Shock Flashcards
What is shock defined as?
Widespread reduction in tissue perfusion which causes cellular metabolic oxygen demands to exceed the supply
What is the main cause of shock?
A loss of support of cardiac output
What is hypovolaemic shock?
Where there is insufficient circulating volume, the primary cause is fluid loss
What is cardiogenic shock?
Failure of the heart pump, this could either be the speed or the direction of blood flow (e.g arrhythmia)
What is distributive shock?
Insufficient blood volume due to vasodilation means that blood is wrongly redistributed
Blood outside of vessels rather than inside
reduced total peripheral resistance
What is obstructive shock?
Where there is an obstruction to the flow of blood, e.g pneumothorax
or pericarditis- pericardium is pressed to the walls of the heart
This stops blood flowing in the heart
What are some clinical signs of shock early on in the process?
Panting, rapid heart rate,
Where is arteriolar constriction in response to shock most pronounced?
Skeletal muscle, Cutaneous muscle and splanchic vascular beds
What lowers the hydrostatic pressure in the capillaries?
Arterial hypotension, Arteriolar constriction, and reduced venous pressure
What does lowering the hydrostatic pressure in the capillaries promote?
It promotes the reabsorption of interstitial fluid into the vascular compartment
What are some clinical signs of shock found later on?
Pale skin and pale mucous membranes, drop in body temp and a slow respiratory rate
What does a reduction in arterial BP decrease?
in terms of receptors
Decreases the stimulation of baroreceptors in the carotid sinuses and aortic arch
What is essentially being lost when you have burns?
(during hypovlaemic shock)
Fluid loss such as blood plasma
What occurs during the cardiovascular response?
Increase in heart rate and myocardial contractility (this indirectly increases perfusion)
Autotransfusion- many other organs vasoconstrict so that more blood is supplied to the heart and the brain e.g from splanchic
How much vasoconstrcition occurs in the coronary/ cerebral arteries during shock?
Almost none, to protect them at the expense of other organs
What is the effect of having low hydrostatic pressure on interstitial fluid?
It promotes the reabsorption of interstitial fluid (as there will be less fluid leaving)
What is the effect of interstitial fluid reabsorption on the osmotic pressure?
It dilutes the concentration of plasma proteins and hence reduces the osmotic pressure
What does a low arterial BP indirectly stimulate?
Indirectly stimulates peripheral chemoreceptors in the aortic bodies, carotid bodies and the heart
What do the peripheral chemoreceptors do?
Chemoreceptors sense pH
So they sense changes in O2 and CO2 through tissue hypoxia
and therefore enhance the existing vasoconstriction and casue respiratory stimulation (increased breathing rate)
What are some examples of endocrine stimulation when shock occurs?
Release of catecholamines such as adrenaline and noradrenaline
Release of vasopressin (ADH) to stimulate the reabsorption of water Activation of the RAAS system
Release of Erythropoietin
What is Cardiogenic shock?
The heart struggles to pump blood that meets the tissues demand
decreased blood volume
decreased blood volume leads to hypotension
What is Cardiogenic shock?
The heart struggles to pump blood that meets the tissues demand
decreased blood volume
decreased blood volume leads to hypotension
What are some of the clinical signs of cardiac failure?
coughing, exercise intolerance, swollen abdomen, changes in mucous membrane colour
What is systolic function?
Impaired contractile function
What is diastolic dysfunction?
Impaired filling due to stiffness or hypertrophy
What is ejection fractioning?
Measuring the volume of blood both before and after it has been rejected (using the ventricle size)
What is fractional shortening?
Cut the ventricles into a sheet and look at their shortening/ how much they squeeze
How could you calculate the volume of the blood ejected each beat?
EDV- ESV
What is the cardiovascular response to shock?
There is decreased firing in the baroreceptors (found in aortic arch and carotid sinuses)
therefore there is increased heart rate and myocardial contractility
as well as autotransfusion of blood
What is autotransfusion of blood?
Occurs during the cardiovascular response
It is the redistribution of blood from other organs e.g GIT to the heart and the brain whcih are priority organs
What is the issue with arteriolar constriction/ reduced venous pressure
in terms of hydrostatic pressure
Increased arteriolar constriction decreases the hydostatic pressure
Therefore there is increased reabsorption of interstitial fluid into the capillaries
This dilutes the concentration of plasma proteins in the colloid/ decreased osmotic pressure
Therefore the long-term recovery requires plasma protein synthesis in the liver and more water/ electrolyte synthesis
What are the three different types of distributive shock?
Septic (toxins)
Anaphylactic (histamine)
Neurogenic
What is the function of catecholamines?
They are released in response to stress
(adrenaline and noradrenaline)
they are part of the sympathetic nervous system and therefore assist in increasing blood pressure
What is the difference between systolic and diastolic dysfunction?
systolic dysfunction is where the heart fails to pump out as much blood as normal (impaired contractile function)
diastolic dyfunction is where the ventricles are too stiff to fill (impaired filling)
What is EF?
a measurement of how well the heart is pumping blood around the body (volumetric fraction of the hearts ability)
What effect does low BP have on the baroreceptors?
decreased stimulation/firing
therefore there is generalised vasoconstriction to increase TPR and increased venoconstriction for increased venous return
venoconstriction is the generalised constriction of a vein
When does renal venoconstriction occur?
only in cases of haemorrage
What are some of the clinical signs of cardiac failure?
coughing, intolerance to exercise, swollen abdomen, lethargy, difficulty breathing, collapsing episodes
