Myocardial protection part 2

Question 1

heart takes up oxygen over time so blood cardioplegia must

Answer 1

be delivered over time not a volume

Question 2

Four Main Objectives of Cardioplegia

Answer 2

• Immediate/sustained electromechanical arrest
• Rapid/sustained homogenous myocardial cooling
• Maintenance of therapeutic additives in effective concentrations
• Periodic washout of metabolic inhibitors

Question 3

Two Main Goals of Cardioplegia

Answer 3

Prevent myocardial ischemic damage
(induction/maintenance)
Prevent/minimize injury
(reperfusion)

Question 4

limit these detrimental changes to heart

Answer 4

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+2 accumulation • Cellular edema (inability to consume oxygen)

Question 5

Cardioplegia Setups (types)

Answer 5

Crystalloid
• Single pass system
Blood
• Fixed ratio • Bridged
• Non-bridged • Variable/controlled ratio
MPS
• Microplegia

Question 6

3 Phases of Cardioplegia

Answer 6

I. Induction of arrest II. Maintenance of arrest III. Reperfusion

Question 7

Cold Induction Solutions: Crystalloid and Blood

Answer 7

ECF cardioplegia solution Potassium depolarization arrest
• Depolarizes the cardiac myocyte with hyperkalemia
• Ca2+ATPase and Na+/K+ATPase still operative and need energy

Question 8

Pure Crystalloid Cardioplegia Induction Advantages

Answer 8

• History of use • Ease • Cheap, low viscosity

Question 9

Pure Crystalloid Cardioplegia Induction pitfalls

Answer 9

• Cellular edema •Low O2 capacity • Left shift oxy-Hgb curve •Activates platelets, leukocytes, and complement
• Impaired membrane stabilization• Hemodilution

Question 10

Lactated Ringer’s 1000 mL electrolyte concentration

Answer 10

KCL 20 mEq MgCl 32 mEq Mannitol 12.5 g NaHCO2 6.5 mEq. Add prior to use Procaine 10% 2.7 mL

Question 11

Normosol 1000 mL concentrations

Answer 11

NaHCO2 35 mEq KCL 35 mEq Mannitol 25% 12.5 g

Add prior to use Lidocaine 75 mg Ntg 500 mcg Albumin 25% 12.5 g

Question 12

Cold Blood Cardioplegia Induction Advantages

Answer 12

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

Question 13

Cold Blood Cardioplegia Induction pitfalls

Answer 13

Sludging Oxy-Hgb curve disruption •Possible red cell damage

Question 14

Warm Blood Cardioplegia Induction Advantages

Answer 14

• Improved aerobic metabolism
• Improved LV function
• Improves compromised hearts

Question 15

Warm Blood Cardioplegia Induction pitfalls

Answer 15

•Expensive due to additives

Question 16

Example: Warm Induction Solution (8:1)

Answer 16

• D50 11ml • D5 27ml• CPD 67ml• THAM •83ml Aspartate/Glutamate •62ml KCL 2meq/L 60mEq •Lidocaine 100mg

Question 17

Low Potassium Maintenance

Answer 17

Usually every 15 to 20 minutes Cold blood cardioplegia or crystalloid Restores arrest post wash-out

Question 18

Preparation for Reperfusion

Answer 18

• Substrate-enhanced warm cardioplegia • Limit calcium • Limit PO2 •Controlled reperfusion
The endothelium is damaged during ischemia,
damage can increase through unregulated reperfusion
Upon XC MAP → 40 mmHg for 1-2 minutes. Removal: MAP → 70 mmHg after 2 minutes.
• De-air adequately • Avoid ventricular distension

Question 19

The “Hot Shot” (when?)

Answer 19

Just prior to removal of the aortic cross clamp

In addition to cross clamp drugs

Question 20

Whats in the hot shot

Answer 20

• Aspartate Glutamate • Tham • Dextrose • CPD

Due to cost – warm blood may be substituted

Question 21

Typical Warm Reperfusion Solution

Answer 21

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

Question 22

Custodial Cardioplegia (HTK)
Histidine-Tryptophan-Ketoglutarate

Answer 22

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

Question 23

Benefits of HTK Cardioplegia

Answer 23

• Initial use: organ preservation • Now used in cardiac surgery
• Longer safe time of ischemia • During valve surgery • Minimally invasive procedures

Question 24

Del Nido Solution (4:1)

Answer 24

Plasmalyte base which is similar to ECF: • 140 mEq/L sodium • 5m Eq/L potasium • 3 mEq/L magnesium
• 98 mEq/L chloride • 27 mEq/L acetate • 23 mEq/L gluconate

Question 25

del nido solution additives

Answer 25

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

Question 26

additional solutions

Answer 26

• Plegisol ,Baxter Cardioplegia, St. Thomas Solution, University of Wisconsin Solution

Question 27

Warm Continuous Retrograde Blood Cardioplegia | • Lichtenstein (1991) suggested that the heart could be maintained at

Answer 27

37oC throughout the cross clamp period to enhance perioperative myocardial function.

