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CVPR 326 Pediatric Perfusion > Infant and Pediatric Myocardial Protection / Pedi Exam 2 > Flashcards

Infant and Pediatric Myocardial Protection / Pedi Exam 2 Flashcards

1
Q

Adult hearts get more plegia and less cold, Pedi hearts get what ?

A

more cold and less plegia

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2
Q

What are the 3 differences between adult and pediatric myocardium?

A
  • Histological
  • Physiologic
  • Metabolic
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3
Q

What patient population can tolerate ischemia at 20 degrees a lot better than adults ?

A

Neonates

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4
Q

At birth the RV and the LV are ?

A

The same thickness

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5
Q

Heart increases in size X2 in the first ?

A

6 months

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6
Q

Heart increases in size X3 in the first ?

A

Year

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7
Q

What is the capillary to muscle fiber ratio in the adult?

A

1 : 1

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8
Q

What is the capillary to muscle fiber ratio in the neonate ?

A

6 : 1

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9
Q

The increased capillary to muscle fiber ratio in the neonate give it an increased ability to do two things, what are they?

A

Deliver substrate

Clear metabolic waste

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10
Q

What are two great features of the pediatric coronary vasculature?

A

Thicker walls

Lower resistance

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11
Q

How do thicker vascular walls that offer a lower resistance, reduce the potential for edema?

A

Reduced hydrostatic pressure gradient.

Resistance to capillary leakage

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12
Q

Who’s myocardium holds a higher water content ?

A

Pediatrics

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13
Q

Nuclei and mitochondria in the pediatric patient are both centrally located which leads to a rounded appearance with less contractile proteins per unit mass. What are the contractile proteins percentages for the adult and pediatric patient ?

A

Adult: 60%

Pediatric: 30%

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14
Q

Ultrastructural differences in the heart of the pediatric patient result in what ?

A
  • Decreased shortening potential
  • Decreased compliance
  • Decreased force of contraction
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15
Q

Ultrastructural differences in the heart of the pediatric patient result in decreased shortening potential, compliance, and force of contraction. Consequently neonatal hearts are always functioning at ?

A

The top of the Frank-Starling Curve.

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16
Q

Cardiac function of a neonate is very dependent on what?

A

Filling Pressure

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17
Q

In the mature myocardium, what is responsible for delivering the membrane potential to membrane bound Dihydropirodine Receptor (DHPR) ?

A

T - Tubule

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18
Q

In the mature myocardium, the membrane bound Dihydropirodine Receptor (HDPR) triggers Ryanodine (RyR) receptors on the SR to release what ?

A

Ca++ into the cytoplasm via CICR

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19
Q

What is ATPs involvement during CONTRACTION ?

A

cocking of the myosin head

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20
Q

What is ATPs involvement during RELAXATION ?

A

to break the actin-myosin bridge

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21
Q

Contraction and relaxation are dependent on what?

A

Ca2+ & ATP

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22
Q

What percentage of an adults Ca2+ comes from the sarcoplasmic reticulum ?

A

80%

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23
Q

During Contraction Ca2+ is required to expose the Actin binding site otherwise described as ?

A

Move Troponin

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24
Q

ATP is required to initiate what?

A

Myosin activation and cocking

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25
Q

During relaxation, Ca2+ must be removed from the cytoplasm in an ATP dependent process otherwise what happens ?

A

Actin Binding sites remain exposed

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26
Q

ATP is required for Actin and Myosin dissociation. Without ATP what happens?

A

Rigor

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27
Q

Neonatal hearts lack ?

A

Lack T-Tubules & have immature Sarcoplasmic Reticulum

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28
Q

The lack of t-tubules and an immature SR makes neonates to have an ?

A

Increased dependence on extracellular Ca2+

Reduced ability for Ca2+ reaccumulation and storage

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29
Q

Neonatal Ca2+ movement is dependent on what ?

A

Voltage dependent Ca2+ channels

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30
Q

Neonatal cardiac CONTRACTION is very dependent on what?

A

extracellular Ca2+

31
Q

Neonatal RELAXATION is ?

A

Slower, therefore systole is longer

32
Q

Although the Neonatal heart is extremely unique, REDUCED SR Ca2+ stores generates what ?

A

Increased resistance to Calcium Paradox

33
Q

Calcium Paradox is virtually not seen in hearts less than ?

A

15 days old

34
Q

Neonatal hearts have fewer mitochondria (Immature) which leads to less intricacy, which leads to a reduced surface area which leads to what ?

A

Reduced potential ATP production

35
Q

In regards to metabolism, what is the primary fuel source for adults ?

A

Fatty Acids

129 Mole ATP / Mole Palpitate

36
Q

In regards to metabolism, what is the primary fuel source for Neonates ?

What facilitates this process?

A

Glucose

38 Mole / Mole of Glucose

Increased capillary density

37
Q

What are 4 positive things of having Anaerobic Metabolism in the Neonatal Heart ?

A 
↑ Glycogen Stores 
↑ ability for gluconeogenesis 
↑ ability to use ADP & AMP as 
   energy. 
↑ Intracellular buffering ability
38
Q

The best positive thing of having Anaerobic Metabolism allow the Neonatal Heart to have what ?

