Exam 5 - Cardioplegia

Question 1

Myocardium O2 consumption

Answer 1

70-75%

Question 2

Arrested heart O2 consumption

Answer 2

2 ml O2 / 100 g tissue

Question 3

Resting heart O2 consumption

Answer 3

8 ml O2/min/100 g

Question 4

Heavy exercise O2 consumption

Answer 4

70 ml O2/min/100g

Question 5

Other O2 consumption

Answer 5

Brain: 3
Kidney: 5
Skin: 0.2
Resting/Active muscle: 1/50

Question 6

Coronary perfusion pressure equation

Answer 6

DBP - LVEDP or LA

• Gradient of 15 needed for survival
• Hard to get that low

Question 7

W/O cardioplegia

Answer 7

• 20 min before permanent damage

Question 8

W/ cardioplegia

Answer 8

4-5 hours without permanent damage

Question 9

Phase 0

Answer 9

Na influx

Question 10

Phase 1

Answer 10

Transient K efflux

Question 11

Phase 2

Answer 11

Ca influx

Question 12

Phase 3

Answer 12

K efflux

Question 13

Phase 4

Answer 13

Na/K pump

Question 14

K arrest

Answer 14

• knocks out phase 3
• K efflux stage
• no repolarization

Question 15

Low K arrest (custodial)

Answer 15

• knocks out phase 0
• Na influx
• No depolarization

Question 16

Del Nido arrest (Low Ca)

Answer 16

• knocks out phase 2
• Ca influx stage
• No contraction phase

Question 17

Antegrade

Answer 17

Pros: simple / like normal flow / quick arrest
Cons: need good aortic valve / interrupt surgery / bad for CAD

• 10-15 ml/kg initial dose (30 in peds)
• 4:1
• more doses are less K and less volume
• Line pressure: 125-150 / root pressure: 50-100
• Flow is 250-400 ml/min

Question 18

Retrograde

Answer 18

Pros: avoids bad AI / CAD / No interruption / helps de-air
Cons: hard to place catheter / can blow sinus / poor R heart coverage

VENT ON

• balloon stops backflow AND holds in place
• flow is 200 ml/min
• Sinus pressure of 30-40 mmHG

Question 19

Integrated

Answer 19

Pros: uniform distribution of cpg
Cons: complex / need to monitor pressures

Question 20

Ostial delivery

Answer 20

• used in AVR / aneurysm / dissection
• 250-300 mmHg circuit pressure (tiny cannula orifice)
• 150-250 ml/min
• 5-8% of CO

Question 21

Graft delivery

Answer 21

• can check anastomosis / flow
• flow 50-100 ml/min
• can’t do it in every case

Question 22

Pressure and cpg

Answer 22

• NEED a pressure to prevent sinus/root blow up
• need to know pressure drop across system
• high flow -> larger pressure drop

Question 23

Goal of perfusionist with cpg

Answer 23

• uniform delivery
• effective delivery
• look at EKG and temp

Question 24

Crystalloid benefits

Answer 24

• simple
• cheap
• better visibility
• better distal perfusion
• low Ca

Question 25

Crystalloid cons

Answer 25

- minimal buffering - low O2 capacity - hemodilution - must be cold

Question 26

Blood cpg benefits

Answer 26

- better metabolic environment - can be warm - smaller crystalloid volume (but watch reservoir)

Question 27

Blood cpg cons

Answer 27

- shifts oxy curve left - increase viscosity - complex - cost

Question 28

Blood vs crystalloid

Answer 28

- blood better - better systolic function and diastolic function - better protection and recovery

Question 29

Quest

Answer 29

- all blood - small volume cpg - controllable - expensive and complex

Question 30

Standard temp

Answer 30

10 C Target is 10-15 - but better recovery with warm cpg

Question 31

Intermittent delivery

Answer 31

- improved exposure - lower volume - BUT more acidosis

Question 32

Continuous delivery

Answer 32

- normal perfusion - better LV function - less inotropic help - BUT wet field / complex for perfusionist and surgeon

Question 33

Common additives

Answer 33

- KCl: maintain diastolic arrest - THAM: buffer - Mannitol: Osmolarity AND radical scavenger - Aspartate: gentle Cardioplegia BUT expensive - CPD: citrate / lowers free Ca / prevent stone heart - MgCl2: less Ca - Glucose: metabolic substrate - Blood: oxygen carrying capacity

Question 34

Typical cpg solution

Answer 34

``` KCl THAM MgSO4 Dex CPD ```

Question 35

St Thomas solution

Answer 35

``` Na K Ca Mg Cl Na Bicarb 320 Osmolarity ```

Question 36

Custodial HTK

Answer 36

Histadine Tryptophan Ketogluterate Intracellular ion mixture - One dose for 60 min

Question 37

Del Nido

Answer 37

``` -1:4....one dose needed Plasmalyte base similar to ECF Mannitol MgSO4 Bicarb Lidocaine ```

Question 38

3 phases of cpg

Answer 38

- induction - Maintenance (every 15-20 min) - keep temp down / check grafts / wash out / maintain - reperfusion