Haemorrhage and Shock

Question 1

What is circulatory shock?

Answer 1

Generalised inadequacy of blood flow throughout the body.

Question 2

What happens if circulatory shock is prolonged?

Answer 2

It may be sufficient to cause tissue damage sue to inadequate O2 delivery/waste removal.

Question 3

What is haemorrhage and what does the severity depend on?

Answer 3

Loss of blood.

Effects depend on volume and speed of blood loss.

Question 4

What does chronic, slow but persisant haemorrhage result in?

Answer 4

Iron deficiency anaemia.

Question 5

What does acute large loss of blood result in?

Answer 5

Decreased circulating volume.

Question 6

What is a revealed haemorrhage?

Answer 6

Bleeding is obvious, quantity is hard to measure.

Question 7

What is a concealed haemorrhage?

Answer 7

Eg ruptured spleen or a leaking aortic aneurysm.

Difficult to spot as BP is well maintained.

Question 8

What blood loss is survivable?

Answer 8

20%
50% over 24 hours.

BUT 33% very rapidly may be fatal.

Question 9

Non progressive shock?

Answer 9

Gets better without treatment.

Question 10

Progressive shock?

Answer 10

Without treatment, shock gets progressively worse but is reversible if BP is restored.

Question 11

Irreversible shock?

Answer 11

Progressive shock where a sustained restoration os CO (and survival( can’t be achieved - even if BV is restored.

Question 12

What are the responses to shock mainly aimed at?

Answer 12

Restoring arterial pressure.

Question 13

Explain 3 reflex responses to haemorrhage.

Answer 13

1) Decreased discharge of arterial baroreceptors.
2) Increase discharge of arterial chemoreceptors.
3) Leads to…
…increased sympathetic activity (arteriolar constriction, venous constriction, tachycardia and increase cardiac contractility).
…decrease vagal activity (tachycardia)

Question 14

What is the CNS ischemic reflex?

Answer 14

At pressures below 50mmHg - it’s initiated to STRONGLY activate the sympathetic nervous system as a LAST STAND. If cerebral ischemia persists - vasomotor centre eventually fails.

Question 15

Give 2 examples of vascular events (aimed at maintaining ABP) that increase CO.

Answer 15

S-NS mediated venoconstriction returns extra blood to the heart, increasing preload and therefore CO (Starling’s law).
Delayed complience - similar effect.

Question 16

BP=

Answer 16

COxTPR

Question 17

What does sympathetic vasoconstriction maintain at the expense of blood flow?

Answer 17

BP - NOT in the brain and heart.

Then CO is redistributed to the brain and the heart.

Question 18

Give 3 other mechanisms by which ABP is restored by increasing TPR.

Answer 18

1) INcreased renal sympathetic activity…actviate RAAS….angII - vasoconstrictor,
2) Baroreceptor unloading…ADH released from PP = vasoconstriction.
3) Decreased ANP = increased vasoconstriction (decreased dilation)

Question 19

How is circulating BV restored?

Answer 19

1) Decreased capillary pressure (bfluid from interstitum to capillaries)
2) Renal ischemia - RAAS activation - decrease GFR (increase BV)
3) ADH secretion (stress and atria receptor stimulation)
4) Decreased ANP supressed urinary output
5) ANG II and unloading of venoatrial stretch receptors = THIRST.

Question 20

What happens to [Hb] in haemorrhage.

Answer 20

Initally - normal.
Then decreases as BV is restored (diluted)
Slowly increases for 6 weeks to full recovery.

Question 21

How long does it take for the reticulocyte count to peak at 5-15%?

Answer 21

5-7 days.

Question 22

When are plasma proteins replaced?

Answer 22

2-3 days.

Question 23

Give 7 signs and symptoms related to low central volume/reflex sympathetic responses.

Answer 23

1) Tachycardia - reflex response
2) Low pulse pressure - low SV, high HR
3) Low central venous pressure
4) Faintness when upright - further lowers CVP
5) Pallor, cold extremities - skin vasoconstriction
6) Sweating - symp stimulation
7) Nausea - gut vasoconstriction

Question 24

Give 3 signs and symptoms related to response which slowly restore circulating volume.

Answer 24

1) Decreased urine output - increased ADP, decreased ANP
2) THirst (decrease BV, decrease atrial stretch receptors)
3) [Hb} initially normal, falls over hours.

Question 25

Signs of widespread tissue ischemia?

Answer 25

Increased plasma [lactate]

Question 26

Signs and symptoms of when BP is low?

Answer 26

Hyperpnoea - ischemic carotid bodies = deep breathing.

Anxiety and restlessness - CNS ischemia.

Question 27

What type of shock results in reduced venous return?

Answer 27

Haemorrhage
Burns - loss of plasma, increase viscosity
Dehydration

Question 28

What type of shock result in inadequate pumping of the heart of circulatory obstruction?

Answer 28

Cardiogenic shock due to MI

Pulmonary embolism

Question 29

4 other causes of shock that result in decreased motor tone?

Answer 29

1) Neurogenic shock - deep anaesthesia, brain damage,.
2) Septic shock - vasodilation, increased capillary permeability
3) Anaphylactic shock - histamine - dilation increased cap permeability
4) Vasovagal syncope - fainting, decrease HR and vasodilation.