Exam 5 - Cardioplegia Flashcards
Myocardium O2 consumption
70-75%
Arrested heart O2 consumption
2 ml O2 / 100 g tissue
Resting heart O2 consumption
8 ml O2/min/100 g
Heavy exercise O2 consumption
70 ml O2/min/100g
Other O2 consumption
Brain: 3
Kidney: 5
Skin: 0.2
Resting/Active muscle: 1/50
Coronary perfusion pressure equation
DBP - LVEDP or LA
- Gradient of 15 needed for survival
- Hard to get that low
W/O cardioplegia
- 20 min before permanent damage
W/ cardioplegia
4-5 hours without permanent damage
Phase 0
Na influx
Phase 1
Transient K efflux
Phase 2
Ca influx
Phase 3
K efflux
Phase 4
Na/K pump
K arrest
- knocks out phase 3
- K efflux stage
- no repolarization
Low K arrest (custodial)
- knocks out phase 0
- Na influx
- No depolarization
Del Nido arrest (Low Ca)
- knocks out phase 2
- Ca influx stage
- No contraction phase
Antegrade
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
Retrograde
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
Integrated
Pros: uniform distribution of cpg
Cons: complex / need to monitor pressures
Ostial delivery
- used in AVR / aneurysm / dissection
- 250-300 mmHg circuit pressure (tiny cannula orifice)
- 150-250 ml/min
- 5-8% of CO
Graft delivery
- can check anastomosis / flow
- flow 50-100 ml/min
- can’t do it in every case
Pressure and cpg
- NEED a pressure to prevent sinus/root blow up
- need to know pressure drop across system
- high flow -> larger pressure drop
Goal of perfusionist with cpg
- uniform delivery
- effective delivery
- look at EKG and temp
Crystalloid benefits
- simple
- cheap
- better visibility
- better distal perfusion
- low Ca
Crystalloid cons
- minimal buffering
- low O2 capacity
- hemodilution
- must be cold
Blood cpg benefits
- better metabolic environment
- can be warm
- smaller crystalloid volume (but watch reservoir)
Blood cpg cons
- shifts oxy curve left
- increase viscosity
- complex
- cost
Blood vs crystalloid
- blood better
- better systolic function and diastolic function
- better protection and recovery
Quest
- all blood
- small volume cpg
- controllable
- expensive and complex
Standard temp
10 C
Target is 10-15
- but better recovery with warm cpg
Intermittent delivery
- improved exposure
- lower volume
- BUT more acidosis
Continuous delivery
- normal perfusion
- better LV function
- less inotropic help
- BUT wet field / complex for perfusionist and surgeon
Common additives
- 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
Typical cpg solution
KCl THAM MgSO4 Dex CPD
St Thomas solution
Na K Ca Mg Cl Na Bicarb 320 Osmolarity
Custodial HTK
Histadine
Tryptophan
Ketogluterate
Intracellular ion mixture
- One dose for 60 min
Del Nido
-1:4....one dose needed Plasmalyte base similar to ECF Mannitol MgSO4 Bicarb Lidocaine
3 phases of cpg
- induction
- Maintenance (every 15-20 min)
- keep temp down / check grafts / wash out / maintain
- reperfusion