test 1 part 3

Question 1

3 major differences between pediatrics and adults

Answer 1

Anatomic differences
Metabolic differences
Physiologic differences

Question 2

Anatomic Differences Structural and Functional

Answer 2

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

Question 3

Metabolic Differences

Answer 3

 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)

Question 4

Physiologic differences

Answer 4

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)

Question 5

Most important difference between adults and kids

Answer 5

• 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

Question 6

Glucose control difference between adults and kids

Answer 6

• 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

Question 7

Hematologic Effects difference between adults and kids

Answer 7

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

Question 8

The events that trigger stress:

Answer 8

Ischemia
Hypothermia
Anesthesia
Surgery

Question 9

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

Answer 9

Catecholamines
Cortisol 
ACTH
TSH
Endorphins

Question 10

Cardiac Effects difference between adults and kids

Answer 10

• 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)

Question 11

CNS Effects difference between adults and kids

Answer 11

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

Question 12

Pulmonary difference between adults and kids

Answer 12

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

Question 13

Renal difference between adults and kids

Answer 13

• 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

Question 14

Hypothermia in Children: What can you expect?

Answer 14

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

Question 15

Hypothermia temperatures

Answer 15

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

Question 16

Q10 principle

Answer 16

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

Question 17

Reduction in metabolic rates (2ND Principle)

Answer 17

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

Question 18

Pediatric Monitoring of Temperature during Hypothermia locations:

Answer 18

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

Question 19

Protective effects of hypothermia

Answer 19

• 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.

Question 20

”Safe” Circ Arrest Times

Answer 20

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

Question 21

Negative effects of hypothermia

Answer 21

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

Question 22

DHCA (deep hypothermic circ arrest): overview

Answer 22

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

Question 23

Arterial Cannulation spots

Answer 23

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

Question 24

venous cannulation sites

Answer 24

 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

Question 25

The good of DHCA

Answer 25

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

Question 26

The bad of DHCA

Answer 26

``` Neurologic injury & morbidity Brain is at the most risk >60 min arrest is detrimental >40 min increases risk MUST monitor temp gradients closely ```

Question 27

Temp gradient from art to venous

Answer 27

NOT > 8°C

Question 28

Hypothermic Low Flow vs Cardiopulmonary Bypass (HLFB)

Answer 28

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

Question 29

Hypothermic Intermittent Low Flow Cardiopulmonary Bypass (ILFB)

Answer 29

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

Question 30

Antegrade Cerebral Perfusion

Answer 30

- 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.

Question 31

Retrograde Cerebral Perfusion

Answer 31

- 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.

Question 32

Antegrade Cerebral Perfusion drawbacks

Answer 32

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

Question 33

Ph Stat

Answer 33

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.

Question 34

Ph stat - GOOD

Answer 34

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.

Question 35

Ph stat -BAD

Answer 35

 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

Question 36

Alpha-Stat

Answer 36

 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

Question 37

Alpha- stat: The Good

Answer 37

• 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.

Question 38

Alpha–stat: bad

Answer 38

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

Question 39

The Compromise Combination for acid base management:

Answer 39

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)

Question 40

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

Answer 40

INVOS NONIN EQUANOX FORE-SIGHT