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Flashcards in Bruce's Hypothermia Final prep Deck (30)
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1

4 Physiologic impacts of Hypothermia.

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

2

Reduction of 1 degree C =

metabolic rate reduction of 5%

3

Describes the relationship between biochemical reaction rates and and temperature

Q10

4

Total body oxygen consumption has a rate of

2

5

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

50%

6

5 Technical advantages of Hypothermia

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

7

Mild Hypothermia

32-34 °C

8

Moderate Hypothermia

28-32 °

9

Profound Hypothermia

< 28 °C

10

Deep Hypothermia for circulatory arrest

 ~18°C

11

4 reasons to conduct deep hypothermic circulatory arrest?

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

12

Pathophysiology of Hypothermia

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

13

Gradient based on gas solubility to reduce bubble formation ? 

6°C

14

Hyperthermia (temps > 37) linked to

poor cerebral outcomes

15

Blood Gas Strategies during Hypothermia.
Alpha Stat :

 Maintain the PCO2 at 40 at 37°C

16

Blood Gas Strategies during Hypothermia.
Ph Stat:

Maintain the PCO2 at 40 mmHg at the actual temperature.

17

Temperature sensor in the human body?

-Anterior hypothalamus
-skin
-spinal cord

18

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

Posterior hypothalamus to cause heat conservation by:
-Peripheral vasoconstriction
-Pilo Errection
-Vasodilation of the muscle bed > Shivering

19

1 °C decrease in temp =

DO2 decrease by 5%

20

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

DO2 reduced by 25%

21

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

DO2 reduced by 50%

22

5 ways to minimize cerebral damage?

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

23

As temperature decreases what 3 things happen?

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

24

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

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

25

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

3rd spacing throughout the entire body

26

Decreased core temp causes what to the kidneys?

-Increased urine production "Cold induced diuresis"

27

Decreased core temp causes what to the electrolyte metabolism?

-Decreased effectiveness of the Na+ / K+ pump
- changes in cell membrane permeability

28

Decreased core temp causes what to the Endocrine system?

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

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 ?

Bladder temp &
Esophageal temp to 37°C

30

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

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