Myocardial Protection in Pediatric Cardiac Surgery

1. Myocardial Protection
in Pediatric Cardiac
Surgery

2. No Disclosures

3. High KHigh K++
cardiac arrest
Melrose 1955 –Potassium citrate ( 77m mol/L)
~~20 years(Mortality20 years(Mortality ~~10-20%)10-20%)
Hypothermia: systemic and/or topicalHypothermia: systemic and/or topical
 Bigelow et al. 1950; Shumway et al. 1959; Swan 1973
Continuous or intermittent aortic occlusion
 Cooley et al. 1962
Aortic root or intracoronary blood perfusion
 Kay et al. 1958
Ellectrically induced VF (fibrilator)Ellectrically induced VF (fibrilator)
 Senning 1952
HistoryHistory

4. Pharmacological arrest was firstPharmacological arrest was first
successfully used bysuccessfully used by
Bretschneider* in 1964 (HTK)Bretschneider* in 1964 (HTK)
St. Thomas in 1975St. Thomas in 1975
Blood cardioplegiaBlood cardioplegia
Buckberg et al, in 1978Buckberg et al, in 1978
HistoryHistory
*Bretschneider HJ (1964) U˝ berlebenszeit und Wiederbelebungszeit
des Herzens bei Normo undHypothermie. Verh Deutsch Ges
Kreislaufforschung 30: 11 34.

5. Importance of MP
1.1. IIrreversible ischemic damagerreversible ischemic damage
begins tobegins to occur in theoccur in the normothermicnormothermic
heart after only 20 minheart after only 20 min
2.2. However,However, when current techniqueswhen current techniques
of myocardial protection are used,of myocardial protection are used,
arrest times of more than 4 or 5arrest times of more than 4 or 5
hours may behours may be tolerated withouttolerated without
irreversible damageirreversible damage
1. Reimer KA,et al. Am J Cardiol 1983;52:72A
2. Hosenpud JD, et al. J Heart Lung Transplant 2001;20;805

6. Morphological differences
between pediatric/adult
myocardium
 In the newborn only 30% of theIn the newborn only 30% of the
myocardial massmyocardial mass comprises contractilecomprises contractile
tissue compared with 60% intissue compared with 60% in the maturethe mature
myocardium.myocardium.
 Pediatric myocardium has fewerPediatric myocardium has fewer
mitochondria andmitochondria and less oxidativeless oxidative
capacity.capacity.

7. Clinical differences between
pediatric/adult myocardium
 NNormal immature myocardiumormal immature myocardium has ahas a
greater tolerance to ischemia whengreater tolerance to ischemia when
compared tocompared to mature myocardiummature myocardium11
..
 HHypoxicypoxic neonatal heart is moreneonatal heart is more
sensitive to ischemia than thesensitive to ischemia than the
adultadult2
..
 When cWhen compared with infants,ompared with infants,
childrenchildren havehave had significantly lesshad significantly less
reperfusion injury and better clinicalreperfusion injury and better clinical
outcomeoutcome 3
..
1. Yano Y et al. J Thorac Cardiovasc Surg 1987;94:887
2. Kempsfor RD, et al. J Thorac Cardiovasc Surg 1989;97:856
3. Imura H, et al. Circulation 2001;103:1551

8. 1. Physiological differences
between pediatric/adult
myocardium
 Immature myocardiumImmature myocardium 1-3
 Decreased ventricular complianceDecreased ventricular compliance
 Less preload reserveLess preload reserve
 DecreasedDecreased sensitivity to catecholaminessensitivity to catecholamines inin
immature heartsimmature hearts
 Less inotropic reserve (with maximumLess inotropic reserve (with maximum
adrenergic stimuli)adrenergic stimuli)
 More (-) inotropic response to anestheticMore (-) inotropic response to anesthetic
agentsagents
 Cardiac output in pediatric patients is moreCardiac output in pediatric patients is more
dependent on heart rate and sinus rhythm.dependent on heart rate and sinus rhythm.
 Increase oIncrease o ff afterload will produce significantafterload will produce significant
hemodynamic impairmenthemodynamic impairment
1. Teitel D, et al. J Am Coll Cardiol 1983;1:1183
2. Boudreaux JP, et al. Anesth Analg 1984;63:731
3. Caspi J, et al. Circulation 1991;84(Suppl 3):394

