The Feasibility Of Thyroid Hormone Supplement Before Cardiac Surgery For Children

Objective:To investigate if supplement thyroid hormone before cardiac sugery can influence the level of throid hormone and provide cardioprotection.To provide clinical evidence for supplement thyroid hormone before cardiac sugery.Method:40 aged between 3～12 years old children undergoing simple congenital heart disease surgery under CPB(cardiac pulmonary bypass) were choosed.They were divided into two groups randomly:Blank control group and experimental group. The children in experimental group would take thyroid hormone tablet 0.4mg /(kg.d) for 4 days from the 4th day to the last day to the surgery;no special treatment would be taken to those children in blank control group.The venous blood samples were collected at six time points:after hospitalization(t1),before CPB(t2),the lowest temperature point during CPB(t3),1 day(t4),2 day(t5),and 4 day(t 6)post-operatively.The concentration serum thyroid hormone triiodothyronine(T₃), free triiodothyronine(FT₃),thyroxine(T₄),free thyroxin(FT₄) and thyroid stimulating hormone(TSH) ware assayed.We observed and recorded the hemodynamic parameters,ICU duration,tracheal extubation time in ICU and the administration of inotropic drugs in ICU.Took atria sample from 6 children randomly chosen in each group to detect the heat shock protein 70 by western-blotting and the expression of subtype of thyroid hormone receptor mRNA and subtype of myosin heavy chain mRNA by PCR,the myocardium enzyme would be detected in 24 hours after surgery.Results:The concentration of T₃ in both groups at t2,t3,t4,t5 and t6 is lower than t1(P＜0.05);the concentration of T₄ in experimental group is lower only at t3(P＜0.05),while the concentration of T₄ in blank control group is lower at t3,t4 and t5 (P＜0.01).The concentration of T₃ and T₄ in experimental group is higher than blank control group at t4 and t5(P＜0.01),the concentration of FT₃ in experimental group is higher than blank control group at t3,t4 and t5(P＜0.01),the concentration of FT₄ in experimental group is higher than blank control group at t2,t4 and t6(P＜0.05),the concentration of TSH in experimental group is lower than blank control group at t3(P＜0.05).The ratio of inotropic drug application in experimental group is lower than blank control group(P＜0.05);the CK-MB in experimental group is lower than blank control group(P＜0.05);the positive ratio of TnI in experimental group is lower than blank control group(P＜0.05);the content of HSP70 in experimental group is higher than blank control group;in experimental group,the expression of MHCαmRNA increased while MHCβmRNA decreased(P＜0.05),no significant difference between two groups on thyroid hormone receptor mRNA(P＞0.05).Conclusion:The children of congenital heart disease could develop euthyriod sick syndrome perioperation.Small dosage thyroid hormone supplement before surgery can improve the euthyriod sick syndrome after sugery,reduce the usage of inotropic drug,provide favourable cardioprotection,due to the increase of HSP70 expression.