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Hemodynamics > Hemodynamics: Shock definition and recognition > Flashcards

Hemodynamics: Shock definition and recognition Flashcards

1. Definitions of Shock 2. Categorization of shock states according to cardiac output 3. Analyzation of available tools to diagnose shock.

1
Q

What is the classic definition of shock?

A

When tissue oxygen demand is not coupled with oxygen supply.

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2
Q

What is a modern definition of shock?

A

A condition implying an altered oxygen utilization at the cellular level.

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3
Q

What is the end result of uncorrected shock?

A

Arrest of all metabolic functions, and multiple organ failure.

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4
Q

What is DO2, and how is it expressed as a formula?

A

DO2 is the amount of oxygen delivered by the heart to the cells. DO2 is equal to the cardiac output times the arterial oxygen content and is expressed as DO2 = CO x CaO2.

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5
Q

What is SaO2?

A

The arterial O2 saturation.

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6
Q

What is PaO2?

A

The arterial partial pressure of oxygen.

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7
Q

What is VO2?

A

VO2 is the amount of oxygen taken up by the tissues during a cardiac cycle.

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8
Q

What is SvO2?

A

The mixed venous oxygen saturation

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9
Q

What is the oxygen extraction rate and how is it expressed?

A

The oxygen extraction rate is the difference between arterial and mixed venous saturation (SaO2 - SvO2) and is expressed as O2ER.

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10
Q

What are the two main mechanisms responsible for the establishment of shock?

A
  1. The reduction of the oxygen amount that is available to the cells.
  2. The inability of the cells to use the oxygen delivered by the capillary blood flow.
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11
Q

What are the main two parameters that can classify shock states?

A
  1. CO
  2. SvO2
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12
Q

What is a normal value for SvO2

A

65-70%

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13
Q

What are the four main types of shock?

A
  1. Hypovolemic
  2. Cardiogenic
  3. Obstructive
  4. Distributive
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14
Q

What is the common problem in low-CO shock?

A

The inadequacy of oxygen transport.

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15
Q

Which type of shock is most common in trauma patients?

A

Hypovolemic shock

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16
Q

Hypovolemic shock is attributable to?

A

Internal/external fluid loss

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17
Q

Is CO increased or decreased in hypovolemic shock? Why?

A

Decreased, due decreased preload.

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18
Q

Is SvO2 increased or decreased in hypovolemic shock? Why?

A

Decreased, due to increased extraction rate in response to decreased DO2.

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19
Q

Are cardiac filling pressures high or low in hypovolemic shock?

A

Low

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20
Q

Is SVR high or low in hypovolemic shock?

A

High

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21
Q

Are end-diastolic volumes high or low in hypovolemic shock?

A

Low

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22
Q

What are the echocardiography signs for hypovolemic shock?

A
  1. Small volume of the cardiac chambers.
  2. Normal or high contractility
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23
Q

What are the clinical signs of hypovolemic shock?

A
  1. Cold and pale skin and extremities
  2. Tachycardia
  3. Increased respiratory rate
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24
Q

Which type of shock derives from ventricular failure that is caused by a host of different pathological conditions?

A

Cardiogenic shock

25
Q

Which conditions can lead to cardiogenic shock?

A
  1. Myocardial infarction
  2. End-stage cardiomyopathy (HF)
  3. Arrhythmias
  4. Valvular heart disease
  5. Myocarditis
26
Q

Is CO increased or decreased in cardiogenic shock? Why?

A

Decreased, due to impaired contractility.

27
Q

Is SvO2 low or high in cardiogenic shock? Why?

A

Low, due to increased extraction rate.

28
Q

Are cardiac filling pressures increased or decreased in cardiogenic shock? Why?

A

Increased, due increased end-diastolic volume caused by the inability of the failing heart to empty cardiac chambers at the end of systole.

29
Q

Is SVR high or low in cardiogenic shock?

A

High

30
Q

What are the echocardiography signs of cardiogenic shock?

A
  1. Dilated cardiac chambers
  2. Impaired contractility
31
Q

What are the clinical signs of cardiogenic shock?

