Physiology of shock + how to treat- sudden death

Question 1

what is shock?

Answer 1

a condition of inadequate perfusion to sustain normal function

Question 2

what is hypovolaemic shock?

Answer 2

A loss of circulating volume leading to reduced preload (which reduces SV) and so reduces cardiac output

Question 3

what is cardiac output?

Answer 3

the volume of blood that the heart can pump out of each ventricle per minute

Question 4

calculation for cardiac output?

Answer 4

CO= SV x HR

Question 5

causes of hypovolaemic shock?

Answer 5

-bleeding
-third space losses (loss of fluid into spaces we cant even see)
-severe dehydration

Question 6

what are baroreceptors?

Answer 6

nerves that can sense pressure changes in the arteries and carry info to medulla changing the parasympathetic/ sympathetic signals

Question 7

what are the two types of baro receptors?

Answer 7

-Arterial
-Cardiopulmonary

Question 8

where are the arterial baroreceptors found and what nerves innervate?

Answer 8

Aortic arch- vagus nerve (CNX)
Carotid sinus- glossopharyngeal nerve (CNIX)

Question 9

if aortic arch/ carotid sinus stretch due to increase in bp- what effect does this have?

Answer 9

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

Question 10

what would occur to parasympathetic and sympathetic signals if there is loss of blood- baroreceptor reflex?

Answer 10

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

Question 11

what does the sympathetic nervous system release to increase BP?

Answer 11

Noradrenaline (norepinephrine) and Adrenaline (epinephrine)

Question 12

where is renin released from?

Answer 12

JGA

Question 13

role of renin?

Answer 13

converts angiotensinogen into angiotenis I so that ACE (released from lungs) can convert angiotensin I to angiotensin II

Question 14

treatment of hypovolaemic shock?

Answer 14

Fluids

-make sure to consider the difference between resus and maintenance fluids

Question 15

what is cardiogenic shock?

Answer 15

when there is myocardial dysfunction causing reduction in systolic function and CO

Question 16

causes of cardiogenic shock?

Answer 16

-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

Question 17

clinical signs of cardiogenic shock?

Answer 17

poor forwards flow- hypotension, fatigue, syncope

Backpressure- pulmonary oedema, elevated JVP, hepatic congestion

COLD PERIPHERIES

Question 18

what is positive ionotrophy?

Answer 18

an increase in force of cardiac contraction for any given preload (kinda the nervous system making the heart contact)

Question 19

how can ionotrophy be achieved?

Answer 19

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

Question 20

Management of cardiogenic shock?

Answer 20

Drugs that increase ionotrophy (an increase in force of cardiac contraction):
-Dobutamine (adrenaline)
-Dopamine (dopexamine)

If pharmacological management fails:
-Intra aortic baloon pump

Question 21

what is obstructive shock?

Answer 21

-when there is a physical obstruction to filling of the heart leading to reduced preload and cardiac load

Question 22

causes of obstructive shock?

Answer 22

-Cardiac tamponade
-PE
-Tension pneumothorax

Question 23

what is distributive shock?

Answer 23

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

Question 24

what are the three types of distributive shock?

Answer 24

-Septic shock
-Anaphylactic shock
-Neurogenic shock

Question 25

bacterial endotoxin mediated capillary dysfunction
-what type of shock?

Answer 25

septic shock

Question 26

Mast cell release of histamnergic vasodilators
-what type of shock?

Answer 26

anaphylactic

Question 27

Loss of thoracic sympathetic outflow following spinal injury
-what type of shock?

Answer 27

neurogenic

Question 28

Injury to where in CNS causes neurogenic shock?

Answer 28

-injury to T6 and above (as this is where the sympathetic chain is)

Question 29

pathophysiology of neurogenic shock

Answer 29

-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

Question 30

specific features of neurogenic shock?

Answer 30

Warm peripheries
decrease in HR
spinal cord injury

Question 31

difference between sepsis and septic shock?

Answer 31

sepsis- end organ dysfunction with known infection (10% mortality)

septic shock- sepsis + hypotension despite fluid resus

Question 32

pathophysiology of sepsis?

Answer 32

-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

Question 33

management of sepsis?

Answer 33

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