3. Blood Gas/Hypothermia- Exam 1 Flashcards by melissa griffith

what are the 3 Major differences that exist between adult and pediatric cardiopulmonary bypass

Anatomic differences
Metabolic differences
Physiologic differences

How well did you know this?

Not at all

Perfectly

Anatomic Differences Structural and Functional for Myocytes, myofibrils, mitochondria, sarcoplasmic reticulum, and Activity of Na+/K+ ATPase

-Myocytes and myofibrils: increase in size
-mitochondria: number increases as the oxygen requirements of the heart rises.
-sarcoplasmic reticulum: The amount and its ability
to sequester calcium increase in early development.
-Activity of Na+/K+ ATPase: increases with maturation, and affects the sodium-calcium exchange

How well did you know this?

Not at all

Perfectly

How do anatomic differences effect Ca++ handling?

Ca++ handling in immature myocardium ↑’s intracellular Ca ++ concentrations post ischemia/reperfusion.

How well did you know this?

Not at all

Perfectly

How do anatomic differences effect energy consuming processes?

Activates energy-consuming processes–> decreased
levels of adenosine triphosphatase (ATPase)–> lack of
energy sources for cardiac function

How well did you know this?

Not at all

Perfectly

Anatomic differences contribute to what on bypass?

Contributes to dysfunction observed after CPB

How well did you know this?

Not at all

Perfectly

_____ and _____ activation of these enzymes leads to cellular damage after CPB

Abnormal and uncontrolled

How well did you know this?

Not at all

Perfectly

Increased myocardial oxygen demands is associated with a switch from _______ after birth to a more _________

anaerobic metabolism

aerobic metabolism

How well did you know this?

Not at all

Perfectly

The immature myocardium uses several substrates such as (5)

carbohydrates
glucose
medium, and long-chain fatty acids
ketones
amino acids

How well did you know this?

Not at all

Perfectly

What is the primary substrate In the mature (3-12 mo) heart?

long-chain fatty acids are the primary substrates

–enzymes and an increased number of mitochondria are needed

How well did you know this?

Not at all

Perfectly

Because of the increased ability of the immature myocardium to rely on anaerobic glycolysis, it can withstand ___ better than an adult myocardium can.

ischemic injury

How well did you know this?

Not at all

Perfectly

Premature infants prone to what?

hypocalcemia

–hypoxia, infection, stress, diabetes (mom)

How well did you know this?

Not at all

Perfectly

Effects of hemodilution is enhanced in what group?

neonates

How well did you know this?

Not at all

Perfectly

what are the Effects of hemodilution that is enhanced in neonates

–decreased plasma proteins, coagulation factors, and
Hgb
–reduction increases organ edema, coagulopathy,
and transfusion requirements

How well did you know this?

Not at all

Perfectly

Infants/neonates have high ________ rates

oxygen-consumption

How well did you know this?

Not at all

Perfectly

Infants/neonates have high oxygen-consumption

rates… this requires what kind of flow rates?

require flow rates as high as 200 mL/kg/min at normal temperature (kg based flow rates)

How well did you know this?

Not at all

Perfectly

______/______ and ______ are unique anatomic and physiologic findings in patients with congenital cardiac disease

Intra-cardiac and extra-cardiac shunts and the

reactive pulmonary vasculature

How well did you know this?

Not at all

Perfectly

Adult vs Ped glucose control

Adult= control high blood sugar
Ped= control low blood sugar

How well did you know this?

Not at all

Perfectly

describe adults response to hyperglycemia

CPB => stress response => hyperglycemia

Studies link hyperglycemia with adverse outcomes

How well did you know this?

Not at all

Perfectly

describe peds response to hyperglycemia

–Hyperglycemia has not been linked to adverse
outcomes in pediatric CPB
–more common on pediatric CPB is hypoglycemia
( ↓ glycogen stores)

How well did you know this?

