Physiology of Shock

Question 1

define shock

Answer 1

condition of inadequate perfusion to sustain normal organ function

Question 2

name the 5 classes of shock

Answer 2

hypovolaemic
cardiogenic
obstructive
distributive 
cytotoxic

Question 3

what is the cause of hypovolaemic shock?

Answer 3

loss of circulating volume -> reduced preload and cardiac output

Question 4

what causes hypovolaemic shock?

Answer 4

bleeding
third space losses
severe dehydration

Question 5

clinical features of hypovolaemic shock

Answer 5

> pulse and RR
< BP and PP
< urine output
anxiety, confusion, lethargy

Question 6

describe baroreceptors

Answer 6

stretch sensitive receptors in carotid sinus and aortic arch

Question 7

describe baroreceptor reflex

Answer 7

decreased stretch -> decreased afferent input to medullary CV centres -> inhibition of parasympathetic and enhanced sympathetic output

Question 8

what is the sympathetic mediated neurohormonal response?

Answer 8

release of circulatory vasoconstrictors
redirects fluid from peripheral and secondary organs
resulting lactic acidosis drives chemoreceptors to enhance response

Question 9

name circulatory vasoconstrictors

Answer 9

adrenaline
angiotensin
norad
vasopressin

Question 10

what is the role of capillary absorption of interstitial fluid?

Answer 10

reduced capillary hydrostatic pressure -> inward net filtration

Question 11

what is the hypothalamo-pituitary-adrenal response?

Answer 11

intrarenal baroreceptors mediate renin release from JGA
resulting Ang II enhances vasoconstriction and ADH secretion
enhances renal absorption of sodium and water

Question 12

what are the 3 options to increase CO?

Answer 12

increase HR
increase SV
increase both

Question 13

what causes cardiogenic shock?

Answer 13

myocardial dysfunction causing reduction in systolic function and cardiac output

Question 14

what usually causes cardiogenic shock?

Answer 14

MI or acute valve lesion

Question 15

what are more unusual causes of cardiogenic shock?

Answer 15

myocarditis
cardiomyopathy
myocardial contusion

Question 16

clinical signs of cardiogenic shock

Answer 16

poor forward flow 
- hypotension
- fatigue 
- syncope 
backpressure 
- pulmonary oedema 
- elevated JVP 
- hepatic congestion

Question 17

what is +ve inotropy?

Answer 17

increase in force of cardiac contraction for any given preload

Question 18

how is inotropy achieved normally and pharmacologically?

Answer 18

by the SNS

B and dopaminergic stimulation

Question 19

what is the function of an intra-aortic balloon pump?

Answer 19

to provide counterpulsation

• inflation during diastole
• deflation during systole

Question 20

what is the cause of obstructive shock?

Answer 20

Physical obstruction to filling of the heart caused by an obstruction in the heart itself or great vessels

Question 21

what is the result of obstructive shock?

Answer 21

reduced preload and cardiac output

Question 22

what is the usual cause of obstructive shock?

Answer 22

cardiac tamponade

PE

Question 23

how do you treat a PE?

Answer 23

anticoagulation +/- thrombolysis

Question 24

how do you treat cardiac tamponade?

Answer 24

pericardial drainage

Question 25

how do you treat a tension pneumothorax?

Answer 25

decompression and chest drainage

Question 26

what causes distributive shock?

Answer 26

Significant reduction in SVR beyond the compensatory limits of increased cardiac output

Question 27

what is the result of distributive shock?

Answer 27

initial high CO but insufficient to maintain forward perfusion

Question 28

what causes distributive shock?

Answer 28

septic shock anaphylaxis neurogenic causes

Question 29

what causes shock from sepsis?

Answer 29

bacterial endotoxin mediated capillary dysfunction

Question 30

how do you treat sepsis to prevent shock?

Answer 30

early abs | vasopressors

Question 31

what causes shock in anaphylaxis?

Answer 31

mast cell release of histaminergic vasodilators

Question 32

what causes neurogenic distributive shock?

Answer 32

spinal cord or central trauma causes loss of thoracic sympathetic outflow

Question 33

how do you treat shock caused by neurogenic reasons?

Answer 33

dopamine | vasopressors

Question 34

what causes cytotoxic shock?

Answer 34

Uncoupling of tissue oxygen delivery and mitochondrial oxygen uptake Caused by CO poisoning and CN- poisoning

Question 35

shockable cardiac rhythms

Answer 35

ventricular fibrillation | pulseless ventricular tachycardia

Question 36

non shockable cardiac rhythms

Answer 36

pulseless electrical activity | asytole