S5) Circulatory Shock Flashcards

1
Q

What is haemodynamic shock?

A

Haemodynamic shock is an acute condition of inadequate blood flow throughout the body due to a catastrophic fall in arterial blood pressure

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2
Q

What are the causes for the catastrophic drop in blood pressure which leads to haemodynamic shock?

A
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3
Q

Identify and define three different types of shock occurring due to a fall in cardiac output

A
  • Cardiogenic shock – ventricle cannot empty properly

- Mechanical shock – ventricle cannot fill properly

- Hypovolaemic shock – reduced blood volume leads to poor venous return

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4
Q

What is cardiogenic shock?

A

Cardiogenic shock is the acute failure of the heart to maintain cardiac output (pump failure)

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5
Q

Identify 3 potential causes for cardiogenic shock

A
  • Myocardial infarction (damage to left ventricle)
  • Serious arrhythmias
  • Acute worsening of heart failure
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6
Q

What are the consequences of cardiogenic shock?

A
  • CVP normal/raised
  • aBP lowered
  • Tissues poorly perfused

I. Coronary arteries (exacerbates problem)

II. Kidneys (reduced urine production)

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7
Q

Cardiac tamponade is an example of mechanical shock.

What is this condition?

A

Cardiac tamponade is when blood/fluid builds up in pericardial space, restricting the filling of both sides of the heart and limiting the end diastolic volume

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8
Q

What are the consequences of cardiac tamponade?

A
  • High CVP
  • Low aBP
  • Continued electrical activity
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9
Q

A pulmonary embolism is another example of mechanical shock.

What are the consequences of this?

A
  • High pulmonary artery pressure → right ventricle cannot empty
  • High CVP → reduced return of blood to the left heart
  • Low LAP
  • Low aBP
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10
Q

State two characteristic symptoms of mechanical shock due to PE

A
  • Chest pain
  • Dyspnoea
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11
Q

In four steps, explain how an embolus reaches the lungs

A

⇒ Deep vein thrombosis

⇒ Portion of thrombus breaks off

⇒ Embolus travels in venous system to right side of the heart

⇒ Pumped out via pulmonary artery to lungs

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12
Q

What is hypovolaemic shock?

A

Hypovolaemic shock is a state of shock due to reduced blood volume, most commonly due to haemorrhage

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13
Q

The severity of hypovolaemic shock is related to amount and speed of blood loss.

How does the shock vary with amount of blood loss?

A
  • < 20% blood loss unlikely to cause shock
  • 20-30% blood loss show some signs of shock response
  • 30-40% bloow loss shows substantial decrease in mean aBP and serious shock response
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14
Q

Explain what happens during a haemorrhage

A

⇒ Venous pressure falls

⇒ Cardiac output falls (Starling’s Law)

⇒ Arterial pressure falls

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15
Q

Describe the compensatory response observed in hypovolaemic shock

A

Low aBP detected by baroreceptors

⇒ Increased sympathetic stimulation

Tachycardia, increased contractlity

⇒ Peripheral vasoconstriction and venoconstriction

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16
Q

How does a patient in hypovolaemic shock present?

A
  • Tachycardia
  • Weak pulse
  • Pale skin
  • Cold, clammy extremities
17
Q

Besides haemorrhages, when else can hypovolaemic shock occur?

A
  • Severe burns
  • Severe diarrhoea / vomiting
  • Severe loss of Na+
18
Q

In 5 steps, explain how peripheral vasoconstriction (shutdown) impairs tissue perfusion

A

⇒ Tissue damage due to hypoxia

⇒ Release of chemical mediators

⇒ Vasodilation (TPR & BP falls)

⇒ Vital organs can no longer be perfused

⇒ Multi system failure

19
Q

What is distributive shock?

A
  • Distributive shock is low resistance shock (normovolaemic) due to profound peripheral vasodilation (decrease in TPR)
  • Blood volume is constant, but volume of the circulation has increased
20
Q

Identify two different types of shock due to a fall in total peripheral resistance

A
  • Anaphylactic shock
  • Septic shock
21
Q

What is anaphylaxis?

A

Anaphylaxis is a severe allergic reaction

22
Q

In 5 steps, explain how anaphylaxis leads to a state of distributive shock

A

⇒ Release of histamine from mast cells

Vasodilation (fall in TPR)

⇒ Dramatic drop in arterial pressure

⇒ Increased sympathetic response can’t overcome vasodilation

⇒ Impaired perfusion of vital organs

23
Q

How do patients present with anaphylactic shock?

A
  • Dyspnoea (bronchoconstriction, laryngeal oedema)
  • Collapse
  • Tachycardia
  • Red, warm extremities
24
Q

Anaphylactic shock is an acutely life threatening.

How can it be managed?

A

Adrenaline – vasoconstriction via action at α1 adrenoceptors

25
Q

What is sepsis?

A

Sepsis is a serious life-threatening response to infection, can lead to septic shock

26
Q

What is septic shock?

A

Septic shock is persisting hypotension requiring treatment to maintain blood pressure despite fluid resuscitation

27
Q

In 5 steps explain how sepsis leads to a state of distributive shock (septic shock)

A

Endotoxins released by circulating bacteria

⇒Profound inflammatory response

Vasodilation (& increased permeability)

⇒ Dramatic fall in TPR & aBP

⇒ Impaired perfusion of vital organs

28
Q

How do patients present with septic shock?

A
  • Tachycardia
  • Warm, red extremities initially
  • Vasoconstriction (later on)
29
Q

When would one start to consider cardiac arrest?

A
  • Unresponsiveness associated with lack of pulse
  • Heart has stopped or has ceased to pump effectively
30
Q

Identify and describe the three forms of cardiac arrest

A
  • Asystole – loss of electrical and mechanical activity
  • Pulseless Electrical Activity
  • Ventricular fibrillation – uncoordinated electrical activity
31
Q

How does one manage cardiac arrest?

A
  • Basic life support – chest compression and external ventilation
  • Advanced life support – defibrillation
  • Adrenaline – enhances myocardial function and increases TPR
32
Q

Describe the impact of defibrillation on the heart in advanced life support

A

⇒ Electric current delivered to the heart

⇒ Depolarises all the cells – puts them into refractory period

⇒ Allows coordinated electrical activity to restart