Differences beweeen adult and pediatric CPB, Hypothermia, Nero, Blood gas / Pedi test 2 Flashcards
Infant CPB parameters;
- ) Hemodilution:
- ) Perfusion Pressures:
- ) Hypothermic Temps:
- ) TCA / DHCA:
1.) 150 - 300%
2.) 20 - 50 mmHg
3.) 15 - 20 degrees celcius
common
4.) Common
Early Manifestations of brain injury in children include:
Seizure
Stroke
Choreothasis
Coma
Choreothasis definition ?
Occurrence of involuntary movements in a combination of chorea (irregular migrating contractions) and athetosis (twisting and writhing).
Late Manifestations of brain injury in children include:
- Delayed neurodevelopment
- Motor abnormalities
Reports suggest that transient deficits occur in ______% of all infants undergoing CPB
25%
Deep hypothermia post-CPB effects:
- Reduced cerebral blood flow.
- Disordered brain metabolic activity
- Delayed functional recovery
Cold is a perfusionist’s best friend, cold temperatures serve as a ?
PROTECTIVE mechanism that reduces metabolism & from a TECHNICAL perspective gives a greater safety margin for emergency scenarios
Adult
Brain Weight = 1300 g
Body Weight = 75,000 g
Neonate ?
Brain Weight = 300 g
Body Weight = 3500 g
Adult brain represents <2% of total body weight. Neonatal brain represents what % of total body weight?
9 %
The first truly scientific document in hypothermia was written by ?
1797 - Dr. James Currie
- Royal College of Surgeons
- Recorded temps 94º F
Two Distinct Open-Heart Surgery Strategies Emerged
in 1950, what were they ?
- Cardiopulmonary bypass: maintain normal physiology
- Hypothermia with inflow occlusion
* No Cardiopulmonary Bypass
Who discovered hypothermia with inflow occlusion ?
Dr. W.G. Bigelow
Dr. John F. Lewis
- September 2, 1952 successfully closed a secundum ASD in a 5-year old girl under direct vision.
- Published on a series of ASD closures with 12% mortality
Benefits of Hypothermia w/inflow occlusion were obvious but were limited to?
- ASDs
- Isolated aortic/pulmonic stenosis
What institution incorporated a modified General Motors radiator into the extracorporeal circuit to combine Cardiopulmonary bypass + Hypothermia ?
1958, WC Sealy, Duke University Medical Center
Surface Cooling/Immersion work in what order?
Environment
Skin / Tissues
Blood Vessels
Extracorporeal Blood Cooling worked in what order ?
Blood vessels
Skin / Tissues
Environment
Hypothermia and cardiopulmonary bypass has effects on what 3 sectors?
Biochemical Reactions
Blood Viscosity
Changes in blood gases
CPB + Hypothermia permits
lower pump flows,
less blood trauma,
better organ protection
The concept of Q10
The multiple by which a reaction rate changes for every 10°C change in temperature
Levels of Hypothermia
Mild:
Moderate
Deep
Profound
Mild: 32 -36º C
Moderate 28 - 32º C
Deep 18 - 28º C
Profound < 18º C
Who are the smaller subset of patients using deep hypothermia ± TCA ?
Neonatal heart surgery
Aortic arch reconstruction
Neuro-surgical procedures
Hypothermia ___ blood viscosity.
Increases
Viscosity of blood ____ per °C
2 %
Cooling and Warming gradients ?
Do not exceed 8-10°C
Do not exceed 8-10°C gradient During cooling between:
perfusate and core temp
Do not exceed 8-10°C gradient During rewarming between:
venous blood and heater cooler waterbath
3 Neuroprotective strategies in children undergoing CPB ?
- Deep hypothermia
- Avoidance of long circulatory arrest times
- Blood chemistries
4 Neuroprotective strategies in children undergoing CPB that involve Blood chemistries ?
- HCT levels
- COP
- Blood Gas Strategies
- Hyperoxia
Change in the oxygen-hemoglobin dissociation curve.
Greater affinity = less efficient release of O2 at tissue level, what can we do?!?
Consider HYPEROXIA prior to circulatory arrest
Changes in solubility of O2 and CO2.
As temps ____ gases become more soluble in liquid.
This means that as temp ___ the solubility of gas ____.
Therefore more gas will be dissolved in plasma and the partial pressure will drop. Much more significant for CO2
Decreases
Decreases
Increases
Values that are calculated to actual temperature when the sample is drawn ?
Temperature Corrected
Sample that is measured at normothermia (37º C) ?
Temperature Uncorrected
An Essential Amino Acid
that plays an important part of catalytic sites in certain enzymes ?
Histidine
Histidine Contains a positivily charged ?
The charge state can dictate the structure of the active site.
imidazole functional group
What is responsible for maintaining the temperature-pH relationship in Alpha-stat ?
protein buffering, largely due to the imidazole group of histidine
The imidazole has a degree of dissociation (referred to as alpha) of
0.55 in the intracellular compartment and this remains constant despite changes in temperature (ie the pK is changing with change in temperature).
Alphastat Hypothesis
The degree of ionisation (alpha) of the imidazole groups of intracellular proteins remains constant despite change in temperature.
Rationale for pH-stat; CO2 added to the circuit maintains pH = 7.40
May be beneficial because:
- CO2 may counteract oxy-hemoglobin disassociation . curve
- CO2 is a potent cerebral vasodilator and promotes high CBF
high CBF promotes ?
- More complete and homogeneous cooling
- Prevents cerebral steal due to aorto-pulmonary collateral’s
pH-stat method
Goal:
Keep arterial pH = 7.40 at any given temperature.
ACTUAL or TEMPERATURE CORRECTED SAMPLE
Remember:blood gas measure samples at 37 C.
To accomplish my goal, one must allow CO2 to accumulate
Alpha-stat method
Goal:
Maintain pH = 7.40 in UNCORRECTED SAMPLE eg 37C degrees.
Technically easy. Run normal ABG based upon results of sample
Blood gas strategy for mild/moderate hypothermia?
Alpha-stat
Blood gas strategy for deep hypothermia (pediatrics) ?
pH-stat
Blood gas strategy for deep hypothermia (adult)
Alpha stat
Blood gas strategy for all populations ?
Consider hyperoxia pre-arrest
Careful attention during rewarming to avoid ?
cerebral hyperthermia
Maintain hematocrits at ?
> 25%
What are the 4 different modes ?
- Deep Hypothermic Circulatory Arrest (DHCA)
- Selective Antegrade Cerebral Perfusion (SACP)
- Regional Low flow
- Retrograde cerebral perfusion (RCP)
The clinical team should manage adult patients undergoing moderate hypothermic CPB with ?
Alpha-Stat pH management
The clinical team should manage PEDIATRIC patients undergoing DEEP hypothermic CPB with ?
ASD patients use Alpha Stat
cross-over technique
one cools pH stat and then just prior to arrest crosses back to alpha.
Update on Pediatric Perfusion Practice
in North America Minimal acceptable Hct ?
24 - 30%
Update on Pediatric Perfusion Practice
in North America Termination Hct (cyanotic defects) ?
28 - 45%
Update on Pediatric Perfusion Practice
in North America Termination Hct ( non cyanotic ) ?
21 - 35%
