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CVS > CVS 11 Haemodynamic Shock > Flashcards

CVS 11 Haemodynamic Shock Flashcards

1
Q

What is haemodynamic shock?

A

Acute condition of inadequate blood flow throughout the body due to catastrophic fall in arterial BP

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2
Q

How do you calculate mean arterial BP?

A

Mean arterial BP = CO x TPR

Mean arterial BP = DBP + 1/3 PP

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3
Q

How to calculate pulse pressure?

A

SBP-DBP

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4
Q

What two things can shock be due to?

A

Fall in CO
Fall in TPR

Beyond capacity of heart to cope

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5
Q

What can a fall in cardiac output be due to?

A

Mechanical - pump can’t fill
Pump failure
Loss of blood volume

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6
Q

What can a fall in peripheral resistance be due to?

A

Excessive vasodilation

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7
Q

What types of shocks are due to fall in cardiac output?

A

Cardiogenic shock
Mechanical shock
Hypovolaemic shock

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8
Q

What is cardiogenic shock?

A

Failure of heart to maintain CO due to:
- Pump failure
- Ventricle cannot empty properly

Heart fills but fails to pump effectively

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9
Q

Potential causes of cardiogenic shock

A
  • After a MI - damage to LV
  • due to serious arrhythmias
  • acute worsening on heart failure
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10
Q

What are poorly perfused in cardiogenic shock?

A

Coronary arteries&raquo_space; makes issue worse
Kidneys

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11
Q

What is asystole?

A

Loss of electrical and mechanical activity

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12
Q

What is cardiac arrest?

A

Unresponsiveness associated with lack of pulse

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13
Q

What is the most common form of cardiac arrest?

A

Ventricular fibrillation - inadequate contraction

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14
Q

What can ventricular fibrillation be due to?

A
  • After MI
  • Electrolyte imbalance
  • Some arrhythmia e.g. long QT + Torsades de Pointes
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15
Q

What would you do to a patient in cardiac arrest?

A

Basic life support - CPR + ventriltion
Advanced life support - defibrillation
Adrenaline

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16
Q

Why is adrenaline given in cardiac arrest?

A
  • high conc so act on alpha receptors > vasoconstriction > increases peripheral resistance
  • Enhances myocardial function
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17
Q

How does defibrillation help in cardiac arrest?

A

1- electric current delivered to heart
2- depolarises all cells - puts them into refractory period
3- allows coordinated electrical activity to restart

18
Q

What is a cardiac tamponade?

A

Blood or fluid build up in pericardial space which leads to a decrease in arterial blood pressure

19
Q

Effect of cardiac tamponade

A
  • Heart is compressed
  • Restricts filling of heart volume - limits EDV
  • Affects left + heart sides of heart
  • High central venous pressure&raquo_space; distended neck veins
  • Low arterial blood pressure
20
Q

Why are distended neck veins seen in cardiac tamponade?

A

High central venous pressure due to restricted filing of heart

21
Q

Causes of mechanical shock

A

Cardiac tamponade
Massive pulmonary embolism

22
Q

What is mechanical shock?

A

Acute failure of heart to maintain cardiac output due to ventricles cannot fill properly

23
Q

How does a pulmonary embolism cause mechanical shock?

A
  • embolus occludes large pulmonary artery
  • pulmonary artery pressure is high
  • RV cannot empty
  • CVP high
  • reduced return of blood to left heart
  • limits filling of left heart
  • left atrial pressure low
  • arterial BP low
  • shock (+chest pain + dyspnoea)
24
Q

How would an embolus typically reach the lungs?

A

Deep vein thrombosis

  • portion of thrombus breaks off
  • travels in venous system to right side of heart
  • pumped out via pulmonary artery to lungs
25
Q

What is hypovolaemic shock?

A

Failure of heart to maintain cardiac output due to reduced blood volume

26
Q

What is hypovolaemic shock most commonly due to?

A

Haemorrhage

27
Q

How does the body cope with a haemorrhage?

A
  • venous pressure falls
  • CO falls
  • arterial pressure falls
  • detected by baroreceptors
  • increased sympathetic stimulation
  • tachycardia
  • increased force of contraction
  • peripheral vasoconstriction
  • venoconstriction
28
Q

Causes of hypovolaemic shock

A

Haemorrhage - most common
Severe burns
Severe diarrhoea/vomiting + loss of Na+

29
Q

Signs + symptoms of hypovolaemic shock

A

Tachycardia
Weak pulse
Pale skin
Cold, clammy extremities

30
Q

What is the danger of compensation of haemorrhage?

A
  • peripheral vasoconstriction impairs tissue perfusion
  • tissue damage due to hypoxia
  • release of chemical mediators > vasodilators
  • TPR falls
  • BP falls
  • lack of blood flow to vital organs
  • multi organ failure
31
Q

What shocks are due to low resistance (normvolaemic)?

A

Toxic/septic shock
Anaphylactic shock

32
Q

How can sepsis lead to septic shock?

A
  • endotoxins released by circulating bacteria
  • excessive inflammatory response
  • causes excessive vasodilation
  • fall in TPR
  • fall in arterial pressure
  • impaired perfusion of vital organ

-capillaries become leaky > reduced blood volume

33
Q

What is septic shock?

A

A subset of sepsis where profound circulatory, cellular + metabolic abnormalities substantially increased mortality

34
Q

Signs + symptoms of septic shock

A

Tachycardia
Warm, red extremities initially&raquo_space; later vasoconstriction > localised hypo-perfusion

35
Q

What happens in anaphylactic shock?

A
  • severe allergic reaction
  • release of histamine from mast cells
  • vasodilator effect
  • fall in TPR
  • drop in arterial pressure
  • impaired perfusion of vital organs
  • mediators also cause bronchoconstriction + laryngeal oedema&raquo_space; difficulty breathing

Drop in BP > increase in sympathetic response > increased CO - not enough to overcome vasodilation

36
Q

Signs + symptoms of anaphylaxis shock

A

Difficulty breathing
Collapse
Rapid heart rate
Red, warm extremities

37
Q

What type of shock can haemorrhage cause?

A

Hypovolaemic shock

38
Q

What type of shock can a MI cause?

A

Cardiogenic shock

39
Q

What type of shock can a cardiac tamponade cause?

A

Mechanical shock

40
Q

What type of shock can pulmonary embolisms cause?

A

Mechanical shock

CVS (20 decks)

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