Bleeding Physiology

Question 1

What volumes of blood loss define each class of Haemorrhagic shock

Answer 1

Class I - <750ml
Class II - 750-1500ml
Class III - 1500-2000ml
Class IV - >2000ml

Question 2

Pulse rate and BP in each class of Haemorrhagic shock

Answer 2

Class I - <100, normal
Class II - 100-120, normal
Class III - 120-140, decr
Class IV - >140, decr

Question 3

How does pulse pressure change in different classes of Haemorrhagic shock

Answer 3

Class I - normal/incr
Class II - decr
Class III - decr
Class IV - decr

Question 4

Resp rate and urine output in different classes of Haemorrhagic shock

Answer 4

Class I - 14-20, >30ml/hr
Class II - 20-30, 20-30ml/hr
Class III - 30-40, 5-15ml/hr
Class IV - >35, negligible

Question 5

What type of processes govern the response to bleeding

Answer 5

Inflammatory

Question 6

What is the vascular response to trauma

Answer 6

Incr capillary permeability -> WBCs move to interstitium -> fluid moves from EVS to IVS -> incr central venous volume to maintain normal CO

Question 7

What potential harmful effect can occur when crystalloid fluids are given in trauma

Answer 7

Oedema

Question 8

How can crystalloid fluids lead to oedema when given in trauma

Answer 8

Fluid forced from IVS to EVS -> oedema -> multi organ failure

Question 9

Impacts of vagal tone in trauma

Answer 9

Can be activated by neural pathways (eg eyes)
Involved in inflammatory oathways and inflammatory mediators release
Innervates spleen
Release of TNF in trauma
Affects CVS function

Question 10

Clotting factors in the intrinsic, extrinsic, and common pathways

Answer 10

I - XII, XI, IX, VIII
E - VII, III
C - X, V, II, I, XIII

Question 11

Which process in the clotting cascade involves tissue factor

Answer 11

Extrinsic (actives factor X with factor VIIa)

Question 12

What factors inhibit the clotting cascade

Answer 12

TFPI
Antithrombin
Protein C
Thronbomodulin
Protein S (activates protein C + thrombomodulin to active Protein C)

Question 13

How does trauma impact the fibrinolysis system

Answer 13

Overactivates system

Question 14

Factors leading to trauma induced coagulopathy (TIC)

Answer 14

Fibrinolysis
Inflammation
ATC - acute traumatic coagulopathy
Hypothermia
Acidaemia
Haemorrhage -> loss, dilution

Question 15

Why may hypercoagulability and hyperfibrinolytic blood be beneficial in trauma

Answer 15

Prevents clotting due to Hypovolaemic, low flow state

Question 16

CVS response to bleeding

Answer 16

Initial tachycardia then bradycardia
Hypotension

Question 17

Confounders in the CV response to bleeding

Answer 17

Age
Medications

Question 18

3 main reflexes to haemorrhage

Answer 18

Arterial baroreceptor reflex
Cardiac vagal C fibre reflex
Arterial chemoreceptor reflex

Question 19

Arterial baroreceptor reflex

Answer 19

Haemorrhage -> stretch receptors in wall of aortic arch and carotid sinus detect less stretch -> decr vagal tone and incr sympathetic activity -> sympathetic peripheral vasoconstriction

Question 20

Where are the arterial baroreceptors

Answer 20

Aortic arch
Carotid sins

Question 21

Effect of activating arterial baroreceptor reflex during haemorrhage

Answer 21

Sympathies peripheral vasoconstriction

Question 22

Cardiac vagal C fibres reflex in haemorrhage

Answer 22

Cardiac vagal C fibres in left ventricle myocardium activated by circulating components and reduced preload -> decr SVR -> vagal bradycardia and hypotension

Question 23

Where are cardiac vagal C fibres

Answer 23

Left ventricle myocardium

Question 24

Effect of cardiac vagal C fibre activation in haemorrhage

Answer 24

Vagal bradycardia
Hypotension

Question 25

Arterial chemoreceptor reflex

Answer 25

Incr CO2 or decr O2 -> chemoreceptors in carotids and aortic bodies activated -> incr resp rate

Question 26

Arterial chemoreceptor reflex in haemorrhage

Answer 26

Decr bloodflow mimics incr CO2/decr O2 -> chemoreceptors activated -> incr resp rate

Question 27

How can the arterial chemoreceptor reflex effect cardiac C fibres

Answer 27

Arterial chemoreceptors activated -> incr resp rate -> cardiac C fibres inhibited

Question 28

How does sBP, HR, RR, and GCS change during bleeding

Answer 28

sBP - maintained then rapid drop HR - tachy then Brady RR - tachy GCS - reduced

Question 29

How does sBP, HR, RR, and GCS change with increasing injury level

Answer 29

sBP - hypertensive HR - tachy RR - tachy GCS - reduced

Question 30

3 components of lethal triad

Answer 30

Coagulopathy Acidosis Hypothermia

Question 31

Conditions that mimic Haemorrhage

Answer 31

Head injury Eviscerated abdomen Periosteum Obstructive shock

Question 32

What causes BP RR HR and GCS changes in head injury that mimic haemorrhage

Answer 32

Massive catecholamine release

Question 33

What nerve causes a decr in HR and BP in eviscerated abdomen and periosteum

Answer 33

Vagal nerve

Question 34

Damage control resuscitation

Answer 34

Maintain haemostatic competence in a pt that is **actively bleeding**

Question 35

Aims of DCR

Answer 35

Early haemorrhage control Permissive hypotension Limit fluid infusions Finessed targeting if Coagulopathy

Question 36

Why should fluid infusions be limited in haemorrhage

Answer 36

Avoid diluting coagulation factors

Question 37

Code red criteria

Answer 37

sBP <90 Poor response to initial fluid resuscitation Suspected active haemorrhage

Question 38

TXA dose in massive haemorrhage

Answer 38

1g IV TXA bolus over 10 mins then 1g IV infusion over 8hrs

Question 39

What is done after bleeding is controlled in a code red

Answer 39

Repeat FBC and clotting screen Give platelets if count <100 Give cryoprecipitate if fibrinogen <1.5g/L Give FFP to keep PT/APTT >1.2x normal Keep temp >36 Keep CA2+ >1.0

Question 40

Aims of damage control surgery

Answer 40

Haemorrhage control Manage sepsis Protect from further injury Maintain haemostasis Protect cells and organs Preserve endothelium

Question 41

AIM of ICU after haemorrhage

Answer 41

Restore physiology