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Sudden Death > Physiology of Shock > Flashcards

Physiology of Shock Flashcards

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?

A

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

21
Q

How does pulmonary congestion occur in HF?

A

The heart has decreased contractility

EDV increases to maintain SV

Results in pulmonary congestion

22
Q

What is good practice for giving fluids?

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?

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

What is the commonest myocardial contusion?

A

Baseball to chest

25
Q

What are the clinical signs of cardiogenic shock?

A
  • Poor forward flow- hypotension/shock, fatigue, syncope (everytime they try to walk)
  • Back pressure- pulmonary oedema, elevated JVP, hepatic congestion
26
Q

What is positive inotropy?

A

An increase in the force of cardiac contraction for any given preload

27
Q

How is positive inotropy achieved physiologically?

A

By sympathetic nervous system

28
Q

How is physiological positive inotropy replicated pharmacologically?

A

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
Q

What can be done if positive inotropy cannot be achieved pharmacologically?

A

Insert an intra-aortic balloon pump

30
Q

How does an intraaortic balloon pump work?

A

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
Q

Obstructive shock mainly effects cardiac _____ rather than cardiac ________

A

Obstructive shock mainly effects cardiac filling rather than cardiac ejection

32
Q

What is the treatment for PE causing obstructive shock?

A

Anticoagulation +/- thombolysis

33
Q

What is the treatment for cardiac tamponade causing obstructive shock?

A

Pericardial drainage

34
Q

What is the treatment for tension pneumothorax causing obstructive shock?

A

Decompression and chest drainage

35
Q

If you see hyperkinetic RV apex and bowing of interventricular septum what is the diagnosis?

A

Pulmonary embolism

36
Q

describe the pathologenesis of obstructive shock in tension pneumothorax?

A

Reduction in venous return as intrathoracic pressure in chest increases

Impairs cardiac filling and function

37
Q

Describe the CO in distributive shock

A

Generally intially high CO but insufficient to maintain forward perfusion

38
Q

What are the three main types of distributive shock and their pathogenesis?

A
  • Septic- bacterial endotoxin mediated capillary dysfunction
  • Anaphylactic- mast cell release of histaminergic vasodilators
  • Neurogenic- loss of thoracic sympathetic outflow following spinal injury
39
Q

What is the default position for blood vessels?

A

Dilated, sympathetic tone causes contraction

40
Q

In septic shock rising ______ levels indicate ______ before _______ occurs

A

In septic shock rising lactate levels indicate hypoperfusion before hypotension occurs

41
Q

What should be used early in septic shock

A

Antibiotics and vasopressors

42
Q

Why is adrenaline useful in anaphylactic shock?

A

Acts as a vasoconstrictor and mast cell stabiliser

43
Q

What can be tested to diagnose anaphylactic shock?

A

Serum mast cell tryptase

44
Q

When does neurogenic shock occur?

A

After spinal cord or central trauma

45
Q

What is the key to spotting neurogenic shock?

A

Hypotension follows the loss of descending sympathetic tone, they are bradycardic and hypotensive

46
Q

Inappropriate bradycardia occurs due to what? What can be done to prevent it?

A

Upopposed vagal tone

Don’t stimulate their vagus nerve (PR exam, suction)

47
Q

What are the mainstays of treatment for neurogenic shock?

A

Dopamine and vasopressors

48
Q

What are the 4 H’s and 4 T’s

A

H

  • hypovolaemia
  • hypothermia
  • hypoxia
  • hypokalaemia/hyperkalaemia

T

  • tamponade
  • tension pneumothorax
  • thrombosis
  • toxins

Sudden Death (8 decks)

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