Physiology 8

Question 1

Shock?

Answer 1

Abnormality of circulatory system resulting in inadequate tissue perfusion and oxygenation

Question 2

What does shock lead to? How? (4)

Answer 2

* Cellular failure

How…
* Inadequate tissue perfusion
* Inadequate tissue oxygenation

* Anaerobic metabolism
* Accumulation of metabolic waste products

Question 3

Adequate tissue perfusion depends on? (2)

Answer 3

Adequate blood pressure and adequate cardiac output

Question 4

What 3 factors affect SV?

Answer 4

* Preload (venous return)
* Myocardial contractility
* Afterload

Question 5

What causes hypovolaemic shock? (6)

Answer 5

* Loss of blood volume
* Decreased Venous Return
* Decreased End Diastolic Volume
* Decreased Stroke Volume
* Decreased Cardiac Output and Decreased blood pressure
* Inadequate Tissue Perfusion

Question 6

What is preload (and thus SV) dependent on?

Answer 6

Myocardial fibre lengths which are dependent on EDV

Question 7

Cardiogenic shock? Causes?

Answer 7

* Sustained hypotension caused by decreased cardiac contractility (problem with pump)
* Massive MI or arrhythmia

Question 8

Explain the process of development of cardiogenic shock (4)

Answer 8

* Decreased Cardiac Contractility
* Decreased Stroke Volume
* Decreased Cardiac Output & Decreased blood pressure
* Inadequate Tissue Perfusion

Question 9

What does sympathetic stimulation do to Frank-Starling curve? Parasympathetic? Cardiogenic shock?

Answer 9

* Shifts to left - higher SV at given EDV * Shifts to right - lower SV at given EDV * In cardiogenic shock extreme shift to right since pump no longer functioning

Question 10

Explain process of development of obstructive shock e.g. from tension pneumothorax? (6)

Answer 10

* Increased intrathoracic pressure
* Decreased Venous Return
* Decreased End Diastolic Volume
* Decreased Stroke Volume
* Decreased Cardiac Output and Decreased blood pressure
* Inadequate Tissue Perfusion

Question 11

What are different types of shock? (4) What causes these?

Answer 11

* Hypovolaemic e.g. hemorrhagic, non-hemorrhagic
* Cardiogenic: e.g. acute myocardial infarction
* Obstructive: e.g. cardiac temponade, tension pneumothorax, pulmonary embolism, severe aortic stenosis
* Distributive: neurogenic e.g. spinal cord injury, or Vasoactive e.g. septic shock, anaphylactic shock

Question 12

Explain the process of development of neurogenic shock (5) What kind of shock is neurogenic shock?

Answer 12

* Loss of Sympathetic Tone
* Massive Venous & Arterial Vasodilatation
* Decreased Venous Return & Decreased SVR (TPR)
* Decreased Cardiac Output & Decreased blood pressure
* Inadequate Tissue Perfusion

* Type - distributive shock

Question 13

What is sympathetic tone?

Answer 13

Continuous low-level sympathetic stimulation resulting in continuous release of noradrenaline

Question 14

Explain the process of development of vasoactive shock (5) What is vasoactive shock also known as?

Answer 14

* Release of Vasoactive Mediators
* Massive Venous & Arterial Vasodilatation - also Increased Capillary Permeability
* Decreased Venous Return & decreased SVR (TPR)
* Decreased Cardiac Output & decreased blood pressure
* Inadequate Tissue Perfusion Septic shock, anaphylactic shock

Question 15

How is intravascular blood volume lost in vasoactive shock?

Answer 15

Blood leaks from capillaries

Question 16

What is the treatment for shock? (7)

Answer 16

* ABCDE approach
* High flow oxygen
* Volume replacement (if patient losing volume - NOT in cardiogenic shock)
* Inotropes for cardiogenic shock
* Immediate chest drain for tension pneumothorax
* Adrenaline for anaphylactic shock
* Vassopressors for septic shock

Question 17

Why are inotropes used to treat cardiogenic shock?

Answer 17

Increase cardiac contractility

Question 18

What are causes of hypovolaemic shock? (2)

Answer 18

Haemorrhagic and non-haemorrrhagic

* Haemorrhage e.g. trauma, surgery, GI haemorrhage
* Vomiting, diarrhoea, excessive sweating

Question 19

How does haemorrhage lead to hypovolaemic shock?

Answer 19

* Decrease in blood volume
* Causes decreased CO
* Circulatory shock due to decreased MABP

Question 20

How does non-hemorrhagic hypovolaemia lead to hypovolaemic shock?

Answer 20

* Decrease in ECFV including plasma volume
* Decreased blood volume
* Causes decreased CO
* Circulatory shock due to decreased MABP

Question 21

In hemorrhagic shock, how long can body maintain blood pressure?

Answer 21

Compensatory mechanisms can maintain blood pressure until >30% of blood volume is lost

Question 22

Learn table illustrating different classifications of hemorrhagic shock

Answer 22

…

Question 23

In hemorrhagic shock, what causes tachycardia? Small volume pulse? Cool peripheries?

Answer 23

* Increased HR via baroreceptor reflex
* Decreased SV causes small volume pulse
* Cool peripheries caused by decreased CO and increased systemic vascular resistance via baroreceptor reflex

Question 24

Explain the process of hemorrhagic shock (5)

Answer 24

* Increased HR (tachycardia) via baroreceptor reflex
* Decreased SV (small volume pulse)
* Cardiac output decreased
* Increased systemic vascular resistance via baroreceptor reflex
* Decreased mean arterial blood pressure if >30% loss

Question 25

Does cerebral blood flow change a lot in response to changes in MABP? Why? (2)

Answer 25

No

* As blood pressure increases, cerebral vessels constrict to restrict flow
* As blood pressure decreases, cerebral vessels dilate to increase flow

Question 26

When will cerebral flow vary with MABP?

Answer 26

* If MABP <60, inadequate perfusion of brain
* If MABP >120, will increase cerebral blood flow