Impact of crystalloid HTK and St. Thomas' cardioplegia on myocardial fluid balance and postcardioplegic stunning
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Objective: Crystalloid cardioplegia may alter microvascular barrier integrity. These alterations in myocardial fluid balance contribute to post cardiopulmonary bypass (CPB) edema formation and cardiac dysfunction. Methods: 17 dogs were subjected to CPB and one hour of hypothermic arrest followed by 30 min of reperfusion. Dogs received either HTK cardioplegia (HTK), St. Thomas' cardioplegia (STH), or STH with mannitol equimolar to HTK (m-STH). Myocardial water content was determined using microgravimetry, and preload recruitable stroke work (PRSW) using sonomicrometry and micromanometry. Myeloperoxidase (MPO) activity was measured to quantify polymorphonuclear neutrophils (PMN) infiltration. Results: Compared with STH, HTK dogs had an increased PRSW two hours post CPB (p<0.05), which was associated with better recovery of contractility (p<0.05) and lower myocardial water content 15 and 40 min after cardioplegic arrest (p<0.05). Addition of mannitol to STH (m-STH) resulted in better recovery of contractility and less edema formation compared to STH and similar to HTK. No difference in MPO activity was observed between HTK and STH. Conclusions: Our study demonstrates the impact of crystalloid cardioplegia on myocardial fluid balance. Moreover, data show differences with intra- and extracellular cardioplegic solutions as measured by LV function and edema formation. Findings also suggest that mannitol contributes to the superiority of HTK cardioplegia. Since PMN accumulation does not appear to be modulated by mannitol, the observed alterations might be related to its hyperosmolarity.
