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Cardio Week 2 > Lecture 20: Shock and Inadequate Circulatory States > Flashcards

Lecture 20: Shock and Inadequate Circulatory States Flashcards

1
Q

What is the difference between shock and heart failure?

A

Shock is acute while heart failure is result of chronic processes

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2
Q

What is shock?

A

INADEQUATE delivery of oxygen and other metabolic substrates to tissue
Acute circulatory collapse

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3
Q

What are characteristics of shock?

A

May result from a variety of diverse pathophysiologic processes
Results in irreversible organ dysfunction if prolonged
High mortality despite therapy

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4
Q

What are the stages of shock?

A
  1. Pre-shock
  2. Frank shock
  3. end organ failure
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5
Q

Can you find shock by listening to the lungs or BP?

A

No

Shock is “buried in the tissues” which means you need to measure oxygen delivery to tissues

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6
Q

What are the principal determinates of tissue perfusion?

A
  1. CO
  2. SVR
  3. distribution of blood flow to vital organs
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7
Q

What are the equations pertaining to shock?

A 
CO = SV x HR
MAP = CO x SVR + CVP (central venous pressure)
MAP = DBP + 1/3(SBP-DBP)
DBP = diastolic
SBP = Sytolic
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8
Q

What regulates organ perfusion?

A
  1. large arteries
  2. arterioles provide resistance and control blood flow
  3. systemic vascular resistance regulated by
    i. SNS, baroreceptors, chemoreceptors,
    ii. local autoregulation
    iii. human control (RAS)
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9
Q

What is oxygen consumption determined by?

A 
Varies tremendously with different shock states
O2 consumption affected by:
1. physical activity
2. work of breathing
3. endogenous hormones
4. exogenous factors
5. fever
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10
Q

How do we use the PA (pulm artery) catheter to measure for shock?

A
  1. Right heart pressures (RA and RV)
  2. Pulm artery wedge pressure (PAWP) as a measure of LV diastolic pressure (LVED volume)
  3. Measure cardiac output via Fick or thermodilution methods
  4. Calculate SVR using measured pressures and CO
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11
Q

What is the wedge pressure?

A

Pressure seen by PA catheter

Indirect measure of preload

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12
Q

What are the shock states?

A
  1. Hypovolemic
  2. Cardiogenic
  3. Distributive
  4. Obstructive
    Processes of shock can be interchangeable
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13
Q

What are the 4 measurements used to assess shock?

A
  1. RA/RV pressure
  2. PAWP
  3. CO
  4. SVR
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14
Q

What is the distinguishing feature of cardiogenic shock?

A

Low cardiac output

RA/RV, PAWP and SVR are all increased

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15
Q

What is the distinguishing feature of hypovolemic shock?

A 
Low RA/RV, PAWP and CO
Increased SVR (to compensate for less volume)
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16
Q

What is the distinguishing feature of distributive shock?

A

Low SVR
High CO
Normal RA/RV, PAWP (heart is fine but systemic vascular resistance is not high enough to perfuse tissue)

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17
Q

What is the distinguishing feature of obstructive shock?

A

High RA/RV pressure and High SVR
Low CO and Low PAWP
Obstruction in PA

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18
Q

What are the characteristics of hypovolemic shock?

A

Blood loss or volume depletion
Primary pathophysiologic derangement is DECREASED PRELOAD
Resultant decreased stroke volume and cardiac output

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19
Q

What causes hypovolemic shock?

A

Something that causes blood loss or volume depletion (dehydration)

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20
Q

What is the compensation for hypovolemic shock?

A

Maintain adequate cardiac output
Reflex SNS activation
Increased heart rate
Increases SVR

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21
Q

What happens when you hemorrhage a certain amount of blood?

A

15% volume loss = tachycardia
25% volume loss = orthostatic hypotension
40% volume loss = hypotension and oliguria
>40% volume loss = obtundation and circulatory collapse

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22
Q

What is obtundation?

A

A greatly reduced level of consciousness

23
Q

What are the characteristics of distributive shock?

A

This is what we think of in SEPTIC SHOCK
Endogenous and exogenous factors promote excess VASODILATION with MALDISTRIBUTION of blood flow
Impaired O2 delivery to tissues
Shunting of blood away tissues because blood goes through metarterioles (not vasoconstriction of arterioles to control blood flow)
Wastefully increased cardiac output!

24
Q

What are the two types of shock?

A
  1. Early septic shock
    • warm shock
  2. Late septic shock
    • cold shock
25
Q

What are the characteristics of early/warm shock?

A
  1. Decreased SVR

2. increased CO (due to decreased afterload and increased HR)

26
Q

What are the characteristics of late/cold shock? Significance?

A
  1. increased SVR
  2. Decreased filling pressure
  3. Decreased CO
    Can be confused with cardiogenic shock because of low CO…latest manifestation of sepsis
27
Q

What are the causes of distributive shock?

A
  1. sepsis
  2. toxic shock syndrome
  3. post operative state
  4. pancreatitis
  5. trauma
  6. Adrenal crisis (Addison’s)
  7. Hypothyroid crisis (myxedema)
  8. Anaphylaxis
28
Q

What is sepsis syndrome?

A 
Constellation of clinical findings that identifies an inflammatory process with multi-system involvement
Mediators like
	i. endotoxin
	ii. interleukins
	iii. TNF
29
Q

What mediates sepsis syndrome?

