Bruce's Hypothermia Final prep

Question 1

4 Physiologic impacts of Hypothermia.

Answer 1

↓ metabolic rate
↓oxygen consumption
↓ enzymatic activity
– prolonged reaction rates

Question 2

Reduction of 1 degree C =

Answer 2

metabolic rate reduction of 5%

Question 3

Describes the relationship between biochemical reaction rates and and temperature

Answer 3

Q10

Question 4

Total body oxygen consumption has a rate of

Answer 4

2

Question 5

If you lower the temperature by 10 deg you will reduce oxygen consumption by ?

Answer 5

50%

Question 6

5 Technical advantages of Hypothermia

Answer 6

↓blood flow 
↓ flow through collaterals 
– Improved operating conditions 
↓ fewer passes through circuit = Less trauma to blood  
↓ 3rd Spacing

Question 7

Mild Hypothermia

Answer 7

32-34 °C

Question 8

Moderate Hypothermia

Answer 8

28-32 °

Question 9

Profound Hypothermia

Answer 9

< 28 °C

Question 10

Deep Hypothermia for circulatory arrest

Answer 10

 ~18°C

Question 11

4 reasons to conduct deep hypothermic circulatory arrest?

Answer 11

•  Repair of complex congenital 
   cardiac lesions 
•  Aortic arch reconstruction / type 1 Aortic dissections.
•  Uncontrollable 
   hemorrhage 
•  When ever exsanguinous 
   surgical field is essential

Question 12

Pathophysiology of Hypothermia

Answer 12

•  Blood flow redistribution
•  Electrolyte imbalances
•  Catecholamine release
– increased SVR

Question 13

Gradient based on gas solubility to reduce bubble formation ? 

Answer 13

6°C

Question 14

Hyperthermia (temps > 37) linked to

Answer 14

poor cerebral outcomes

Question 15

Blood Gas Strategies during Hypothermia.

Alpha Stat :

Answer 15

 Maintain the PCO2 at 40 at 37°C

Question 16

Blood Gas Strategies during Hypothermia.

Ph Stat:

Answer 16

Maintain the PCO2 at 40 mmHg at the actual temperature.

Question 17

Temperature sensor in the human body?

Answer 17

• Anterior hypothalamus
• skin
• spinal cord

Question 18

Receptors in the skin, spinal cord, and abdomen stimulate what ?

Answer 18

Posterior hypothalamus to cause heat conservation by:

• Peripheral vasoconstriction
• Pilo Errection
• Vasodilation of the muscle bed > Shivering

Question 19

1 °C decrease in temp =

Answer 19

DO2 decrease by 5%

Question 20

Core temp has reached 32°C. what is the DO2

Answer 20

DO2 reduced by 25%

Question 21

Core temp has reached 28°C. what is the DO2

Answer 21

DO2 reduced by 50%

Question 22

5 ways to minimize cerebral damage?

Answer 22

• < 60 min circ arrest
• Slow uniform cooling
• Control of hyperglycemia
• Control of acid base management
• Use of cerebral perfusion techniques in prolonged arrest

Question 23

As temperature decreases what 3 things happen?

Answer 23

• CO2 becomes more soluble.
• PaCO2 decreases
• Ph increases

Question 24

Why might you observe an increase in reservoir volume after initiating CPB with cold arterial blood being pumped?

Answer 24

Hypothalamus orders the release of Epi & Nor-epi > peripheral vasoconstriction > Increased bloow flow into the deep arteries > increased volume in the reservoir.

Question 25

Deep hypothermia 18-28°C to Profound Hypothermia 0-18°C may lead to what ?

Answer 25

3rd spacing throughout the entire body

Question 26

Decreased core temp causes what to the kidneys?

Answer 26

-Increased urine production “Cold induced diuresis”

Question 27

Decreased core temp causes what to the electrolyte metabolism?

Answer 27

• Decreased effectiveness of the Na+ / K+ pump

- changes in cell membrane permeability

Question 28

Decreased core temp causes what to the Endocrine system?

Answer 28

Insulin secretion is blocked > decreased movement of glucose into the cell > Hyperglycemia for the duration of hypothermia.

Question 29

During rewarming, the brain rewarms much faster than any other tissue bed. This creates a risk for cerebral hyperthermia while other tissue beds are still rewarming. Monitor the following ?

Answer 29

Bladder temp &

Esophageal temp to 37°C

Question 30

Hypothalamus exerts ____ times as much influence on vasoactivity as does the skins thermoreceptors.

Answer 30

10 - 20