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Gastrointestinal pathophysiology > Shock > Flashcards

Shock Flashcards

1
Q

What is the medical definition of shock?

A

Failure of the circulation that results in INADEQUATE TISSUE PERFUSION

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2
Q

Where are baroreceptors found?

A

They are found within the aortic arch and carotid bodies

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3
Q

What is the role of baroreceptors?

A
  1. They detect blood pressure, they stimulate the cardiac vagal (vagus) motor neurons which has an inhibitory effect on heart rate (stimulating the vagus nerve slows the heart rate down)
    - If there is a drop in blood pressure, baroreceptors decrease firing, which decreases the stimulation of the vagus nerve, alleviating the inhibitory effect on the heart rate (>HR and >BP)
  2. Inhibitory effect on the catecholamine neurones
    - These neurones normally cause vasoconstriction and also vasopressin release
    - Inhibiting these neurones will therefore decrease blood pressure
    - A drop in BP will cause a reduction of this inhibitory effect, allowing vasoconstriction and vasopressin release –> Increased blood pressure
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4
Q

How can you test autoregulation?

A

Valsalva manoeuvre

- Forceful expiration against a closed glottis, this increases intrathoracic pressure which prevents venous return

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5
Q

What are the 3 ways that the body autoregulates blood pressure?

A
  1. The RAAS
  2. Barorceptor response
  3. Localised tissue response
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6
Q

Different types of shock

A
  1. Anaphylaxis: secondary to a bee sting or antibiotics
  2. Cardiogenic: secondary to an MI or heart failure (pump failure)
  3. Hypovolaemic: lost blood volume
  4. Neurogenic: spinal cord transection
  5. Septic: following meningococcal sepsis
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7
Q

Equation for cardiac output?

A

CO = stroke volume vs heart rate

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8
Q

Equation for mean arterial pressure/blood pressure?

A

MAP = CO x systemic vascular resistance

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9
Q

Alternate equation for cardiac output? (*not SV x HR)

A

CO = MAP /SVR

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10
Q

What is the definition of hypotension?

A

SBP <90mmHg

- SBP 20mmHg below patients normal

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11
Q

NOTE SLIDE: For each type of shock there exists:

  1. A prime problem
  2. Compensatory changes
  3. Clinical consequences
A
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12
Q

What are the following for hypovolaemia?

  1. A prime problem
  2. Compensatory changes
  3. Clinical consequences
A
  1. Prime problem = inadequate volume or fall in cardiac output
  2. Compensation = increased resistance, tachycardia (but cardiac output falls), hypotension = THIS IS THE BARORECEPTOR RESPONSE
  3. Clinical consequences = Cold & clammy peripheries, tachycardia, prolonged cap refill time, empty veins
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13
Q

What are the following for pump failure?

  1. A prime problem
  2. Compensatory changes
  3. Clinical consequences
A
  1. Prime problem = fall in cardiac output
  2. Compensatory changes = baroreceptor response = increased resistance and tachycardia
  3. Clinical consequences = cold & clammy peripheries, tachycardia, prolonged cap refill time, raised JVP
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14
Q

What are the following for vasodilatation?

  1. A prime problem
  2. Compensatory changes
  3. Clinical consequences
A
  1. Prime problem = vasodilatation
  2. Compensatory changes = tachycardia, >cardiac output, autoregulation
  3. Clinical consequences = warm & dry peripheries, tachycardia (due to >CO), short cap refill time and BOUNDING pulse
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15
Q

Clinical manifestations of shock

A
  1. Signs = related to poor tissue perfusion (skin, gut, liver, kidneys, brain, heart)
    - Oliguria
    - Altered conscious level (particularly in those with meningococcal sepsis)
    - Cold, clammy skin but could also be warm and dry depending on the case
    - Cyanosis
    - Rapid pulse
    - Nausea/vomiting
    - Fatigue
    - Enlarged pupils
  2. Signs of compensation
    - Fright, fight or flight response
  3. Signs of correction of acidosis
    - Tachypnoea
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16
Q

Initial assessment/management of shock

A

ABC response

A) Airway with OXYGEN therapy
- Give high flow oxygen

B) Breathing with VENTILATORY assessment/assistance
- Resp exam

C) Circulation with FLUID RESUSCITATION

  • Check peripheral perfusion — cool and clammy vs warm and dry
  • Pulse - volume/rate
  • IV access
  • Fluid challenge is nearly always the first ‘C’ treatment - crystalloids vs colloids

D) Disability

  • Conscious level — AVPU vs GCS
  • Pupils

E) Exposure, environment and other examination
- Causes: revealed bleeding, concealed bleeding, peripheral oedema

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17
Q

Is hypotension required for shock to exist?

