4: Physiology and treatment of shock Flashcards
What is shock?
Inadequate perfusion of the vital organs
What happens if shock isn’t promptly treated?
Organ failure
Death
What are the five different types of shock?
Hypovolaemic
Cardiogenic
Septic
Anaphylactic
Neurogenic
Septic, anaphylactic and neurogenic shock are also known as ___ shock.
Why?
distributive
Problem is with the distribution of fluid, not the volume
So the blood is there, it’s just not in the right place
Which types of shock are also known as distributive shock?
Septic
Anaphylactic
Neurogenic
What is hypovolaemic shock?
Inadequate organ perfusion caused by an insufficient blood volume
typically the shock caused by massive haemorrhage
What are some causes of hypovolaemic shock apart from bleeding?
Excessive vomiting
Burns
How is hypovolaemic shock managed?
Assuming all else OK (oxygenated, warm, U&Es):
IV fluids
Blood
How does blood pressure change in hypovolaemic shock?
1. Initially stays the same because tachycardia compensates (CO=HRxSV)
2. Reduced when patient exhausted
What is cardiogenic shock?
Inadequate organ perfusion caused by the failure of the heart to act as a pump
What are some causes of cardiogenic shock?
MI
Heart failure
PE
Cardiac tamponade
Severe valvular disease
Arrhythmias e.g VF, VT
In hypovolaemic shock, the skin is cool and pale.
How does it appear in cardiogenic shock?
Flushed and swollen
because blood collects inferiorly (heart isn’t working)
How is cardiogenic shock managed?
Assuming all else OK (heart rhythm, oxygen, U&Es etcccc)
Inotropes - dobutamine - increases force of contractility i.e SV
Vasopressors - adrenaline - increases TPR, increasing blood pressure
Then treat underlying cause
What is the pathophysiology of anaphylactic shock?
1. Allergens enter bloodstream and bind to B cells, which produce IgE antibodies
2. IgE antibodies bind to mast cells and cause them to degranulate…
3. …releasing histamine, cytokines
4. Histamine causes widespread vasodilation > hypotension. Cytokines recruit WBCs, causing widespread inflammation (pruritus, SOB, urticaria, oedema)
How is anaphylactic shock managed?
IV adrenaline
Causes vasoconstriction (improving BP and perfusion) + bronchodilation (improving oxygenation)
Below which BP is a patient thought to be hypotensive?
90/60 mm Hg
though in reality you should just compare it to whatever they were before and use common sense, say 25-30% decrease
How do you calculate MABP?
MABP = 2(diastolic BP) + systolic BP all over 3
What is the minimum MABP needed to perfuse the vital organs?
60 mm Hg
What is the pathophysiology of septic shock?
WBCs encounter pathogen - inflammation, vasodilation and leaky vessels > hypotension
What is the SEPSIS 6 bundle?
Give oxygen, fluids and antibiotics
Take lactate, urine output and sample for culture
Apart from SEPSIS 6, what other drug should patients in septic shock be given?
Vasopressor e.g adrenaline
What skin changes occur in septic shock?
Initially warm
Then cold
What is neurogenic shock?
Inadequate organ perfusion caused by spinal cord anaesthesia or injury
More specifically loss of sympathetic function (branch from spinal nerves), causing unopposed parasympathetic vasodilation and bradycardia
How do you tell neurogenic shock apart from other types of shock?
BRADYCARDIA
Hx suggestive spinal cord injury (e.g RTA, fall from height)
Why does neurogenic shock cause bradycardia and not tachycardia?
In other types of shock, tachycardia is compensation for hypotension
But in neurogenic shock the sympathetic supply to heart is cut off, so parasympathetic (bradycardia) unopposed
How is neurogenic shock managed?
Suss out cause (might be irreversible)
Vasopressor - adrenaline - causes vasoconstriction, ups heart rate and force of contraction
What is the mnemonic for remembering the reversible causes of cardiac arrest?
4 Hs
4 Ts
What are 4 Hs which cause reversible cardiac arrest?
Hypoxia
Hypothermia
Hypovolaemia
HypERkalaemia
What are 4 Ts which cause reversible cardiac arrest?
Cardiac tamponade
Tension pneumothorax
Thrombosis
Toxins
What are the 4 Hs and 4 Ts of reversible cardiac arrest?
Hypoxia, hypovolaemia, hypothermia, hyperkalaemia
Tension pneumothorax, tamponade, thrombosis, toxins
What metabolic disturbance can cause cardiac arrest?
Hyperkalaemia
