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Medicine Cardiovascular > Shock > Flashcards

Shock Flashcards

1
Q

What is shock?

A

An abnormality of the circulatory system resulting in inadequate tissue perfusion and oxygenation

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2
Q

Steps in how shock leads to cellular failure

A

Shock → inadequate tissue perfusion → inadequate tissue oxygenation → anaerobic metabolism → accumulation of metabolic waste products that are toxic to the cell → cellular failure

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3
Q

What does adequate tissue perfusion depend on?

A

Adequate blood pressure and adequate cardiac output

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4
Q

What does stroke volume depend on?

A

Preload, myocardial contractility, afterload

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5
Q

Afterload

A

The resistance against which the heart is pumping

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6
Q

Myocardial contractility

A

How well the heart can contract

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7
Q

Hypovolaemic shock

A

Loss of blood volume

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8
Q

How can hypovolaemic shock lead to inadequate tissue perfusion?

A

Loss of blood volume → decreased blood volume → decreased venous return → decreased end diastolic volume → decreased stroke volume → decreased CO and BP → inadequate tissue perfusion

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9
Q

Cardiogenic shock

A

Sustained hypotension caused by decreased cardiac contractility

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10
Q

Example on when cardiogenic shock can occur

A

When the heart is severely damaged e.g. after a myocardial infarction

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11
Q

How can cardiogenic shock lead to inadequate tissue perfusion?

A

Decreased cardiac contractility → decreased stroke volume → decreased CO and BP → inadequate tissue perfusion

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12
Q

Obstructive shock

A

Increased intrathoracic pressure

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13
Q

What can cause obstructive shock?

A

Tension pneumothorax

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14
Q

How can obstructive shock lead to inadequate tissue perfusion?

A

Increased intrathoracic pressure → decreased venous return → decreased end diastolic volume → decreased stroke volume → decreased CO and BP → inadequate tissue perfusion

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15
Q

Why does increased intrathoracic pressure cause decreased venous return?

A

Venous return depends on the pressure gradient outside and inside the chest

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16
Q

Neurogenic shock

A

Loss of sympathetic tone to blood vessels and heart

17
Q

What can cause neurogenic shock?

A

Spinal cord injury

18
Q

How can neurogenic shock lead to inadequate tissue perfusion?

A

Loss of sympathetic tone to blood vessels and heart → massive venous and arterial vasodilation causing effect on heart rate → decreased venous return and decreased SVR leads to decreased heart rate → decreased CO and BP → inadequate tissue perfusion

19
Q

What is different in how neurogenic shock leads to inadequate tissue perfusion compared to other types of shock?

A

Heart rate decreases

20
Q

Vasoactive shock

A

Release of vasoactive mediators

21
Q

Examples of vasoactive shock

A

Septic shock, anaphylactic shock

22
Q

How can vasoactive shock lead to inadequate tissue perfusion?

A

Release of vasoactive mediators → massive venous and arterial vasodilation and increased capillary permeability (vessels become leaky) → decreased venous return and decreased SVR → decreased CO and BP → inadequate tissue perfusion

23
Q

Treatment of shock

A
  • ABCDE approach
  • High flow oxygen
  • Volume replacement
  • Call for help early
  • Treat the cause as appropriate
24
Q

For which type of shock would you not give volume replacement as treatment?

A

Cardiogenic shock

25
Q

Additional treatment for cardiogenic shock

A

Inotropes

26
Q

Treatment for tension pneumothorax

A

Immediate chest drain

27
Q

Treatment for anaphylactic shock

A

Adrenaline

28
Q

Treatment for septic shock

A

Vasopressors

29
Q

Causes of hypovolaemic shock

A

Haemorrhage e.g. trauma, surgery, GI haemorrhage

Vomiting, diarrhoea, excessive sweating

30
Q

How can vomiting lead to circulatory shock?

A

Vomiting leads to decreased extracellular fluid volume → decrease in blood volume → decrease in CO → circulatory shock and decreased MAP

31
Q

Until what stage in haemorrhagic shock can compensatory mechanisms maintain blood pressure?

A

Until greater than 30% of blood volume is lost

32
Q

Compensatory mechanisms to maintain blood pressure in haemorrhagic shock

A

Increased heart rate, decreased stroke volume → cardiac output may be decreased
Increased systemic vascular resistance

33
Q

Class I haemorrhagic shock:

  • Blood loss (mL and % blood volume)
  • Pulse rate
  • Blood pressure
  • Pulse pressure
  • Resp rate
  • Urine output
  • Central nervous system/mental status
A
  • Up to 750ml, up to 15% blood volume
  • <100
  • Normal
  • Normal or increased
  • 14-20 per minute
  • > 30 ml/hour
  • Slightly anxious
34
Q

Class II haemorrhagic shock:

  • Blood loss (mL and % blood volume)
  • Pulse rate
  • Blood pressure
  • Pulse pressure
  • Resp rate
  • Urine output
  • Central nervous system/mental status
A
  • 750-1500ml, 15-30% blood volume
  • 100-120
  • Normal
  • Decreased
  • 20-30 per minute
  • 20-30 ml/hour
  • Mildly anxious
35
Q

Class III haemorrhagic shock:

  • Blood loss (mL and % blood volume)
  • Pulse rate
  • Blood pressure
  • Pulse pressure
  • Resp rate
  • Urine output
  • Central nervous system/mental status
A
  • 1500-2000ml, 30-40% blood volume
  • 120-140
  • Decreased
  • Decreased
  • 30-40 per minute
  • 5-15 ml/hour
  • Anxious/confused
36
Q

Class IV haemorrhagic shock:

  • Blood loss (mL and % blood volume)
  • Pulse rate
  • Blood pressure
  • Pulse pressure
  • Resp rate
  • Urine output
  • Central nervous system/mental status
A
  • > 2000ml, >40%
  • > 140
  • Decreased
  • Decreased
  • > 35 per minute
  • Negligible
  • Confused/lethargic

Medicine Cardiovascular (24 decks)

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