Not at all

Perfectly

Adult vs Ped hematologic response to CPB

–Adult: Inflammatory response upon surgery/CPB
–Pediatric: Exaggerated response to surgery/CPB. Inflammatory response inversely proportional to
age

How well did you know this?

Not at all

Perfectly

Name 4 events that trigger stress

Ischemia
Hypothermia
Anesthesia
Surgery

How well did you know this?

Not at all

Perfectly

CPB causes hormone release and also releases what 5 things

Catecholamines
Cortisol
ACTH
TSH
Endorphins

How well did you know this?

Not at all

Perfectly

What affects the release of hormone release

immature organs

How well did you know this?

Not at all

Perfectly

describe adult cardiac characteristics

Less ischemia tolerance
May/may not be preconditioned to ischemia
More tolerant of overfilling

How well did you know this?

Not at all

Perfectly

describe ped cardiac characteristics

Tolerate ischemia Higher lactates seen (cost of tolerating ischemia) Prone to stretch injury (overfilling)

describe adult CNS characteristics

More neurological injuries Multifaceted etiology Stem from disease processes

describe ped CNS characteristics

Neuro problems rare with routine CPB | Increased with DHCA (?25%)

describe adult pulmonary characteristics

Lungs fully developed Less reactive vasculature May have preexisting disease

describe ped pulmonary characteristics

Lungs not fully developed More reactive vasculature Usually without existing disease

describe adult renal characteristics

The normal urine output for adults can be 0.5 to 1 ml/min, regardless of weight. That translates to 60 ml/hr. --Average 70kg adult would be expected to produce 35-70 mL/hour of urine

describe ped renal characteristics

For children, the expected urine output is closer to 1ml/kg/hour of urine. --Average 5 kg child would be expected to produce 5 mL/hour

Due to the complex nature of congenital heart repairs you will see that children are often brought to __________ more frequently than adults

colder temperatures

Smaller children ____more rapidly than adults

cool

what method of hypothermia is most often used for peds

DHCA

Warm temp=

36-37 C

Mild Hypothermia temp=

32-35 C

Moderate Hypothermia temp=

28-31 C

Deep Hypothermia temp=

18-27 C

Profound Hypothermia temp=

below 18 C

define Q10

Reaction Rates: factor by which the rate of a reaction increases or decreases by 50% for every 10-degree increase/decrease in the temperature

is Oxygen consumption is a reaction

yes

Q10= [formula]

(R2/R1)^(10/[T2-T1])

define Q7

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

Q7: at 37C (normothermic) what the %decrease of oxygen consumption and what is the temp in F?

0% | 98.6F

Q7: at 34C (mild) what the %decrease of oxygen consumption and what is the temp in F?

25% | 93.2F

Q7: at 30C (moderate) what the %decrease of oxygen consumption and what is the temp in F?

50% | 86.0F

Q7: at 23C (deep) what the %decrease of oxygen consumption and what is the temp in F?

75% | 73.4F

Q7: at 16C (profound) what the %decrease of oxygen consumption and what is the temp in F?

87. 5% | 60. 8F

Q7: at 9C (almost frozen) what the %decrease of oxygen consumption and what is the temp in F?

94% | 48.2F

Q7: at 0C (frozen) what the %decrease of oxygen consumption and what is the temp in F?

