Lecture 7: Shock (Exam I)

Question 1

For a normal person, how much can CO increase when needed?
What if the person trains?
What if the person is a world-class athlete?

Answer 1

• 23 - 25 L/min (400% increase)
• 30 - 35 L/min
• 40 - 45 L/min (600% increase)

Question 2

What expands cardiac reserve?
What diminishes it?

Answer 2

• Exercise expands cardiac reserve whilst pathology diminishes it.

Question 3

What two disease processes result in no cardiac reserve?

Answer 3

• Severe valvular disease
• Severe MI

Question 4

Describe what is occurring in this graph.

Answer 4

• A myocardial infarction has detrimentally impacted someone’s cardiac output curve resulting in A.
• B - E are body’s attempt to maintain CO by increasing volume (RAP).
• F is eventual fluid overload resulting in worsening CO & death.

Question 5

In the figure below, which state would pulmonary edema be most likely to develop in?

Answer 5

F

Question 6

Describe what is occurring in the graph below.

Answer 6

• Severe MI leads to inadequate CO initially.
• Inadequate CO is overcome with volume retention and autonomic compensation.
• Either recovery of cardiac tissue or pharmaceutical help.

Question 7

What curve shift would be seen from a digoxin-treated heart post severe myocardial infarction?

Answer 7

Left shift

Question 8

Can MAP be utilized alone to determine tissue perfusion? Why or why not?

Answer 8

Gap between MAP and CO demonstrates lack of tissue perfusion despite decent MAP.

Question 9

What is the gold standard for CO measurement? What are other ways it can be measured?

Answer 9

• Swan-Ganz catheter
• Flo-track (meh)
• Blood gasses
• Manual CO w/ cold injectate
• SvO₂
• Impedance changes
• Echocardiogram

Question 10

When assessing cardiac output via manual cold saline injectate, what would a more diluted sample at the sensor indicate?

Answer 10

• A higher CO

slow dilution = ↓CO
fast dilution = ↑CO

Question 11

What is the formula for the Fick equation?

Answer 11

CO = (O₂ absorbed per min by lungs mL/min)
÷
(Arteriovenous O₂ difference mL/dL of blood)

Question 12

How many mL/dL of O₂ return to the heart from systemic circulation?

Answer 12

• 15 mL/dL

Question 13

How many mL/dL of O₂ leave the heart?

Answer 13

• 20 mL/dL

Question 14

Calculate cardiac output from the following parameters:
- V̇O₂ = 240 mLO₂
- Arterial O₂ = 20 mLO₂
- Venous O₂ = 14 mLO₂

Answer 14

4 L/min

Question 15

What is V̇O₂?
How is it measured?

Answer 15

• O₂ absorbed per minute by the lungs.
• Via spectrometer (gas in vs gas out)

Question 16

How does coronary ΔO₂ (essentially O₂ consumption) compare to that of systemic?

Answer 16

• Coronary consumption of O₂ is much greater than that of systemic with ΔO₂ = 15mL/dL

Question 17

Below is a CO measurement obtained from ultrasonic flowmeter. What is indicated by the green circle?

Answer 17

• Retrograde perfusion as the aortic valve closes funneling blood into the coronary arteries.

Question 18

Below is a CO measurement obtained from ultrasonic flowmeter. What general concept is important to note from this graph?

Disregard the green circle for this question

Answer 18

Pulsatile nature of CO (CO isn’t a steady state of 5 L/min, its formed from pulses up to 20 L/min with periods of ~ 0 L/min).

Question 19

When is an echocardiogram most useful in the assessment of cardiac output?

Answer 19

• Best for monitoring changes in CO over time.

Question 20

How many heart beats are in a normal respiratory cycle?

Answer 20

• 8 beats per respiratory cycle.

Question 21

What is the normal pulse pressure variation noted with the respiratory cycle called?

Answer 21

• Pulsus paradoxus

Question 22

What would a systolic blood pressure drop of greater than 10mmHg during inspiration indicate?

Answer 22

• Hypovolemic status (the patient needs a bolus or passive leg raise).

Question 23

Increasing preload will have what effect on PPV (pulse pressure variation)?

Answer 23

• ↑ preload = ↓ PPV

Question 24

What component of shock results in direct cardiac depression?

Answer 24

• Toxin release from tissue ischemia

Question 25

What occurs when capillaries become ischemic?

Answer 25

• Necrosis via lysosomes resulting in loss of colloids and edema.

Question 26

How is capillary necrosis secondary to shock treated?

Answer 26

1. Prevention
2. Steroids (↓necrosis)

Question 27

What are the treatment options for shock?

Answer 27

• Pressors (preserving perfusion to VRGs)
• Inotropes
• Steroids
• Fluid replacement
• Colloids
• Positioning
• O₂ (not super helpful, Hgb is usually saturated)

Question 28

What will eventually happen with colloid replacement for shock?

Answer 28

• Colloid overload will stress the kidneys and eventually just become excreted.

Question 29

What stimulates SNS reflexes?

Answer 29

• Poor perfusion to the medulla of the brain stem.

Question 30

What organ is a reservoir of Hgb?
Where is the largest reservoir of blood?

Answer 30

• Spleen
• GI tract

Question 31

What is the strongest CV reflex in the body?

Answer 31

• CNS Ischemic Response - all blood vessels squeeze to maintain perfusion to the brainstem.

Question 32

Which capillary pressure forces favor filtration?

Answer 32

• P_CAP
• P_ISF
• π_ISF

Question 33

Which capillary forces disfavor filtration?

Answer 33

π_CAP

Question 34

How would arterial NFP (net filtration pressure) be calculated?

Answer 34

NFP = (P_CAP + P_ISF + π_ISF) - π_CAP

Question 35

Which capillary force changes when talking about the capillary forces on the venous end of the capillary beds?
How does it change?
How does this affect NFP?

Answer 35

• P_CAP changes from 30 to 10.
• NFP becomes -7. Filtration becomes disfavored