2. Oxygen Delivery & Shock

Question 1

What is CaO₂?

Answer 1

Concentration of arterial oxygen (mL/dL)

Question 2

What is Hgb?

Answer 2

hemoglobin concentration (mg/dL)

Question 3

What is SaO₂?

Answer 3

arterial oxygen saturation (%)

Question 4

What is PaO₂?

Answer 4

arterial oxygen pressure (mmHg)

Question 5

What is normal CaO₂?

Answer 5

17–20 mL/dL

Question 6

What is the primary contributor to arterial oxygen content?

Answer 6

Hgb and SaO₂ (oxygen bound to hemoglobin)

Question 7

What are the 5(+1) factors that contribute to oxygen delivery?

Answer 7

1. Hgb
2. SaO₂
3. CO
4. VO₂
5. Hgb oxygen affinity
6. microcirculatory regulation

Question 8

Why are the 5(+1) factors that impact oxygen delivery and not just 5?

Answer 8

We cannot change microcirculatory regulation

Question 9

What is DO₂?

Answer 9

delivery of oxygen to tissues (mL/min/m²)

Question 10

What is CO?

Answer 10

cardiac output (L/min/m²)

Question 11

What is normal DO₂?

Answer 11

550–650 mL/min/m²

Question 12

What are the 2 components that contribute to CO?

Answer 12

HR and SV

Question 13

What is CvO₂?

Answer 13

concentration of venous oxygen (mL/dL)

Question 14

What is SvO₂?

Answer 14

venous oxygen saturation (%)

Question 15

What is PvO₂?

Answer 15

venous oxygen pressure (mmHg)

Question 16

What is a normal CvO₂?

Answer 16

15 mL/dL

Question 17

What is the primary contributor to venous oxygen content?

Answer 17

Hgb and SvO₂ (oxygen bound to hemoglobin)

Question 18

What is VO₂?

Answer 18

oxygen consumption by tissues (mL/min/m²)

Question 19

What is normal CaO₂ – CvO₂?

Answer 19

4–6 mL/dL

Question 20

What is normal VO₂?

Answer 20

115–165 mL/min/m²

Question 21

Since humans cannot store oxygen, the amount of oxygen consumed is the difference between _______ and __________.

Answer 21

CaO₂ and CvO₂

Question 22

An SvO₂ < ____% is incompatible with life.

Answer 22

50%

Question 23

What factors may cause Hgb to have an increased affinity for oxygen?

Answer 23

• decreased temperature
• decreased 2-3 DPG
• alkalosis

Question 24

What factors may cause Hgb to have a reduced affinity for oxygen?

Answer 24

• increased temperature
• increased 2-3 DGP
• acidosis

Question 25

At a cellular level, oxygen diffusion is determined by what?

Answer 25

pressure gradients

Question 26

How can utilization of oxygen can be estimated?

Answer 26

SvO₂

Question 27

Describe stage 1 of shock.

Answer 27

- BP normal - HR/RR elevated - mild respiratory alkalosis - anxiety/agitation

Question 28

Describe stage 2 of shock.

Answer 28

- BP low - obvious hypoperfusion (oliguria, AMS) - metabolic acidosis due to lactate

Question 29

Describe stage 3 of shock?

Answer 29

- BP very low - severe lactic acidosis - cardiac dysfunction - arrhythmia, tachycardia, ischemia - intubation required - high mortality

Question 30

If a patient survives stage 3 shock, what is likely to occur?

Answer 30

multi-organ failure

Question 31

What is the goal of early management of shock?

Answer 31

restore oxygenation

Question 32

What 3 steps are taken to restore oxygenation in shock?

Answer 32

- fluid resuscitation - vasopressors/inotropes - blood products

Question 33

What are the steps to discovering the etiology of shock?

Answer 33

- H&P | - lab data

Question 34

ANS compensation of shock is mediated how?

Answer 34

carotid and aortic arch baroreceptors

Question 35

ANS compensates for shock by releasing ______ in response to _______.

Answer 35

- catecholamines (EPI, NE) | - BP reduction

Question 36

What are the 3 major effects of ANS compensation?

Answer 36

1. Arteriolar vasoconstriction (↑ SVR) 2. Reduction in venous capacitance (↑ venous return) 3. Increase in heart rate/contractility

Question 37

What are the hormonal responses to shock?

Answer 37

Increased serum cortisol leads to - water retention - sodium retention - insulin resistance and hyperglycemia

Question 38

Each organ system can autoregulate blood flow. (T/F)

Answer 38

True

Question 39

What are the major categories of shock?

Answer 39

- hypovolemic - cardiogenic - distributive - neurogenic - obstructive

Question 40

What is always the problem with shock, no matter the category

Answer 40

poor tissue oxygenation

Question 41

What is the main disturbance with hypovolemic shock?

Answer 41

reduction in intravascular volume

Question 42

What is the prototype of hypovolemic shock?

Answer 42

hemorrhagic shock

Question 43

What is the main treatment for hypovolemic shock?

Answer 43

volume restoration

Question 44

What is the main disturbance with cardiogenic shock?

Answer 44

reduction in pump function

Question 45

What is the prototype of cardiogenic shock?

Answer 45

post-MI

Question 46

What is the main treatment of cardiogenic shock?

Answer 46

- careful volume restoration - correction of underlying problem - inotropic support

Question 47

What is the main disturbance of distributive shock?

Answer 47

Loss of microcirculatory autoregulation (compounded by increased metabolic demand)

Question 48

What is the prototype of distributive shock?

Answer 48

sepsis

Question 49

What is the main treatment of distributive shock?

Answer 49

- volume restoration | - vasopressor support

Question 50

What is the main disturbance of neurogenic shock?

Answer 50

loss of sympathetic tone

Question 51

What is the prototype of neurogenic shock?

Answer 51

spinal cord trauma

Question 52

What is the main treatment of neurogenic shock?

Answer 52

vasopressor/inotropic support

Question 53

What is the main disturbance of obstructive shock?

Answer 53

- impaired venous return | - decreased CO

Question 54

What is the prototype of obstructive shock?

Answer 54

- tension pneumothorax - pericardial tamponade - massive pulmonary embolism

Question 55

What is the treatment of obstructive shock?

Answer 55

correction of underlying physiology