Sevoflurane before or after Ischemia Improves Contractile and Metabolic Function while Reducing Myoplasmic Ca2+Loading in Intact Hearts

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Abstract
Background: Ca(2+) loading occurs during myocardial reperfusion injury. Volatile anesthetics can reduce reperfusion injury. The authors tested whether sevoflurane administered before index ischemia in isolated hearts reduces myoplasmic diastolic and systolic [Ca(2+)] and improves function more so than when sevoflurane is administered on reperfusion. Methods: Four groups of guinea pig hearts were perfused with crystalloid solution (55 mmHg, 37 degrees C): (1) no treatment before 30 min global ischemia and 60 min reperfusion (CON); (2) 3.5 vol% sevoflurane administered for 10 min before ischemia (SBI); (3) 3.5 vol% sevoflurane administered for 10 min after ischemia (SAI); and (4) 3.5 vol% sevoflurane administered for 10 min before and after ischemia (SBAI). Phasic myoplasmic diastolic and systolic [Ca(2+)] were measured in the left ventricular free wall with the fluorescence probe indo-1. Results: Ischemia increased diastolic [Ca(2+)] and diastolic left ventricular pressure (LVP). In CON hearts, initial reperfusion greatly increased diastolic [Ca2+] and systolic [Ca(2+)] and reduced contractility (systolic-diastolic LVP, dLVP/dt(max)), relaxation (diastolic LVP, dLVP/dt(min)), myocardial oxygen consumption (MvO(2)), and cardiac efficiency. SBI, SAI, and SBAI each reduced ventricular fibrillation, attenuated increases in systolic and systolic-diastolic [Ca(2+)], improved contractile and relaxation indices, and increased coronary flow, percent oxygen extraction, MvO(2), and cardiac efficiency during 60 min reperfusion compared with CON. SBI was more protective than SAI, and SBAI was generally more protective than SAI. Conclusions: Sevoflurane improves postischemic cardiac function while reducing Ca(2+) loading when it is administered before or after ischemia, but protection is better when it is administered before ischemia. Reduced Ca(2+) loading on reperfusion is likely a result of the anesthetic protective effect.

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