9. 2. Physiological differences
between pediatric/adult
myocardium
 Immature myocardium is more sensitive toImmature myocardium is more sensitive to
extracellular Ca levels than mature myocardiumextracellular Ca levels than mature myocardium 1,21,2
..
 TheThe sarcoplasmic reticulum is underdeveloped in thesarcoplasmic reticulum is underdeveloped in the
pediatricpediatric heartheart
 reduced storage capacity for calciumreduced storage capacity for calcium 33
 The activity of the SR Ca ATPase is lower than inThe activity of the SR Ca ATPase is lower than in
the adult heartthe adult heart
 Antioxidant defenseAntioxidant defense systemsystem is reduced in cyanoticis reduced in cyanotic
heart defectsheart defects4,54,5
 Catalase ↓Catalase ↓
 Superoxide dismutase ↓Superoxide dismutase ↓
 Glutathione reductase ↓Glutathione reductase ↓
1. Gombosova I, et al. Am J Physiol 1998;274:H2123
2. Boucek RJ, et al. Pediatr Res 1984;18:948
3. Boland R, et al. J Biol Chem 1974;249:612
4. Teoh KH,et al. J Thorac Cardiovasc Surg 1992; 104:159
5. del Nido PJ,et al. Circulation 1987;76:174

10. Differences between the immature and
mature myocardium on primary sourse of
ATP

11. Myocardial protection in
pediatric cardiac surgery
 Cardioplegic arrest
 On-pump beating heart

12. The advantages of
cardioplegia
 Diastolic arrest of the contractive
components and cessation of electrical
activity
 Reduction of metabolic activity (arrest and
hypothermia)
 Intermittent oxygen delivery (blood)
 Maintaining acid-base balance
 Maintaining high osmotic P counteracts
tissue edema
 Modifying reperfusion (prevention of
reperfusion injury)
 Reversible
 Low toxicity

13. TThehe type of cardioplegiatype of cardioplegia
here is still no consensus on the
type of cardioplegia
There are 167 different cardioplegic
solutions used for only heart
transplantation in USA 1
.
emmy TL, et al. Ann Thorac Surg 1997;63:262

14. Cardioplegia Composition
and additives
 K+
 Mg++
 Ca++
 Buffering Systems
(HCO3
-
, THAM)
 Glutamate–aspartate
 Glucose
 Insulin
 Oxygen-derived free
radical scavengers
 Superoxide dismutase,
catalase,
 Glutathione peroxidase,
 Glutathione,
 Vit E,A, ascorbate,
 Allopurunol
 Desferrioxamine
rocainamide
eta blockers (esmolol)
a+
-H+
exchange inhibitor
(Amiloride, Cariporide)
a+
blocker (lidocaine,
tetrodotoxin)
-Arginine
+
channel openers
 Aprikalim, pinacidil,
nicorandil
a++
channel blockers

15. Blood vs crystalloid
cardioplegia
rystalloid cardioplegia
Delivery is simple and cheap
One single shot is possible
lood cardioplegia
Hemoglobin is used for O2 transportation
Metabolic substrates
Physiological buffers
Physiological osmotic P
Less hemodilution
Endogeneous oxygen free radical scavenger
Blood C is superior to crystalloid C over 1 h* Corne AF. J Thorac Cardiovasc Surg 93:163:19872,*

16. Hypothermia
Hypothermia has been used sinceHypothermia has been used since
1950 for myocardial protection1950 for myocardial protection
The methods to cool the heartThe methods to cool the heart
Cold cardioplegiaCold cardioplegia
Systemic coolingSystemic cooling
Topical myocardial cooling » damage toTopical myocardial cooling » damage to
phrenic nerve !!phrenic nerve !!
Less OLess O22 consumption in arrested heartconsumption in arrested heart

18. Warm cardioplegia
Hypothermia -Hypothermia - depletion of myocardialdepletion of myocardial
energy suppliesenergy supplies
 Lichtenstein * 1989 6.5 h CC
(normothermic continuous blood
cardioplegia)
*Lichtenstein SV et al, Lancet 1989.
**Lichtenstein SV et al, Ann Thorac Surg 1991.

