Effects of open-heart surgery on thyroid hormone levels
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Heart surgery patients undergoing cardiopulmonary bypass had lower thyroid hormone levels pre-operatively. This may contribute to postoperative low cardiac output syndrome.
Area of Science:
- Cardiology
- Endocrinology
- Surgical Science
Background:
- Thyroid hormones (thyroxine [T4] and triiodothyronine [T3]) significantly impact myocardial contractility.
- Understanding their role in cardiac surgery is crucial for managing postoperative outcomes.
Purpose of the Study:
- To investigate the effect of cardiopulmonary bypass (CPB) on plasma T3 and T4 levels in patients undergoing heart surgery.
- To explore the relationship between pre-operative stress markers and thyroid hormone levels in relation to CPB use.
Main Methods:
- Plasma levels of T4, T3, dopamine-beta-hydroxylase, and growth hormone were measured in 19 patients.
- Patients were divided into two groups: those undergoing heart surgery with CPB and those without.
Main Results:
- Patients in the CPB group exhibited significantly lower pre-operative plasma T4 and T3 levels compared to the non-CPB group.
- Elevated pre-operative dopamine-beta-hydroxylase and growth hormone levels were observed in the CPB group, suggesting greater stress.
- Postoperatively, thyroid hormone levels showed a tendency to decrease in the non-CPB group, whereas a slight increase was noted in the CPB group.
Conclusions:
- Pre-operative stress may contribute to lower thyroid hormone levels in patients undergoing CPB.
- The observed alterations in thyroid hormone levels during heart surgery, particularly with CPB, might play a role in the development of postoperative low cardiac output syndrome.
Abstract:
The effect of heart surgery with and without cardiopulmonary by-pass on plasma levels of thyroxine (T4) and triiodothyronine (T3) was studied in 19 patients. It was found that even before the operation the plasma levels of T4 and of T3 were significantly lower in the by-pass group of patients in comparison with those without by-pass. This lower level of thyroid hormones could be explained by greater pre-operative stress. This presumption is supported by the finding of the greater pre-operative plasma concentrations of dopamine-beta-hydroxylase and growth hormone in patients of the by-pass group. While in patients not undergoing CPB a tendency to the decrease of plasma thyroid hormones was observed during the early postoperative phase, in patients of the by-pass group a small increase was observed. On the basis of the finding that thyroid hormones exercise powerful and specific effect on myocardial contractility, it is suggested that the low hormone level might have a role in the pathogenesis of postoperative low cardiac output syndrome.