Shock

Question 1

What is the medical definition of shock?

Answer 1

Failure of the circulation that results in INADEQUATE TISSUE PERFUSION

Question 2

Where are baroreceptors found?

Answer 2

They are found within the aortic arch and carotid bodies

Question 3

What is the role of baroreceptors?

Answer 3

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

Question 4

How can you test autoregulation?

Answer 4

Valsalva manoeuvre

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

Question 5

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

Answer 5

1. The RAAS
2. Barorceptor response
3. Localised tissue response

Question 6

Different types of shock

Answer 6

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

Question 7

Equation for cardiac output?

Answer 7

CO = stroke volume vs heart rate

Question 8

Equation for mean arterial pressure/blood pressure?

Answer 8

MAP = CO x systemic vascular resistance

Question 9

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

Answer 9

CO = MAP /SVR

Question 10

What is the definition of hypotension?

Answer 10

SBP <90mmHg

- SBP 20mmHg below patients normal

Question 11

NOTE SLIDE: For each type of shock there exists:

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

Question 12

What are the following for hypovolaemia?

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

Answer 12

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

Question 13

What are the following for pump failure?

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

Answer 13

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

Question 14

What are the following for vasodilatation?

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

Answer 14

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

Question 15

Clinical manifestations of shock

Answer 15

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

Question 16

Initial assessment/management of shock

Answer 16

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

Question 17

Is hypotension required for shock to exist?

Answer 17

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

Question 18

Explain the circulatory features of hypovolaemia

• Perfusion = cold & clammy vs warm & dry?
• Pulse = weak vs bounding?
• Veins = empty vs full?

Answer 18

1. Perfusion = cold and clammy
2. Pulse = weak
3. Veins = empty

Question 19

Explain the circulatory features of pump failure

• Perfusion = cold & clammy vs warm & dry?
• Pulse = weak vs bounding?
• Veins = empty vs full?

Answer 19

1. Perfusion = cold and clammy
2. Pulse = weak (poor CO)
3. Veins = full, note JVP

Question 20

Explain the circulatory features of vasodilation

• Perfusion = cold & clammy vs warm & dry?
• Pulse = weak vs bounding?
• Veins = empty vs full?

Answer 20

1. Perfusion = warm and dry
2. Pulse = bounding
3. Veins = full

Question 21

What are different causes of hypovolaemia?

Answer 21

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

Question 22

Different causes of pump failure, intrinsic vs extrinsic

Answer 22

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

Question 23

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

Answer 23

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

Question 24

What is septic shock defined as?

Answer 24

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%

Question 25

What is sepsis defined as?

Answer 25

SIRS + confirmed or presumed infections | - Mortality = 10-15%

Question 26

What is severe sepsis defined as?

Answer 26

Sepsis with organ dysfunction | - Mortality = 17-20%

Question 27

What can cause a SIRS response?

Answer 27

1. Trauma 2. Burns 3. Pancreatitis 4. Other

Question 28

What can cause a sepsis response?

Answer 28

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

Question 29

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

Answer 29

Peripheral vasoconstriction

Question 30

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

Answer 30

Arteriolar vasodilatation

Question 31

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

Answer 31

1. Inotropy 2. Chronotropy 3. Renin secretion

Question 32

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

Answer 32

>HR >SV Vasoconstrictor — >BP

Question 33

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

Answer 33

>HR >SV Vasodilator

Question 34

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

Answer 34

>HR | Splanchnic vasodilator

Question 35

What are the actions of noradrenaline? (alpha receptor)

Answer 35

Vasoconstrictor

Question 36

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

Answer 36

Fluids (crystalloids or colloids)

Question 37

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

Answer 37

- This is your MI patient: cardiogenic shock - Inotropes - Possible vasodilators: because these patients are very vasoconstricted

Question 38

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

Answer 38

Vasopressors: NA | - Maybe fluids

Question 39

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

Answer 39

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

Question 40

What are the main treatments for sepsis?

Answer 40

1. Antibiotics 2. Crystalloids 3. Vasopressors 4. SEPSIS 6

Question 41

What is the sepsis six?

Answer 41

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