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Myocardial Protection in Pediatric Cardiac Surgery

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Myocardial Protection in Pediatric Cardiac Surgery

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Myocardial Protection in Pediatric Cardiac Surgery

  1. 1. Myocardial Protection in Pediatric Cardiac Surgery
  2. 2. No Disclosures
  3. 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. 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. 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. 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. 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. 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. 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. 10. Differences between the immature and mature myocardium on primary sourse of ATP
  11. 11. Myocardial protection in pediatric cardiac surgery  Cardioplegic arrest  On-pump beating heart
  12. 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. 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. 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. 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. 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
  17. 17. 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.
  18. 18. Warm and cold combined cardioplegia Warm and cold combined bloodWarm and cold combined blood cardioplegiacardioplegia Warm inductionWarm induction Cold cardioplegiaCold cardioplegia Hot shotHot shot
  19. 19. 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
  20. 20. 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
  21. 21. 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
  22. 22. 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
  23. 23. 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)
  24. 24. Myocardial protection in our clinic iniplegia – Anterograde n-pump beating BDCPS, Fontan PS, PVR, TVR
  25. 25. 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
  26. 26. 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..
  27. 27. 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
  28. 28. 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.
  29. 29. T Thank You!

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