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CVS > CVS 11 Haemodynamic Shock > Flashcards

CVS 11 Haemodynamic Shock Flashcards

(41 cards)

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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?

Study These Flashcards
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?

Study These Flashcards
A

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

19
Q

Effect of cardiac tamponade

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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?

Study These Flashcards
A

High central venous pressure due to restricted filing of heart

21
Q

Causes of mechanical shock

Study These Flashcards
A

Cardiac tamponade
Massive pulmonary embolism

22
Q

What is mechanical shock?

Study These Flashcards
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?

Study These Flashcards
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?

Study These Flashcards
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
What is hypovolaemic shock?
Failure of heart to maintain cardiac output due to reduced blood volume
26
What is hypovolaemic shock most commonly due to?
Haemorrhage
27
How does the body cope with a haemorrhage?
- venous pressure falls - CO falls - arterial pressure falls - detected by baroreceptors - increased sympathetic stimulation - tachycardia - increased force of contraction - peripheral vasoconstriction - venoconstriction
28
Causes of hypovolaemic shock
Haemorrhage - most common Severe burns Severe diarrhoea/vomiting + loss of Na+
29
Signs + symptoms of hypovolaemic shock
Tachycardia Weak pulse Pale skin Cold, clammy extremities
30
What is the danger of compensation of haemorrhage?
- 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
What shocks are due to low resistance (normvolaemic)?
Toxic/septic shock Anaphylactic shock
32
How can sepsis lead to septic shock?
- 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
What is septic shock?
A subset of sepsis where profound circulatory, cellular + metabolic abnormalities substantially increased mortality
34
Signs + symptoms of septic shock
Tachycardia Warm, red extremities initially >> later vasoconstriction > localised hypo-perfusion
35
What happens in anaphylactic shock?
- 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 >> difficulty breathing Drop in BP > increase in sympathetic response > increased CO - not enough to overcome vasodilation
36
Signs + symptoms of anaphylaxis shock
Difficulty breathing Collapse Rapid heart rate Red, warm extremities
37
What type of shock can haemorrhage cause?
Hypovolaemic shock
38
What type of shock can a MI cause?
Cardiogenic shock
39
What type of shock can a cardiac tamponade cause?
Mechanical shock
40
What type of shock can pulmonary embolisms cause?
Mechanical shock
41
Outline neurogenic shock
- occurs after spinal cord transaction at high level - causes decreases sympathetic tone or increases parasympathetic tone - both cause decreased peripheral vascular resistance - causing decreased preload + cardiac output - decreases peripheral tissue perfusion

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