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Perf Tech II (exam 1) > Topic 5 - Hypothermia: physiology /clinical use > Flashcards

Topic 5 - Hypothermia: physiology /clinical use Flashcards

1
Q

Hypothalamus regulates -

A

vascular regulation

skeletal muscle activity

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2
Q

Hypothermia activates the Endocrine system’s – (2)

A

metabolic regulation

stress response

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3
Q

Hypothalmus senses cold where and causes?

A

sensed by thermoreceptors in the skin

  • causes hypothalamus to trigger sympathetic nervous system
  • vasoconstriction of skin vessels (to decrease heat loss)
  • vasodialtion of skeletal muscular beds (to produce heat when tensing shivering)
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4
Q

Can you shiver when you are paralyzed?

A

NO

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5
Q

Endocrine System increases what? (4)

A

Increases: Oxygen consumption, HR, CO, and BP

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6
Q

Temp range

- Mild hypothermia

A

32-35 C

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7
Q

Temp range

- Moderate hypothermia

A

28-31 C

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8
Q

Temp range

- Deep hypothermia

A

18-27 C

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9
Q

Temp range

- Profound hypothermia

A

<18 C

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10
Q

Hypothermia mechanism of protection (3)

A
  • reduction in metabolic rate and oxygen consumption (esp enzymatic reactions)
  • preservation of high-energy phosphate stores(use less=more availability)
  • reduction of excitatory neurotransmitter release due to ischemia(CNS protection)
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11
Q

The safe period of hypothermic CPB is ____ then the period predicted on the basis of __ ___ activity alone.

A

longer

reduced metabolic activity

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12
Q

reduction of excitatory neurotransmitter release due to ischemia - how?

A
  • glutamate accumulation opens Ca channels and activated multiple destructive enzymatic systems
  • important in CNS protection
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13
Q

general effects of hypothermia (4)

A
  • allow lower pump flows
  • better myocardial protection
  • less blood trauma (bc low flow/low damage)
  • better overall organ protection
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14
Q

% of platelets are toast when you go on bypass?

A

70%

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15
Q

Cardiac Index on:

- 34-37 C

A

2.4 L/min/m2

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16
Q

Cardiac Index on:

- 30-34 C

A

2.0 L/min/m2

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17
Q

Cardiac Index on:

- 25-30 C

A

1.8 L/min/m2

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18
Q

Cardiac Index on:

- 20-18 C

A

1.5 L/min/m2

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19
Q

Cardiac Index on:

- <18 C

A

1.0 L/min/m2

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20
Q

DHCA - deep(profound) hypothermia with circ arrest

A
  • repair complex congenital heart defects - small infants and children
  • operations involving aortic arch
  • operations where maintenance of venous drainage is difficult
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21
Q

If arrest period longer than 60 minutes

A
  • use intermittent arrest with brief periods of hypothermic flow
  • low-flow hypothermic perfusion is safer than total arrest
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22
Q

physiology of hypothermia

  • biochemical
A

metabolic regulation

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23
Q

physiology of hypothermia

  • chemical
A

acid-base regulation

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24
Q

As temperature decreases —- biochemical reactions do what?

A

ALL reaction decrease in rate
decrease: Metabolic (producing & utilizing)
Humoral and coagulation cascades
Cellular maintenance of cell funct

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25
Q

Cold = diminished …..

A

diminished neurotransmission, receptor function ad protein activity

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26
Q

the cold effect is ____ with CPB

A

GLOBAL

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27
Q

Q10 principle

A

relates an increase or decrease in reaction rates to a change in 10C
a unitless quantity

ex Q10=2 a decrease in temp 10C will result in a 50% in reaction rates

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28
Q

Normal Q10 range?

A

are 1.9-4.2

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29
Q

oxygen consumption is a —

A

reaction

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30
Q

Q10 - temperature

A

in C

the factor by which a rate changes and is a useful way to express the temp dependence of a process

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31
Q

7C Principle

A

Reduction in Oxygen Consumption (VO2)

Every 7C drop in temperature will result in a 50% decease in oxygen consumption

32
Q

from 37 to 30C what % decrease in Oxygen consumption?

A

50% decrease in oxygen consumption

“moderate”

33
Q

37 to 23 C what % decrease in Oxygen consumption?

A

75% decrease in Oxygen consumption

“deep”

34
Q

2nd Principle (Q7) - Reduction in metabolic rate

A

Oxygen demand is reduced 50% for every 7 C drop in temperature

ex @30C VO2=50% normal

35
Q

2nd Principle (Q7) - Reduction in metabolic rate adjuncts ?

A

anesthesia (give cerebral vascular protection drugs, relaxants)

36
Q

Gas solubility is ____ related to temperature

A

inversely

37
Q

gas content in solution =

A

partial pressure of gas x solubility

38
Q

decrease temp what happens to:
solubility?
partial pressure?
total content?

