CVS Shock

Question 1

What do organic nitrates do when used for angina?

Answer 1

Release NO which VENOdilates so reduces pre-load of the heart

Question 2

What is cardiac arrest?

Answer 2

There is unresponsiveness associated with a lack of pulse. Heart has either stopped or ceased to pump effectively

Question 3

What is pulseless electrical activity?

Answer 3

A type of cardiac arrest where there is a dissociation between electrical and mechanical activity of the heart
(can happen in severe hypoxia)

Question 4

What is shock?

Answer 4

An acute condition of inadequate blood flow throughout the body. It is caused by a catastrophic fall in arterial BP

Question 5

What is the equation for mean arterial blood pressure and how does this relate to the cause of shock?

Answer 5

Mean arterial BP = CO x TPR

Therefore shock can be caused by:

• fall in CO
• fall in TPR beyond the capacity of the heart to cope

Question 6

What types of shock cause a fall in cardiac output?

Answer 6

1. Cardiogenic shock (pump failure)
2. Mechanical shock (obstruction preventing filling)
3. Hypovolaemic shock (poor venous return)

Question 7

What are the potential causes of cardiogenic shock?

Answer 7

• damage to LV following MI
• acute worsening of heart failure
• serious arrhythmias eg severe bradycardia or ventricular tachycardia

Question 8

What would happen to central venous pressure and arterial BP in cardiogenic shock?

Answer 8

CVP increase

Mean arterial BP decrease

Question 9

What is the equation for cardiac output?

Answer 9

CO = SV x HR

Question 10

What is the cause of mechanical shock?

Answer 10

Cardiac tamponade - restricts filling so limits end diastolic volume
Massive pulmonary embolism - RV cannot empty

Question 11

What would happen to central venous pressure and arterial BP in mechanical shock?

Answer 11

CVP high - may see distension of neck due to high JVP

Low arterial BP

Question 12

What are the causes of hypovolaemic shock?

Answer 12

Heamorrhage

• less than 20% loss unlikely to cause shock
• 20-30% mild shock
• over 30% serious shock

(also severe burns or diarrhoea)

Question 13

What factors is the severity of hypovolaemic shock related to?

Answer 13

AMOUNT and SPEED of blood loss

Question 14

What happens to central venous pressure and mean arterial blood pressure in hypovolaemic shock?

Answer 14

CVP falls

Arterial BP falls

Question 15

What are the symptoms of hypovolaemic shock?

Answer 15

Huge sympathetic drive results in:

• tachycardia
• weak pulse
• pale skin
• cold, clammy extremities

Question 16

What is decompensation wrt hypovolaemic shock?

Answer 16

Peripheral vasoconstriction impairs tissue perfusion
There is tissue damage due to hypoxia –> releases vasodilator mediators –> TPR falls –> BP falls dramatically leading to multi system failure

Question 17

What types of shock cause a fall in TPR?

Answer 17

1. Toxic shock

2. Anaphylactic shock

Question 18

What is toxic shock?

Answer 18

Also known as septicaemia

Circulating bacteria release endotoxins which cause profound vasodilation and leaky capillaries

Question 19

What happens to arterial pressure and heart rate during toxic shock?

Answer 19

Arterial pressure falls

Heart rate increase

Question 20

What are the symptoms of toxic shock?

Answer 20

• tachycardia

- warm red extremities

Question 21

What causes anaphylactic shock?

Answer 21

A severe allergic reaction. Releases histamine from mast cells which have a powerful vasodilator affect.
Mediators can also cause bronchoconstriction and laryngeal oedema - difficulty breathing

Question 22

What are the symptoms of anaphylactic shock?

Answer 22

Tachycardia
Difficulty breathing
Red warm extremities

Question 23

How is anaphylactic shock acutely treated?

Answer 23

Adrenaline (EpiPen)

- vasoconstricts via a1