A

No it is not, but it is frequently a sign of de-compensation which means that you are in trouble and things will happen quickly

18
Q

Explain the circulatory features of hypovolaemia

  • Perfusion = cold & clammy vs warm & dry?
  • Pulse = weak vs bounding?
  • Veins = empty vs full?
A
  1. Perfusion = cold and clammy
  2. Pulse = weak
  3. Veins = empty
19
Q

Explain the circulatory features of pump failure

  • Perfusion = cold & clammy vs warm & dry?
  • Pulse = weak vs bounding?
  • Veins = empty vs full?
A
  1. Perfusion = cold and clammy
  2. Pulse = weak (poor CO)
  3. Veins = full, note JVP
20
Q

Explain the circulatory features of vasodilation

  • Perfusion = cold & clammy vs warm & dry?
  • Pulse = weak vs bounding?
  • Veins = empty vs full?
A
  1. Perfusion = warm and dry
  2. Pulse = bounding
  3. Veins = full
21
Q

What are different causes of hypovolaemia?

A
  1. Intravascular
    - Blood loss: revealed (visual bleeding seen) or concealed (e.g. femoral fracture)
  2. Extravascular
    - Evaporation
    - GI losses
    - Polyuria
22
Q

Different causes of pump failure, intrinsic vs extrinsic

A
  1. Intrinsic
    - Muscle
    - Conduction tissue
    - Valves
  2. Extrinsic
    - Obstruction: PE
    - Compression: tamponade
    - Blood supply
23
Q

What is systemic inflammatory response syndrome (SIRS) defined as?

A

2 or more of:

  1. Heart rate >90
  2. Fever >38 or <36
  3. WCC >12000 or <4000
  4. Respiratory rate >20 or pCO2 <32
24
Q

What is septic shock defined as?

A

Septic shock is sepsis with refractory hypotension

  1. Evidence of infection
  2. End organ failure
  3. Refractory hypotension: hypotension that does not respond to fluid
    - Mortality = 43-54%
25
Q

What is sepsis defined as?

A

SIRS + confirmed or presumed infections

- Mortality = 10-15%

26
Q

What is severe sepsis defined as?

A

Sepsis with organ dysfunction

- Mortality = 17-20%

27
Q

What can cause a SIRS response?

A
  1. Trauma
  2. Burns
  3. Pancreatitis
  4. Other
28
Q

What can cause a sepsis response?

A

Infection:

  1. Bacteria (bacteria predominantly cause sepsis)
  2. Fungi
  3. Parasites
  4. Viruses
  5. Other
29
Q

What is the response of alpha receptor stimulation, in short?

A

Peripheral vasoconstriction

30
Q

What is the response of B2 receptor stimulation, in short?

A

Arteriolar vasodilatation

31
Q

What is the response of B1 receptor stimulation, in short?

A
  1. Inotropy
  2. Chronotropy
  3. Renin secretion
32
Q

What are the actions of adrenaline? (B1receptor, B2receptor, alpha receptor)

A

> HR
SV
Vasoconstrictor — >BP

33
Q

What are the actions of dobutamine? (B1R, B2R)

A

> HR
SV
Vasodilator

34
Q

What are the actions of dopexamine? (B2R, DA receptor)

A

> HR

Splanchnic vasodilator

35
Q

What are the actions of noradrenaline? (alpha receptor)

A

Vasoconstrictor

36
Q

What is the principle management for patients with shock: reduced capacitance

A

Fluids (crystalloids or colloids)

37
Q

What is the principle management for patients with shock: pump failure

A
  • This is your MI patient: cardiogenic shock
  • Inotropes
  • Possible vasodilators: because these patients are very vasoconstricted
38
Q

What is the principle management for patients with shock: reduced resistance (distributive)

A

Vasopressors: NA

- Maybe fluids

39
Q

How does noradrenaline cause a drop in heart rate if its main action is vasoconstriction?

A

Vasoconstriction —> Increased blood pressure —> baroreceptor response —> increased vagal tone —> decreased heart rate

40
Q

What are the main treatments for sepsis?

A
  1. Antibiotics
  2. Crystalloids
  3. Vasopressors
  4. SEPSIS 6
41
Q

What is the sepsis six?

A

BUFALO

  1. Give O2 sats above 94%
  2. Take blood cultures
  3. Give IV antibiotics
  4. Give a fluid challenge
  5. Measure lactate
  6. Measure urine output

Gastrointestinal pathophysiology (22 decks)

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