds

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12
Q

what happens to vagal tone after haemorrhage

A

decreased parasympathetic stimulation in order to increase HR

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13
Q

what happens to sympathetic tone after haemorrhage

A

increases to:

  • increase vasoconstriction,
  • increase HR and cardiac contractility
  • increase release of renin angiotensin-aldosterone
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14
Q

How does CNS respond to haemorrhage

A
  • decreased parasympathetic/vagal tone
  • increased sympathetic tone
  • increased cortisol and ADH
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15
Q

what responds to change in blood volume after haemorrhage

A

cardiopulmonary receptors in the atria ventricles.

send signals to CNS

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16
Q

What responds to change in arterial BP after haemorrhage

A

baroreceptors in the aortic arch & carotid sinuses signal to CNS

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17
Q

why does vasoconstriction occur after haemorrgahe

A
  • to increase central venous pressure

- to increase TPR

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18
Q

what reduces excretion of Na+ and water, and increases thirst

A
  • cortisol
  • ADH
  • renin angiotensin-aldosterone
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19
Q

role of renin angiotensin-aldosterone post haemorrhage

A
  • reduces excretion of Na+ and water
  • increases thirst
  • causes vasoconstriction
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20
Q

3 main response systems immediately after haemorrhage

A
  • baroreceptors
  • chemoreceptors
  • CNS
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21
Q

main response to haemorrhage after days

A

renal blood volume pressure control

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22
Q

role of baroreceptor reflex in haemorrhage

A

contributes to maintaining arterial BP close to normal range

- allows each vascular bed to change its flow without lowering arterial BP

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23
Q

where is renin released and when

A

released from the kidneys stimulated by drop in blood pressure

24
Q

what does renin do

A

renin contributes to production angiotensin

25
Q

what does angiotensin do

A

powerful vasoconstrictor

- reduces excretion of salt and water by the kidney

26
Q

what is a more powerful vasoconstrictor than angiotensin

A

ADH

27
Q

what is released from pituitary in severe blood loss

A

ADH, a very powerful vasoconstrictor

28
Q

where is ADH released

A

anterior pituitary

29
Q

what happens when capillary pressure is reduced by 2mmHg

A

a 11%r reduction of capillary pressure = 7x more absorption
= net inward force of -2.3

30
Q

what is maintained better - CO or ABP?

A

arterial blood pressure is maintained near normal levels during haemorrhage for longer than CO

31
Q

which is maintained better during haemorrhage and why? CO or ABP

A
  • sympathetic reflexes have a greater vasoconstrictor effect on arterioles than veins
  • plateau occurs at 50% of ABP from activation of CNS - ischaemic response
32
Q

what kicks in when ABP drops to ~50%

A

CNS as part of ischaemic response

- causes profound vasoconstriction

33
Q

how does a 10% blood loss affect CO and ABP

A

virtually no effect, similar to blood donation of 500ml

34
Q

blood volume of average 70kg man

A

5.4L

35
Q

blood volume in men

A

77ml/kg

36
Q

blood volume women

A

67ml/kg

37
Q

effects of % blood loss

A
  • 10% - virtually no effect on CO and BP
  • 20% unlikely to elicit shock
  • 20-30% can induce shock. BP may drop
  • 20-50% causes severe shock and profound fall in ABP and BP that may be irreversible
  • more than 50% death generally inevitable
38
Q

what has an effect of severity of volume of blood loss

A

the rate at which the blood is lost

e.g rapid loss of 30% fatal, but 50% loss over 24 hours could be survived

39
Q

circulatory shock

A

acute failure of the CV system to perfuse the tissues of the body adequately

40
Q

type of circulatory shock

A
  • cardiogenic
  • septic
  • hypovolaemic
41
Q

cardiogenic shock

A

caused by acute impairment of cardio function
- myocardial infarction
- myocarditis
85% mortality

42
Q

septic shock

A

caused by bacteraemia, especially endotoxin

43
Q

what is endotoxin

A

powerful CV toxin that causes septic shock

44
Q

hypovolaemic shock

A

caused by fall in blood or plasma volume

  • diarrhoea
  • vomiting
  • dehydration
  • haemorrhage most common
45
Q

stages of shock

A
  1. non-progressive
  2. progressive
  3. irreversible shock
46
Q

which stage of shock is reversible

A
  • non- progressive

- progressive with therapy

47
Q

which stage of shock is irreversible

A

irreversible shock

no form of therapy is adequate to save person’s life

48
Q

what is non-progressive shock

A

shock will not progress because the sympathetic reflexes and other factors compensate enough to the loss of blood, which prevents further deterioration of circulation

49
Q

how is compensation achieved in non-progressive shock

A
  • baroreceptor reflex
  • CNS ischaemic response
  • formation of angiotensin in the kidneys by renin
  • release of ADH by pituitary
  • absorption of fluid from GI and interstitial space of body into capillaries
50
Q

what is the golden hour

A

when body tried to compensate. if fails, transfusion will happen at 1 hour and either progressive shock will occur which can be treated, or irreversible shock which cannot be treated

51
Q

what time frame is reversible shock

A

30-60 mins post haemorrhage

52
Q

what % blood loss is reversible and irreversible shock

A

45%

53
Q

what can cause progression of shock

A

positive feedback

54
Q

how does positive feedback cause progression of shock

A
  • APB becomes excessive low, so coronary blood flow decreases well below level required for adequate nutrition of the myocardium
  • lack of nutrition weakens the heart muscle
  • weaken heart muscle = even more reduced CO
  • reduced CO reduces coronary blood flow even more
    = shock becomes more and more severe
55
Q

what causes shock to become more severe

A

positive feedback cycle

Exercise & Environment (14 decks)

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