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Block 2 > Shock > Flashcards

Shock Flashcards

(37 cards)

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1
Q

Define shock.

A

Shock is present when the BP or circulation BV is reduced to a level where tissue oxygenation is inadequate leading to cellular hypoxia + irreversible tissue injury

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2
Q

What 3 humoral control mechanisms exist for circulating blood?

A
  1. RAAS
  2. Aldosterone
  3. ADH
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3
Q

What 3 neural control mechanisms exist for circulating blood?

A
  1. Carotid + aortic baroreceptors
  2. Medullary cardiac + vasomotor centres
  3. PNS
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4
Q

How does the RAAS system control circulation blood?

A
  1. Decreased NaCl, BP or ECV
  2. Glomerulus granule cells in kidney secrete renin
  3. Renin converts angiotensinogen (liver) to angiotensin I
  4. ACE (lungs) converts angiotensin I to angiotensin II
  5. Angiotensin II has many effects to increase BP + BV
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5
Q

What effects does aldosterone have?

A
  1. Stimulates kidney to add Na+ channels
  2. More Na+ reabsorbed into EC space
  3. H2O follows osmotically
  4. Increased H2O back into EC space
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6
Q

What effects does ADH have?

A
  1. Stimulates the addition of aquaporins into the collecting tubule membrane in the kidneys
  2. Increased H2O back into EC space
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7
Q

What effects does angiotensin II have?

A
  1. Stimulates adrenal cortex to produce aldosterone
  2. Stimulates ADH secretion
  3. Stimulates thirst in brain to increase fluid intake
  4. Arterial smooth muscle activated to constrict to increase BP
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8
Q

What are baroreceptors? When do they fire?

A

Mechanoreceptors for pressure than fire with each heart beat so reduced BP will reduce firing and vice versa

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9
Q

How does the baroreceptor reflex work?

A
  1. Increased BP is detected by aortic arch + carotid sinus baroreceptors
  2. Increased firing of CN IX + X afferents
  3. Cardiac + vasomotor centers in medulla detect this
  4. Increased firing of CN X efferent -> decreased HR
  5. Decreased firing of sympathetic nerves -> negative inotropy/chronotropy
  6. Decreasing firing to vessels -> vasodilation
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10
Q

How can you work out the mean arterial blood pressure?

A

1/3 (SBP - DBP) + DBP

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11
Q

What is the average mean arterial blood pressure in the autoregulatory range?

A

~90

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12
Q

What are the 3 different types of shock?

A
  1. Vasodilatory
  2. Cardiogenic
  3. Hypovolaemic
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13
Q

What are the 3 causes of vasodilatory shock?

A
  1. Anaphylaxis
  2. Neurogenic (NOT spinal)
  3. Septic
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14
Q

How is septic shock caused?

A

Inflammatory mediators causes SIRS -> vasodilation + increased vascular permeability

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15
Q

What can cause cardiogenic shock?

A

Myocardial damage
Arrhythmias
Extrinsic compression (pericardial disease)
Outflow obstruction

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16
Q

What is Starling’s law?

Study These Flashcards
A

The force of contraction of the cardiac muscle depends on its initial length i.e. heart pumps out blood that is returned to it or blood that it allows to return to it

17
Q

What is the definition of hypotension?

Study These Flashcards
A

SBP < 90mmHg or 20mmHg below patients normal

18
Q

What are the pitfalls of the definitions of hypotension?

Study These Flashcards
A

May not know patients normal BP
Young + previously fit
Elderly
Drugs

19
Q

Why can mean arterial blood pressure be useful?

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A

Good index of tissue perfusion

20
Q

What are the mechanisms of shock?

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A

C: inadequate Circulating volume
P: failure of pump (Pressure)
R: damage to control of Resistance

21
Q

What are the 3 problems that can occur with preload i.e. capacitance?

Study These Flashcards
A
  1. Hypovolaemia
  2. Vasodilatation
  3. Heart failure
22
Q

Why do autoregulation mechanisms exist in the body?

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A

To maintain blood flow and perfusion of tissues in the autoregulatory range

23
Q

For each type of shock there exists 3 aspects, what are these?

Study These Flashcards
A
  1. Prime problem
  2. Compensatory changes
  3. Clinical consequences
24
Q

What occurs in shock due to inadequate circulating volume with reference to the 3 aspects of shock?

Study These Flashcards
A
  1. Prime problem: inadequate volume + fall in CO (P)
  2. Compensation: increased R + tachycardia (but CO falls)
  3. Consequences: hypotension which clinically will cause:
    - Cold/clammy peripheries
    - Tachycardia
    - Thready pulse
    - Prolonged cap refill
    - Empty veins
25
What occurs in shock due to pump/pressure failure with reference to the 3 aspects of shock?
1. Prime problem: fall in CO (P) 2. Compensation: increased R + tachycardia which causes further problem due to increased capacitance (C) 3. Clinical consequence: - Cold/clammy peripheries - Tachycardia (maybe) - Thready pulse - Prolonged cap refill - Raised JVP (maybe) - Peripheral oedema - Hepatomegaly - Bi-basal crackles
26
What occurs in shock due to vasodilatation (R control damaged) with reference to the 3 aspects of shock?
1. Prime problem: vasodilation (R) + hypotension 2. Compensation: tachycardia + CO (P) rise 3. Clinical consequence: - Warm/dry peripheries - Tachycardia - Short cap refill - Bounding pulse
27
What signs of shock present as a result of poor tissue perfusion?
Lactic acidosis Oliguria Altered conciousness
28
What signs of shock present as a result of compensation?
Fight/flight response Tachypnoea (blow CO2 off) Renal response (e.g. UO)
29
What is the pneumonic to remember how to initially assess and manage shock?
A: airway with O2 therapy B: breathing with ventilatory assessment/assistance C: circulation with fluid resuscitation D: disability E: exposure, environment + other examination
30
What would you do first to initially assess and manage shock?
Deal with airway compromise | Give high flow O2
31
What would you do second to initially assess and manage shock?
Do RR | Inspect, palpate, percuss + auscultate
32
What would you do third to initially assess and manage shock?
``` Assess peripheral perfusion (are peripheries cool/clammy or warm/dry?) Do pulse (volume/rate) IV access (blood, which tests?) Fluid challenge (if hypotension exists) ```
33
What would you do fourth to initially assess and manage shock?
Assess conscious level with AVPU in acute environment + look at pupils
34
What would you do fifth to initially assess and manage shock?
Investigate causes e.g. revealed bleeding, concealed bleeding, peripheral oedema etc.
35
What are the causes of hypovolaemia?
1. Intravascular: blood (revealed or concealed) | 2. Extravascular: evaporation, GI losses or polyuria
36
What is transcellular fluid?
That which lies in epithelial lined spaces having passed through the lining
37
What are the different causes for pump failure?
1. Intrinsic: muscle, conductive tissue or valves | 2. Extrinsic: obstruction, compression or blood supply

Block 2 (45 decks)

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