Oral Thyroid Hormone Pretreatment In Heart Function After Cardiopulmonary Bypass Surgery

[Background]: The present study demonstrates that thyroid hormone function is greatly suppressed in pateints after cardiac surgery. Alterations in serum concentrations of freetriio-dothyronine, freethyroxine,thyroid-stimulating hormone occur in patients with patients undergoing cardiopulmonary bypass.These changes are caused by the trauma of the surgery,hypothermia, disturbances in the hypothalamo-pituitary-thyroidaxis, nunpulsrefusion, hemodilution, thyroidhormonemetabolism. Thyroid hormone has many effects on the heart and vascular system. Hypothyroidism results in decreased cardiac output as a consequence of diminished heart rate,stroke volume and contractility.some researchers proved that impact of triiodothyronine can support heart function after ischemia and cardiopulmonary bypass.Ojective: The aim of this study was to find out if infants after cardiopulmonary bypass develop changes of serum concentrations of thyroid hormone. The study was also undertaken to further define the effect of supplement of extra thyroid hormone on heart function after cardiopulmonary bypass.Material and mothods: forty patients undergoing cardiopulm- onary bypass participate in this prospective,randomized trial.The thyroid hormone(TH) group and control group were equally divided. All patients were euthyroid before surgery and were given no drugs that could have influenced thyroidhormone. The two groups werenot Statistically different with respect to a variety of preoperative and intraoperative factors,such as age,body weight, Serum concentrations of hormones before operation,Aortic cross clmp time, Cardiopulmonary bypass time. Patients randomized to the TH group received TH 0.2mg/(kg.d)orally the day just before operation and from first to third day after operation.Patient in control group were given classical treatment at the same time.Outcome variables included perioperative hemodynamic data,inotropic requirments.The thyroid profile was determined before cardiopulmonary bypass (CPB),duringCPB,1day,3day,5day,7day after CPB. Serum was separated from blood by centrifugation and stored at -20℃until assayed.Serum concentrations of hormones were measured by radioimmunoassays. The data of EF and FS were mearured before and five day after operation. Data were analyzed by paired Student's t-test(comparing each time value by means of a 0.05 level for significance).Results:Before operation,the levels of TH in all patiens were in normal range.Changes of TH serun level were detcted in both group. TH serun level in TH group showed a sooner recovery.Patient in the TH group demonstrated a higher EF and FS than patients in the control group in the post-CPB perids(p<0.01),Mean inotropic requuiements remained lower in the TH group than in the control group(p<0.05).there is no hospital death in two groups.Conclusion:Our study showed changes of serum thyroid hormone(TH)during CPB surgery and the benefits of oral TH administration on the heart function in patients who undergoing cardiopumonary bypass.