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Sudden Death > Physiology of Shock > Flashcards

Physiology of Shock Flashcards

(48 cards)

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1
Q

Define shock

A

Condition of inadequate perfusion to sustain normal organ function

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2
Q

What are the 5 main classes of shock?

A

Hypovolaemic Cardiogenic Obstructive Distributive Cytotoxic

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3
Q

Describe the pathophysiology of hypovolaemic shock?

A

Loss of circulating volume causing reduced preload and cardiac output

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4
Q

Describe the pathophysiology of cardiogenic shock?

A

Myocardial dysfunction causing reduction in systolic function and cardiac output

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5
Q

Describe the pathophysiology of obstructive shock?

A

Physical obstruction of the filling of the heart leading to reduced preload and cardiac output

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6
Q

Describe the pathophysiology of distributive shock?

A

Significant reduction in SVR beyond the compensatory limits of increased cardiac outpu

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7
Q

Describe the pathophysiology of cytotoxic shock?

A

Uncoupling of tissue oxygen delivery and mitochondrial oxygen uptake

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8
Q

What causes hypovolaemic shock?

A

Bleeding Third space loss Severe dehydration

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9
Q

What causes cardiogenic shock?

A

MI, acute valve lesion

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10
Q

What causes obstructive shock?

A

Tamponade PE tension pneumothorax

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11
Q

What causes distributive shock?

A

Circuit is too big -septic shock -anaphylactic shock -neurogenic shock

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12
Q

What causes cytotoxic shock?

A

CO poisoning Arsenic

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13
Q

__-__% of out blood volume is in our secondary organs

A

20-30% of out blood volume is in our secondary organs

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14
Q

What are the compensatory mechanisms for shock?

A
  • Baroreceptor reflex
  • Sympathetic mediated neurohormonal response
  • Capillary absorption of interstitial fluid
  • Hypothalamopituitary-adrenal response
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15
Q

Describe the baroreceptor reflex

A

Stretch sensitive receptors in the carotid sinus (CNIX) and aortic arch (CNX)

Decreased stretch –> decreased afferent input to medullary CV centres

Inhibition of parsympathetic (CNX) and enhanved sympathetic output

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16
Q

What is the sympathetic mediated neurohormonal response

A

Release of circulating vasoconstrictors- adrenaline, angiotensin, noradrenaline, vasopressin

Redirects fluid from peripheral and secondary organs

Resulting lactic acidosis causes chemoreceptors to enhance response

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17
Q

How does capillary absorption of interstitial fluid compensate for shock?

A

There is reduced capillary hydrostatic pressure, and so an inward net filtration

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18
Q

What is the hypothalamopituitary-adrenal response to shock?

A

Intrarenal baroreceptors mediate renin release from JGA

Resulting angiotensin II enhances vasoconstriction and ADH secretion

Enhances renal absorption of sodium and water

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19
Q

What are the hearts 3 options to increase CO?

A

Increase HR

Increase SV

Increase both

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20
Q

Why does our heart rate get lower as we age?

Study These Flashcards
A

As children can’t increase their SV and so HR must be higher

21
Q

How does pulmonary congestion occur in HF?

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A

The heart has decreased contractility

EDV increases to maintain SV

Results in pulmonary congestion

22
Q

What is good practice for giving fluids?

Study These Flashcards
A
  1. Fluids are a drug- treat them as such- what is in it?
  2. Consider the indivudual patient
  3. Consider both the fluid AND electrolyte requirements
  4. Consider the difference between resuscitation and maintenance
23
Q

What can cause cardiogenic shock?

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A
  • MI
  • Acute mitral prolapse
  • Myocarditis
  • Cardiomyopathy
  • Myocardial contusion
24
Q

What is the commonest myocardial contusion?

Study These Flashcards
A

Baseball to chest

25
What are the clinical signs of cardiogenic shock?
* Poor forward flow- hypotension/shock, fatigue, syncope (everytime they try to walk) * Back pressure- pulmonary oedema, elevated JVP, hepatic congestion
26
What is positive inotropy?
An increase in the force of cardiac contraction for any given preload
27
How is positive inotropy achieved physiologically?
By sympathetic nervous system
28
How is physiological positive inotropy replicated pharmacologically?
By B and dopaminergic stimulation * dobutamine (β1-agonist), adrenaline (alpha and beta agonist) * dopamine (alpha and beta agonist), dopexamine (dopamine analogue) * milrinone (phosphodiesterase 3 inhibitor that works to increase the heart's contractility and decrease pulmonary vascular resistance)/levosimendan(calcium sensitiser)
29
What can be done if positive inotropy cannot be achieved pharmacologically?
Insert an intra-aortic balloon pump
30
How does an intraaortic balloon pump work?
Provides counter pulsation * inflation during diastole (augmented diastole)- increasing coronary flow * deflation during ventricular systole (reduced afterload)- reducing myocardial wall stress and your oxygen demands * improves oxygen supply and reduces oxygen demands
31
Obstructive shock mainly effects cardiac _____ rather than cardiac \_\_\_\_\_\_\_\_
Obstructive shock mainly effects cardiac filling rather than cardiac ejection
32
What is the treatment for PE causing obstructive shock?
Anticoagulation +/- thombolysis
33
What is the treatment for cardiac tamponade causing obstructive shock?
Pericardial drainage
34
What is the treatment for tension pneumothorax causing obstructive shock?
Decompression and chest drainage
35
If you see hyperkinetic RV apex and bowing of interventricular septum what is the diagnosis?
Pulmonary embolism
36
describe the pathologenesis of obstructive shock in tension pneumothorax?
Reduction in venous return as intrathoracic pressure in chest increases Impairs cardiac filling and function
37
Describe the CO in distributive shock
Generally intially high CO but insufficient to maintain forward perfusion
38
What are the three main types of distributive shock and their pathogenesis?
* Septic- bacterial endotoxin mediated capillary dysfunction * Anaphylactic- mast cell release of histaminergic vasodilators * Neurogenic- loss of thoracic sympathetic outflow following spinal injury
39
What is the default position for blood vessels?
Dilated, sympathetic tone causes contraction
40
In septic shock rising ______ levels indicate ______ before _______ occurs
In septic shock rising lactate levels indicate hypoperfusion before hypotension occurs
41
What should be used early in septic shock
Antibiotics and vasopressors
42
Why is adrenaline useful in anaphylactic shock?
Acts as a vasoconstrictor and mast cell stabiliser
43
What can be tested to diagnose anaphylactic shock?
Serum mast cell tryptase
44
When does neurogenic shock occur?
After spinal cord or central trauma
45
What is the key to spotting neurogenic shock?
Hypotension follows the loss of descending sympathetic tone, they are bradycardic and hypotensive
46
Inappropriate bradycardia occurs due to what? What can be done to prevent it?
Upopposed vagal tone Don't stimulate their vagus nerve (PR exam, suction)
47
What are the mainstays of treatment for neurogenic shock?
Dopamine and vasopressors
48
What are the 4 H's and 4 T's
H * hypovolaemia * hypothermia * hypoxia * hypokalaemia/hyperkalaemia T * tamponade * tension pneumothorax * thrombosis * toxins

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