Topic 11B Flashcards
Two Main Goals of Cardioplegia
- Prevent myocardial ischemic damage (induction/maintenance)
- Prevent/minimize injury (reperfusion)
limit detrimental changes such as (7)
- rapid cellular conversion from aerobic (O2) to anaerobic metabolism (no O2)
- high-energy phosphate (e.g. ATP) depletion
- intracellular acidosis
- calcium influx
- cell membrane disruption
- Intracellular Ca++ accumulation
- Cellular edema (inability to consume oxygen)
Cardioplegia Setups include:
crystalloid
blood
MPS
Crystalloid=
Single pass system
Blood cardioplegia setup=
- Fixed ratio (Bridged or Non-bridged)
2. Variable/controlled ratio
MPS=
microcardioplegia
3 Phases of Cardioplegia include
Induction of arrest
Maintenance of arrest
Reperfusion
Cold Induction Solutions (Crystalloid and Blood)= (4)
- ECF cardioplegia solution
- Potassium depolarization arrest
- Depolarizes the cardiac myocyte with hyperkalemia
- Ca++ ATPase and Na+/K+ATPase still operative and need energy
Pure Crystalloid Cardioplegia Induction:
Advantages (4)
History of use
Ease
Cheap
Low viscosity
Pure Crystalloid Cardioplegia Induction:
Disadvantages (6)
Cellular edema Low O2 capacity Left shift oxy-Hgb curve Activates platelets, leukocytes, and complement Impaired membrane stabilization Hemodilution
Generic Crystalloid Solutions: Lactated Ringer’s 1000 mL KCL= MgCl= Mannitol= NaHCO2=
KCL 20 mEq
MgCl 32 mEq
Mannitol 12.5 g
NaHCO2 6.5 mEq
Lactated Ringer’s 1000 mL: What do you add prior to use?
Procaine 10% 2.7 mL
Generic Crystalloid Solutions: Normosol 1000 mL NaHCO2= KCL= Mannitol=
NaHCO2 35 mEq
KCL 35 mEq
Mannitol 25% 12.5 g
Normosol 1000 mL: What do you give prior to use? (3)
Lidocaine 75 mg
Ntg 500 mcg
Albumin 25% 12.5 g
Cold Blood Cardioplegia Induction
Advantages (4)
O2 carrying capacity
Reduced hemodilution
Buffering/oncotic effects
O2 radical scavengers present
Cold Blood Cardioplegia Induction
Disadvantages (3)
Sludging
Oxy-Hgb curve disruption
Possible red cell damage
Warm Blood Cardioplegia Induction
Advantages (3)
Improved aerobic metabolism
Improved LV function
Improves compromised hearts
Warm Blood Cardioplegia Induction
Disadvantages
Expensive due to additives
Low Potassium Maintenance= (3)
- Usually every 15 to 20 minutes
- Cold blood cardioplegia or crystalloid
- Restores arrest post wash-out
Preparation for Reperfusion= (6)
Substrate-enhanced warm cardioplegia Limit calcium Limit PO2 Controlled reperfusion De-air adequately Avoid ventricular distension
Know the SV per tubing size
look at lab notes from last quarter
Controlled reperfusion=
The endothelium is damaged during ischemia–damage can increase through unregulated reperfusion
•Upon XC Removal: MAP → 40 mmHg for 1-2 minutes then MAP→ 70 mmHg after 2 minutes
Hot Shot=
- Just prior to removal of the aortic cross clamp
- In addition to cross clamp drugs
Cross clamp drugs (4)
Aspartate Glutamate Tham Dextrose CPD --Due to cost: warm blood may be substituted
Custodial Cardioplegia =(HTK)
Histidine Tryptophan Ketoglutarate
Custodial Cardioplegia (HTK): Intracellular cardioplegia solution (4)
Low sodium concentration
Histidine
Tryptophan
Mannitol
Benefits of HTK Cardioplegia: Initial use
organ protection
Benefits of HTK Cardioplegia: Now used in cardiac surgery because (3)
Longer safe time of ischemia
During valve surgery
Minimally invasive procedures
Del Nido Solution (4:1)=
Plasmalyte base which is similar to ECF
Warm Continuous Retrograde Blood Cardioplegia:
Lichtenstein (1991) suggested that the heart
could be maintained at
37ºC throughout the cross clamp period to enhance perioperative myocardial function
Warm Continuous Retrograde Blood Cardioplegia:
“Warm Heart Trial” (1994): Studied nearly 2000 patients randomized to normothermic or hypothermic cardioplegia– they found that…
Normothermic patients experienced a lower incidence
of post-operative low output syndrome with no differences in mortality or myocardial infarction
Warm retrograde cardioplegia flow must be
> 100 mL/min to minimize myocardial lactate production
Cross clamp drugs right after cross clamp removal
lidocaine
mannitol