Question 28

Warm Continuous Retrograde Blood Cardioplegia Normothermic patients experienced a lower incidence

Answer 28

of post-operative low output syndrome with no differences in mortality or myocardial infarction.

Question 29

Warm retrograde cardioplegia flow must be

Answer 29

>100 mL/min to minimize myocardial lactate production

Question 30

Single Clamp Technique

Answer 30

One clamp episode One unclamp episode Distals and proximals done during one ischemic time • Used with calcified stiff aortas

Question 31

Side Biting Clamp Technique

Answer 31

Two clamp episodes Two unclamping episodes Distals done during first ischemic time Proximals done during second ischemic time • Ischemic time is only with fully clamped aorta • Shorter clamp times

Question 32

Intermittent Crossclamp

Answer 32

* Increased risk of stroke • Not commonly used | * Clamp time is the sum of all fully ischemic times

Question 33

Fibrillatory Arrest Creates a nearly motionless heart by placing an

Answer 33

alternating current generator in contact with the left ventricle.

Question 34

fib arrest Left side of heart can be opened without the fear

Answer 34

of ejecting air into the aorta.

Question 35

fib arrest should be used in conjunction with

Answer 35

hypothermia

Question 36

Fibrillatory Arrest Advantages:

Answer 36

• Avoid cross clamp • Quiescent heart with coronary perfusion

Question 37

fib arrest Disadvantages:

Answer 37

•Higher energy requirement than arrested heart • Spontaneous ejection will result in air emboli Keep MAP elevated

Question 38

Additional Strategies to Enhance Protection

Answer 38

• 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)

Question 39

Monitoring Effectiveness for the Perfusionist GOAL:

Answer 39

optimize uniformity and effectiveness of delivery (especially retrograde) • Temperature • pH •Electrical Activity

Question 40

Monitoring - Temperature Thermo coupled needle usually inserted

Answer 40

septal muscle (myocardial temp probe)

Question 41

monitoring temp. Ensure delivery of

Answer 41

adequate dose (is it going where it belongs?)

Question 42

monitoring temp. See efficacy of delivery

Answer 42

• Antegrade - cases of aortic insufficiency • Retrograde - cannula position ( in RA?)

Question 43

Determine when next dose needed use

Answer 43

timers

Question 44

reasons for failure to arrest

Answer 44

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

Question 45

Myocardial Protection for Off-Pump Procedures

Answer 45

Regional ischemia unavoidable • May become global problem when multiple vessels grafted Use of suction-based stabilizers has reduced the problem of working on a moving target • Provide good exposure without excess compression of ventricle Ischemic preconditioning • Brief period of vessel occlusion before occluding for construction of the anastomosis

Question 46

Myocardial Protection: Off-Pump Procedures cont.

Answer 46

Myocardial Protection: Off-Pump Procedures • Keep normal to high systemic blood pressure • May increase flow through collaterals vessels • Attach proximal end of graft before attaching distal • Immediate re-establishment of flow to ischemic area • Use of intracoronary shunt • Perfusion-assisted direct coronary artery bypass (PADCAB) • Perfuse completed grafts

Question 47

K ACTION

Answer 47

electromechanical arrest

Question 48

Na action

Answer 48

↓ edema/intracelluar Ca++ buildup

Question 49

Ca++ action

Answer 49

Membrane stabilization

Question 50

NaHCO3 action

Answer 50

↑ pH

Question 51

THAM action

Answer 51

↑ pH

Question 52

glucose action

Answer 52

Substrate, ↑ Osmolarity, ↓ edema

Question 53

Mannitol

Answer 53

↑ Osmolarity

Question 54

high potassium solution concentrations

Answer 54

KCl 100mmol/L. THAM 12mmol/L. MgSO4 9 mmol/L Dextrose 250 mmol/L CPD 20ML

Question 55

low potassium solution concentrations

Answer 55

KCL 40 mmol/L THAM 12 mmol/L MgSO4 9 mmol/L | Dextrose 250 mmol/l CPD 20 mL