Protective Effects Of Sevoflurane-Induced Preconditioning On Myocardial Ischemia-Reperfusion Injury In Open Heart Surgery With Cardiopulmonary Bypass

Objective To study the protective effects of sevoflurane-induced preconditioning on myocardial ischemia-reperfusion injury in open heart surgery with cardiopulmonary bypass (CPB).Methods Twenty patients (ASAⅡ～Ⅳ) scheduled for elective cardiac valve replacement with CPB were randomly divided into two groups: control group (group C, n=10) and sevoflurane preconditioning group (group S, n=10). Anesthesia was induced with intravenous injection of midazolam (0.08～0.12mg·kg^-1), fentanyl (5～10μg·kg^-1) and pipecuronium (0.1mg·kg^-1) and was maintained with intermittent i.v. boluses of midazolam, fentanyl and pipecuronium. In group S, 1vol% sevoflurane was continuously inhaled from the beginning of operation to the beginning of CPB, and no anesthetic was inhaled in group C. Plasma levels of cardiac troponin I (cTnI), creatine phosphokinase (CK) and creatine phosphokinase isoenzyme (CK-MB) were measured after induction of anesthesia (T₁), immediate after aorta clamping (T₂), immediate after (T₃) and 30min after (T₄) aorta unclamping, 2h (T₅), 6h (T₆), 12h (T₇) and 24h (T₈) after discontinuation of CPB, respectively. Myocardial samples of left ventricle for electronic microscopy were obtained before aorta clamping and 5 minutes after aorta unclamping. Results Plasma cTnI, CK and CK-MB levels were within normal range before CPB and there were no significant differences in cTnI, CK and CK-MB between both groups at T₁. In group C, plasma levels of cTnI at T₄, T₅, T₆, T₇ and T₈ were higher than that at T₁ (P<0.001), and reach the peak level at T₆, then declined at T₇. In group S plasma level of cTnI at T₄, T₅ and T₆ was higher than that at T₁ (P<0.001), and declined to normal range at T₈. Increasing amplitude of plasma cTnI was lower at T₄, T₅, T₆, T₇ and T₈ in group S than that in group C (P<0.05～0.01). Plasma levels of CK and CK-MB at T₃, T₄, T₅, T₆, T₇ and T₈ were higher than that at T₁ (P<0.05～0.001) in both two groups. There were no significant differences in plasma levels of CK and CK-MB between two groups at T₃, T₄, T₅, T₆ and T₇, but the values were lower in group S than that in group C at T₈ (P<0.05). Ischemic and hypoxic changes in myocardial biopsy were obviously observed with electric microscope 5min after aorta unclamping in group C. No distinct changes were found in group S. In group C, the heart beat conversed automatically in four patients and conversed electrically in six cases, and ventricular tachycardia occurred in two patients, ventricular premature beat appeared in one patient and ventricular fibrillation happened in one case, and six patients were supported with inotropic drugs. In group S, heart beat conversed automatically in eight patients and was conversed electrically in two cases, and no arrhythmia appeared and no inotropic drugs were used in all patients. The rate of automatic conversion was higher in group S than that in group C (P<0.05). The volume of wound drainage in first postoperative day was less in group S than that in group C (P<0.05).Conclusion The findings of the present study demonstrated that during peri-CPB stage for patients undergoing cardiac valve replacement, myocardium and cardiac function was damaged. Sevoflurane-induced preconditioning is able to effectively relieve myocardial ischemia-reperfusion injury in open heart surgery with CPB. As a marker of myocardial injury, cTnI is more sensitive and more specific than CK and CK-MB. cTnI is a reliable detecting parameter for the diagnosis of myocardial injury during open heart surgery.