A

Increased ability to tolerate ischemia

39
Q

As the Neonatal heart matures, what happens?

A

Switches to Fat metabolism and looses its ischemic tolerance

40
Q

What are the two primary components of myocardial tissue injury during reperfusion ?

A

Ca2+ Paradox

Oxygen radical production

41
Q

How does the Neonatal Heart protects itself from Ca2+ Paradox injury during reperfusion ?

A
  • Decreased SR Ca2+ stores

- Acid sensitive ATPases inactivate with ↓ pH, which preserves ATP and metabolism during intracellular acidosis.

42
Q

Immature hearts are at great risk in comparison to neonatal hearts in what way?

A

Immature hearts have more mature SR and therefore have a greater risk for Ca2+ Paradox.

43
Q

Neonatal hearts have no inherent protection against what?

A

reactive oxygen species

44
Q

Radical production increases in neonates during ?

45
Q

Oxygen radical formation increases susceptibility to protease damage by what ?

46
Q

What’s the prerequisite for radical formation ?

A

Molecular Oxygen

47
Q

Oxygen radical formation increases what ?

A

cell membrane degradation

48
Q

Route of cardioplegia delivery for a neonate ?

A

Primarily antegrade, retrograde is possible but uncommon.

49
Q

Blood Vs. Crystalloid

What are 2 CONS against using blood?

A

Reduced temperatures = - Reduced oxygen carrying capacity of blood.
- Increase in viscosity of blood.

50
Q

Blood vs. Crystalloid

When utilizing blood as cardioplegia, it increases delivery pressure. What is a negative consequence as a result ?

51
Q

Blood Vs. Crystalloid

What are 2 PROS for using blood?

A

Distribution is improved with blood solutions

Blood has many helpful components

52
Q

Blood vs. Crystalloid

The use of blood cardioplegia is more important in the recovery of ventricular function at temperatures of ?

A

20 degrees celcius than at 4 or 10 degrees

53
Q

Blood vs. Crystalloid

At lower temperatures developed pressure (DP) is improved by ?

A

crystaloid cardioplegia.

54
Q

Considering the dependence of the immature myocardium on glucose as a fuel source, it would seem logical that it would be included in plegia solution. What do studies show in regards to this ?

A

Addition of glucose has harmful effects

55
Q

Calcium levels in the neonate are

A

Normal to slightly below normal

56
Q

Blood cardioplegia with/without Ca++ chelating agents

A

(ACD, CPD)

57
Q

Magnesium has been shown to?

A

reduce the trans-sarcolemmal flux of Ca++ into cytoplasm.

Inhibits Na+ influx from extracellular space

Is an important cofactor in many enzymatic
reactions

58
Q

During ischemic cardiac arrest what happens to magnesium ?

A

Is known to be lost from myocardium

59
Q

Alpha Stat pH management in the neonate population.

A

Reduces post ischemic electrical disturbances during normothermia and moderate hypothermia.

60
Q

pH Stat pH management in the neonate population.

A

Improves post ischemic cardiac output during profound hypothermia (DHCA)

61
Q

What is the normal Osmolarity ?

What is the Osmolarity in the neonatal population

A

Normal = 280 mOsm/L

Neonates = 300 - 320 mOsm/L

62
Q

Adult hearts get more plegia and less cold Pedi hearts get what ?

A

more cold and less plegia

63
Q

How much cardiolegia is enough, Recovery was significantly worse after ?

A

90 minutes of ischemia when multiple doses was administered.

also with 120 min

64
Q

What were the results while Utilizing topical cooling with control, 60 min, 90 min, and 120 min ?

A

Great! greater than 90% recovery rate.

65
Q

What were the results while Utilizing (single dose cardioplegia) with control, 60 min, 90 min, and 120 min ?

A

Great! greater than 85% recovery rate.

66
Q

Patients which are particularly susceptible to intraoperative myocardial damage due to (Poor coronary blood flow)
include:

A

ALCA,

hypoplastic systemic ventricle

67
Q

Patients which are particularly susceptible to intraoperative myocardial damage due to (Myocardial Hypertrophy)
include:

A

Obstructive lesions

68
Q

Patients which are particularly susceptible to intraoperative myocardial damage include:

A 
– Heart failure 
– Numerous bronchial  
   collaterals 
– Defects with reduced 
   pulmonary blood flow
  * (RVOT) obstruction
69
Q

Why is INITIATION a period of vulnerability ?

A

Hyperoxygenation of hypoxic myocardium may produce oxygen radicals

70
Q

Why is PRE CROSS CLAMP a period of vulnerability ?

A

Hypotension to the warm decompressed hypertrophied myocardium may compromise subendocardial perfusion

71
Q

Why is CROSS CLAMP a period of vulnerability ?

A

Maintaince of intracellular pH, ATP and Ca++ homeostasis is crucial

72
Q

Maintaince of intracellular pH, ATP and Ca++ homeostasis is crucial. What are 4 other items to keep in mind during clamping period?

A

Temperature,
collateral wash out,
electrical arrest,
uniform delivery

73
Q

Why is REPERFUSION a period of vulnerability ?

A

Oxygen and Ca++ return to ischemic tissue

CVPR 326 Pediatric Perfusion (23 decks)

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