Myocardial Protection-Exam 2 Flashcards by Briana Lieberman

What is already in Lactated Ringer’s 1000mL?

KCL 20mEq
MgCl 32 mEq
Mannitol 12.5 g
NaHCO2 6.5 mEq

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What do you need to add prior to use in Lactated Ringer’s 1000mL?

Procaine 10% 2.7 mL

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What is already in Normosol 1000mL?

NaHCO2 35 mEq
KCL 35 mEq
Mannitol 25% 12.5 g

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What do you need to add to Normosol 1000mL prior to use?

Lidocaine 75 mg
Ntg 500 mcg
Albumin 25% 12.5g

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Pure Crystalloid Cardioplegia Advantages

Hx of Use
Ease
Cheap
Low viscosity

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Pure Crystalloid Cardioplegia Pitfalls

Cellular edema
Low O2 capacity
left shift oxy-hgb curve
Activates plts, leukocytes, and complement
Impaired membrane stabilization
Hemodilution

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What are the two generic crystalloid solutions?

Lactated Ringer’s

Normosol

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Cold Blood Cardioplegia Advantages

O2 carrying capacity
Reduced hemodilution
Buffering/oncotic effects
O2 radical scavengers present

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Cold Blood Cardioplegia Disadvantages

Sludging
Oxy-Hgb curve disruption
Possible red cell damage

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Primary energy source for adults vs kids

Adults: Free fatty acids
Kids: glucose

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What is the purpose of dextrose?

Big macromolecules; brings in water

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How do you prepare for reperfusion?

Substrate-enhanced warm cardioplegia
• Limit calcium
• Limit PO2
De-air adequately
• Avoid ventricular distension

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What pressures do you use in controlled reperfusion?

Upon XC MAP → 40 mmHg for 1-2 minutes.

Removal: MAP → 70 mmHg after 2 minutes.

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When do you do a “Hot shot”

Just prior to removal of the aortic cross clamp

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What is in a hot shot?

It is in addition to XC drugs.

Aspartate Glutamate
• Tham
• Dextrose
• CPD

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Typical Warm Reperfusion SOlution

THAM (0.3 M) solution – 225 mL
• CPD – 225 mL
• Dextrose 50% - 40 mL
• MSA/MSG 0.46 M – 250 mL
• Dextrose 5% - 200 mL
• KCl (2 mEq/L) – 15 mL

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What’s another name for custodial cardioplegia?

HTK

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HTK

Histidine- Tryptophan- Ketoglutarate

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What is in Custodial cardioplegia?

Intracellular cardioplegia solution
• Low sodium concentration
• Histidine
• Tryptophan
• Mannitol

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What was HTK initially used for?

Organ preservation

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What are the advantages of HTK?

Longer safe time of ischemia
• During valve surgery
• Minimally invasive procedures

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Del Nido Solution (4:1) uses what kind of base?

Plasmalyte

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What’s in a plasmalyte base?

140 mEq/L sodium
• 5m Eq/L potasium
• 3 mEq/L magnesium
• 98 mEq/L chloride
• 27 mEq/L acetate
• 23 mEq/L gluconate

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What additives do you add to Del Nido solution? (4:1)

Mannitol 20% 16.3 mL
MgSO4 50% 4 mL
NaHCO2 8.4% 13 mL
KCL 2 mEq/L 13 mL
Lidocaine 1 % 13 mL

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What should be the flow for warm retrograde cardioplegia in order to minimize myocardial lactate production?

>100 ml/min

What clamp technique is used with calcified and stiff aortas?

Single Clamp Technique

One clamp episode • One unclamp episode • Distals and proximals done during one ischemic time

When is the ischemic time of the Side Biting Clamp technique?

Ischemic time is only with fully | clamped aorta

Side Biting Clamp Technique

Two clamp episodes • Two unclamping episodes • Distals done during first ischemic time • Proximals done during second ischemic time Shorter clamp times

What is the clamp time within the intermittent clamp technique?