19. Warm and cold combined
cardioplegia
Warm and cold combined bloodWarm and cold combined blood
cardioplegiacardioplegia
Warm inductionWarm induction
Cold cardioplegiaCold cardioplegia
Hot shotHot shot

20. Delivery techniques
Antegrade, retrograde, or combined?
nterograde delivery:
dvantages and
disadvantages
 Simple
 Uniform distribution
of cardioplegia
 AI: poor antegrade
coronary perfusion
 Aortic valve or root
surgery
 injury to the
coronary ostia

21. Delivery techniques
Antegrade, retrograde, or combined?
etrograde delivery:
dvantages and
disadvantages
 Nonphysiological
 Nonhomogenous
distribution
 Decreased flow to
the right ventricle
and septum
 The advantage in AI
and aortic root
surgery
 Risk of ruptere of

22. Single-dose/multi-dose/multi-dose
CardioplegiaCardioplegia
Single-doseSingle-dose
Continuous (adult heart)Continuous (adult heart)
Multi-dose cardioplegiaMulti-dose cardioplegia
Cold cardioplegia every 20-30 minCold cardioplegia every 20-30 min
Warm cardioplegia every 15-20 minWarm cardioplegia every 15-20 min

23. Myocardial injury after surgery
 Ventricular hypertrophyVentricular hypertrophy
 Pre-ischemic energy depletionPre-ischemic energy depletion
 Length of the ischemic intervalLength of the ischemic interval
 Incomplete myocardial protectionIncomplete myocardial protection
 Ventricular distention (failure to vent the LA
adequately)
 Retraction and stretch injury to the
myocardium
 Ventriculotomy
 edema (hemodilution or low colloid oncotic P)
 Reperfusion injuryReperfusion injury
 Coronary artery injury or embolism of airCoronary artery injury or embolism of air
bubblesbubbles

24. Low output after surgery
ypocalcemia, acidosis, hypoxia
esiduel volume overload (VSD, PY,AY)
esidual pressure overload (LVOTO,RVOTO)
ardiac compression (oedema, tamponade)
ecreased preload (hypovolemia, diastolic
dysfunction)

25. Myocardial protection in our
clinic
iniplegia
– Anterograde
n-pump beating
BDCPS, Fontan
PS, PVR, TVR

27. The cystalloid composition
for Miniplegia
 Infusion pump composition
30 meq K+
10 meq Mg++
20 ml 30% dextrose
 Induction [[KK++
]] 25 meq/L25 meq/L
 Maintenance [[KK++
]] 13 meq/L13 meq/L

29. 1. Result1. Result
 WhenWhen a medicala medical center decidecenter decide ss onon
the myocardial protection method,the myocardial protection method,
the most important determinants arethe most important determinants are
thethe clinical resultsclinical results and theand the
surgeons’ experiences.surgeons’ experiences.
 ThThisis methodmethod shouldshould be effective,be effective,
simple, cheap andsimple, cheap and shouldshould bebe
accepteacceptedd byby allall surgeonssurgeons..

30. 2. Results2. Results
 Myocardial protection is challengingMyocardial protection is challenging inin
some casessome cases
 LLongong operationsoperations
 CComplexomplex operationsoperations which recurrentwhich recurrent
cardioplegia delivery from thecardioplegia delivery from the openopen
aortic rootaortic root isis requiredrequired
 Newborn patientsNewborn patients
 Preoperatively damaged myocardiumPreoperatively damaged myocardium

31. 3. Results3. Results
 TheThe medicalmedical centercenter shouldshould evaluate theevaluate the
protection method with respect to theprotection method with respect to the
outcome in different proceduresoutcome in different procedures
If the morbidity and mortality rate isIf the morbidity and mortality rate is
high in especially long and complexhigh in especially long and complex
procedures,procedures, thethe myocardial protectionmyocardial protection
methodmethod must also be considered as amust also be considered as a
risk factor.risk factor.

32. T
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