Lecture 10: Hemorrhage & Shock

Question 1

What does the severity of a hemorrhage depend on?

Answer 1

Amount of blood lost

Speed of loss (severe = more than 1L)

Question 2

Why does arterial pressure fall more than ventricular pressure?

Answer 2

Thinner walls

More compliant

Question 3

What does a reduction in LV EDV cause?

Answer 3

Fall in SV
Low CO
Low arterial pressure

Question 4

What does low arterial pressure cause?

Answer 4

Reduced baroreceptor firing
Increased chemoreceptor firing (O2 drops)
Activation of pressore centre neurons in medulla
Activation of sympathetic nerves

Question 5

What does sympathetic stimulation cause?

Answer 5

Noradrenaline release
Cardiac b-adrenergic receptors:
- Increase HR to increase CO
- Increased cardiac contractility
Arterial a-adrenergic receptors"
- Redistribution of CO
- Redistribution of blood volume

Question 6

Why does heart rate increase?

Answer 6

To increase CO

Is limited by diminishing diastolic filling time

Question 7

What are the two responses to hemorrhage?

Answer 7

Respiratory stimulation

Restoration of circulating volume

Question 8

What is shock?

Answer 8

Persistently low BP causes failure to deliver blood to support organ function
Capillaries break down & tissue factors are released
May be irreversible
2 types:
- reduced blood volume (hypovolemic)
- reduced CO (cardiogenic)
- reduced TPR (vasodilation)

Question 9

What is hypovolemic shock?

Answer 9

Blood loss - hemorrhage
Fluid deficiency - dehydration
Protein-rich fluid loss - burns

Question 10

What is cardiogenic shock?

Answer 10

Systolic failure:
- myocardial death
- myocardial inflammation/infection
- rhythm disturbance
- valve failure
Diastolic failure:
- cardiac compression

Question 11

What is vasogenic shock?

Answer 11

Profound vasodilation
Neural - spinal cord injury
Toxins - sepsis
Drugs

Question 12

What are the 3 stages of shock?

Answer 12

Compensated - able to stop it from happening
Decompensated
Irreversible

Question 13

What is the compensated stage of shock?

Answer 13

Early phase
Physiological responses activated
Tissue perfusion maintained

Question 14

What is the decompensated stage of shock?

Answer 14

Uncorrected cause
Failing compensatory responses
Functional deterioration 
- loss of vascular function
- impaired tissue metabolism
- compromised organ function

Question 15

What is the irreversibility stage of shock?

Answer 15

Failed responses 
Failed organs 
Progressive acidosis
Renal, pulmonary, hepatic failure
Gastrointestinal death & toxin release
Brain failure
Cardiac failure

Question 16

What is septic shock?

Answer 16

Bacterial infection
Cell wall LPS - endotoxin:
- binds to macrophages
- causes the release of cytokines, autacoids, coagulation factors, complement, interferon

Question 17

What is anaphylaxis?

Answer 17

Rapid, progressive, fulminant
Antigen-antibody reaction
Basophil and mast cell release of 
- histamine
- bradykinin
- lerukotrienes
- prostaglandins 
which cause vasodilation, increased capillary permeability, bronchial smooth muscle contraction