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Perf Tech > Myocardial protection part 2 > Flashcards

Myocardial protection part 2 Flashcards

1
Q

heart takes up oxygen over time so blood cardioplegia must

A

be delivered over time not a volume

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2
Q

Four Main Objectives of Cardioplegia

A
  • Immediate/sustained electromechanical arrest
  • Rapid/sustained homogenous myocardial cooling
  • Maintenance of therapeutic additives in effective concentrations
  • Periodic washout of metabolic inhibitors
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3
Q

Two Main Goals of Cardioplegia

A

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

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4
Q

limit these detrimental changes to heart

A

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)

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5
Q

Cardioplegia Setups (types)

A 
Crystalloid
• Single pass system
Blood
• Fixed ratio • Bridged
• Non-bridged • Variable/controlled ratio
MPS
• Microplegia
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6
Q

3 Phases of Cardioplegia

A

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

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7
Q

Cold Induction Solutions: Crystalloid and Blood

A

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

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8
Q

Pure Crystalloid Cardioplegia Induction Advantages

A

• History of use • Ease • Cheap, low viscosity

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9
Q

Pure Crystalloid Cardioplegia Induction pitfalls

A
  • Cellular edema •Low O2 capacity • Left shift oxy-Hgb curve •Activates platelets, leukocytes, and complement
  • Impaired membrane stabilization• Hemodilution
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10
Q

Lactated Ringer’s 1000 mL electrolyte concentration

A

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

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11
Q

Normosol 1000 mL concentrations

A

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

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12
Q

Cold Blood Cardioplegia Induction Advantages

A

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

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13
Q

Cold Blood Cardioplegia Induction pitfalls

A

Sludging Oxy-Hgb curve disruption •Possible red cell damage

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14
Q

Warm Blood Cardioplegia Induction Advantages

A
  • Improved aerobic metabolism
  • Improved LV function
  • Improves compromised hearts
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15
Q

Warm Blood Cardioplegia Induction pitfalls

A

•Expensive due to additives

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16
Q

Example: Warm Induction Solution (8:1)

A

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

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17
Q

Low Potassium Maintenance

A

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

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18
Q

Preparation for Reperfusion

A

• 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

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19
Q

The “Hot Shot” (when?)

A

Just prior to removal of the aortic cross clamp

In addition to cross clamp drugs

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20
Q

Whats in the hot shot

A

• Aspartate Glutamate • Tham • Dextrose • CPD

Due to cost – warm blood may be substituted

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21
Q

Typical Warm Reperfusion Solution

A
  • 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
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22
Q 
Custodial Cardioplegia (HTK)
Histidine-Tryptophan-Ketoglutarate
A
  • Intracellular cardioplegia solution • Low sodium concentration
  • Histidine • Tryptophan • Mannitol
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23
Q

Benefits of HTK Cardioplegia

A
  • Initial use: organ preservation • Now used in cardiac surgery
  • Longer safe time of ischemia • During valve surgery • Minimally invasive procedures
24
Q

Del Nido Solution (4:1)

A

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

25
Q

del nido solution additives

A

Mannitol 20% MgSO4 50% NaHCO2 8.4% KCL 2 mEq/L Lidocaine 1 %

16.3 mL 4 mL 13 mL 13 mL 13 mL

26
Q

additional solutions

A

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

27
Q

Warm Continuous Retrograde Blood Cardioplegia

• Lichtenstein (1991) suggested that the heart could be maintained at

A

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

28
Q

Warm Continuous Retrograde Blood Cardioplegia Normothermic patients experienced a lower incidence

A

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

29
Q

Warm retrograde cardioplegia flow must be

A

> 100 mL/min to minimize myocardial lactate production

30
Q

Single Clamp Technique

A

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

31
Q

Side Biting Clamp Technique

A

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

32
Q

Intermittent Crossclamp

A
  • Increased risk of stroke • Not commonly used

* Clamp time is the sum of all fully ischemic times

33
Q

Fibrillatory Arrest Creates a nearly motionless heart by placing an

A

alternating current generator in contact with the left ventricle.

34
Q

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

A

of ejecting air into the aorta.

35
Q

fib arrest should be used in conjunction with

A

hypothermia

36
Q

Fibrillatory Arrest Advantages:

A

• Avoid cross clamp • Quiescent heart with coronary perfusion

37
Q

fib arrest Disadvantages:

A

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

38
Q

Additional Strategies to Enhance Protection

A

• 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)

39
Q

Monitoring Effectiveness for the Perfusionist GOAL:

A

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

40
Q

Monitoring - Temperature Thermo coupled needle usually inserted

A

septal muscle (myocardial temp probe)

41
Q

monitoring temp. Ensure delivery of

A

adequate dose (is it going where it belongs?)

42
Q

monitoring temp. See efficacy of delivery

A

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

43
Q

Determine when next dose needed use

A

timers

44
Q

reasons for failure to arrest

A

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

45
Q

Myocardial Protection for Off-Pump Procedures

A

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

46
Q

Myocardial Protection: Off-Pump Procedures cont.

A

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

47
Q

K ACTION

A

electromechanical arrest

48
Q

Na action

A

↓ edema/intracelluar Ca++ buildup

49
Q

Ca++ action

A

Membrane stabilization

50
Q

NaHCO3 action

A

↑ pH

51
Q

THAM action

A

↑ pH

52
Q

glucose action

A

Substrate, ↑ Osmolarity, ↓ edema

53
Q

Mannitol

A

↑ Osmolarity

54
Q

high potassium solution concentrations

A

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

55
Q

low potassium solution concentrations

A

KCL 40 mmol/L THAM 12 mmol/L MgSO4 9 mmol/L

Dextrose 250 mmol/l CPD 20 mL

Perf Tech (14 decks)

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