Haemodynamic Shock

Question 1

What is haemodynamic shock

Answer 1

Acute condition of inadequate blood flow throughout the body

A catastrophic fall in arterial BP leading to circulatory shock

Question 2

How is mean arterial BP calculated

Answer 2

maBP = CO x TPR

CO = SV x HR

Question 3

What are the two causes of shock

Answer 3

Fall in cardiac output

Fall in peripheral resistance

Question 4

What are the types of shock due to a fall in cardiac output

Answer 4

Cardiogenic shock - ventricle cannot empty properly

Mechanical shock - ventricle cannot fill properly

Hypovolaemic shock - reduced blood volume leads to poor venous return

Question 5

What is cardiogenic shock and what are some causes

Answer 5

Acute failure of the heart to maintain CO - pump failure. Heart fills but fails to pump effectively causing drop in arterial BP and tissues to become poorly perfused

Central venous pressure may be normal or raised

Causes:

Following a MI

Due to serious arrhythmias

Acute worsening of heart failure

Question 6

What is cardiac arrest

Answer 6

Unresponsiveness associated with a lack of pulse

Heart has stopped or has ceased to pump effectively

Question 7

What are the types of cardiac arrest

Answer 7

Asystole - loss of electrical and mechanical activity

Pulseless Electrical Activity (PEA) - electrical but no mechanical activity

Ventricular fibrillation

Question 8

What are the most common forms of cardiac arrest

Answer 8

Following a MI

Electrolyte imbalance

Caused by some arrhythmias

Question 9

What is cardiac tamponade

Answer 9

Where blood or fluid builds up in pericardial space which restricts filling of the heart, limiting EDV

Affects both left and side sides of the heart

Causes a high CVP - heart cannot fill properly

Causes low ABP - stroke volume reduced

Sign is veins in the neck will bulge out

Question 10

How does a pulmonary embolism cause mechanical shock

Answer 10

Large embolus occludes large pulmonary artery

Increases pulmonary artery pressure

RV cannot empty, increasing CVP

Reduced return to left side of heart limiting output, this lowers arterial pressure causing shock

Also get chest pain and dyspnoea

Question 11

What are two causes of mechanical shock

Answer 11

Cardiac tamponade

Pulmonary embolism

Question 12

What is hypovolaemic shock and what are the ranges where shock is produced

Answer 12

Shock caused by reduced blood volume, typically due to haemorrhage. Can be due to severe burns or severe diarrhoea or vomiting and loss of Na

<20% blood loss unlikely to cause shock

20-30% some signs of shock

30-40% substantial decrease in maBP and serious shock response

Question 13

What are the symptoms of hypovolaemic shock

Answer 13

Tachycardia

Weak pulse

Pale skin

Cold, clammy extremities

Low CVP

Question 14

What is distributive shock and what are two examples

Answer 14

Low resistance shock where there has been profound peripheral vasodilation which decreases the TPR. Blood volume constant (normovolaemic) but volume of circulation has increased

Toxic shock

Anaphylatic shock

Question 15

How doe sepsis cause septic shock

Answer 15

Endotoxins released by bacteria cause inflammatory response which initiates profound vasodilation

This drastically decreases TPR, decreasing arterial pressure and impairing organ perfusion

Capillaries also become leaky, reducing blood volume

Question 16

What are the symptoms of septic shock

Answer 16

Tachycardia

Initially warm, red extremities but later stages there is vasoconstriction and localised hypoperfusion

Question 17

How does anaphylaxis cause an anaphylatic shock

Answer 17

Severe allergic reaction causes release of histamine and other mediators which have powerful vasodilator effect

This causes a fall in TPR which cannot physiologically be overcome

There is then impaired perfusion of vital organs

Question 18

As well as causing vasodilation, what else do mediators of a severe allergic reaction cause. What do you give to treat this

Answer 18

Cause bronchoconstriction and laryngeal oedema

Makes it difficult to breath

Bronchodilators and anti-histamines

Question 19

What symptoms will a patient suffering anaphylactic shock have

Answer 19

Difficulty breathing

May have collapsed

Rapid heart rate

Red, warm extremities

Question 20

What do you give to a patient suffering anaphylactic shock

Answer 20

Adrenaline (EpiPen) - causes vasoconstriction at alpha-1 adrenoceptors