What is shock?
Some abnormality of the circulatory system resulting in inadequate tissue perfusion and oxygenation
Outline the steps leading from shock to cellular failure.
Shock
Inadequate tissue perfusion
Inadequate tissue oxygenation
Anaerobic metabolism
Accumulation of metabolic waste products
Cellular failure
What two factors does adequate tissue perfusion depend on?
- Adequate blood pressure
- Adequate cardiac output
What is hypovolaemic shock?
Shock caused by loss of blood volume
Outline the steps of hypovolaemic shock between loss of volume and inadequate tissue perfusion.
- Loss of blood volume
- Decreased venous return
- Decreased end diastolic volume
- Decreased stroke volume
- Decreased cardiac output and blood pressure
- Inadequate tissue perfusion
Briefly summarise the Frank-Starling Law of the heart.
Increased/decreased EDV = increased/decreased stroke volume –> cardiac output
What is cardiogenic shock?
Sustained hypotension caused by decreased cardiac contractility
Outline the steps of cardiogenic shock.
Decreased cardiac contractility
Decreased stroke volume
Decreased cardiac output and blood pressure
Inadequate tissue perfusion
Give an example of a condition which may cause obstructive shock.
Tension pneumothorax
Imagine a patient has presented with a tension pneumothorax. Outline the steps of obstructive shock which lead to inadequate tissue perfusion.
Increased intrathoracic pressure
Decreased venous return
Decreased end diastolic volume
Decreased stroke volume
Decreased CO and BP
Inadequate tissue perfusion
Give an example of an injury which may trigger neurogenic shock.
Spinal cord injury
Outline the steps of neurogenic shock following an event like a spinal cord injury.
Loss of sympathetic tone
Massive venous and arterial vasodilatation
Decreased venous return and TPR
Decreased CO and BP
Inadequate tissue perfusion
Outline the steps of vasoactive shock.
Release of vasoactive mediators
Massive venous & arterial vasodilation
Decreased venous return and TPR
Decreased CO and BP
Inadequate tissue perfusion
Which mnemonic should be the first thing you think of when someone presents with shock?
ABCDE
Apart from ABCDE, which other general treatments are given for shock?
High flow O2
Volume replacement
What is a treatment which can be given for cardiogenic shock?
Positive inotropes (e.g Digoxin)
Say someone had obstructive shock due to a tension pneumothorax - what is an immediate treatment?
Immediate chest drain
What immediate treatment is given for anaphylactic shock?
Adrenaline
What type of drug would you give to someone suffering septic shock?
Vasopressors (which cause vasoconstriction
Name a cause of hypovolaemic shock.
Haemorrhage
Vomiting
Diarrhoea
Excessive sweating
Compensatory mechanisms can maintain blood pressure until which percentage of total blood volume is lost?
> 30%