A
  1. endotoxin = LPS contained in cell wall of gram negative bacteria
  2. Interleukins and TNF
    • released into systemic circulation activating immune cells to produce widespread endothelial damage
30
Q

What are the characteristics of cardiogenic shock?

A

Usually results as a consequence of massive MI
LOSS of pump function, in continuum with heart failure
>40% loss of LV myocardium
High mortality regardless of treatment
Decreased CO results in elevated filling pressures with COMPENSATORY INCREASE in SVR

31
Q

What is the compensatory mechanism for cardiogenic shock?

A

Increased SVR and HR

32
Q

Why is SVR increased?

A

Because of SNS compensatory mechanisms for decrease in CO

33
Q

What is the vicious cycle of cardiogenic shock?

A

LV contractile dysfunction (from ischemia)  decreased CO  decreased coronary perfusion  LV ischemia  more LV contractile dysfunction
Need to break cycle to treat cardiogenic shock

34
Q

How do you treat cardiogenic shock?

A

Revascularization of the patient in order to relieve pump dysfunction

35
Q

What are examples of cardiogenic shock examples in addition to ischemia?

A
  1. pump failure
  2. acute valvular disease
  3. acute mechanical complication of MI
  4. Tachy or bradyarrhythmia (extreme abnormal heart rhythms)
36
Q

What are the characteristics of obstructive shock?

A
  1. results from obstruction to right heart flow, thereby reducing LV preload
  2. Mimics hypovolemic shock with regards to LV filling indices, SV, CO and SVR but you see ELEVATED RIGHT HEART PRESSURES
    Example: acute pulmonary embolism with obstruction of portion of PA, acute PHTN with right heart failure
    -Think of it as emboli consequence
    Low LV preload but high RV preload
37
Q

What is the relationship between cardiac tamponade and obstructive shock?

A

Cardiac tamponade causes a type of obstructive shock

38
Q

What is pericardial tamponade?

A

What happens when fluid accumulates in pericardium

39
Q

What are the two types of pericardial tamponade?

A
  1. acute tamponade

2. Chronic tamponade

40
Q

What are the characteristics of acute tamponade?

A

trauma, LV rupture or aortic dissection will allow small amt of fluid to increase intra-pericardial pressure with acute tamponade (150-200cc)

41
Q

What are the characteristics of chronic tamponade?

A

When fluid accumulates more slowly, eventually limiting cardiac filling…up to 2000cc

42
Q

What are the consequences of pericardial tamponade?

A

Venous return compromised throughout diastole, when cardiac volume and pericardial pressures are maximal (does not allow that shit to refill)
Cardiac filling is compromised!
Decreased LV preload and not RV preload because septum bulges to the left upon inspiration (in order to accommodate increased inspiratory venous return)

43
Q

What is the pulsus paradox?

A

Inspiratory decrease in thoracic pressure transmitted to the pericardium and right heart
-increases venous return from cava
INCREASED RIGHT HEART FILLING
Distension of the right ventricle is limited to the interventricular septum which bulges to the left, contributing to decreased filling of the left ventricle
Results in lower LV preload and stroke volume with inspiration
Can measure BP drop with cuff
Pulsus paradox = lower SBP with inspiration

44
Q

What is the relationship between pulsus paradox and cardiac tamponade?

A

Pulsus paradox is EXAGGERATED in cardiac tamponade

45
Q

What kind of cardiac tamponade is it when the fluid is over 300 cc?

46
Q

What kind of cardiac tamponade is it when the fluid is 150-200cc?

47
Q

What happens to velocity through mitral valve in inspiration and expiration?

A

Velocity decreases upon inspiration because that increases RV venous return and less blood to LV

48
Q

What happens when O2 delivery is inadequate?

A
  1. anaerobic metabolism
  2. glycolysis and lactate is produced
  3. inefficient use of energy
  4. cell death
49
Q

What are the cellular abnormalities in shock?

A
  1. damage to cell membranes
  2. mitochondrial damage
  3. Lysosomal enzyme release
  4. Complement activation
  5. Eventual cell death
50
Q

What types of organ dysfunction can result from shock?

A
  1. skeletal muscle rhabdomyolysis
  2. mucosal damage to GI tract
  3. ischemic acute renal tubular necrosis
  4. Alveolar injury in lungs, capillary injury
  5. Impaired hepatic detoxification
  6. myocardial depression
51
Q

What are the characteristics of preshock?

A
  1. Early “compensated” stage
  2. When reflex sympathetic activation leads to
    i. tachycardia
    ii. increased contractility
    iii. peripheral vasoconstriction
  3. BP and CO initially maintained
52
Q

Is shock characterized by low blood pressure?

A

NO IT IS NOT
That is only distributive shock ninja…that is the most commonly thought of, but hypovolemic, cardiogenic, and obstructive shock all have high blood pressures, bitch

53
Q

What are the characteristics of frank shock?

A
  1. When the regulatory mechanisms are overwhelmed
  2. Corresponds to
    i. 25% reduction in systemic blood volume
    ii. large fall in cardiac index (<2.5 L/min/M^2)
  3. Signs of end-organ dysfunction are just STARTING to appear
  4. Tachypnea, tachycardia, low BP, oliguria
54
Q

What are the characteristics of end organ failure?

A
  1. Urine output declines due to ischemic acute tubular necrosis
  2. Altered mental status with eventual coma
  3. Lactic acidosis (which will impair catecholamine function and further decrease CO)
  4. multi system organ failure
  5. death

Cardio Week 2 (11 decks)

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