Physiology of shock + how to treat- sudden death Flashcards
what is shock?
a condition of inadequate perfusion to sustain normal function
what is hypovolaemic shock?
A loss of circulating volume leading to reduced preload (which reduces SV) and so reduces cardiac output
what is cardiac output?
the volume of blood that the heart can pump out of each ventricle per minute
calculation for cardiac output?
CO= SV x HR
causes of hypovolaemic shock?
-bleeding
-third space losses (loss of fluid into spaces we cant even see)
-severe dehydration
what are baroreceptors?
nerves that can sense pressure changes in the arteries and carry info to medulla changing the parasympathetic/ sympathetic signals
what are the two types of baro receptors?
-Arterial
-Cardiopulmonary
where are the arterial baroreceptors found and what nerves innervate?
Aortic arch- vagus nerve (CNX)
Carotid sinus- glossopharyngeal nerve (CNIX)
if aortic arch/ carotid sinus stretch due to increase in bp- what effect does this have?
Baroreceptors recognise the stretch of the arteries, send more signals to the brain
Causes inhibition of sympathetic and stimulates parasympathetic nervous system (causing arterioles and veins to dilate)
Veins dilating causes decrease venous return, decrease preload and so decrease cardiac output, decreasing BP
what would occur to parasympathetic and sympathetic signals if there is loss of blood- baroreceptor reflex?
Baroreceptors would sense that there is less stretching of the arteries (aortic arch and carotid sinus) as the BP decreases due to blood loss
Baroreceptors send signals to the medulla
Causes inhibition of the parasympathetic and stimulate sympathetic, making arterioles + veins constrict, increasing venous return + preload and so increasing cardiac output
what does the sympathetic nervous system release to increase BP?
Noradrenaline (norepinephrine) and Adrenaline (epinephrine)
where is renin released from?
JGA
role of renin?
converts angiotensinogen into angiotenis I so that ACE (released from lungs) can convert angiotensin I to angiotensin II
treatment of hypovolaemic shock?
Fluids
-make sure to consider the difference between resus and maintenance fluids
what is cardiogenic shock?
when there is myocardial dysfunction causing reduction in systolic function and CO
causes of cardiogenic shock?
-MI
-Myocarditis
-Acute valve lesion
The heart is having trouble pumping, this causes a decrease in CO, decrease in BP and a backlog of fluid in the heart (raised JVP, oedema), decrease in CO and causes increase in systemic vascular resistance to try and get more blood to vital organs. This directs the blood to the vital organs and away from peripheral and that why you have cold skin
clinical signs of cardiogenic shock?
poor forwards flow- hypotension, fatigue, syncope
Backpressure- pulmonary oedema, elevated JVP, hepatic congestion
COLD PERIPHERIES
what is positive ionotrophy?
an increase in force of cardiac contraction for any given preload (kinda the nervous system making the heart contact)
how can ionotrophy be achieved?
ionotrophy- an increase in force of cardiac contraction for any given preload
Achieved physiologically by sympathetic nervous system
Can be replicated pharmacologically but beta and dopaminergic stimulation
Management of cardiogenic shock?
Drugs that increase ionotrophy (an increase in force of cardiac contraction):
-Dobutamine (adrenaline)
-Dopamine (dopexamine)
If pharmacological management fails:
-Intra aortic baloon pump
what is obstructive shock?
-when there is a physical obstruction to filling of the heart leading to reduced preload and cardiac load
causes of obstructive shock?
-Cardiac tamponade
-PE
-Tension pneumothorax
what is distributive shock?
significant reduction in systemic vascular resistance beyond the compensatory limits of increased CO
-usually initial high CO but insuffiecient to maintain forwards perfusion
aka hot shock because peripheries will be warm
what are the three types of distributive shock?
-Septic shock
-Anaphylactic shock
-Neurogenic shock
bacterial endotoxin mediated capillary dysfunction
-what type of shock?
septic shock
Mast cell release of histamnergic vasodilators
-what type of shock?
anaphylactic
Loss of thoracic sympathetic outflow following spinal injury
-what type of shock?
neurogenic
Injury to where in CNS causes neurogenic shock?
-injury to T6 and above (as this is where the sympathetic chain is)
pathophysiology of neurogenic shock
-Spinal cord injury at T6 or above
-disruption to sympathetic chain
-Parasympathetic chain still works
-this causes vasodilation (sympathetic chain would cause vasocontstriction) and decrease in HR
-decreases overall bp, systemic vascular resistance, cardiac output
-peripherals are warm as there is a decrease in systemic vascular resistance and so blood is not getting directed to the organs
specific features of neurogenic shock?
Warm peripheries
decrease in HR
spinal cord injury
difference between sepsis and septic shock?
sepsis- end organ dysfunction with known infection (10% mortality)
septic shock- sepsis + hypotension despite fluid resus
pathophysiology of sepsis?
-infection gets into blood
-wbc release cyotkines and NO when fighting off infection
-causes vasodilation
-fluid starts to leave (third space loss)
-systemic vascular resistance decreases and BP decreases
-DIC occurs
-blood is not travelling specifically to the vital organs as there is no systemic vascular resistance and so causes warm peripheries
management of sepsis?
Give 3 take 3
or BUFALO
BLOODS- take at least 1 and try do before antibiotics
URINE OUTPUT- using catheter
FLUID CHALLENGE- 250 to 500 mls 0.9% saline over 15 mins
ANTIBIOTICS- metranidazole, amoxicillin + gentamycin (vancomycin instead of amoxicillin if pen allergy)
LACTATE- >2 is worrying
OXYGEN
