Shock

Question 1

What is shock?

Answer 1

The clinical syndrome of tissue hypoperfusion due to circulatory failure.
Common, life threatening (40-80%), acute

Question 2

What is the pathophysiology behind shock?

Answer 2

MAP below necessary (approx. 50-60mmHg, higher in diseased atherosclerotic vessels)
Slow flow to organs (even leading to thrombus formation-Virchow’s)
Inadequate perfusion for cellular metabolic requirements (Leading to acidosis and lactate formation)

Question 3

What does inadequate perfusion cause?

Answer 3

Systemic Acidosis (pH < 7.35), further worsening global enzyme function and cellular performance
Microcapillary thrombus with patchy tissue injury and even large vessel thrombus with organ infarction
Eventual cellular necrosis results in mortality
In survivors, a degree of tissue injury may be irreversible, contributing to chronic morbidity

Question 4

What micro-circulatory changes can occur in shock?

Answer 4

Capillary blood flow is reduced, intermittent or terminated

Question 5

How is shock recognised?

Answer 5

Immediate Impression:
Mottling
Glasgow Coma Score- <15– Confusion, Agitation
Urine Output <0.5ml/kg/h

Question 6

How is shock confirmed?

Answer 6

Lactate Levels:
0.75mmol/L higher than normal carries a worse prognosis
>2mmol/L arguably diagnostic
>4mmol/L significant mortality

Question 7

Describe cardiogenic shock

Answer 7

Reduced force of cardiac contraction and stroke volume and therefore cardiac output and mean arterial pressure
Compensatory increase in SVR, resulting in cool, clammy peripheries

Question 8

What is the pathophysiology involved in cardiogenic shock?

Answer 8

HR reduced in some caes
SV reduced due to low contractility
Leads to CO reduced
SVR increased to compensate
MAP likely decreased

Question 9

What is the treatment of cardiogenic shock due to decreased HR?

Answer 9

Arrythmia- Drugs +- cardioversion

Poisoning- Drugs +- dialysis

Question 10

What is the treatment of cardiogenic shock due to decreased SV?

Answer 10

MI- Drugs +- PCI
Cardiomyopathy- Drugs
Valve failure- Drugs +- surgery

Question 11

Describe obstructive shock

Answer 11

Obstruction to cardiac outflow (otherwise similar to cardiogenic)
Evidence of raised JVP and distended neck veins may be prominent

Question 12

What is the pathophysiology behind obstructive shock?

Answer 12

Similar to cardiogenic
CO blocked
Leading to venous back pressure

Question 13

How is obstructive shock due to cardiac tamponade treated?

Answer 13

Trauma/Aortic Dissection: Pericardiocentesis +- Thoractomy +- Surgery

Question 14

How is obstructive shock due to tension pneumothorax treated?

Answer 14

Trauma/Pleural Pathology: Thoracocentesis + Thoracostomy +- Surgery

Question 15

How is obstructive shock due to PE treated?

Answer 15

Stasis (post op/partum): Anticoagulation +- Thrombolysis or direct lysis

Question 16

Describe hypovolaemic shock

Answer 16

Reduced blood volume
Lower venous return to the heart (ventricular filling = end-diastolic volume)
Reduced force of cardiac contraction and Cardiac Output (Frank-Starling law)

Question 17

What is the pathophysiology in hypovolaemic shock?

Answer 17

HR increased to compensate
SV reduced due to low preload
CO may be reduced
SVR increased to compensate
Likely reduction in MAP

Question 18

What signs of haemorrhage will occur in class I volume loss (<15%=750ml)?

Answer 18

Normal RR
Normal HR
Normal (Or increased) BP
No change in mental state
Urine output >30ml/h

Question 19

What signs of haemorrhage will occur in class II volume loss (<30%=1500ml)?

Answer 19

>20 RR
>100 HR
Decreased pulse pressure
Anxious 
Urine output <30ml/h

Question 20

What signs of haemorrhage will occur in class III volume loss (<40%=2000ml)?

Answer 20

>30 RR
>120 HR
Decreased BP
Confused
Urine output <315ml/h

Question 21

What signs of haemorrhage will occur in class IV volume loss (>40%=over 2000ml)?

Answer 21

>35 RR
>140 HR
Decreased BP
Lethargic
Urine output negligible

Question 22

What can cause haemorrhage, in turn causing hypovolaemia?

Answer 22

Trauma- Overt Haemorrhage, Pelvic Fracture, Long Bone Fracture, Abdominal Visceral, Intrathoracic
Gastrointestinal Bleeding
Post-operative Bleeding

Question 23

How is haemorrhage treated?

Answer 23

Temporising Measures (Pressure, Splint, Binding Sengstaken)
Find & Stop Bleeding (Surgery, Endoscopy)
Cross-match, Blood, Blood Products

Question 24

What can cause dehydration, in turn causing hypovolaemia?

Answer 24

Gastrointestinal Loss (Diarrhoea, Stoma, Vomiting, Starvation)
Epithelial Loss (Burns)
Renal/Cellular Loss (Addisonian Crisis, Diabetic Ketoacidosis)

Question 25

How is dehydration treated?

Answer 25

Fluids, Electrolytes
Specialist Unit Care
Steroids/Insulin

Question 26

Describe distributive shock

Answer 26

Reduced Systemic Vascular Resistance due to Vasodilatation with warm, red peripheries
Reduced Mean Arterial Pressure
Compensatory increase in Cardiac Output

Question 27

What may be the aetiology of an inflammatory cause of distributive shock (may be complicated by hypovolaemia or cardiogenic shock)?

Answer 27

Sepsis (Lung, Kidney, Intra-abdominal…)
SIRS, including Pancreatitis and Burns
Anaphylactic shock

Question 28

How would an inflammatory cause of distributive shock be treated?

Answer 28

Antibiotics +/- Noradrenaline (Vasopressor)
Supportive Therapy
Adrenaline (Vasopressor and Inotrope)

Question 29

How would a neurogenic cause of distributive shock be treated?

Answer 29

Spinal cord damage: Neurosurgery

Iatrogenic (spinal/epidural): Support +- vasopressors