Haemodynamic Shock

Question 1

What is the term Haemodynamic Shock used to describe?

Answer 1

Acute circulatory failure with either inadequate or inappropriately distributed tissue perfusion, resulting in generalised lack of oxygen supply to cells

Question 2

What are 2 types of causes of haemodynamic shock

Answer 2

• Fall in Cardiac Output

- Fall in Total Peripheral Resistance beyond capacity of heart to cope

Question 3

Describe 3 causes of a fall in Cardiac Output that can lead to Haemodynamic Shock

Answer 3

Cardiogenic shock;
- Inability of heart to eject enough blood

Hypovolaemic shock;
- Due to loss of circulating fluid volume

Mechanical shock;

• Due to a restriction of the filling of the heart
• Obstructed blood flow through the lungs

Question 4

Suggest 1 cause of Cardiogenic and Hypovolaemic Shock.

Suggest 2 for Mechanical Shock

Answer 4

Cardiogenic shock;
- MI (Also, arrhythmia, worsening of heart failure)

Hypovolaemic shock;
- Haemorrhage

Mechanical shock;

• Pulmonary embolism
• Cardiac tamponade

Question 5

Describe 1 cause of a fall in TPR, leading to Haemodynamic Shock

Answer 5

Distributive/ normovolaemic shock

- Due to excessive vasodilation

Question 6

Suggest 2 causes of Distributive/ Normovolaemic shock

Answer 6

• Sepsis

- Anaphylaxis

Question 7

In Cardiogenic shock, the heart fills but fails to pump effectively.

Describe the;

• Central Venous Pressure
• Arterial BP
• Tissue perfusion

Answer 7

CVP: May be normal or raised
Arterial BP: Large decrease

Tissues: Poorly perfused (If in kidneys-> Reduced urine-Oliguria)

Question 8

Cardiac arrest is defined as “Unresponsiveness association with lack of pulse”

What are 3 forms of Cardiac Arrest?

Answer 8

• Asystole
• Pulseless Electrical Activity (PEA)
• Ventricular fibrillation (most common, often after MI)

Question 9

What are 3 ways of treating a Cardiac Arrest?

Answer 9

• Basic life support (chest compression, external ventilation)
• Advanced life support (Defibrillation depolarises all cells, putting them in refractory period)
• Adrenaline

Question 10

What is Cardiac Tamponade?

How are the Central Venous Pressure and Arterial Blood Pressure affected?

Answer 10

Blood/ fluid build up in pericardial space to the point where filling of the heart is affected

CVP: High
ABP: Low

Question 11

Pulmonary Embolisms can present with Chest Pain and Dyspnoea, and can lead to Mechanical Shock.

Describe the;

• Pulmonary Artery Pressure
• Central Venous Pressure
• Left Atrial Pressure
• Arterial Blood Pressure

Answer 11

Pulmonary Artery: High
CVP: High
Left Atrial: Low
Arterial: Low

Question 12

What percentage of blood must be lost for there to be a substantial decrease in mean Arterial Blood Pressure, with serious shock response

Answer 12

30% - 40%

20% - 30% blood loss shows some signs of shock response

Question 13

A fall in arterial pressure is detected by baroreceptors. This leads to a COMPENSATORY RESPONSE

List 4 features of this compensatory response

Answer 13

Increased sympathetic stimulation;

• Tachycardia
• Increased force of contraction
• Peripheral vasoconstriction
• Venoconstriction

Question 14

Normally, there is a small net movement of fluid out of capillaries and into tissues.

Explain how this is affected by Hypovolaemic Shock?

Answer 14

This is reversed

• Increased TPR reduces the capillary hydrostatic pressure (less blood downstream of site of vasoconstriction)
• Therfore, there is a net movement of fluid into capillaries

Question 15

What are 5 features of Hypovolaemic shock

Answer 15

• Tachycardia
• Weak pulse
• Pale skin
• Cold, clammy extremities
• Low Central Venous Pressure

Question 16

Other than haemorrhage, name 2 causes of Hypovolaemic shock

Answer 16

• Severe burns

- Severe diarrhoea/ vomiting and Na+ loss

Question 17

How can Hypovolaemic Shock lead to Decompensation

Answer 17

• Peripheral vasoconstriction leads to tissue damage to hypoxia
• Release of chemical mediators causing vasodilation
• Dramatic fall in blood pressure
• Vital organs can’t be perfused-> Multi-system failure

Question 18

Distributive/ normovolaemic shock involves a normal blood volume, but a large drop in total peripheral resistance.

What are 2 causes?

Answer 18

• Toxic/ septic shock

- Anaphylactic shock

Question 19

How do Bacteria cause septic/ toxic shock?

Answer 19

• Release endotoxins, cause excessive inflammatory response, producing cytokines
• Endotoxins and cytokines cause vasodilation, so fall in arterial pressure-> Impaired vital organ perfusion
• Capillaries become leaky
• Increased coagulation and hypo-perfusion (later stages)

Question 20

In Septic shock, why do we get Tachycardia?

Answer 20

• Low arterial pressure detected by baroreceptors, so increased sympathetic output
• Vasoconstrictor effect< Vasodilator effect
• HR and SV increased (Increased CO)

Question 21

How does a Septic Shock patient present? In 3 ways

Answer 21

• Tachycardia
• Initially, warm red extremities (due to vasodilation)
• In later stages, localised hypo-perfusion

Question 22

Anaphylactic shock is due to a severe allergic reaction (anaphylaxis).

This involves the release of histamine from mast cells (and other mediators). What 4 effects does this have?

Answer 22

• Vasodilation-> Fall in TPR
• Increased sympathetic response, but can’t overcome vasodilation
• Mediators also cause bronchoconstriction
• Impaired vital organ perfusion

Question 23

How does a patient in anaphylactic shock present? In 4 ways

How do you treat?

Answer 23

• Difficulty breathing
• Collapsed
• Tachycardia
• Red, warm extremities (vasodilation)

Adrenaline (causes vasoconstriction through Alpha 1 receptors)