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PHYL3002 CVS and Respiratory > Lecture 22: Shock > Flashcards

Lecture 22: Shock Flashcards

1
Q

What is circulatory shock?

A

Inadequate peripheral perfusion, lack of tissue oxygenation

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2
Q

Circulatory shock is __________ and ___________ but can cause death

A

Common and treatable

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3
Q

Inadequate perfusion leads to ________

A

Cell death

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4
Q

What is Hypovolemic shock?

A
  • Blood loss (trauma)
  • Plasma loss (burns)
  • Water loss (vomiting, diarrhoea, increased urination and breathing [minor])
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5
Q

Outline the mechanism of uncompensated Haemorrhagic Shock:

A

Blood loss –> ↓central venous pressure –> ↓EDV –> ↓SV –> ↓CO –> ↓MAP

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6
Q

What happens when you lose ~60% of aortic pressure?

A

Compensatory mechanisms fail to return to you normal

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7
Q

What is Class 1 haemorrhage and it’s symptoms?

A
  • loss of 0-15%
  • slight tachycardia
  • usually no significant change in BP, PP or respiratory rate
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8
Q

What is Class 2 haemorrhage and it’s symptoms?

A
  • loss of 15-30%
  • HR>100
  • Tachypnea
  • ↓PP
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9
Q

What is Class 3 haemorrhage and it’s symptoms?

A
  • loss of 30-40%
  • Marked tachycardia and tachypnea
  • ↓ SBP
  • Oliguria (↓urine production)
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10
Q

What is Class 4 haemorrhage and it’s symptoms?

A
  • loss >40%
  • Tachycardia
  • ↓SBP, ↓PP
  • No urinary output
  • Immediately life threatening
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11
Q

How does the body respond when you lose 40% of blood volume?

A

Large sympathetic and adrenal stimulation

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12
Q

What are baroreceptors sensitive to?

A
  • Stretch receptors int eh carotid sinus and aortic arch

- Sensitive to Δ pressure and to the rate of change

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13
Q

↓ in MAP causes a _______ in Barorecptor firing. This causes ___________ activation and __________ inhibition

A

↓ in BR firing
Sympathetic
Parasympathetic

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14
Q

Chemoreceptors are important when the MAP

A

60mmHg

Abdominothoracic pump

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15
Q

How do we compensate for hypovolemic shock?

A
  • Increase circulating vasoconstrictors via catelcholamine secretion
  • Increase ADH secretion
  • increase renal water retention via Angiotensin II
  • Increase HR and VR
  • Activation of thirst mechanism
  • Haematopoesis
  • Redistribution of Interstitial fluid
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16
Q

When MAP<60mmHg, cerebral perfusion ↓, what is the response?

A

Cerebral ischaemia produces a very intense sympathetic discharge

17
Q

What is decompensated shock?

A

Severe haemorrhage leads to a positive feedback loop that further decreases MAP.

18
Q

Describe the mechanism of decompensated shock:

A

↓↓CO –> ↓MAP –> ↓Coronary Perfusion –> ↓Ionotropy –> ↓CO

↓MAP –> ↓Organ perfusion –> ↓Tissue Hypoxia –> Vasodilation due to sympathetic escape (desensitisation to sympathetics) –> ↓MAP

19
Q

What does decompensated shock cause:

A
  • Cardiac Failure
  • Acidosis
  • CNS depression
  • Increase capillary permeability
  • Toxin formation
  • Vessel blockage by thrombosis
20
Q

What is neurogenic shock?

A

Distributive shock: Loss of ANS signals to the vascular smooth muscle (due to CNS damage or depression) which causes vasodilation and pooling of blood

21
Q

What is Psychogenic shock?

A

Sudden dilation of blood vessels and hypoperfusion of the brain that lead to loss of consciousness brought on my stress, pain or fright

22
Q

What is Septic Shock?

A

Shock caused by bacterial infection that leads to vasodilation and increased capillary permeability and activation of clotting (Decrease in Blood volume and flow = ↓MAP)

23
Q

What is anaphylatic shock?

A

Severe allergic reaction releases histamine causing vasodilation and blood vessel leakage. Also cause extravascular muscle spasm causes breathing problems.

24
Q

What is Cardiogenic shock?

A

Shock related to failure of the heart to pump properly (caused by injury, valve defects, heart failure etc)

25
Q

What is Obstructive Shock?

A 
Obstruction to blood flow --> ↓CO
caused by:
- Cardiac Tamponade
- Tension Pneumothorax
- Pulmonary Embolism
26
Q

What are the symptoms of shock?

A
  • Restlessness and anxiety
  • ↓ level of conciousness
  • Dull eyes
  • Rapid shallow inspo
  • Nausea and vomiting
  • Thirst
  • ↓ Urine output
  • Tachycardia
  • Pale, cool and clammy in Hypovolemic and Cardiogenic shock
  • Dry flushed skin in sepsis, Anaphylaxis and neurogenic shock
27
Q

How do we treat shock?

A
  • Increase volume
  • Treat cause
  • Correct acidosis
  • Use ionotropic chronotropic agents
  • vasoactive substances to increase SVR

PHYL3002 CVS and Respiratory (21 decks)

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