Clamp time is the sum of all | fully ischemic times

Intermittent Crossclamp Risk

Stroke; not commonly used

How is fibrillatory arrest performed?

Creates a nearly motionless heart by placing an alternating current generator in contact with the left ventricle.

Fibrillatory Arrest Advantages

Left side of heart can be opened without the fear of ejecting air into the aorta. Avoid cross clamp • Quiescent heart with coronary perfusion

What should be used in conjuction with the fibrillatory arrest technique?

hypothermia | Keep MAP elevated

Fibrillatory arrest disadvantages

Higher energy requirement than arrested heart | • Spontaneous ejection will result in air emboli

Additional Strategies to Enhance Protection

``` Anesthetic agents (↑ preconditioning) • Acute normovolemic hemodilution (↓ A fib) • Neutrophil depletion (↓ V fib) • Erythropoietin (↓ myocardial injury) • N-acetylcysteine (↓ oxidative stress) • Deferoxamine (↓lipid peroxidation) • Statins (↑NO release) ```

Anesthetic Agents: Pros and Cons

Pro: Preconditioning; ameliorate deleterious effects of reactive oxygen species Cons: unclear which agents are best

Acute normovolemic hemodilution: Pros and cons

Pro: less myocardial injury; decreased inotrope requirement; reduced A fib and conduction block Cons: Efficacy not demonstrated in all patient groups; some patients are too anemic for this tehchnique

Neutrophil Depletion: Pros and Cons

Pros: Decreases post bypass v-fib; lower inotrope use; lower postoperative cardiac enzyme release Cons: cost; complexity

Erythropoietin: Pros and Cons

Pro: limits myocardial injury Con: cost

N-acetylcysteine: Pros and Cons

Pro: may reduce oxidative stress Con: may interfere with preconditioning, cost, complexity

Deferoxamine: Pros and Cons

Pro: decreased lipid peroxidation; increased myocardial protection, LVEF; decreased postoperative wall motion abnormalities Cons: cost; complexity; not proven in large studies

Statins: Pros and Cons

Pros: increased nitric oxide release; anti-inflammatory properties; antioxidative properties; decreased monocyte adhesion

What 3 parameters do you monitor to determine myocardial protection?T

Temperature pH electrical activity

Possible causes of failure to arrest

``` Aortic insufficiency • Cross-clamp or cardioplegia needle malpositioned. • Inadequate solution (low potassium) • Low flow? • Low pressure? • Temperature? ```

PADCAB

Perfusion-assisted direct coronary artery bypass; perfuse completed grafts

K+

electromechanical arrest

Na+

↓ edema/intracelluar Ca++ buildup

Ca++

Membrane stabilization

NaHCO3

increase pH

THAM

increase pH

Glucose

Substrate, ↑ Osmolarity, ↓ edema

Mannitol

↑ Osmolarity

High Potassium Common Solution Concentrations

``` KCl 100 mmol/L THAM 12 mmol/L MgSO4 9 mmol/L Dextrose 250 mmol/l CPD 20 mL ```

Low Potassium Common Solution Concentrations

``` KCl 40mml/L THAM 12 mmol/L MgSO4 9 mmol/L Dextrose 250 mmol/l CPD 20 mL ```

Vein Grafts: Pressure and Flow Rate

50mmHg | 50-100 ml/min

Direct Ostial: Pressure and Flow Rate

250 mmHg | 50-150 ml/min

What percent of CO is direct ostial?

5-8% of CO

Retrograde: Pressure and Flow rate

40 mmHg | 150-200 ml/min

Antegrade: Pressure and Flow Rate

50-100 mmHg aortic root P 250-400 ml/min 150 ml/min/m2

Antegrade Dose

Initial: 10-15 ml/kg | Up to 30 ml/kg

Combined doses

1-1.5L Antegrade | 500 ml Retrograde

We should assume the P drop across system is

175 mmHg

P drop is proportional to

Velocity; Shear F, viscosity