Shock

Question 1

what is shock

Answer 1

condition of inadequate perfusion to sustain normal organ function

Question 2

what are the 5 main types of shock

Answer 2

hypovolaemic 
cardiogenic
obstructive 
distributive 
cytotoxic

Question 3

what is cytotoxic shock

Answer 3

uncoupling of tissue oxygen delivery and mitochondrial uptake

Question 4

what can cause cytotoxic shock

Answer 4

CO poisoning 
CN poisoning (cyanide)

Question 5

what is hypovolaemic shock

Answer 5

insufficient circulating volume to fill the circuit

Question 6

what can cause hypvolaemic shock

Answer 6

blood loss
interstitial fluid
pure water deficit (severe dehydration -rare)
third space losses (interstitial/ extravascular/ extracellular)

Question 7

what are the clinical features of hypovolaemic shock

Answer 7

depends on degree of hypovolaemia

• tachycardia
• hypotension
• tachypnoeic
• reduced urine output
• anxious -> confused and lethargic

Question 8

who is most at risk in hypovolaemic shock

Answer 8

young people- as compensate very well and then crash

Question 9

what are the compensatory mechanisms for hypovolaemic shock

Answer 9

baroreceptor reflexes
sympathetic mediated neurohormonal response
capillary absorption of interstitial fluid
hypothalamo-pituitary response

Question 10

explain the baroreceptor compensatory mechanism for hypovolaemic shock

Answer 10

stretch sensitive receptors in the carotid sinus (CNIX) and aortic arch (CNX) sense decrease stretch
=decreased afferent input to medullary CV centres
=inhibition of parasympathetic (CNX) and enhanced sympathetic output

=increase HR and inotropy

Question 11

explain the sympathetic mediated neurohormonal response compensatory mechanism for hypovolaemic shock

Answer 11

sympathetic chronotropy and inotropy from baroreceptor reflex
=release of circulating vasoconstrictors (adrenaline, angiotensin, norad, vasopressin)
=redirects fluid from peripheral and secondary organs
=lactic acidosis
=drives chemoreceptors to enhance response

in decompensatory stage circulating vasodilators also increased

Question 12

explain capillary absorption as a compensatory mechanism for hypovolaemic shock

Answer 12

reduced capillary hydrostatic pressure causes inward net filtration of interstitial fluid

Question 13

explain the hypothalamo-pituitary-adrenal response as a compensatory mechanism for hypovolaemic shock

Answer 13

internal baroreceptors mediate renin release from juxtaglomerular apparatus
resulting Ang II enhances vasoconstriction and ADH secretion
=enhances renal reabsorption of sodium and water

Question 14

what is a increase in inotropy

Answer 14

increase in heart contractility

Question 15

how does the heart increase its cardiac output

Answer 15

increase rate (nerves, hormones)
increase stroke volume (blood volume, vascular resistance)
or increase both

Question 16

how does inotropy affect the frank starling curve

Answer 16

shifts it upwards- increases contractility

Question 17

what happens to the frank starling curve in heart failure

Answer 17

failing heart has decreased contractility - curves shifts down

EDV increases to maintain SV but this results in pulmonary congestion

Question 18

what does it mean when a patient is sensitive to fluids

Answer 18

given fluid when someone is hypovolaemic will have a much bigger effect - a small change in preload will result in a significant increase in contraction
this response lessens as the patient becomes more hypervolaemic

Question 19

what do you need to consider before giving fluids

Answer 19

know what they are and the dose needed
consider constitution of patient
consider fluid and electrolyte balance
consider difference in fluid for resus and maintenance

Question 20

what is cardiogenic shock

Answer 20

inability of the heart to pump to meet circulatory demands

myocardial dysfunction causing reduction in systolic function and cardiac output

Question 21

what can cause cardiogenic shock

Answer 21

mostly complication of MIs
acute valve lesion e.g acute mitral prolapse, MI affecting papillary muscle- valve prolapse 
myocarditis 
cardiomyopathy 
myocardial contusion (trauma)

Question 22

what are the clinical signs of cardiogenic shock

Answer 22

(caused by poor forward flow): hypotension/ shock, fatigue, syncope

(backpressure): pulmonary oedema, elevated JVP, hepatic congestion

Question 23

what is positive inotropy

Answer 23

increase in force of cardiac contraction regardless of preload

Question 24

what increases inotropy physiologically

Answer 24

sympathetic nervous stimulation

Question 25

what drugs increase inotropy

Answer 25

beta and dopaminergic agents beta- dobutamine, adrenaline dopamine- dopamine, dopexamine others- milrinone/ levosimendan

