test 1 part 2 Flashcards
Neonates and pediatric overview
Many pediatric organ systems are immature / vulnerable
Neonates have higher metabolic demands
Neonates have IMMATURE MYOCARDIUM (matures 3-12 months)
Neonates utilize GLUCOSE OXIDATION
Immature myocardium prone to “stretch injury”
Utilize alpha-stat and pH-stat blood gas management
adults overview
Adult circuits tend to be “one size fits all”
Many adult organ systems have acquired disease
Some organ systems have failed
Adults utilize FATTY ACID DEPENDENT energy source
Not affected as much by prime volume dilution
Mature clotting cascade and organ systems
Utilize mostly alpha-stat and some pH-stat blood gas management
estimating blood volumes: Weight (kg): <10 11-20 21-30 31-40 >40
Blood volume (cc/kg) < 10 = 85 11-20 = 80 21-30 = 75 31-40 = 70 > 40 = 65 - used for calculating post dilutional hematocrit
Circuits are commonly called: 3/16” x ¼” ¼” x ¼” ¼” x 3/8” 3/8” x 3/8” 3/8” x ½”
3/16” x ¼” = Neonatal Pack ¼” x ¼” = Infant Pack ¼” x 3/8” = Pediatric/Small Adult Pack 3/8” x 3/8” = Adult Pack 3/8” x ½” = Large Adult Pack
Sequence to choosing an appropriate pediatric CPB circuit
- Determine BSA (kg weight may suffice)
- Determine maximum flow rate (KG weight based or BSA based)
- Choose oxygenator
4.Choose appropriate pump boot - Determine arterial line size
- Determine venous line size
*Packs (1/8” x 3/16”, 3/16”x3/16”, 3/16”x¼”, ¼” x ¼”, ¼”x3/8”, 3/8”x3/8”, 3/8”x½”) - Pick arterial cannula
- Pick venous cannula
Kg weight - based flows Weight (kg) 0-3 3-10 10-15 15-30 >30 >55
0-3 = 200 cc/kg 3-10 = 150 cc/kg 10-15 = 125 cc/kg 15-30 = 100 cc/kg >30 = 75 cc/kg >55 = 65 cc/kg
Terumo Baby RX05 (Max Flow and Prime volume)
Max Flow: 1.5 L/min (in red)
Prime volume: 43 cc (in red)
Terumo RX10
Max Flow: 4 L/min
Prime volume: 135 cc
-used for bigger kids
Terumo RX15
Max Flow: 5 L/min
Prime volume: 135 cc
-used for bigger kids
Sorin Kids D100
Max Flow: 0.7 L/min
Prime volume: 31 cc (in red)
Sorin Kids D101
Max Flow: 2.5 L/min
Prime volume: 87 cc
Stroke volume/ revolution for boot diameter: 3/16” ¼” 3/8” ½”
3/16” = 7 cc
¼” = 13 cc
3/8” = 27 cc
½” = 45 cc
do NOT exceed how many RPM’s for maximum tubing flows
100 RPM’s
Max tubing flows for: 3/16” ¼” 3/8” ½”
3/16” 7 cc => (x 100 =700 cc)
¼” 13 cc => (x 100= 1300 cc)
3/8” 27 cc => (x 100= 2700 cc)
½” 45 cc => (x 100= 4500 cc)
Reynolds number
Reynolds number = (velocity of fluid x density of fluid x diameter of pipe) / viscosity of fluid
Poisueille’s law
- total volume that flows through a tube
Flow = (change in pressure x pi x radius^4) / (length of tube x viscosity of fluid x 8) - radius is the only thing that changes
how does turbulent flow effect the critical velocity
- Turbulence decreases flow at any given perfusion pressure
- turbulence increases the perfusion pressure required for a given flow
- there is a “critical reynolds number” that when it is exceeded, there is a difference between turbulent flow and laminar flow
Choosing arterial tubing size base on max blood flow and how much prime it contains 1/8 3/16” ¼” 3/8”
1/8 => 700 mls/min => 3 mls/ft
3/16 => 1100 mls/min => 7 mls/ft
1/4 => 2000 mls/min => 10 mls/ft
3/8 => 6500 mls/min => 20 mls/ft
why is venous line normally larger
- need a bigger line to drain more
Choosing arterial tubing size base on max blood flow and how much prime it contains 3/16” ¼” 3/8” ½”
3/16 => 1100 mls/min => 7 mls/ft
1/4 => 2000 mls/min => 10 mls/ft
3/8 => 6500 mls/min => 20 mls/ft
½ = > ———- => 40 mls/ft
Resistance in the venous reservoir
- We will not be dealing with a wide open venous line
- Resistance in your reservoir can be a factor in venous return
◦ Since your venous line goes into the sock, a certain amount of volume is “delayed” there
◦ This is called “holdup volume”
◦ As your viscosity goes up - so may your holdup volume
Pediatric Cannula Selection
- Cannulation can be achieved in various vessels depending on the anomaly
- Look for high flow – low pressure drops
- Thin walled reinforced and thin wall metal cannula give good flow with lower pressure drops
- It’s all about the ID (inner diameter) (for us) and the OD (outer diameter) (for surgeons)
Pediatric Cannula Selection: arterial
Aim: utilize the smallest cannula w/ the highest flow rate
Do NOT exceed pressure drop > 100 mmHg
Critical velocity is reached when laminar flow becomes turbulent (Reynolds #)
Higher pressures = higher sheer stress = hemolysis = bad
Pediatric Cannula Selection: venous
Aim: drain the patient with the smallest cannulas
Be aware if the cannulation is bicaval or single atrial cannula
Pressure drop is in the -30 to -40 range (pressure-flow curve)
Vacuum Assist Venous Drainage (VAVD) may help but at a cost (micro-emboli may be associated with VAVD)
Determining arterial cannula
Determine max flow:
Cannulation may be aortic / femoral / neck
Pressure drop should not exceed 100 mmHg
Anticipate larger flow needs when warming
Anticipate viscosity changes
Main ascending aortic cannulae
DLP wire reinforced
main femoral arterial cannulae
Biomedicus arterial cannulae
Determining venous cannula
Determine max flow
Cannulation utilizes Bicaval or Single Atrial
Pressure drop -30 to -40 mmHg
( MEASURE IT - its gravity!)
Anticipate larger flow needs when warming
Anticipate viscosity changes
when choosing a cannula, it’s all about what
- resitance
priming with 25% albumin
- Start with prime then take out the filter and put in your albumin. displace all of the prime and all that is left in there is pretty much albumin
Aids passification of tubing
Elevates C.O.P. and serum osmolarity
Good osmotic “pull” from tissues - make sure tubing isn’t coated with X-coating which calls for priming with crystalloid first
Cefazolin (Kefzol, Ancef) dose
25 mg/kg (max dose = 1 g)
Pump prime may contain how much solumedrol (methylprednixolone)
30 mg/kg up to 500mg
bicarbonate equation
0.3(kg wt)(BE) = NaHCO3 mEq
Mannitol calculation
0.25 g/kg in prime
CaCl
If priming with blood, a good rule of thumb is to use 1 mg CaCl per 1 mL of blood product
for neonates/infants < 5kg
- 100 ml PRBC’s are added to the prime to avoid a prolonged period a asanguineous perfusion.
calculate the PDHCT
- practice
hemochron vs hepcon (ACT)
- hemochron gives you abnormally high values compared to the hepcon
- could result in having clotting problems in the circuit
Platelet works
Assesses platelet function and compares functional and nonfunctional platelets by percentage (%)
- does not tell you a platelet count
