Circulatory shock

Question 1

circulatory shock occurs when

Answer 1

blood pressure stays low and causes poor perfusion of vital organs.
profound ciculatory failure causing poor perfusion of vital organs

Question 2

3 main causes of (cirulatory) shock

Answer 2

Hypovolaemic
Cardiogenic
Septic

Question 3

Surrounding basal lamina there is a

Answer 3

layer of elastic tissue.
- The whole vessel is elastic like and ‘springy’, allowing it to collapse when no blood is in it or open up when blood is present

Question 4

If the vessel is contracting

Answer 4

the elastic tissue becomes folded up

Question 5

Around basal lamina/elastic are

Answer 5

smooth muscle cells

Question 6

Blood pressure (in normal usage) =

Answer 6

arterial pressure
Normally = 120/80 (systolic/diastolic)
[Venous pressure is much lower]

Question 7

Normal blood pressure relies on:

Answer 7

• Enough blood in system (about 5 litres in an adult)
• Smooth muscle in vessels having a certain ‘tone’
• Heart pumping blood

Question 8

No blood in vessel causes

Answer 8

it to collapse and blood pressure becomes low then unrecordable

Question 9

If smooth muscle tone is decreased

Answer 9

the vessel will dilate.
If enough vessels are affected then blood pressure may fall.

Someone who is not toned (fit) will be fat and so bigger in size.

Question 10

If heart does not pump enough blood

Answer 10

then blood pressure will fall

Question 11

How does body detect blood flow/blood pressure/Oxygen

Answer 11

Main ‘detector system’ is carotid bodies

• Bifurcation (splitting) of artery into internal and external carotid arteries
• There are 2 carotid bodies on either side of the neck

Question 12

The 2 carotid bodies consist of

Answer 12

groups of cells which sense the blood going past them

Question 13

The 2 carotid bodies respond, more specifically, to

Answer 13

the partial pressure of oxygen

Question 14

If blood pressure drops

Answer 14

so does the partial pressure of oxygen.

- the carotid bodies respond by nerve signals to the brain stem

Question 15

how does the brain stem respond to reduced partial pressure signal coming from carotid bodies?

Answer 15

It tells the heart to pump harder and faster, via nerve signals (sympathetic nervous system, which is part of the autonomic nervous system).
- If heart pumps faster, pulse is faster

Question 16

So physiological response to low blood pressure =

Answer 16

faster (heart rate) pulse

Question 17

Brainstem also does other things to keep person alive: Sympathetic nervous system stimulation causes
number 1

Answer 17

Increased vascular tone in vessels in limbs and abdomen —-> blood pushed up to chest and head

Results in circulation of remaining blood around heart, lungs and brain – keeps vital organs alive

Question 18

Brainstem also does other things to keep person alive: Sympathetic nervous system stimulation causes
number 2

Answer 18

Adrenal glands secrete adrenaline —> heart pumps even harder and faster

Question 19

In practice cirulatory shock present if:

Answer 19

Low blood pressure (eg 60/40) combined with
Fast pulse (eg > 100)

Question 20

Hypovolaemic shock - Example

35 year old man walking across road. Hit by car. Fractured left rib goes through spleen. Spleen ruptures with loss of 3 litres (of his 5 litre blood volume) into abdominal cavity. Abdominal pain.
Rib penetrates spleen and causes major bleed (bleed = haemorrhage)
Systemic (arterial) blood pressure normal for a small period of time, but then……

Answer 20

As blood flows out of damaged spleen less blood is present in other vessels —> vessels collapse as they have no blood in them
- Eventually there is less blood in inferior vena cava which also collapses
- If inferior vena cava has no blood in it then venous pressure falls to virtually zero
- Now almost no blood enters the right side of the
heart
- Now very little blood goes through lungs, brain and
rest of body
- Systemic blood pressure now drops

Carotid bodies upregulate the sympathetic nervous system —> various signs (in addition to low blood pressure)

Question 21

Hypovolaemic shock symptoms and treatment

Answer 21

• Patient usually feels very ‘ill’
• Rapid breathing.
• Fast heartbeat – pulse fast and may be weak
• Pale, sweaty skin
• Tender abdomen
• Blood pressure 60/40, pulse 120 = Shock
• Diagnosis of abdominal trauma with hypovolaemic shock.
• Transfused blood. Operation to remove spleen.

Question 22

Hypovolaemic shock:

- Low blood pressure reflects

Answer 22

severe reduction in amount of blood in circulation

Question 23

Hypovolaemic shock:

- High pulse reflects

Answer 23

physiological response to low blood pressure

Question 24

Example 2:

70 year old man with heart disease
Heart starts failing and eventually can no longer pump enough blood to maintain blood pressure
Blood pressure falls, pulse rate goes up

Answer 24

Diagnosis = cardiogenic shock (not due to blood loss – so venous pressure is normal or even increased)

Treatment = drugs to increase heart function

Question 25

Example 3:

30 year old woman gets urinary tract infection which then causes kidney infection then bacteria go into blood (= septicaemia)
Eventually molecules released cause generalised vasodilatation

Answer 25

Vasodilatation is general and results in pooling of blood in veins (of for instance legs)

• Not enough blood gets back to heart (venous pressure and filling are low)
• Not enough blood can now go to brain and rest of body

Infection in blood causing generalised vasodilitation and shock is called ‘septic shock’

Question 26

septic shock =

Answer 26

Infection in blood causing generalised vasodilitation and shock

Question 27

Complications of shock:

Answer 27

Decreased perfusion of brain

• initially reversible but then permanent
• Brain injury (ischaemic infarction of brain tissue)

Decreased perfusion of kidneys

• initially reversible, then more severe
• renal injury (ischaemic infarction of renal tubules)

Question 28

Name 2 organs which can be damaged by shock

Answer 28

brain

kidney