100% | 32.0F

Name 5 central/core temperature monitoring locations

``` Bladder (not on small children) Nasopharyngeal Tympanic Esophageal Venous ```

Name 2 shell/peripheral temperature monitoring locations

Rectal | Skin

What temperatures do you feel are the most accurate indicator of being cold or warm?

venous

Excitatory neurotransmitter release is _____ with hypothermia

reduced

Hypothermia helps to protect organs against injury caused by what?

the compromised substrate supply to tissues resulting from reduced flow.

why does hypothermia work?

because of a reduced metabolic rate and decreased oxygen consumption.

The metabolic rate is determined by what?

enzymatic activity, which, in turn, depends on temperature

The safe period of hypothermic CPB is _____ than the period predicted on the basis of reduced metabolic activity alone

longer

safe period for DHCA above 32C

less than 10 min

safe period for DHCA at 28C

10-20 min

safe period for DHCA at 18C

20-45 min

safe period for DHCA below 18C

45-60min

brain blood flow loses _______ at extreme temperatures which makes blood flow highly dependent on extracorporeal perfusion

autoregulation

DHCA provides excellent surgical exposure by doing what

eliminating the need for several cannulas in the surgical | field and by providing a motionless and bloodless field

how is Cooling is started before CPB

cooling the room

describe the process for how DHCA is carried out

1. CPB is started and cooling is begins for at least 20-30 minutes. The patient's body temperature is monitored. 2. After adequate cooling is achieved, the circulation is arrested. The desired duration of DHCA is limited to the shortest time possible. 3. After circulation is resumed, the final repairs are done on warming

with DHCA, when you turn the pump off during arrest- what do you have to do

recirculate through oxygenator recirc line to prevent blood from clotting

Cannulation for PHCA/DHCA is usually a?

SAC | -The heart is NOT opened until circulatory arrest

Cannulation for PHCA/DHCA can and will be done with BICAVAL also, here the heart _____?

is/can be opened before circulatory arrest

name 3 DHCA benefits

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

name 5 DHCA disadvantages

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

what should the arterial to venous temp gradient for DHCA not exceed

NOT > 8°C

Trials to compare the 2 methods (DHCA vs. HLFB) have demonstrated what?

lowered rates of neural dysfunction in patients undergoing HLFB.

some groups have combined the 2 approaches mentioned above by using DHCA with INTERMITTENT LOW FLOW BYPASS (ILFB) for ____ min every ____ min

1-2 minutes every 15-20 minutes

There is __ specific consensus on what is the best method to allow complex repairs in neonates. The use of DHCA, PHCA, HLFB, ILFB, antegrade and retrograde cerebral perfusion are all used to varying extents

The secret formula may very well lie in the _____ of these techniques and not the ______

mixture | techniques alone

how is antegrade cerebral perfusion performed

Via head vessels/shunt

how is retrograde cerebral perfusion performed

Via SVC

The concept of RCP originated in the treatment of what?

massive air embolism during CPB

describe the RCP procedure

When RCP is started, the SVC is snared, antegrade arterial flow is terminated, and the arterial cannula is connected to the arterial return line to the SVC cannula. Pressure in the SVC is maintained at 15-20 mm Hg

Mechanisms with which retrograde cerebral perfusion may accomplish neuroprotection include (3)

1. the flushing of air and atheromatous embolic material from the cerebral circulation 2. the maintenance of cerebral hypothermia, and the provision of nutritive cerebral flow 3. RCP can be given continuously or intermittently

However, incidents of cerebral edema after retrograde cerebral perfusion, particularly when the perfusion pressure exceeds __ mm Hg, are reported

25 mmHg

Despite signs of oxygen uptake observed in several studies, the amount of perfusate that provides cerebral nutrition is low, corresponding to only about _% of total retrograde flow

RCP is used ___ commonly than ACP used in the pediatric population.

less

Antegrade cerebral perfusion can be achieved by using?

an open end of a modified Blalock-Taussig (BTT) shunt after the proximal anastomosis is constructed in neonates who require arch reconstruction (i.e Norwood operation).

what is the perfusate temp and pressure for ACP

