12.6 D

Question 1

What is the Fick Method?

Answer 1

the gold standard for measuring cardiac output

Question 2

What does the Fick Method essentially say?

Answer 2

the amount of blood flowing through the systemic circulation (cardiac output) is equal to the rate of oxygen consumption by the systemic organs divided by the difference in oxygen concentration in arterial and venous blood

Question 3

Under normal conditions, how much oxygen is in arterial blood?

Answer 3

20 mL oxygen per 100 mL blood

Question 4

Under normal conditions, how much oxygen is in venous blood?

Answer 4

15 mL oxygen per 100 mL blood

Question 5

According to Fick’s law, if blood flow to the organs is increased but oxygen consumption remains constant, what must be true?

Answer 5

less oxygen will be removed form each 100 mL of blood

Question 6

According to Fick’s law, if blood flow to the organs remains constant but oxygen consumption increases, what must be true?

Answer 6

more oxygen will be removed from each 100 mL of blood

Question 7

What is the Fick Equation?

Answer 7

CO = (consumption)/(arterial O2 content - venous O2 content)

Question 8

Because of clinical challenges, what is the modified Fick Equation?

Answer 8

CO = (oxygen uptake)/(arterial O2 content - venous O2 content)

Question 9

What is the thermal dilution technique?

Answer 9

an indirect Fick method used to measure cardiac output by injecting cold saline and measuring temperature downstream with a thermocouple

Question 10

The magnitude of a shunt is equal to what?

Answer 10

the difference between pulmonary blood flow and cardiac output

Question 11

What happens to the blood O2 content in the area where a shunt originates?

Answer 11

it isn’t altered

Question 12

What is the role of renin?

Answer 12

to increase circulating levels of angiotensin II

Question 13

What is angiotensin II?

Answer 13

a potent vasoconstrictor

Question 14

In addition to being a vasoconstrictor, angiotensin II triggers release of what substance?

Answer 14

aldosterone

Question 15

What is aldosterone?

Answer 15

a molecule that promotes resorption of sodium and water from the kidney

Question 16

What happens to total blood volume in an individual with a ventricular septal defect?

Answer 16

it increases because low LV SV triggers release of aldosterone

Question 17

How does blood volume in the left ventricle change with a interventricular shunt?

Answer 17

it is initially decreased but the resulting decrease in MAP and release of aldosterone restores and even raises it

Question 18

Why does the left ventricle hypertrophy when there is an interventricular shunt?

Answer 18

because aldosterone raises the overall blood volume to compensate

Question 19

Describe the MEA of a newborn compared to a healthy adult?

Answer 19

newborns have experience right ventricular hypertrophy and a right axis deviation at birth because of the high resistance to flow in their lungs

Question 20

What happens to end diastolic volume of the left ventricle in someone with patent ductus arteriosus?

Answer 20

it is increased

Question 21

Shunts always result in what compensation? How does this affect the heart?

Answer 21

• increase in blood volume

- hypertrophy of the left atrium and ventricle, and often the right ventricle