Dr Narinder Pal Singh Dr Minati Choudhary Cardioplegia Dr Narinder Pal Singh Dr Minati Choudhary www.anaesthesia.co.in anaesthesia.co.in@gmail.com

Cardioplegic Strategies sufficient reduction of oxygen demands delivery to all cardiac regions provide unimpaired vision

Advantages Immediate arrest Hypothermia Provide substrate Maintain pH Avoid reperfusion damage Avoid edema

Cardioplegic solutions 1 Electrolyte composition Intracellular no/ low conc. of sodium and calcium Extracell. Na depletion, loss of memb. Pot. Extracellular higher conc. of sodium, calcium, Mg hyperkalemic depol. of cell memb.

Calcium 2 pH 3 Osmolality Calcium paradox solutions devoid of ca2+ should never be used 2 pH Ischemia-intracellular pH ↓ as lactate accumulates. Buffers should be added. 3 Osmolality Important in limiting myocardial edema Blood- Iso-osmolar Crystalloid- hypo/ iso / hyper (albumin, mannitol, glucose)

Additives KCl Diastolic arrest THAM/Histidine Buffer Mannitol Osmolality/Free Radical Scavenger Aspartate/Glutamate Substrate MgCl2 Ca2+ antagonist CPD ↓ free Ca2+ conc Glucose Blood O2 carrying

Types of Cardioplegia crystalloid blood (2:1, 4:1, 8:1, blood only)

Crystalloid Cardioplegia Does not contain hemoglobin Delivers dissolved oxygen only Can be used only with myocardial hypothermia

Intracellular

Extra cellular

BLOOD 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.

endogenous antioxidants and free radical scavengers. Provides substrate less complex than other solutions to prepare. Various forms- warm, cold, hot shot Better ATP replenish Lower periop morbidity & mortality

Cold Blood Cardioplegia Advantages Lowers myocardial oxygen demands Pitfalls Hypothermic inhibition of mitochondrial enzymes Shifts oxyhaemoglobin dissociation curve to left Activates platelets, leukocytes, complement Impaired membrane stabilization

Warm Induction (resuscitation of the heart) severe left ventricular dysfunction cardiogenic shock preischaemic depletion of energy stores warm induction showed improved aerobic metabolism and LV function

Warm Reperfusion (hot-shot) early myocardial metabolic recovery while maintaining electro-mechanical arrest repletion of energy stores

Continuous Warm Cardioplegia avoidance of direct myocellular injury inflicted by any cold solution or environment increased rate of perioperative stroke and neurological events (randomised trial-1001 patients)

“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 GD J Thorac Cardiovasc Surg 1991;102:895-903

Cardioplegic 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

retrograde (coronary sinus) Combined (ante/retro) Cardioplegic Route antegrade (aorta) retrograde (coronary sinus) Combined (ante/retro)

Antegrade Cardioplegia Initial flow rate 150ml/min/m2 Initial dose- 10-15ml/kg (upto 1 litre) Perfusion pressure- 70-100mm Hg

Antegrade Cardioplegia Advantages Produces prompt arrest Pitfalls poor distribution in coronary patients poor distribution in patients with AR risk of ostial injury from direct perfusion interruption of procedure during mitral surgery

Retrograde Cardioplegia Correct catheter placement flow rate = 200mL/min perfusion pressure < 40 mmHg prevent perivascular haemorrhage and oedema

Retrograde Cardioplegia Advantages Distribution of CP to regions supplied by occluded/stenosed vessels Improved subendocardial CP delivery Flushing of air and/or atheromatous debris Pitfalls Shunting of CP into ventricular cavities via Thebesian channels Perfusion defects especially right ventricle and posterior septal regions

Combined (ante/retro) Studies have demonstrated better myocardial protection Various techniques Arrest with antegrade, additional doses given retrogradely with venting of aortic root Alternating technique-retrograde cardioplegia administered frequently+ interrupted antegrade cardioplegia down each completed graft Simultaneous method- retrograde continued while antegrade is given down each graft.

inadequate protection postop RV dysfn coronary ostial stenosis COMPLICATIONS inadequate protection postop RV dysfn coronary ostial stenosis coronary sinus injury aortic root injury

CONTROVERSY ‘ideal’ cardioplegic technique different crystalloid cardioplegia crystalloid versus blood cardioplegia Although recent rand trials - improved metabolic and functional myo preserv with blood CP -decreased mortality and morbidity not consistently demonstrated between blood and crystalloid cardioplegia.

Therefore, institutional and the individual surgeon's experience remain the most important determinants of myocardial protection strategy at this moment.

Thank you www.anaesthesia.co.in anaesthesia.co.in@gmail.com