Week 4: Shock

Question 1

What is shock?

Answer 1

Shock is a syndrome characterised by decreased tissue perfusion and impaired cellular metabolism
Cell demand for oxygen exceeds supply

Question 2

What conditions are required for tissue oxygenation and perfusion?

Answer 2

Ability of lungs to oxygenate blood
Ability of heart to pump blood to tissues
Adequate haemoglobin and blood volume
Effective vasculature

Question 3

What is stroke volume?

Answer 3

Amount of blood pumped into the aorta with each contraction of the left ventricle

Question 4

What is cardiac output?

Answer 4

Amount of blood pumped per minute into the aorta by the left ventricle
CO = SV X HR

Question 5

What is mean arterial pressure?

Answer 5

Is a product of CO and systemic vascular resistance

DP + (SP –DP)/3

Question 6

What are the consequences of shock?

Answer 6

Tissue hypoperfusion
Activation of the sympathetic nervous system
Activation of neurohormonal responses
Systemic Inflammatory response
Multi organ dysfunction

Question 7

What are the classifications of shock?

Answer 7

Hypovolaemic
Cardiogenic
Circulatory or distributive
Anaphylactic
Neurogenic
Septic

Question 8

What are the classifications for hypovolaemic shock?

Answer 8

Absolute fluid loss
Haemorrhage
Gastrointestinal losses -vomiting and/or diarrhoea
Water loss e.g. diabetes insipidus
Relative fluid loss
Fluid volume moves out of the intravascular space into the extravascular spaces (e.g. burns fluid leaks into the interstitial space)

Question 9

Include pathophysiology and S + S hypovolaemic shock

Answer 9

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Question 10

What is cardiogenic shock?

Answer 10

Results from either diastolic or systolic dysfunction and there is reduced cardiac output

Question 11

What is systolic dysfunction?

Answer 11

Inability of the heart to pump blood forward

Question 12

What is the main cause of systolic dysfunction?

Answer 12

Myocardial infarction

Question 13

Include pathophysiology and S + S cardiogenic shock

Answer 13

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Question 14

What are the types of distributive shock?

Answer 14

Anaphylactic
Neurogenic
Septic

Question 15

What is the pathophysiology of distributive shock?

Answer 15

Massive peripheral vasodilation –> reduced preload –> reduced SV –> reduced CO

Question 16

What is neurogenic shock?

Answer 16

Can occur within 30 minutes of spinal cord injury above T5

Loss of sympathetic tone causes unopposed parasympathetic tone (results in vasodilation)

Question 17

Include S + S of neurogenic shock

Answer 17

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Question 18

What is the difference between spinal shock and neurogenic shock?

Answer 18

Spinal:
decreased reflexes
loss of sensation
flaccid paralysis

Neurogenic:
loss of vasomotor tone
vasodilation
hypotension
bradycardia

Question 19

What is anaphylactic shock?

Answer 19

Chemical cascade from immune system causes vasodilation and increased capillary permeability

Question 20

What is the pathophysiology of anaphylactic shock?

Answer 20

Vasodilation –> blood flow to peripheries –> decreased preload –> decreased SV –> decreased CO
Increased capillary permeability –> fluid leaking into interstitial space (third spacing)

Question 21

Include S + S anaphylactic shock

Answer 21

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Question 22

What is septic shock?

Answer 22

Chemical cascade from infection causes vasodilation and increased capillary permeability

Question 23

What is the pathophysiology of septic shock?

Answer 23

Vasodilation –> blood flow to peripheries –> decreased preload –> decreased SV –> decreased CO
Increased capillary permeability –> fluid leaking into interstitial space (third spacing)
Myocardial depression
Decreased circulation to micro-circulation –> tissue hypoxia

Question 24

Include S + S septic shock

Answer 24

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Question 25

What are the stages of shock?

Answer 25

Compensatory: neurohormonal responses compensate for decreased CO Progressive: compensatory mechanisms begin to fail Activation: inflammatory and immune responses occur

Question 26

What are the compensatory mechanisms against shock?

Answer 26

Increased RR and depth of breathing ``` SNS: Increased CO Increased HR (B1) Increased myocardial contractility (B1) Increased systemic vascular resistance - afterload Venoconstriction --> increased preload ``` Hormonal activation: Aldosterone and ADH to increase preload Angiotensin 2 for vasoconstriction

Question 27

What is the progressive stage of shock?

