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Pediatrics > test 1 part 3 > Flashcards

test 1 part 3 Flashcards

1
Q

3 major differences between pediatrics and adults

A

Anatomic differences
Metabolic differences
Physiologic differences

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2
Q

Anatomic Differences Structural and Functional

A

Myocytes and myofibrils increase in size as they mature
The number of mitochondria increases as the oxygen requirements of the heart rises.
The amount of sarcoplasmic reticulum and its ability to sequester calcium similarly increase in early development.
Activity of Na+/K+ adenosine triphosphatase (ATPase) increases with maturation, and affects the sodium-calcium exchange. (big effect on bringing the cell back to its resting membrane potential)
Ca++ handling in immature myocardium ↑’s intracellular Ca ++ concentrations post ischemia/reperfusion.
Activates energy-consuming processes -> decreased levels of adenosine triphosphatase (ATPase) -> lack of energy sources for cardiac function
Contributes to dysfunction observed after CPB

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3
Q

Metabolic Differences

A

 Increased myocardial oxygen demands
 associated with a switch from anaerobic metabolism after birth to a more aerobic metabolism.
the increased ability of the immature myocardium to rely on anaerobic glycolysis, it can withstand ischemic injury better than an adult myocardium can.
 In the mature (3-12 mo) heart, long-chain fatty acids are the primary substrates (increased mitochondria needed)

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4
Q

Physiologic differences

A

Premature infants prone to:
 HYPOCALCEMIA, hypoxia, infection, stress, diabetes
Effects of hemodilution is enhanced in neonates
decreased plasma proteins, coagulation factors, and Hgb
 Infants/neonates have high oxygen-consumption rates
require flow rates as high as 200 mL/kg/min at normal temperature (kg based flow rates)

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5
Q

Most important difference between adults and kids

A
  • Presence of Intra-cardiac and extra-cardiac shunts and the reactive pulmonary vasculature are unique anatomic and physiologic findings in patients with congenital cardiac disease
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6
Q

Glucose control difference between adults and kids

A
  • Adult: Control high blood sugar
    CPB => stress response => hyperglycemia
    Studies link hyperglycemia with adverse outcomes
  • Peds: Control low blood sugar
    Hypoglycemia is due to decreased glycogen stores and reduced hepatic gluconeogenesis
    more common on pediatric CPB is hypoglycemia
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7
Q

Hematologic Effects difference between adults and kids

A

Adult:
 Inflammatory response upon surgery/CPB
Pediatric:
Exaggerated response to surgery/CPB (because their immune response isn’t built up yet)

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8
Q

The events that trigger stress:

A

Ischemia
Hypothermia
Anesthesia
Surgery

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9
Q

Stress Response: CPB causes hormone release and also releases: (adults and kids)

A 
Catecholamines
Cortisol 
ACTH
TSH
Endorphins
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10
Q

Cardiac Effects difference between adults and kids

A
  • Adult
    Less ischemia tolerance (because of their aerobic metabolism)
    May/may not be preconditioned to ischemia
    More tolerant of overfilling (myocardium more mature)
  • Pediatrics
    Tolerate ischemia
    Higher lactates seen (cost of tolerating ischemia)
    Prone to stretch injury (overfilling)
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11
Q

CNS Effects difference between adults and kids

A 
- Adult
        More neurological injuries
        Multifaceted etiology
        Stem from disease processes
- Pediatrics
        Neuro problems rare with routine CPB
        Increased with DHCA (?25%)
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12
Q

Pulmonary difference between adults and kids

A 
- Adult
        Lungs fully developed
        LESS REACTIVE VASCULATURE
        May have preexisting disease
- Pediatrics
        Lungs not fully developed
        MORE REACTIVE VASCULATURE
        Usually without existing disease
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13
Q

Renal difference between adults and kids

A
  • Adults
    The normal urine output for adults can be 0.5 to 1 ml/min, regardless of weight. That translates to 60 ml/hr.
  • Peds
    For children, the expected urine output is closer to 1ml/kg/hour of urine
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14
Q

Hypothermia in Children: What can you expect?

A

Due to the complex congenital heart repairs you will see that children are often brought to colder temperatures more frequently than adults
Different temperature monitoring sites in pediatrics (not a lot of bladder, see a lot of rectal)
Smaller children cool more rapidly than adults
DHCA is more often utilized

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15
Q

Hypothermia temperatures

A 
Warm => 36-37°C
 Mild Hypothermia => 32-35°C
 Moderate Hypothermia => 28-31°C
Deep Hypothermia => 18-27°C
Profound Hypothermia => < 18°C
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16
Q

Q10 principle

A
  • Relates the increase or decrease in reaction rates or metabolic processes to a temperature change of 10 degrees C
  • Oxygen consumption is a
    reaction
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17
Q

Reduction in metabolic rates (2ND Principle)

A

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

18
Q

Pediatric Monitoring of Temperature during Hypothermia locations:

A 
I. Core (central)
         Bladder (not on small children)
         Nasopharyngeal
         Tympanic
         Esophageal
         Venous
         Rectal
II. Shell (peripheral)
         Skin
19
Q

Protective effects of hypothermia

A
  • Excitatory neurotransmitter release is reduced with hypothermia
  • Hypothermia helps to protect organs against injury caused by the compromised substrate supply to tissues resulting from reduced flow.
  • This protection occurs because of a reduced metabolic rate and decreased oxygen consumption.
20
Q