- -The perfusate temperature is usually set at 18°C - -Flow is set at 10-20 mL/kg/min or adjusted to maintain a pressure of 40-50 mm Hg in the right radial artery. * **Higher flows of 30-40 mL/kg/min are recommended for neonates***

what ACP flows are recommended for neonates

Higher flows of 30-40 mL/kg/min

Several drawbacks are associated with those various cannulation techniques and are mainly related to complications of direct cannulation of arch vessels. Give 6 examples

1. dissection of the arterial wall 2. air 3. atheromatous plaque embolization 4. malposition of the cannula 5. overcrowding of the operative field with cannulas 6. ACP can be given continuously or intermittently

However, incidents of cerebral edema antegrade cerebral perfusion, particularly when the perfusion pressure exceeds __ mm Hg, are reported

25 mmHg

During hypothermia, the solubility of carbon dioxide in blood _____, and for a given concentration of carbon dioxide in blood, PCO2 ______ and the blood becomes _____

increases decreases alkalotic

During pH-stat acid-base management, the patient's | pH is managed at the patient's?

temperature | --pH-stat pH management is temperature-corrected

Compared to alpha-stat, pH stat (which aims for a pCO2 of 40 and pH of 7.40 at the patient's actual temperature) leads to what?

higher pCO2 (respiratory acidosis), and increased cerebral blood flow

with pH stat- ___ is deliberately added to maintain a pCO2 of 40 mm Hg during hypothermia

CO2

In pH-stat , to compensate for increased carbon dioxide solubility, carbon dioxide is added to the gas mixture in the ______ to maintain the hypothermic pH at 7.40 and the PCO2 at 40 mm Hg

oxygenator

with pH-stat, When blood samples are warmed to room temperature, blood gases are ______ and _______

hypercapnic and acidotic

with pH-stat, CDI: READ ABG’s AT _________

PERFUSATE TEMPERATURE

Data have suggested that the pH-stat strategy is best for the

pediatric population

name 3 things that pH-stat cause as a final result

Improved neurologic outcome hastened EEG recovery times reduced number of postop seizures

physiologically, when using pH stat- what 3 things increase and what 1 thing decreases

- -increases= cortical oxygen saturation before arrest, brain-cooling rates, and CBF during reperfusion - -decreases= cortical oxygen metabolic rates during arrest

when using pH stat- increased CBF can potentially cause what

can increase embolic events, high CBFs during reperfusion, and reperfusion injury

Acid load induced by pH-stat strategy may impair what?

enzymatic function and metabolic recovery. | --To retain the benefits of the pH-stat method on cooling and to eliminate its negative effect on enzymatic function

pH stat can do what to autoregualtion

Lose autoregulation-perfusion pressure then rules

During alpha-stat acid-base management, the ionization state of histidine is maintained by?

managing a standardized pH (measured at 37C)

Alpha-stat pH management is not ...

temperature-corrected as the patient's temperature falls, the partial pressure of CO2 decreases (and solubility increases)

The alpha-stat method allows blood pH to increase during cooling, which leads to what?

hypocapnic and alkalotic blood in vivo

with alpha-stat, Blood samples warmed to room temperature have a pH of 7.4 and a PCO2 of 40 mm Hg. These conditions allow the alpha-imidazole group of the histidine moiety on blood/cellular proteins to maintain what?

a constant buffering capacity, which enhances enzyme function and metabolic activity.

with alpha-stat, the increase in pH parallels the increase in the ...?

hydrogen ion dissociation constant of water during cooling, which can maintain a constant ratio of OH- ions to H+ ions

with alpha stat, you read the ABGs at?

37C

with alpha stat, Cerebral Blood Flow (CBF) autoregulation is maintained, which allows for what?

metabolism and blood flow coupling.

with alpha stat, CBF can be adjusted depending on what?

the patient's cerebral metabolic activity and oxygen needs.

with alpha stat, how is autoregulation and enzyme function handled

Autoregulation is intact | Normal enzyme function

with alpha stat, Most studies of this approach have been performed in ____

adults

with alpha stat, name 2 disadvantages

- Vasoconstriction | - Poor Cooling, which potentiates problems at the cellular level

combined ph/alpha management=

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)

what 3 cerebral oximeters FDA approved in the United States for use in the infant population

INVOS NONIN EQUINOX FORE-SIGHT

3. Blood Gas/Hypothermia- Exam 1 Flashcards

(116 cards)