Answer 27

Compensatory mechanisms begin to fail Activation of inflammatory and immune responses occur Biochemical mediators case myocardial depressions Microcirculation fails leading to increase capillarity permeability and further compromising tissue oxygenation Development of interstitial oedema Activation of the coagulation system

Question 28

How does SaVO2 relate to tissue perfusion?

Answer 28

The ability to provide oxygen to the cells is called oxygen delivery ( DaO2) Cell use about 25% of the available oxygen (VO2) When cells need more oxygen they can extract more oxygen When demand is greater than supply cells switch to anaerobic metabolism leading to lactic acidosis causing a metabolic acidosis

Question 29

What is the irreversible stage of shock?

Answer 29

Cellular and tissue injury severe | Patient exhibits signs of multi organ dysfunction syndrome

Question 30

What is the management for hypovolaemic shock?

Answer 30

``` Restoring intravascular volume Fluids blood Restoring oxygen carriage Resolving the cause ```

Question 31

What is the management for cardiogenic shock?

Answer 31

↑myocardial oxygen delivery (↑FiO2) Maximising cardiac output Decreasing ventricular workload Fluids to provide adequate filling without ventricular overdistention Diuretics to reduce preload Nitrates for veno and vasodilation Narcotics and sedatives to ↓myocardial oxygen consumption

Question 32

What are the pharmacological interventions for shock?

Answer 32

``` Sympathomimetics: Vasopressors cause peripheral vasoconstriction Noradrenaline Adrenaline Vasopressin (not for cardiogenic shock) ``` ``` Vasodilators for cardiogenic shock to decrease afterload sodium nitroprusside Venodilatorsto reduce preload Glyceryltrinitrate Sodium nitroprusside ``` Drugs to increase myocardial contractility ( inotropes) adrenaline dopamine dobutamine

Question 33

What are the types of Central Venous Access Devices?

Answer 33

Hickmans: surgically implanted in chest, tunnelled Peripheral inserted central catheters: peripherally inserted into anticubital fossa. Power PICC can withdraw blood and infuse CT contrast Port a Cath: implantable CVAD, accessed by a Huber needle. Power port can infuse CT contrast Central venous catheters: centrally inserted into subclavian, intrajugular or femoral vein

Question 34

What is the purpose of a Central Venous Access Device?

Answer 34

``` Deliver multiple infusions Deliver multiple medications Measure CVP Deliver TPN Deliver medication that causes phlebitis, e.g. hyperosmolar substances or vancomycin ```

Question 35

What is phlebitis?

Answer 35

Inflammation of the walls of a vein

Question 36

Which lumen on a Central Venous Access Device is used for CVP measurement?

Answer 36

Distal lumen, it is largest

Question 37

Which line on a Central Venous Access Device is used for large volumes of fluid?

Answer 37

Distal line

Question 38

How can you prevent CVAD associated infection?

Answer 38

``` Hand hygiene Aseptic technique Skin antisepsis Catheter site dressing and change Securing catheter Face mask ```

Question 39

What equipment is used to remove a CVAD?

Answer 39

``` Suture cutter Dressing pack Sterile gauze Sterile glove Chlorhexidine 2% (preferred) Occlusive dressing Goggles/face shield ```

Question 40

What is the procedure for removing a CVAD?

Answer 40

Explain procedure to patient Lie patient flat Remove non-sterile dressing Wash hands Set-up sterile field Wash hands – sterile gloves Clean site as per dressing technique Remove sutures or device holding CVC in place Instruct patient in valsalva maneuver Deep breath, bear down on glottis Prevents air embolism Remove CVC Hold CVC near insertion site with one hand In other hand place sterile gauze over insertion site Whilst patient is performing valsalva maneuver pull CVC firmly and gently out Apply pressure to insertion site with other hand as you remove CVC Maintain pressure until bleeding from insertion site has stopped Check catheter tip to ensure it is intact If CVC tip is to be cultured follow protocol Clean insertion site with chlorhexidine Allow to dry Cover insertion site with occlusive dressing Assess ever 24hours, once epithelialisation has occurred, occlusive dressing may be removed