Question 26

when might you give inotropic drugs

Answer 26

when someone has cardiogenic shock after MI but also have pulmonary oedema due to heart failure

Question 27

what is an intra-aortic balloon pump

Answer 27

given to people in cardiogenic shock to due heart failure after an MI - inflates during ventricular diastole to increase diastolic pressure and increase coronary artery perfusion - deflates during systole to decrease systolic pressure (reduces the pressure the heart has to beat against lowering myocardial wall stress and O2 demands)

Question 28

what is obstructive shock

Answer 28

involves a physical obstruction to either the heart of great vessels = reduced preload and cardiac output mainly affects cardiac filling rather than ejection

Question 29

what is the treatment for obstructive shock

Answer 29

depends on cause: PE- anticoagulation +/- thrombosis cardiac tamponade- pericardial drainage tension pneumothorax- decompression and chest drainage

Question 30

what are the causes of obstructive shock

Answer 30

PE- stops blood getting back from lungs | tamponade and tension pneumothorax- heart compressed and unable to fill

Question 31

what does a PE look like on echo

Answer 31

dilated, hypokinetic RV (right side not contracting well due to high pressure) bowing of interventricular septum to the left (less pressure on left side) hyperkinetic RV apec (McConnels sign)

Question 32

what does a pericardial effusion/ tamponade look like on echo

Answer 32

fluid accumulation in pericardial sac compresses each of the chamber impairs cardiac filling and contraction in all four chambers

Question 33

why does a tension pneumothorax cause obstructive shock

Answer 33

air trapped in pleural cavity increases intrathoracic pressure- if this higher than venous pressure wont get cardiac filling also displacement of mediastinal structures by air impairs cardiac filling and function

Question 34

what is disruptive shock

Answer 34

Significant reduction in SVR beyond the compensatory limits of increased cardiac output (circuits too big) aka vasodilatory/ warm shock generally high cardiac output but insufficient to maintain forward perfusion

Question 35

what are the subtypes of distributive shock

Answer 35

septic- bacterial endotoxin mediated capillary dysfunction anaphylactic- mast cell release of histaminergic vasodilators neurogenic- loss of thoracic sympathetic outflow follow spinal injury

Question 36

what is the role of sympathetics in blood vessels

Answer 36

tonically constricts them

Question 37

how can you detect hypoperfusion in septic shock before hypotension occurs

Answer 37

shown in rising lactate levels

Question 38

what is the management for septic shock

Answer 38

sepsis 6 + vasopressors after usually 2 bags of fluid with no response

Question 39

what is anaphylactic shock

Answer 39

uncontrolled activation and degranulation of mast cells =release of histamine =uncontrolled widespread vasodilation =distributive shock

Question 40

how does adrenaline help in anaphylatic shock

Answer 40

acts as a vasoconstrictor and a mast cell stabiliser

Question 41

what test confirms analphylaxis

Answer 41

serum mast cell tryptase levels

Question 42

what is neurogenic shock

Answer 42

form of distributive shock commonly follows spinal cord/ central trauma =loss of sympathetic tone =hypotension also = unopposed vagal tone= inappropriate bradycardia (this can be exacerbated by suction, PR exams as these stimulate the vagal nerve)

Question 43

what is the treatment for neurogenic shock

Answer 43

dopamine + vasopressors

Question 44

what is spinal shock

Answer 44

NOT SAME AS NEUROGENIC SHOCK | loss of spinal reflexes following a cord transection (can be temporary)

Question 45

cord transection above what level causes you to loose sympathetic function

Answer 45

T1/2

Question 46

why does the vagus nerve still work in a cord transection

Answer 46

as is a cranial nerve

Question 47

what are the reversible causes of cardiac arrest

Answer 47

4H's - hypovolaemia - hypoxia - hypokalaemia/ hyperkalaemia - hypothermia 4T's - tamponade - tension pneumothorax - thrombosis - toxins

Question 48

why are recoils important in CPR

Answer 48

release of intrathoracic pressure allows blood to be sucked into the chest before it is pushed out again

Question 49

what are the four rhythms you can get in cardiac arrest

Answer 49

shockable: VF (will not have a pulse), pulseless VT non shockable: pulseless electrical activity (could be normal rhythm but no pulse), asystole

Question 50

what usually causes pulseless electrical activity

Answer 50

hypovolaemia- will have sinus tachycardia on ECG but no pulse

Question 51

what usually causes asystole

Answer 51

(bad) severe hypoxia usually an end stage for other forms of arrest associated with significant brain damage if do resuscitate

Question 52

what usually causes the shockable rhythms of arrest

Answer 52

acute MI toxins electrolyte abnormalities