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Perf Tech > Topic 5 > Flashcards

Topic 5 Flashcards

1
Q

Human body is homeostatic in regulation and is controlled by

A

Hypothalmic and Endocrine Systems

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2
Q

Hypothalamus regulates

A

vascular regulation

skeletal muscle activity

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3
Q

Endocrine system regulates

A

metabolic regulation

stress response

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4
Q

Cold is sensed by _______ in the skin- Causes hypothalamus to trigger _____ nervous system response

A

thermoreceptors

sympathetic

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5
Q

Vasoconstriction of the skin vessels=

A

Decrease heat loss (convection)

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6
Q

Vasodilation of skeletal muscle vascular beds=

A

Increase muscular activity to produce heat by tensing/ shivering

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7
Q

Mild Hypothermia=

A

32-35°

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8
Q

Moderate Hypothermia=

A

28-31°

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9
Q

Deep Hypothermia=

A

18-27°

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10
Q

Profound Hypothermia=

A

< 18°

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11
Q

Induced hypothermia=

A

-not physiological
-clinical use – global or localized to an area
During bypass provides:
•degree of organ & organism protection
•margin of safety

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12
Q

Mechanisms of protection=

A
  1. reduction in metabolic rate and oxygen consumption
  2. preservation of high-energy phosphate stores
  3. reduction of excitatory neurotransmitter release due to ischemia
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13
Q

reduction in metabolic rate and oxygen consumption=

A

reduction in reaction rate of all biochemical processes especially enzymatic reactions

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14
Q

preservation of high-energy phosphate stores=

A

less energy usage = more availability

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15
Q

reduction of excitatory neurotransmitter release due to ischemia=

A
  • important central nervous system protection

- glutamate accumulation opens calcium channels and activates multiple destructive enzymatic systems

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16
Q

The safe period of hypothermic cardiopulmonary bypass (CPB) is …

A

longer than the period predicted on the basis of reduced metabolic activity alone

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17
Q

Hypothermia general effects

A
  1. Allows lower pump flows (better surgeon visualization)
  2. Better myocardial protection
  3. Less blood trauma (low flow = low damage)
  4. Better overall organ protection
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18
Q 
Flow= 2.4 L/min/m2
Temp= ?
A

34-37˚C

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19
Q 
Flow= 2.0 L/min/m2
Temp= ?
A

30-34˚C

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20
Q 
Flow= 1.8 L/min/m2
Temp= ?
A

25-30˚C

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21
Q 
Flow= 1.5 L/min/m2
Temp= ?
A

18-20˚C

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22
Q 
Flow= 1.0 L/min/m2
Temp= ?
A

<18˚C

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23
Q

Methods of Hypothermia Induction=

A
  1. Surface cooling (ice)
  2. Surface cooling with supplementary partial bypass
  3. Core cooling – Total extracorporeal circulation
    •Deep hypothermic total circulatory arrest (DHCA)
    •Low-flow, deep/profoundly hypothermic bypass (HLFB)
    •Intermittent, low flow deep/profoundly hypothermic bypass (HILFB)
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24
Q

Surface cooling=

A
  • Inverse effect related to size: small infants less than 5 kg
  • Myocardial cooling used on adults and peds
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25
Q

Profound hypothermia with arrest (DHCA)=

A
  • repair complex congenital heart defects – small infants & children
  • operations involving the aortic arch
  • operations where maintenance of venous drainage difficult
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26
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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27
Q

Important items: hot and cold

A
  1. Warming/cooling blanket
  2. Blanketrol water warmer
  3. Warm air blower
  4. Blanket warmer cabinet
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28
Q

Physiology of Hypothermia=

A
  1. Biochemical= metabolic regulation

2. Chemical= acid-base regulation

29
Q

Biochemical Reactions=

A
  1. all reactions decrease in rate as temperature decreases
    •Metabolic – energy producing/utilizing
    •Humoral and coagulation cascades
    •Cellular – maintenance of cellular function
    •communication pathways
    •receptor mechanisms
    •membrane proteins (enzymatic & environmental)
30
Q

Cold=

A
  1. decreased energy
  2. more bleeding
  3. diminished neuro transmission, receptor function, and protein activity
    THIS EFFECT IS GLOBAL WITH CPB
31
Q

Q10 Principle=

A

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

32
Q

Most physiological rates Q10 are

A

2-3 in the body

33
Q

Oxygen consumption is a

A

reaction

34
Q

Q10 is a useful way to express the

A

temperature dependence of a process

35
Q

If your Q10 = 2 then a decrease in temperature 10° C will result in a

A

50% reduction in reaction rates.

