4Cardioplegic solutions 1 Electrolyte compositionIntracellularno/ low conc. of sodium and calciumExtracell. Na depletion, loss of memb. Pot.Extracellularhigher conc. of sodium, calcium, Mghyperkalemic depol. of cell memb.
5Calcium 2 pH 3 Osmolality Calcium paradox solutions devoid of ca2+ should never be used2 pHIschemia-intracellular pH ↓ as lactate accumulates.Buffers should be added.3 OsmolalityImportant in limiting myocardial edemaBlood- Iso-osmolarCrystalloid- hypo/ iso / hyper (albumin, mannitol, glucose)
11BLOOD CARDIOPLEGIA oxygenated environment. intermittent reoxy of the heart during arrest.limit hemodilution when large vol of CP used.excellent buffering capacity.osmotic properties.electrolyte composition and pH are physiologic.
12endogenous antioxidants and free radical scavengers. Provides substrateless complex than other solutions to prepare.Various forms- warm, cold, hot shotBetter ATP replenishLower periop morbidity & mortality
15Warm Induction (resuscitation of the heart) severe left ventricular dysfunctioncardiogenic shockpreischaemic depletion of energy storeswarm induction showed improved aerobicmetabolism and LV function
16Warm Reperfusion (hot-shot) early myocardial metabolic recovery while maintaining electro-mechanical arrestrepletion of energy stores
17Continuous Warm Cardioplegia avoidance of direct myocellular injury inflicted by any cold solution or environmentincreased rate of perioperative stroke and neurological events (randomised trial-1001 patients)
18“The heart takes up oxygen over time rather than by dose, so that blood cardioplegic solutions must be delivered over a time interval, rather than by volume”Buckberg GDJ Thorac Cardiovasc Surg 1991;102:
19Cardioplegic Temperature cold (9 0C)tepid (29 0C)warm (37 0C)Hayashida et al- compared cold (8°C), tepid (29°C), or warm (37°C) in 72 pts of CABG.tepid CP- most effective in reducing anaerobic lactate acid release during the arrest period.Whether tepid cardioplegia confers better protection over other current methodologies remains to be determined
22Antegrade Cardioplegia AdvantagesProduces prompt arrestPitfallspoor distribution in coronary patientspoor distribution in patients with ARrisk of ostial injury from direct perfusioninterruption of procedure during mitral surgery
24Retrograde Cardioplegia AdvantagesDistribution of CP to regions supplied by occluded/stenosed vesselsImproved subendocardial CP deliveryFlushing of air and/or atheromatous debrisPitfallsShunting of CP into ventricular cavities via Thebesian channelsPerfusion defects especially right ventricle and posterior septal regions
25Combined (ante/retro) Studies have demonstrated better myocardial protectionVarious techniquesArrest with antegrade, additional doses given retrogradely with venting of aortic rootAlternating technique-retrograde cardioplegia administered frequently+ interrupted antegrade cardioplegia down each completed graftSimultaneous method- retrograde continued while antegrade is given down each graft.
29CONTROVERSY‘ideal’ cardioplegic techniquedifferent crystalloid cardioplegiacrystalloid versus blood cardioplegiaAlthough recent rand trials - improved metabolic and functional myo preserv with blood CP -decreased mortality and morbidity not consistently demonstrated between blood and crystalloid cardioplegia.
30Therefore, institutional and the individual surgeon's experience remain the most important determinants of myocardial protection strategy at this moment.