A
  1. Cold extremities
  2. Dyspnea
  3. Peripheral edema
  4. JVD
32
Q

What is the cause of obstructive shock?

A

An obstruction, such pericardial tamponade, pulmonary embolism, or tension pneumothorax.

33
Q

Is CO increased or decreased in obstructive shock? Why?

A

Decreased, due to low preload (tamponade, tension pneumothorax), or because there is an obstruction to the ventricle efflux as with pulmonary embolism.

34
Q

Is SvO2 low or high in obstructive shock?

A

Low, due to increased extraction fate.

35
Q

In obstructive shock, are cardiac filling pressures increased or decreased? Why?

A

Increased, due to different underlying mechanisms including the increase in pleural pressure seen in tension pneumothorax, the rise of end-diastolic volume as seen in PE, or the increased diastolic compliance of cardiac tamponade.

36
Q

Is SVR low or high in obstructive shock?

A

High

37
Q

What are the echocardiography signs of obstructive shock due to pericardial tamponade?

A
  1. Pericardial effusion
  2. Small right and left ventricles
38
Q

What are the echocardiography signs of obstructive shock secondary to tension pneumothorax?

A

Small cardiac chambers

39
Q

What are the echocardiography signs of obstructive shock as seen in pulmonary embolism?

A

Small left ventricle that is compressed by dilated right ventricle

40
Q

What are the clinical signs of obstructive shock?

A
  1. JVD
  2. Dyspnea
  3. Increased respiratory rate
  4. Tachycardia
41
Q

What is the main problem in high-CO shock states such as septic shock or anaphylactic shock?

A

The periphery, as DO2 is preserved but extraction rate is impaired.

42
Q

What is the most common type of shock in ICU patients?

A

Distributive shock

43
Q

What characterizes distributive shock?

A
  1. Systemic vasodilation due to a release of inflammatory factors during sepsis/anaphylaxis or a decrease in sympathetic tone in neurogenic shock.
44
Q

Is CO high or low in distributive shock?

A

high, due the hyperdynamic state caused by the decrease in SVR.

45
Q

In distributive shock, is SvO2 high or low?

A

High, due to a decrease in extraction rate in the periphery and to the increase in DO2 related to a high CO.

46
Q

What are the echocardiographic signs seen in distributive shock?

A
  1. Normal cardiac chambers
  2. Preserved contractility (except in septic cardiomyopathy)
47
Q

What are the clinical signs of distributive shock?

A
  1. Mottled skin
  2. Tachycardia
  3. Elevated or reduced body temperature
  4. Dyspnea
48
Q

What is the most common, but not necessarily the first, sign of shock?

A

Hypotension

49
Q

List several diagnostic tools used in the recognition of shock?

A
  1. Clinical signs
  2. Lactate
  3. ScvO2, SvO2
  4. CO2gap
  5. Respiratory quotient
  6. Echocardiography
50
Q

What is the first step of individuating a patient at risk or already in shock?

A

Clinical evaluation

51
Q

Based on the latest guidelines, a systolic arterial pressure less than 100, respiratory rate above 22, and altered mental status is indicative of?

A

Sepsis

52
Q

Why would MAP remain normal in shock states of low CO? What does this tell you?

A

Increased SVR as a compensatory mechanism of the body. It implies that hypotension is not always a clinical sign in early shock.

53
Q

What is the definition of hypotension?

A

SBP < 90, or MAP < 65

54
Q

Which chemical has increased production in conditions of anaerobic metabolism and is a good indicator of shock?

A

Lactic acid

55
Q

Lactic acid greater than which value is associated with increased mortality?

A

> 2 mmol/L

56
Q

Which two parameters are indicative of peripheral extraction rate and can be used to guide therapies of patients in shock?

A

ScvO2, SvO2

57
Q

Which shock diagnostic parameter is inversely correlated with CO, so that an increase in it is indicative of inadequate CO?

A

CO2gap

58
Q

At what level can CO2gap be an alert sign indicating low cardiac output with peripheral CO2 stagnation?

A

> 6 mmHg

Hemodynamics (2 decks)

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