Shock - Full summary Flashcards
What is meant by shock?
An abnormality of the circulatory system, resulting in inadequate tissue perfusion and oxygenation
How can shock cause cellular failure?
Inadequate tissue perfusion can lead to anaerobic metabolism, which results in accumulation of metabolic waste, resulting in cellular failure
What 2 factors does adequate tissue perfusion depend on?
Adequate Mean arterial pressure (MAP)
Adequate Cardiac Output (CO)
What are the 4 main classes of shock?
Hypovolaemic shock
Cardiogenic shock
Obstructive shock
Distributive shock
What is hypovolaemic shock?
Shock caused by a loss of blood volume
What are the 2 types of hypovolaemic shock?
Haemorrhagic shock
Non-Haemorrhagic shock
What causes haemorrhagic shock?
This is a decrease in blood volume caused by direct loss of blood, either by trauma, surgery or GI haemorrhage
What causes non-hemorrhagic shock?
This is shock caused by a loss of fluid in the body by processes such as vomiting, diarrhoea or excessive sweating
Describe the pathophysiology of hypovolaemic shock
Loss of blood volume
Decreased venous return
Decreased end diastolic volume
Decreased stroke volume (Frank-Starling)
Decreased cardiac output and MAP
Inadequate tissue perfusion
Up until what percentage of blood loss can compensatory mechanisms maintain blood pressure?
30%
How do compensatory mechanisms increase blood pressure?
Decrease in blood volume causes a decrease in blood pressure
Baroreceptors detect this and stimulate an increase in SVR and heart rate
What are some common symptoms of hypovolaemic shock?
Cold peripheries
Tachycardia
Small volume pulse
What is meant by Class I haemorrhagic shock?
≤15% blood loss (750mL) and normal BP
What is meant by class II haemorrhagic shock?
15-30% blood loss (750-1500mL) and normal BP
What is meant by class III haemorrhagic shock?
30-40% blood loss (1500-2000mL) and low BP
What is meant by class IV haemorrhagic shock?
> 40% blood loss (2000mL) and low BP
What is meant by cardiogenic shock?
This is shock caused by sudden, severe impairment of heart function, meaning it is unable to pump sufficient blood to perfuse the brain
What is an example a condition that can lead to cariogenic shock?
Myocardial infarction
Describe the pathophysiology of cardiogenic shock
Decreased cardiac contractility
Decreased stroke volume
Decreased CO and MAP
Inadequate tissue perfusion
What medication is indicated in cardiogenic shock?
Adrenaline or dopamine injection
(Inotropes)
What treatment is contraindicated in cariogenic shock?
IV fluids
What is meant by obstructive shock?
This is shock due to physical obstruction of circulation, either in or out of the heart
What are some conditions that can cause obstructive shock?
Cardiac tamponade
Tension pneumothorax
Pulmonary embolism
Severe aortic stenosis
Describe the pathophysiology of obstructive shock in tension pneumothorax
Increased intra-thoracic pressure
Decreased venous return
Decreased end diastolic volume
Decreased stroke volume
Decreased CO and MAP
Inadequate tissue perfusion
What is meant by distributive shock?
Shock caused by excessive vasodilation and abnormal distribution of shock
What are the 2 types of distributive shock?
Vasoactive
Neurogenic
What is an example of a cause of neurogenic shock?
Spinal cord injury
What are some examples of vasoactive shock?
Septic shock
Anaphylactic shock
Describe the pathophysiology of neuroactive shock in spinal cord injury?
Loss of sympathetic tone to heart and vessels
Massive vasodilation and decreased heart rate
Decreased CO and MAP
Inadequate tissue perfusion
Describe the pathophysiology of vasoactive shock
Release of vasoactive mediators
Massive vasodilation and capillary permeability
Decreased venous return and SVR
Decrease in CO and MAP
Inadequate tissue perfusion
What is the 1st line treatment option in anaphylactic shock?
Adrenaline
What is the 1st line treatment in septic shock?
Vasopressors (e.g. epinephrine, ADH)
How should all cases of shock be managed first?
ABCDE
High flow oxygen
Fluid replacement (Not in cardiogenic)