”Safe” Circ Arrest Times

A

37 - 32⁰ C (mild) = < 10 mins
31 –28⁰ C (moderate) = 10-20 mins
27 - 18⁰ C (deep) = 20-45 mins
< 18 ⁰ C (Profound) (rare) = 45-60 mins

21
Q

Negative effects of hypothermia

A

Cerebral blood flow loses autoregulation at extreme temperatures (20 degrees C) which makes blood flow highly dependent on extracorporeal perfusion.
this uncoupling of autoregulation is a serious issue and is the basis for the Alpha stat/pH stat debate

22
Q

DHCA (deep hypothermic circ arrest): overview

A

DHCA provides excellent surgical exposure by eliminating the need for several cannulas in the surgical field and by providing a motionless and bloodless field.
Cooling is started before CPB by simply cooling room.
CPB is started and cooling begins for at least 20-30 minutes. After adequate cooling is achieved, the circulation is arrested. The desired duration of DHCA is limited to the shortest time possible.
After circulation is resumed, the final repairs are done on warming

23
Q

Arterial Cannulation spots

A

 Ascending aorta
 Innominate (first branch off of aorta)
 Femoral

24
Q

venous cannulation sites

A

 Usually a single venous (RA)
 The heart is not opened until circulatory arrest
 If Bicaval
 Usually if intracardiac repairs are necessary
 Heart can be opened before circulatory arrest, while cooling

25
Q

The good of DHCA

A

Allows exposure
Reduces metabolic rate and molecular movement
Allows cessation of
circulation

26
Q

The bad of DHCA

A 
Neurologic injury &amp; morbidity
Brain is at the most risk
>60 min arrest is detrimental
>40 min increases risk
MUST monitor temp gradients closely
27
Q

Temp gradient from art to venous

A

NOT > 8°C

28
Q

Hypothermic Low Flow vs Cardiopulmonary Bypass (HLFB)

A

• Trials to compare the 2 methods (DHCA vs. HLFB) have demonstrated lowered rates of neural dysfunction in patients undergoing HLFB.

29
Q

Hypothermic Intermittent Low Flow Cardiopulmonary Bypass (ILFB)

A

 using DHCA with INTERMITTENT LOW FLOW BYPASS (ILFB) for 1-2 minutes every 15-20 minutes

30
Q

Antegrade Cerebral Perfusion

A
  • Perfusing the head vessels in an antegrade fashion to perfuse the brain during DHCA
  • Via head vessels/shunt
  • pressure of 40-50 mm Hg in the right radial artery.
  • Higher flows of 30-40 mL/kg/min are recommended for neonates.
31
Q

Retrograde Cerebral Perfusion

A
  • Perfusing the head vessels in a retrograde fashion to perfuse the brain during DHCA
  • Via SVC
  • The concept of RCP originated as the treatment of massive air embolism during CPB.
    Pressure in the superior vena cava is maintained at 15-20 mm Hg otherwise cerebral edema
  • cerebral edema formation when pressure exceeds 25 mmHg
     the amount of perfusate that provides cerebral nutrition is low, corresponding to only about 5% of total retrograde flow
    Most of this flow is drained from the SVC into the inferior vena cava given the rich network of collaterals between the veins.
32
Q

Antegrade Cerebral Perfusion drawbacks

A

dissection of the arterial wall
air
atheromatous plaque embolization
malposition of the cannula
overcrowding of the operative field with cannulas
ACP can be given continuously or intermittently

33
Q

Ph Stat

A

pH-stat pH management is temperature-corrected. (at the patient’s temperature)
pH stat leads to higher pCO2 (respiratory acidosis), and increased cerebral blood flow.

34
Q

Ph stat - GOOD

A

Improved neurologic outcome, shorter EEG recovery times, and reduced number of postop seizures.
Decreased pulmonary collateral circulation flow during CPB
Increased cortical oxygen saturation before arrest
Decreased cortical oxygen metabolic rates during arrest
Increased brain-cooling rates
CBF during reperfusion increases by using a pH stat management strategy.

35
Q

Ph stat -BAD

A

 increased CBF can increase embolic events, high CBF during reperfusion, and reperfusion injury, cerebral edema
Acid load induced by pH-stat strategy may impair enzymatic function and metabolic recovery.
Lose autoregulation
- perfusion pressure then rules

36
Q

Alpha-Stat

A

 Blood samples warmed to room temperature have a pH of 7.4 and a PCO2 of 40 mmHg. These conditions allow the alpha imidazole group of the histidine moiety on blood/cellular proteins to maintain a constant buffering capacity, which enhances enzyme function and metabolic activity.
- READ ABG’s AT 37°C

37
Q

Alpha- stat: The Good

A

• Cerebral Blood Flow (CBF) autoregulation is maintained, which allows for metabolism and blood flow coupling. CBF can be adjusted depending on the patient’s cerebral metabolic activity and oxygen needs.
• Normal enzyme function
 Most studies of this approach have been performed in adults.

38
Q

Alpha–stat: bad

A
  • Vasoconstriction

* Poor (slows down) Cooling, which potentiates problems at the cellular level

39
Q

The Compromise Combination for acid base management:

A

That is, initial cooling is accomplished with the pH stat method, which is then switched to alpha-stat method to normalize the pH in the brain before ischemic arrest is induced (some do it on the last gas before arrest)

40
Q

Three cerebral oximeters Food and Drug Administration approved in the United States for use in the infant population

A

INVOS
NONIN EQUANOX
FORE-SIGHT

Pediatrics (37 decks)

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