test 1

Question 1

What is the Purpose of Cardiopulmonary Bypass?

Answer 1

 Maintain adequate tissue perfusion so the energy supply versus demand equality is maintained even when many of the normal physiological mechanisms are impaired or non-functional and thus ensure full return of pre-operative function to all organ systems

Question 2

What normal physiological functions or mechanisms are changed or impaired during bypass?

Answer 2

• arterial BP
• arterial vascular tone
• blood viscosity
• CBV
• coagulation
• distribution of blood flow
• fluid balance
• hematocrit
• hematology
• immune response
• pulsatility
• temp
• systemic blood flow
• venous BP
• venous vascular tone

Question 3

How can we monitor the patient’s physiological status?

Answer 3

• acid base status
• arterial blood gases
• blood pressure
• cardiac electrical activity
• CO/BF
• cerebral function
• coagulation status
• electrolyte concentration
• filling pressure
• hematologic status
• level in reservoir
• muscle activity
• O2 consumption / delivery
• renal function
• temp

Question 4

what is the overall goal of perfusion?

Answer 4

• Supply the metabolic need of each tissue according to its demand.

Question 5

flow rates can be calculated in two ways:

Answer 5

 Body wt. (mls / min / kg)

 Cardiac index (L / min / m2)

Question 6

Average flow at normothermia (37 degrees) for adults (body weight and cardiac index)

Answer 6

Body weight: 60 to 70 mls/min/kg

CI: 2.2 to 2.6 L/min/m2

Question 7

Average flow at normothermia (37 degrees) for pediatrics (body weight and cardiac index)

Answer 7

Body weight: 80 to 100 mls/min/kg

CI: 2.4 to 2.8 L/min/m2

Question 8

Average flow at normothermia (37 degrees) for neonates (body weight and cardiac index)

Answer 8

Body weight: 120 to 150 mls/min/kg

CI: 3.0 to 3.4 L/min/m2

Question 9

Maintain minimum mean arterial pressure of

Answer 9

 > 50 mmHg

Question 10

Normothermia BP range of 50-80 mmHg

Answer 10

 Necessary for proper organ function

Question 11

what happens when Decreased perfusion pressures < 50 mmHg

Answer 11

 Cerebral injury / kidney function reduced

Question 12

what happens when Increased perfusion pressures > 90 mmHg

Answer 12

 Increased intracranial pressures
 Excessive blood return to heart
 Fluid shifts create edema
 Increased SVR may decrease tissue perfusion

Question 13

Normal SvO2

Answer 13

 > 70%

- O2 extracted from the arterial blood

Question 14

Factors Affecting SvO2

Answer 14

 Oxygen consumption
 Hemoglobin (hematocrit)
 Blood flow
 Temperature
 Level of anesthesia
 Anything that affects oxygen consumption

Question 15

Normal Urinary output on bypass

Answer 15

 .5 to 1 mls / kg / hr

Question 16

Acid-Base status shows

Answer 16

 May not indicate metabolic acidosis

Question 17

Normal pH, pCO2, bicarb, lactate

Answer 17

 pH: 7.35 – 7.45
 pCO2: 32 – 42 mmHg
 Bicarbonate: 2.2 – 2.4 mEq/Liter
 Lactate: < 2.0 mmole/Liter

Question 18

should you give a vasoactive drug first when BP is high or low?

Answer 18

• No

- Calculate the SVR to see if it is normal or not

Question 19

Is accurate simulation of normal physiology required during bypass?

Answer 19

• Yes
• keeping the normal values during bypass is important for better outcomes
• trending toward normal values of the specific patient

Question 20

What might cause inadequacy of perfusion?

Answer 20

1) venous cannulae
2) a lot of urine output
3) bleeding (especially bleeding unnoticed)

Question 21

When should perfusion be deemed inadequate?

Answer 21

• when the numbers say it

Question 22

What are the signs of inadequate perfusion?

Answer 22

• SvO2 is lower than 70%