A
  • solubility increases which increase the amount dissolved
  • Partial pressure decreases which decreases the amount dissolved
  • total content does not change
39
Q

pH responds to changes in?

A

CO2 content

NOT changes in the CO@ components

40
Q

How does temp affect O2/CO2 content?

A

Temp does not change O2 or CO2 content – just the prop of the components (dissolved vs partial)

41
Q

Henry’s Law

A
    • As pressure increases, solubility of gasses in liquids increase (more pressure = more gas can be dissolved in a liquid)
  • As temperature increases, solubility of gasses in liquids decreases (warm liquid gas starts to come out of solution)
42
Q

Henrys Law equation?

A

Content = Partial pressure x Solubility

43
Q

Temperature is ____ related to partial pressure

A

DIRECTLY

44
Q

Temperature is ___ related to solubility

A

INVERSELY

45
Q

At a constant temp, the amount of a given gas that dissolves in a given type and volume of liquid is directly prop to the _____ of that gas in equilibrium with that liquid

A

partial pressure

46
Q

Increase temp:
Solubility?
pO2 & pCO2?

A

Decrease solubility

increase pO2 & pCO2 (no change in content)

47
Q

decreased temp:
Solubility?
pO2 & pCO2?

A

Increase solubility

Decreased pO2 & pCO2

48
Q

Concerns with Profound Hypothermia? (2)

A

Homogeneity of cooling and warming

49
Q

Homogeneity of cooling

A

rate of cooling
temperature gradients

– concern with profound hypothermia

50
Q

recommended rate of cooling?

A

1 C per min

51
Q

recommended rate of warming

A

1 C per 3 to 5 minutes

52
Q

Consequence of cooling/warming too fast? (3)

A
  • development of temperature gradients w/in tissues
  • body cooling after bypass
  • exposure to hypothermia
53
Q

Limitation of rate of cooling/warming? (3)

A
  • water temp of heat exchanger
  • bld pressure and SVR
  • flow rate
54
Q

Temp gradients - max for adults and peds?

A

reduces probability of GME generation
limit temp gradient btwn arterial and venous blood
- adults <8 C

55
Q

Reduces probability of GME generation

- arterial PO2 mmHg <?

A

keep arterial pO2 <200mmhg

when coming off bypass have a smaller gradient

56
Q

HYPERTHERMIA - how does it happen?

A

Time pressure of rewarming
efficiency of HE
high water temps
perfusion inattention

Risk cerebral injury

57
Q

Techniques of hypothermic bypass (3)

A

DHCA
HLFB
HILFB (hypothermic intermittent low flow bypass)

58
Q

DHCA - cool to?

A

to 18-20 C

can turn off pump for 30-60 minutes

59
Q

During DHCA what organ is at greatest risk?

A

Brain function, developmental capacity and IQ

60
Q

Safe Circ Arrest times @ 37 C:
O2 consumption?
safe arrest time?

A

100%

4-5 minutes

61
Q

Safe Circ Arrest times @ 29 C:
O2 consumption?
safe arrest time?

A

50%

8-10 min

62
Q

Safe Circ Arrest times @ 22 C:
O2 consumption?
safe arrest time?

A

25%

16-20 min “deep”

63
Q

Safe Circ Arrest times @ 16 C:
O2 consumption?
safe arrest time?

A

12%

32-40min “profound”

64
Q

Safe Circ Arrest times @ 10 C:
O2 consumption?
safe arrest time?

A

6%

64-80min

65
Q

Standard safe circ arrest temperature ?

A

18 C

66
Q

Disadvantages of DHCA (4)

A

Neurologic injury and morbidity
Brain is at the most risk
>60 min arrest is detrimental
>40 min increases risk

67
Q

Advantages to DHCA (4)

A
  • exposure
  • reduces metabolic rate and molecular movement
  • allows cessation of circulation
  • excitatory neurotransmitter reduction
68
Q

DHCA >40 minutes

A

increases risk

69
Q

DHCA <60min

A

arrest is detrimental

70
Q

HLFB and HILFB (intermittant low flow bypass) patients demonstrated __ __ of neural dsyfunction in patient

A

lowered rate compared to DHCA

71
Q

can combine HILFB and DHCA for __ mins every __ min

A

1-2 mins every 15-20 mins

72
Q

Increase tolerance of brain to ischemic insult - meds(2)

A

Thiopental

Solumedral

73
Q

Thiopental

A

short acting barbituate

Increase tolerance of brain to ischemic insult

74
Q

Solumedral

A

anti-inflammatory, stabilize cell membranes

Increase tolerance of brain to ischemic insult

75
Q

Homogenous Temp (4)

A

rate of cooling/warming
hemodilution
acid-base management
head in ice

76
Q

Recovery - reperfusion conditions

A

perfusate temp

perfusate composition: mannitol, bicarbonate, others…

Perf Tech II (exam 1) (9 decks)

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