心脏手术体外循环时低血浆T3状态对心肌的影响

目的研究心脏手术体外循环时低血浆T_3状态对心肌的影响。方法以14只绵羊分为治疗组（T3组n＝7）及对照组（n＝7）进行实验研究。对比手术前后体内血浆T3、T4及反向T3（rT3）的变化。结果实验对比发现T3在两组转流后均下降，由24±0.26pmol／L降至13±0.15pmol／L（阻断后15min）。阻断时间延长，FT3下降更为明显，而rT3呈轻度上升。对照组及治疗组转流前（0.32±0.24；0.38±0．023nmol／L）与再灌注60min（0．43±0．042；0．47±0．034nmol／L）有显著差异（P＜0．05），但各时点两组间对照均无差异（P＞0．05）。心肌ATP在阻断45min后两组均呈降低，但两组间无差别；再灌注60min时治疗组比对照组有明显升高（P＜0．05）。心肌乳酸含量在再灌注60min时对照组比治疗组有明显升高（P＜0．01）。结论T3能通过促进心肌缺血后再灌注期的能量代谢恢复并有利于心功能改变。

Low Plasma T3 during Extracorporeal Perfusion and Cardiac Surgery and the Influence of T3 on Myocardial Energy Metabolism

Objective To study on the effect of low plasma triiodothyronine on myocardial energy metabolism during extracorporeal perfusion and cardiac surgery.Methods Fourteen sheep were divided into two groups: control group (C, n=7) and T3 group (T, n=7). Plasma free T3, T4 and rT3 were determined before cardiopulmonary bypass (CPB),15, 30min after aortic cross clamping and 15, 30, 60min after reperfusion. Myocardial ATP, ADP, AMP and myocardial lactate were determined before ischemia, after ischemia for 45min and after reperfusion for 15, 60min. Results There were no significant differences between the two groups in level of T3, T4 and rT3 before CPB. In both groups, there was an initial fall in level of rT3 at the initiation of ischemia and a return to normal after reperfusion. There were no significant differences in level of myocardial ATP, ADP, AMP and lactate before myocardial ischemia in both groups of animals. There was a significant fall in ATP after myocardial ischemia in both groups. In control group, a steady increase of myocardial lactate occurred after reperfusion. There was a significant difference in lactate level between the two groups. The change of AMP was consistent with lactate. Sixty minutes after reperfusion, the myocardial ATP level was significantly higher in T. Serum LDH was significantly lower in T after reperfusion for 60min. Myocardial oxygen was utilized more efficiently in T. Conclusion It seems that T3 leads to both increasing the synthesis as well as utilization of high energy phosphate, which results in improved myocardial performance.