36
Q

Reduction in Oxygen Consumption (VO2) (7°C Principle)=

A

Every 7°C drop in temperature will result in a 50% decrease in oxygen consumption/demand

37
Q

Gas solubility is ______ related to temperature

A

inversely

38
Q

gas content in solution =

A

partial pressure of gas x solubility

39
Q

if you decrease the temperature, then solubility

A

increases which increases the amount dissolved

40
Q

Temperature does not change

A

O2 or CO2 content – just the proportion of the components (dissolved vs. partial pressure)

41
Q

pH responds to changes in

A

CO2 content, not changes in the CO2 components

42
Q

Henry’s Law part 1=

A
  1. As pressure increases, solubility of gasses in liquids increases
    Part one in English: More pressure means more gas can be dissolved in a liquid. Decreasing pressure causes that gas to come out of the liquid. (Δ P = Δ solubility - direct relation)
43
Q

Henry’s Law part 2=

A
  1. As temperature increases, solubility of gasses in liquids decreases
    Part two in English: Colder liquids hold more gas than warmer liquids. As a liquid warms up, the gas starts to come out of solution. (Δ T = Δ solubility – inverse relation)
44
Q

Henry’s Law formula

A

Content = Partial pressure x Solubility

45
Q

At a constant temperature, the amount of a given gas that dissolves in a given type and volume of liquid is

A

directly proportional to the partial pressure of that gas in equilibrium with that liquid

46
Q

Temperature is DIRECTLY related to

A

partial pressure

47
Q

Temperature is INVERSELY related to

A

solubility

48
Q

Increased temperature=

A

Decreased solubility

Increased partial pressure

49
Q

Decreased temperature=

A

Increased solubility

Decreased partial pressure

50
Q

Rate of Cooling

A

cool at 1C per minute

51
Q

Rate of Warming

A

warm at 1C per 3 to 5 minutes

52
Q

Consequences of cooling/warming too fast

A
  1. development of temperature gradients within tissues
  2. body cooling after bypass
  3. exposure to hyperthermia
53
Q

Cooling/warming limitations

A
  1. water temperature of heat exchanger
  2. blood pressure and systemic vascular resistance
  3. flow rate
54
Q

Importance of Temperature Gradients=

A
  1. Gaseous micro emboli (CME) formation (gas solubility and temperature)
  2. Temperature gradients (between heat exchanger and venous blood/ between arterial blood and patient)
  3. Reduce probability of GME generation
55
Q

Reduce probability of GME generation=

A
  1. limit temperature gradient between arterial and venous blood (adults: <200 mmHg
56
Q

How does Exposure to Hyperthermia happen

A

time pressure of rewarming

  1. efficiency of heat exchanger (more or less than expected)
  2. high water temperatures
  3. perfusionist inattention
57
Q

Consequence of hyperthermia

A

risk of cerebral injury

58
Q

Deep Hypothermic Circulatory Arrest (DHCA)=

A
  1. Cool patient to 18 to 20C. Turn off pump for limited period of time (30 to 60 minutes)
  2. Organ at greatest risk – brain
  3. Optimal depth of cooling-temperature monitoring – multiple sites. EEG cessation
59
Q

DHCA Safe Circ Arrest Times- 4 – 5 min
Temp?
O2 consumption?

A

37C

100%

60
Q

DHCA Safe Circ Arrest Times- 8 – 10 min (Moderate)
Temp?
O2 consumption?

A

29C

50%

61
Q

DHCA Safe Circ Arrest Times- 16 – 20 min (Deep)
Temp?
O2 consumption?

A

22C

25%

62
Q

DHCA Safe Circ Arrest Times- 32- 40 min (Profound)
Temp?
O2 consumption?

A

16C

12%

63
Q

DHCA Safe Circ Arrest Times- 64 – 80 min
Temp?
O2 consumption?

A

10C

6%

64
Q

DHCA Benefits

A
  1. Allows exposure
  2. Reduces metabolic rate and molecular movement
  3. Allows cessation of circulation
  4. Excitatory neurotransmitter reduction
65
Q

DHCA disadvantages

A
  1. Neurologic injury & morbidity
  2. Brain is at the most risk
    • >40 min increases risk
    • >60 min arrest is detrimental
66
Q

Increase tolerance of brain to ischemic insult by using

A
  1. thiopental – short acting barbituate

2. solumedrol – anti-inflammatory, stabilize cell membranes

67
Q

Homogenous temperature=

A
  1. rate of cooling / warming
  2. hemodilution
  3. acid-base management
  4. head in ice
68
Q

Recovery – reperfusion conditions=

A
  1. perfusate temperature

2. perfusate composition: mannitol, bicarbonate, others

Perf Tech (8 decks)

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