Haemodynamic Shock

Question 1

Mean Arterial pressure = ? OR ?

Answer 1

Stroke Volume x Heart rate x Total Peripheral Pressure

Cardiac Output x Total Peripheral resistance

Question 2

What is haemodynamic shock?

Answer 2

Inadequate blood flow around the blood, fall in arterial blood pressure leading to shock.
Fall in cardiac output or fall in total peripheral resistance

Question 3

What does a fall in cardiac output lead to?

Answer 3

Pump cannot fill
Pump failure
Loss of blood volume

Question 4

What does a fall in peripheral resistance lead to?

Answer 4

Excessive vasodilation

Lack of tissue perfusion

Question 5

What is cardiogeneic shock?

Answer 5

Where the ventricle cannot empty properly - pump failure

Question 6

What are some causes of cardiogenic shock?

Answer 6

Following a myocardial infarction (damage to left ventricle)
Serious arrhythmia (pumping top slowly)
Worsening heart failure

Question 7

What happens to venous and arterial pressure in cardiogenic shock?

Answer 7

Venous pressure normal or raised

Drop in arterial BP

Question 8

What can cardiogenic shock lead to?

Answer 8

Poorly perfused tissues - especially kidneys

Oliguira - reduced urine output

Question 9

What is the difference between Asystole and Pulseless Electrical Activity?

Answer 9

Aystole - loss of electrical and mechanical activity

PEA - no pulse but some electrical activity

Question 10

What can be done in the case of cardiac arrest?

Answer 10

Basic Life Support
Defibrillation - depolarises cells and puts them in refractory period to allow co-ordinated electrical activity.
Adrenaline - enhances myocardial function

Question 11

What is mechanical shock (cardiac tamponade)?

Answer 11

Blood or fluid filling up the pericardial space which restricts filling of heart.

Question 12

What impact does mechanical shock have in arterial and venous pressure?

Answer 12

High venous pressure

Low Arterial pressure

Question 13

How would a pulmonary embolism cause mechanical shock?

Answer 13

Embolus occludes pulmonary artery
Right ventricle cannot empty 
Central venous pressure rises
Reduced return of blood to left heart
Limits filling of left heart
Left atrial pressure low
Arterial BP low
Shock

Question 14

What is hypovolemic shock?

Answer 14

Reduced blood volume commonly due to a haemorrhage.

Question 15

How much blood % can you lose before you go into shock?

Answer 15

20%

Question 16

Explain how the sympathetic nervous system can cause a compensatory responses following hypovolaemic shock due to a haemorrhage.

Answer 16

Haemorrhage
Venous pressure falls
Cardiac output falls
Arterial output falls
This is detracted by the baroreceptors

Leads to increased sympathetic stimulation
Tachycardia
Increased force of constriction
Vasoconstriction

Question 17

Apart from activating the symmetric system, what other systems does the body use to bring up blood volume following a haemorrhage?

Answer 17

Normally the body there is a net movement of fluid out to the tissues due to interstitial oncotic pressure and hydrostatic pressure.

After a haemorrhage, increased peripheral resistance (as less dilated) reduces capillary hydrostatic pressure and there is a net movement of fluid into the capillaries.

Question 18

What are some signs of hypovolaemic shock?

Answer 18

Tachycardia
Weak pulse
Pale skin
Cold, clammy extremities

Question 19

In hypovolaemic shock, lack of tissue perfusion can lead to the release of vasodilators. How does this worsen the situation?

Answer 19

Total peripheral resistance falls
BP falls
Vital organs cannot be perfused
Organ failure

Question 20

What is distributive shock?

Answer 20

Low resistance shock.

Due to profound peripheral vasodilation.

Question 21

How can a inflammatory response in relation to sepsis lead to septic shock?

Answer 21

Inflammatory shock leads to vasodilation
Dramatic fall in total peripheral resistance
Fall in arterial pressure
Impaired tissue perfusion

Leaky capillaries due to fluid exudate also reduces blood volume

Question 22

How does anaphylaxis causes an anaphylactic shock?

Answer 22

Severe allergic reaction
Release of histamine - vasodilation - fall in total peripheral resistance
Drop in arterial pressure
Sympathetic response activated but not enough to overcome vasodilation
Impaired perfusion

Question 23

What are effects of anaphylaxis (minus anaphylaxis shock) can be fatal to the patient?

Answer 23

Brochoconstriction

Laryngeal oedema

Question 24

What treatment is given to someone to anaphylactic shock?

Answer 24

Adrenaline - vasoconstriction via action at the alpha adrenoceptors

Question 25

Apart from a haemorrhage, what is another traumatic cause of hypovolaemic shock?

Answer 25

Severe burns