Response to injury, hypoxia and hypovolemia

Question 1

What happens when your skin is injured?

Answer 1

Mast cells release inflammatory cytokines and histamines
Histamines cause redness and heat
Increase in WBCs and leakage from endothelial cells = swelling

Question 2

Dalton’s law

Answer 2

Each gas in a mixture has its own partial pressure as if no other gases were present

Question 3

henry’s law

Answer 3

The quantity of gas that will dissolve in a liquid is proportional to the partial pressure of the gas and its solubility

Question 4

Factors that will shift o2 dissociation curve to the right

Answer 4

• Low pH
• High pCO2
• High temp
• High 2,3 BPG
• These characteristics are in metabolically active cells - oxygen offloaded to tissues that need it most

Question 5

What happens when there is a high concentration of co2?

Answer 5

Chemoreceptors detect
Chemoreceptors stimulate dorsal group in medulla 
Stimulates hyperventilation 
Eliminates higher quantity of co2 
Decrease in pco2
Increases p

Question 6

T1RF

Answer 6

• Hypoxia without hypercapnia
• PaO2 >8
• V/Q mismatch
• Pulmonary disorders - can’t oxygenate blood
• Causes: high altitude, alveolar failure (oedema, haemorrhage, fibrosis, collapse
• Pulmonary embolism/hypertension

Question 7

What is a pulmonary shunt?

Answer 7

Deoxygenated blood from RHS to LHS of heart with no exchange

Causes pulmonary oedema as alveoli filled with fluid but can’t exchange gas

Question 8

T2RF

Answer 8

• Hypoxia with hypercapnia - PaCO2 >6kPA
• Increase in CO2 production or reduction in excretion (ventilation failure)
• Decreased CNS drive (drugs, opioids, anaesthesia, local lesions), neuromuscular disease (myasthenia gravis, MND), obstructive fatigue (asthma, COPD, kyphoscoliosis, obesity)
• Ventilation failure, not perfusion

Question 9

Cardiac cycle

Answer 9

Atria contract
Isovolumetric contraction 
Ventricular ejection 
Isovolumetric relaxation 
Ventricular filling 
Atrial contraction

Question 10

Preload

Answer 10

Degree of stretch in heart before contraction

Question 11

Afterload

Answer 11

Pressure that must be exceeded for ejection to occur

Question 12

Effects of reduced ECF

Answer 12

• Decreased tissue perfusion/oxygenation
• Reduced venous return and cardiac filling
• Reduced stroke volume
• Heart contractility increased by +ve anatropic agents - adrenaline and noradrenaline
• -ve anatropic agents reduce contractility and stroke volume

Reduced stroke volume → reduced cardiac output → reduced BP

Baroreceptors found in aortic arch/carotid sinus, reduced stretching leads to sympathetic tone increasing

Baroreceptors stimulate sympathetic nervous system - increased heart rate and secretes adrenaline - fight or flight response

Question 13

Fight or flight

Answer 13

Decreased cap pressure moves fluid from ECF to vascular space
Venoconstriction and increased cardiac preload
Arteriole constriction to increase BP
Renal decreased excretion and increased reabsorption of fluid
Increased HR and contractility

Question 14

Hypovolemic shock

Answer 14

• Decreased O2 delivery + increased O2 consumption + inadequate O2 utilisation → circulatory collapse
• Sx: cold, clammy, pale, increased CRT, tachycardic, collapsed veins, confusion, anxiety, oliguria, tachypnoea
• BP will have biphasic response: early (good systolic with increased diastolic) and late (significant hypotension)