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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

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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
During relaxation, Ca2+ must be removed from the cytoplasm in an ATP dependent process otherwise what happens ?
Actin Binding sites remain exposed
26
ATP is required for Actin and Myosin dissociation. Without ATP what happens?
Rigor
27
Neonatal hearts lack ?
Lack T-Tubules & have immature Sarcoplasmic Reticulum
28
The lack of t-tubules and an immature SR makes neonates to have an ?
Increased dependence on extracellular Ca2+ Reduced ability for Ca2+ reaccumulation and storage
29
Neonatal Ca2+ movement is dependent on what ?
Voltage dependent Ca2+ channels
30
Neonatal cardiac CONTRACTION is very dependent on what?
extracellular Ca2+
31
Neonatal RELAXATION is ?
Slower, therefore systole is longer
32
Although the Neonatal heart is extremely unique, REDUCED SR Ca2+ stores generates what ?
Increased resistance to Calcium Paradox
33
Calcium Paradox is virtually not seen in hearts less than ?
15 days old
34
Neonatal hearts have fewer mitochondria (Immature) which leads to less intricacy, which leads to a reduced surface area which leads to what ?
Reduced potential ATP production
35
In regards to metabolism, what is the primary fuel source for adults ?
Fatty Acids 129 Mole ATP / Mole Palpitate
36
In regards to metabolism, what is the primary fuel source for Neonates ? What facilitates this process?
Glucose 38 Mole / Mole of Glucose Increased capillary density
37
What are 4 positive things of having Anaerobic Metabolism in the Neonatal Heart ?
``` ↑ Glycogen Stores ↑ ability for gluconeogenesis ↑ ability to use ADP & AMP as energy. ↑ Intracellular buffering ability ```
38
The best positive thing of having Anaerobic Metabolism allow the Neonatal Heart to have what ?
Increased ability to tolerate ischemia
39
As the Neonatal heart matures, what happens?
Switches to Fat metabolism and looses its ischemic tolerance
40
What are the two primary components of myocardial tissue injury during reperfusion ?
Ca2+ Paradox Oxygen radical production
41
How does the Neonatal Heart protects itself from Ca2+ Paradox injury during reperfusion ?
- Decreased SR Ca2+ stores | - Acid sensitive ATPases inactivate with ↓ pH, which preserves ATP and metabolism during intracellular acidosis.
42
Immature hearts are at great risk in comparison to neonatal hearts in what way?
Immature hearts have more mature SR and therefore have a greater risk for Ca2+ Paradox.
43
Neonatal hearts have no inherent protection against what?
reactive oxygen species
44
Radical production increases in neonates during ?
Acidosis
45
Oxygen radical formation increases susceptibility to protease damage by what ?
No and Mo
46
What's the prerequisite for radical formation ?
Molecular Oxygen
47
Oxygen radical formation increases what ?
cell membrane degradation
48
Route of cardioplegia delivery for a neonate ?
Primarily antegrade, retrograde is possible but uncommon.
49
Blood Vs. Crystalloid What are 2 CONS against using blood?
Reduced temperatures = - Reduced oxygen carrying capacity of blood. - Increase in viscosity of blood.
50
Blood vs. Crystalloid When utilizing blood as cardioplegia, it increases delivery pressure. What is a negative consequence as a result ?
Edema
51
Blood Vs. Crystalloid What are 2 PROS for using blood?
Distribution is improved with blood solutions Blood has many helpful components
52
Blood vs. Crystalloid The use of blood cardioplegia is more important in the recovery of ventricular function at temperatures of ?
20 degrees celcius than at 4 or 10 degrees
53
Blood vs. Crystalloid At lower temperatures developed pressure (DP) is improved by ?
crystaloid cardioplegia.
54
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 ?
Addition of glucose has harmful effects
55
Calcium levels in the neonate are
Normal to slightly below normal
56
Blood cardioplegia with/without Ca++ chelating agents
(ACD, CPD)
57
Magnesium has been shown to?
reduce the trans-sarcolemmal flux of Ca++ into cytoplasm. Inhibits Na+ influx from extracellular space Is an important cofactor in many enzymatic reactions
58
During ischemic cardiac arrest what happens to magnesium ?
Is known to be lost from myocardium
59
Alpha Stat pH management in the neonate population.
Reduces post ischemic electrical disturbances during normothermia and moderate hypothermia.
60
pH Stat pH management in the neonate population.
Improves post ischemic cardiac output during profound hypothermia (DHCA)
61
What is the normal Osmolarity ? What is the Osmolarity in the neonatal population
Normal = 280 mOsm/L Neonates = 300 - 320 mOsm/L
62
Adult hearts get more plegia and less cold Pedi hearts get what ?
more cold and less plegia
63
How much cardiolegia is enough, Recovery was significantly worse after ?
90 minutes of ischemia when multiple doses was administered. also with 120 min
64
What were the results while Utilizing topical cooling with control, 60 min, 90 min, and 120 min ?
Great! greater than 90% recovery rate.
65
What were the results while Utilizing (single dose cardioplegia) with control, 60 min, 90 min, and 120 min ?
Great! greater than 85% recovery rate.
66
Patients which are particularly susceptible to intraoperative myocardial damage due to (Poor coronary blood flow) include:
ALCA, | hypoplastic systemic ventricle
67
Patients which are particularly susceptible to intraoperative myocardial damage due to (Myocardial Hypertrophy) include:
Obstructive lesions
68
Patients which are particularly susceptible to intraoperative myocardial damage include:
``` – Heart failure – Numerous bronchial collaterals – Defects with reduced pulmonary blood flow * (RVOT) obstruction ```
69
Why is INITIATION a period of vulnerability ?
Hyperoxygenation of hypoxic myocardium may produce oxygen radicals
70
Why is PRE CROSS CLAMP a period of vulnerability ?
Hypotension to the warm decompressed hypertrophied myocardium may compromise subendocardial perfusion
71
Why is CROSS CLAMP a period of vulnerability ?
Maintaince of intracellular pH, ATP and Ca++ homeostasis is crucial
72
Maintaince of intracellular pH, ATP and Ca++ homeostasis is crucial. What are 4 other items to keep in mind during clamping period?
Temperature, collateral wash out, electrical arrest, uniform delivery
73
Why is REPERFUSION a period of vulnerability ?
Oxygen and Ca++ return to ischemic tissue

CVPR 326 Pediatric Perfusion (23 decks)

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